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posted on 13 February 2018

February 13, 2018 Weather and Climate Report - Another Cold Air Intrusion

Written by Sig Silber

NOAA has to integrate and balance many different, and in some cases conflicting, sources of information to make their forecasts. Recently the conflicts were so severe in some cases that various sources were totally discounted rather than assigned a lower weight in the forecast. This is not totally unusual and NOAA has skill at doing this. It seems that they are now highly confident that they have figured things out for the next two weeks. Most of this is described in the NOAA discussion for the week 3-4  forecast. Part of the challenge is to figure out the possible changing of the WP-NPO pattern. NOAA has concluded in their discussion today that any such change will not occur in the next two weeks. As you read my report, I will point out where some of these choices have been made. And of course we will cover the extreme precipitation event forecast for the Ohio River and Mid-Mississippi Valleys which has the potential for significant flooding. 

  Forecasting Model Roulette


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Some housekeeping: There was a new Seasonal Outlook issued by NOAA on January 18 which we reported on January 20 which you can access here  NOAA updated their Outlook for February on Wednesday January 31 and we reported on that the following Thursday night and that report can be accessed here. A new NOAA Seasonal outlook will be issued on February 15 and we will report on that Saturday evening February 17.
Remember if you leave this page to go to links or if you have clicked to enlarge a graphic, in order to get back you need to hit the return arrow usually located on the left of your URL box on the upper left of the screen. Also most of the small graphics are designed to become full size when you click on them. If that does not work, an alternative way to view the larger graphics is to right click and then hit "view image".  That should always work.
 If you have additional suggestions for improvement, please make them in the comments section following the article.

Let's change topics.

Because it is Winter we make it easy to get a snow forecast. This is the six-hour snow forecast.

6 hr Snow

Looking further out.

NOAA Snow Forecast looking ahead to Days 4,5 (top Row) 6 and 7 (bottom row). When you view these graphics you can click on them to enlarge them.

Day 4 Day 5
Day 6 Snow Forecast Day 7 Snow

 

I think they are only showing large areas so locally there could be other areas especially at high elevation that also receive significant snowfall. The pattern is clearly across the northern tier of CONUS with the major impact in the Northeast as the cool anomaly moves east. You can obtain additional forecasts here..

A. Now we return to our  regular approach and focus on Alaska and CONUS (all U.S.. except Hawaii) 

I am starting with a summary first for temperature and then for precipitation of small images of the three short-term maps. You can click on these maps to see larger versions. The easiest way to return to this report is by using the "Back Arrow" usually found top left corner of your screen to the left of the URL Box. Larger maps are available later in the article with the discussion and analysis.

For most people, the summary with the small images will be sufficient. Later in the article for those with sufficient interest there is a full description of the factors determining the maps shown here with a detailed analysis of the ENSO situation which so dramatically impacts the forecasts below.

First Temperature

6 - 10 Day Forecast Temperature

Transitioning from the 6 to 10 day outlook on the left (also called Week One) to the 8 to 14 day outlook (Week Two) on the right                          →

8 - 14 Day Temperature

The pattern is not progressive. The pattern is rather static.

To the right is the week 3 and 4 Forecast.

There is a single warm anomaly in Alaska and a large warm anomaly covering 2/3ds of CONUS with the Northwest quadrant being EC with an embedded cool anomaly.                      →                  

             

3 - 4 Week Temperature

                     ↑

←  The transition from the 8 -14 day forecast shown above to the week 3/4 shown to the left seems feasible but it is big change for the West.
 

And then Precipitation

6 - 10 Day Forecast Precipitation

Transitioning from the 6 to 10 day outlook on the left to the 8 to 14 day outlook on the right.                                         →

8 - 14 Day Precipitation

A continuation of the pattern into the second week (Days 8 - 14) with the wet anomaly intensifying.

To the right is the week 3 and 4 Experimental Forecast.    →               

Western Alaska and the Panhandle is wet. The Northern Tier and East Coast of CONUS are dry. The states along the Gulf Coast are wet.
3 - 4 Week Precipitation

                     ↑

←  The transition from the 8 -14 day forecast shown above to the week 3/4 shown to the left represents a very significant change.

Let us focus on the Current (Right Now to 5 Days Out) Weather Situation.

Water Vapor.

This view of the past 24 hours provides a lot of insight as to what is happening.

Eastern Pacific Animation

You can see most moisture is entering North America north of CONUS. Below is the same graphic as above but without the animation to show the current situation with respect to water vapor imagery for Western North America.

Water Vapor Imagery

Tonight, Monday evening February 12, 2018, as I am looking at the above graphic, you see a lot of clouds streaming into the Midwest. The main action remains north of CONUS.

This graphic is about Atmospheric Rivers i.e. thick concentrated movements of water moisture. More explanation on Atmospheric Rivers can be found by clicking here or if you want more theoretical information by clicking here. The idea is that we have now concluded that moisture often moves via narrow but deep channels in the atmosphere (especially when the source of the moisture is over water) rather than being very spread out. This raises the potential for extreme precipitation events. You can convert this graphic into a flexible forecasting tool by clicking here. One can obtain views of different geographical areas by clicking here.

 Center for Western Weather and Water Extremes, Scripps/UCSD.

We see very little activity in the West and very large inflow from the Gulf of Mexico impacting much of the East

And Now the Day One and Two CONUS Forecasts

Day One CONUS Forecast

Day Two CONUS Forecast

Day 1 Forecast Map

Day 2 Forecast

There is snow shown Mostly for the Northwest but extenting pretty far south with rain in the East ranging NNE from the Gulf Coast.

Earlier I have provided snow forecasts for day 4 through 7 and a link to earlier days.

These graphics update and can be clicked on to enlarge but my brief comments are only applicable to what I see on Monday night prior to publishing.

60 Hour Forecast Animation

Here is a national animation of weather fronts and precipitation forecasts with four 6-hour projections of the conditions that will apply covering the next 24 hours and a second day of two 12-hour projections the second of which is the forecast for 48 hours out and to the extent it applies for 12 hours, this animation is intended to provide coverage out to 60 hours. Beyond 60 hours, additional maps are available at links provided below. The explanation for the coding used in these maps, i.e. the full legend, can be found here although it includes some symbols that are no longer shown in the graphic because they are implemented by color coding.

current highs and lows

You can enlarge the below daily (days 3 - 7) weather maps for CONUS by clicking on Day 3 or Day 4 or Day 5 or Day 6 or Day 7. These maps auto-update so whenever you click on them they will be forecast maps for the number of days in the future shown.

Short term forecasts

What is Behind the Forecasts? Let us try to understand what NOAA is looking at when they issue these forecasts.

Below is a graphic which highlights the forecasted surface Highs and the Lows re air pressure on Day 7. The Day 3 forecast can be found here. the Day 6 Forecast can be found here. Actually all the small graphics below can be clicked on to enlarge them.

Day 7 Highs and Lows

When I look at this Day 7 forecast, there is a large Low west of the Aleutians and southeast of Kamchatka with surface central pressure of  988 hPa. The Aleutian Low is out of position to impact anything but Alaska. There remains a large and not well defined Hudson Bay Low with surface central pressure of 1004 hPa. And very critical is the Pacific Subtropical High with surface central pressure of 1036 hPa. This High extends inland. The Bermuda High off the East Coast is also important with surface central pressure of 1032 hPa. There is a High in Mexico that will impact things

I provided this K - 12 write up that provides a simple explanation on the importance of semipermanent Highs and Lows and another link that discussed possible changes in the patterns of these highs and lows which could be related to a Climate Shift (cycle) in the Pacific or Global Warming. Remember this is a forecast for Day 6. It is not the current situation.

The table below showing the Day 3, Day 4, Day 5, Day 6 and Day 7 of this graphic can be useful in thinking about how the pattern of Highs and Lows is expect to move during the week.

Day 3 Day 4
Day 5 Day 6

From left to right and then down, Days 3 and 4 top row, Days 5 and 6 second row and Day 7 to the right. These are small images but you can if you want click on them and get larger images but even with the small images you can trace the evolution of the pattern. The graphics update but my commentary below does not so it is just a guide for how to read these graphics.

Day 7

There is not a lot of change in the pattern over the five days shown. The High has retrograded offshore just enough to allow troughs to form in the Great Basin.

Things to look for in general are the position and strength of the Aleutian Low, the Hawaiian High and any troughs especially if they extend far to the south and are over water.

Looking at the current activity of the Jet Stream.  The below graphics and the above graphics are very related.

Not all weather is controlled by the Jet Stream (which is a high altitude phenomenon) but it does play a major role in steering storm systems especially in the winter The sub-Jet Stream level intensity winds shown by the vectors in this graphic are also very important in understanding the impacts north and south of the Jet Stream which is the higher-speed part of the wind circulation and is shown in gray on this map. In some cases however a Low-Pressure System becomes separated or "cut off" from the Jet Stream. In that case it's movements may be more difficult to predict until that disturbance is again recaptured by the Jet Stream. This usually is more significant for the lower half of CONUS with the cutoff lows being further south than the Jet Stream. Some basic information on how to interpret the impact of jet streams on weather can be found here and here.  I have not provided the ability to click to get larger images as I believe the smaller  images shown are easy to read.

Current Day 5
Current Jet Stream Jet Stream Five Days Out

Notice, this is a GFS forecast and right now the GFS and ECMWF are not yet in full agreement as to what happens to the cut-off low forming off of LA. How long that Low stays there collecting tropical moisture and then its path and speed will have a large impact on the states that it crosses. As shown, this forecast is for a very short tropical visit by this cut-off low.

Putting the Jet Stream into Motion and Looking Forward a Few Days Also

To see how the pattern is projected to evolve, please click here. In addition to the shaded areas which show an interpretation of the Jet Stream, one can also see the wind vectors (arrows) at the 300 Mb level.

This longer animation shows how the jet stream is crossing the Pacific and when it reaches the U.S. West Coast is going every which way.

Click here to gain access to a very flexible computer graphic. You can adjust what is being displayed by clicking on "earth" adjusting the parameters and then clicking again on "earth" to remove the menu. Right now it is set up to show the 500 hPa wind patterns which is the main way of looking at synoptic weather patterns. This amazing graphic covers North and South America. It could be included in the Worldwide weather forecast section of this report but it is useful here re understanding the wind circulation patterns.

500 MB Mid-Atmosphere View

The map below is the mid-atmosphere 7-Day chart rather than the surface highs and lows and weather features. In some cases it provides a clearer less confusing picture as it shows only the major pressure gradients. This graphic auto-updates so when you look at it you will see NOAA's latest thinking. The speed at which these troughs and ridges travel across the nation will determine the timing of weather impacts. This graphic auto-updates I think every six hours and it changes a lot. Because "Thickness Lines" are shown by those green lines on this graphic, it is a good place to define "Thickness" and its uses. The 540 Level generally signifies equal chances for snow at sea level locations. Thickness of 600 or more suggests very intensely heat and fire danger. Sometimes Meteorologists work with the 500 mb heights which provide somewhat similar readings to the "Thickness" lines but IMO provide slightly less specific information. Thinking about clockwise movements around High Pressure Systems and counter- clockwise movements around Low Pressure Systems provides a lot of information.

7 Day 500 MB Geopotential Forecast

What we see for Day 7 is again similar to the situation in recent weeks with a huge trough over Western CONUS with a ridge to the west and east of the trough. There is intrusion into Western CONUS of the 540 Thickness line so we are likely talking about a better chance for a less moderate cold pattern for the West North Central States and the Northwest. Moderate temperature does not mean moderate amounts of snow. Last week Chicago was on the edge of this pattern and received a lot of snow. The 540 line roughly suggests odds of 50% the precipitation will fall as snow. It is a first approximation only.

Here is the whole suite of similar maps for Days 3,4, 5, 6 and repeated for Day 7. 

     
Day 3 500mb Heights Day 4 500mb Heights http://www.wpc.ncep.noaa.gov/medr/d5500wbg.gif
Day 6 500mb Heights Day 7 500mb Heights Day 3 to 7 500mb Heights

 

Notice the extreme extension of the trough on Day 3. That is the Low leaving the major circulation, being cut off, and not keep up with the major pattern but having it's own ideas about where it will go.

Here is the seven-day cumulative precipitation forecast. More information is available here.

Seven Day WPC Quantitative precipitation forecast

We see a wet Northwest and Southwest and a wet Eastern half of CONUS with a lot of influence from the Gulf of Mexico. The Ohio River and Mid-Mississippi River Valleys are likely to receive a lot of precipitation. Notice how the storm that has moved down the Great Basin is forecast to visit Mexico.

Four - Week Outlook: Looking Beyond Days 1 to 5, What is the Forecast for the Following Three + Weeks?

I use "EC" in my discussions although NOAA sometimes uses "EC" (Equal Chances) and sometimes uses "N" (Normal) to pretty much indicate the same thing although "N" may be more definitive.

First - Temperature

6 - 10 Day Temperature Outlook issued today (Note the NOAA Level of Confidence in the Forecast Released on February 12, 2018 was 5 out of 5

6 - 10 Day Temperature Outlook

8 - 14 Day Temperature Outlook issued today (Note the NOAA Level of Confidence in the Forecast Released on February 12, 2018 was 5 out of 5).

8-14 Day Temperature Outlook

Looking further out.

Experimental Week 3-4 Temperature Outlook

Now - Precipitation

6 - 10 Day Precipitation Outlook Issued Today (Note the NOAA Level of Confidence in the Forecast Released on February 12, 2018 was 5 out of 5)

6 - 10 Day Precipitation Outlook

8 - 14 Day Precipitation Outlook Issued Today (Note the NOAA Level of Confidence in the Forecast Released on January 29, 2018 was 5 out of 5)

Current 8 - 14 Day Precipitation Outlook

Looking further out.

Weeks 3 and 4 Experimental Forecast.

Here is the 6 - 14 Day NOAA discussion released today February 12, 2018 and the Week 3/4 (assumption rich) discussion released Friday February 9, 2018

6-10 DAY OUTLOOK FOR FEB 18 - 22 2018

TODAY'S ENSEMBLE MEAN SOLUTIONS ARE IN VERY GOOD AGREEMENT ON THE EXPECTED 500-HPA FLOW PATTERN OVER THE FORECAST DOMAIN. ALL OF TODAY'S MODEL SOLUTIONS FORECAST AN AMPLIFIED RIDGE OVER MAINLAND ALASKA, A TROUGH OVER MUCH OF CANADA INTO THE WESTERN HALF OF THE CONUS, AND A RIDGE OVER MUCH OF THE EASTERN U.S. THE FORECAST PATTERN IS VERY HIGH AMPLITUDE, INCREASING CONFIDENCE IN THE FORECAST AND RESULTING IN FAIRLY LARGE FORECAST PROBABILITIES. IN ADDITION THERE IS EXCELLENT AGREEMENT BETWEEN THE TOOLS AND BETWEEN TODAY'S GFS, ECMWF,  AND CANADIAN ENSEMBLE MEANS. TODAY'S MANUAL 500-HPA BLEND FAVORS LARGELY POSITIVE HEIGHT ANOMALIES OVER ALL OF ALASKA, NEGATIVE HEIGHT ANOMALIES OVER THE WESTERN HALF OF THE CONUS, AND POSITIVE HEIGHT ANOMALIES OVER THE EASTERN HALF OF THE CONUS.

HIGHLY ANOMALOUS RIDGING OVER ALASKA STRONGLY FAVORS ABOVE NORMAL TEMPERATURES FOR MOST OF ALASKA. PERSISTENT TROUGHING IN THE WESTERN CONUS LEADS TO INCREASED CHANCES FOR BELOW NORMAL TEMPERATURES FOR MUCH OF THE WESTERN AND NORTH-CENTRAL CONUS, ESPECIALLY IN THE NORTHERN PLAINS AND ROCKIES WHERE NEGATIVE HEIGHT ANOMALIES ARE THE LARGEST. A STRONG RIDGE FORECAST OVER THE EASTERN U.S. LEADS TO ENHANCED CHANCES OF ABOVE NORMAL TEMPERATURES.  

THE STRONG RIDGE FORECAST OVER ALASKA IS EXPECTED TO PUSH THE TYPICAL STORM TRACK FARTHER NORTH, LARGELY FAVORING ABOVE NORMAL PRECIPITATION FOR MUCH OF MAINLAND ALASKA, EXCEPT FOR THE SOUTHERN COAST AND ALASKA PANHANDLE WHERE A MORE NORTHERLY STORM TRACK WOULD FAVOR DRIER CONDITIONS. NEAR TO BELOW NORMAL PRECIPITATION IS FAVORED FOR THE WEST COAST, WEST OF THE TROUGH AXIS. A COUPLE OF STORM SYSTEMS ARE FORECAST TO DROP SOUTH INTO THE CONUS, WITHIN THE TROUGH, AND INCREASE THE LIKELIHOOD OF ABOVE NORMAL PRECIPITATION FOR PARTS OF THE GREAT BASIN, ROCKIES AND NORTHERN PLAINS. A STATIONARY FRONT IS EXPECTED TO SETUP ACROSS TEXAS, THE MIDDLE MISSISSIPPI VALLEY, OHIO VALLEY AND NORTHEAST, FAVORING INCREASED STORM SYSTEM ACTIVITY AND ABOVE NORMAL PRECIPITATION. BENEATH THE HIGHLY ANOMALOUS SOUTHEAST RIDGE, BELOW NORMAL PRECIPITATION IS FAVORED FOR PARTS OF THE GULF COAST, MID-ATLANTIC COAST, AND FLORIDA.

THE OFFICIAL 6-10 DAY 500-HPA HEIGHT BLEND CONSISTS OF 60% OF TODAY'S 0Z EUROPEAN ENSEMBLE MEAN CENTERED ON DAY 8, AND 40% OF TODAY'S OPERATIONAL 0Z  ECMWF CENTERED ON DAY 8  [Editors’ Note:  NOAA is all in with the ECMWF model]

FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: WELL ABOVE AVERAGE, 5 OUT OF 5, DUE TO VERY GOOD AGREEMENT AMONG THE MODELS AND TOOLS.  

8-14 DAY OUTLOOK FOR FEB 20 - 26 2018   

BY THE WEEK-2 PERIOD, THE LARGE-SCALE PATTERN OVER THE FORECAST DOMAIN IS  EXPECTED TO BE SHIFTED SLIGHTLY WEST, AND SLIGHTLY LESS AMPLIFIED, BUT REMAIN LARGELY UNCHANGED. THE HEIGHT ANOMALIES DEPICTED IN THE MANUAL 500-HPA BLEND ARE RELATIVELY LARGE FOR THE WEEK-2 PERIOD, SUGGESTING VERY GOOD MODEL  AGREEMENT AND CERTAINTY. THE WEEK-2 TEMPERATURE PROBABILITY FORECAST IS VERY SIMILAR TO THE 6-10 DAY FORECAST, EXCEPT IN THE EASTERN U.S. PROBABILITIES OF ABOVE NORMAL TEMPERATURES ARE EVEN HIGH, DUE TO THE FACT THAT THE RIDGE IS PREDICTED TO MIGRATE SLIGHTLY WESTWARD, WITH THE LARGEST POSITIVE HEIGHT ANOMALIES BECOMING CENTERED ALONG THE EAST COAST. THE WEEK-2 PRECIPITATION PROBABILITY FORECAST IS ALSO VERY SIMILAR TO THE 6-10 DAY FORECAST, EXCEPT PROBABILITIES OF ABOVE NORMAL PRECIPITATION ARE INCREASED OVER THE MIDDLE MISSISSIPPI VALLEY DUE TO VERY GOOD AGREEMENT ON PERSISTENT STORM SYSTEM ACTIVITY ALONG THE STATIONARY FRONT DURING THE WEEK-2 PERIOD.

THE OFFICIAL 8-14 DAY 500-HPA HEIGHT BLEND CONSISTS OF: 40% OF TODAY'S  OPERATIONAL 6Z GFS CENTERED ON DAY 11, AND 60% OF TODAY'S 0Z EUROPEAN ENSEMBLE  MEAN CENTERED ON DAY 11 [Editor’s Note: The GFS was allowed back in. A very small subset of model runs in this forecast]

FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD: WELL ABOVE AVERAGE, 5 OUT OF 5, DUE TO VERY GOOD AGREEMENT AMONG THE MODELS AND TOOLS.

THE NEXT SET OF LONG-LEAD MONTHLY AND SEASONAL OUTLOOKS WILL BE RELEASED ON FEBRUARY 15.  

Week 3-4 Forecast Discussion Valid Sat Feb 24 2018-Fri Mar 09 2018 {Editor's Note: This discussion was issued last Friday but it certainly reads very differently than the discussion released with 6 - 14 Day Forecast today.]

A confluence of various impactful climate modes continues to influence the perspective for the present Week 3-4 outlook. La Nina continues in the equatorial Pacific, while the active phase of the Madden-Julian Oscillation (MJO) is in the far West Pacific (Phase 7). In the extratropics, the North-Pacific Oscillation-West Pacific (NPO-WP) pattern has been highly negative with ridging featured over the Bering Sea and troughing over Hudson Bay. Additionally, the North-Atlantic Oscillation (NAO) has been positive nearly all winter, with models suggesting weakening of this signal prior to the outlook period. Of final note is the anticipated sudden stratospheric warming event prior to the outlook period. However, efforts at CPC to quantify influence of the stratospheric warmings on outlooks for Week-2 and Weeks 3-4 show little in the way of consistent impacts of these events over the U.S. and negligible correlations with lagged responses in North American temperature and precipitation between 10 and 20 days after the event. Given the complex perspective leading into this outlook, confidence is lowered overall. The ECMWF model was favored among all dynamical model guidance for its progression from the Week-2 pattern, with some adjustment made to the forecast outlook based on empirical tools leveraging La Nina, the MJO, and decadal trends. The influence of the CFS and JMA were minimized in the forecast outlook as they show a drastic pattern change from Week-2 into the Week 3 timeframe with anomalous troughing building over the Southeast U.S. and weakly negative height anomalies becoming highly positive across the northern half of the U.S., in disagreement with most every other dynamical model in addition to empirical perspectives. The extended range forecaster is downplaying the GEFS influence on their Week-2 outlook for similar reasons.

Consensus among dynamical model guidance regarding the mid-level circulation is poor in the present outlook. The only thing models agree on is some degree of anomalous ridging in the northeast Pacific, with extension of the jet across East Asia being oriented towards southern Alaska. The favored European model has a reversal of the NAO to its negative phase (anomalous ridging over Greenland, troughing over the North Atlantic) by Week-3 along with upstream ridging over the eastern U.S. and a weakness in height anomalies across the West. The ECMWF also suggests a flip in the NPO-WP to occur during Week-3 with troughing developing over the Bering Sea and Northern Alaska. [Editor's Note: This is an important open issue for the Week 3 -4 forecast]. The discounted CFS features anomalous troughing over the Southeast, with robust anomalous ridging along the length of the Canadian border. This represents a stark departure from its Week-2 perspective which forecasts weakness in its height anomalies through Central Canada into the Northern Plains, further suggesting its Week 3-4 forecast should be discounted.

With the ECMWF model favored during Week 3-4 it became the starting point for the temperature and precipitation outlooks. This portrays chances for above-normal temperatures across the southern half of the lower-48 states and into the Northeast. Highest probabilities for above-normal temperatures from the ECMWF exist from the Appalachians eastward, with values above 80% indicated. Muddying the perspective is the multiple-linear regression tool, conditioned on the La Nina event, Phase 7 MJO, and decadal trends, which has outperformed the ECMWF model over the past year. This empirical tool anticipates anomalous cold over nearly the entire lower-48 states, with the most robust cold signals over the Northern Plains. Cross-validated skill of the multiple-linear regression is highest from the Ohio Valley through New England, resulting in the high probabilities for warmth from the ECMWF being damped substantially in the resulting outlook. The highest probabilities for anomalous warmth in the Lower-48 are modest at only 55-60% from New Mexico through the Carolinas, with this region also colocated with the strongest warming signal from decadal trends. A small area where below-normal temperatures is favored exists in the Northern Plains due to the cold signal of the empirical guidance, the ECMWF model suggesting some possible lingering cold from Week-2, and continued weakness in the height anomalies forecast across this region during Week-3. With extension of the jet favored in the Pacific and anomalous ridging off the west coast, a warm and wet pattern is favored for southern Alaska throughout the outlook period.

Confidence is higher for precipitation relative to temperature in the current outlook. Ridging favored by dynamical models over the Northeast Pacific would tilt odds toward anomalous dryness for the Pacific Northwest. Even if the colder solution favored by empirical guidance were to verify for this area, it portrays the source region for the air masses over the Pacific Northwest to be continental in nature. The ECMWF and empirical guidance also favor below-normal precipitation along the eastern seaboard, with the potential for some above-normal precipitation from the Lower Mississippi Valley through the Tennessee Valley as moisture lifts northward from the Gulf of Mexico. Questions exist as to how far north this moisture will progress based on the forecast circulation discrepancies, in addition to how much shortwave energy would be able to interact with this moisture. There is a slight hint of a southern stream with split flow of the jet across the West in the 500-hPa mean heights that would support such an outcome.

Sea-surface temperatures in the vicinity of Hawaii are near- to slightly above-normal, supportive of enhanced odds for above-normal temperatures. Dynamical model guidance signals for precipitation are mixed across the islands, resulting in a forecast of equal chances.

Some Indices of Possible Interest:

Arctic Oscillation Forecast

Not sure of the official interpretation of the above but to me it looks more negative than neutral.

PNA Forecast

MJO

NCEP-NEFS CFSv2

MJO

CFSv2 Forecast for MJO

 

The distance from the origin is how the graphic artists show strength on this diagram. So it looks like in one model the forecast is for the MJO to stall and weaken and in the other it will be moving across South America, the Atlantic and be back over Africa soon.  Obviously it makes a difference which model you have the most confidence in. It seems NOAA has lost interest in the MJO re their 6 - 14 Day Forecast.

Analogs to the Outlook.

Now let us take a detailed look at the "Analogs" which NOAA provides related to the 5 day period centered on 3 days ago and the 7 day period centered on 4 days ago. "Analog" means that the weather pattern then resembles the recent weather pattern and was used in some way to predict the 6 - 14 day Outlook.

Here are today's analogs in chronological order although this information is also available with the analog dates listed by the level of correlation. I find the chronological order easier for me to work with. There is a second set of analogs associated with the Outlook but I have not been regularly analyzing this second set of information. The first set which is what I am using today applies to the 5 and 7 day observed pattern prior to today. The second set, which I am not using, relates to the correlation of the forecasted outlook 6 - 10 days out with similar patterns that have occurred in the past during the dates covered by the 6 - 10 Day Outlook. The second set of analogs may also be useful information but they put the first set of analogs in the discussion with the second set available by a link so I am assuming that the first set of analogs is the most meaningful and I find it so.

Centered

Day

ENSO

Phase

PDO AMO

Other Comments

Jan 24, 1957 (2) Neutral - -  
Feb 1, 1959 El Nino -(t) +(t) Tail End Modoki Type I
Jan 24, 1975 La Nina - - Part II Following 72/73 El Nino
Jan 31, 1982 Neutral + - Prior to 82/83 El Nino
Feb 2, 1982 Neutral + - Prior to 82/83 El Nino
Feb 5, 1982 Neutral + - Prior to 82/83 El Nino
Feb 5, 1989 La Nina - - Tail End
Feb 13, 1989 (2) La Nina - - Tail End

(t) = a month where the Ocean Cycle Index has just changed or does change the following month.

The spread among the analogs from January 24 to February 13 is 20 days which is very tight and the same as last week. I have not calculated the centroid of this distribution which would be the better way to look at things but the midpoint, which is a lot easier to calculate, is about February 3. These analogs are centered on 3 days and 4 days ago (February 8 or February 9). So the analogs could again be considered to be considerably out of sync with respect to weather that is we are likely to be getting weather that is similar to some extent to what we would expect to normally be getting almost a week ago. That  is not surprising given the projected cold air intrusion. For more information on Analogs see discussion in the GEI Weather Page Glossary.  For sure it is a rough measure as there are so many historical patterns but not enough to be a perfect match with current conditions. I use it mainly to see how our current conditions match against somewhat similar patterns and the ocean phases that prevailed during those prior patterns. If everything lines up I have my own measure of confidence in the NOAA forecast. Similar initial conditions should lead to similar weather. I am a mathematician so that is how I think about models.

Including the duplicates, there are five Neutral Analogs, four La Nina analogs and one El Nino Analog. The phases of the analogs this week strongly correlate with McCabe condition A and to a lesser extent McCabe B. Both are associated with AMO (Negative while in reality it is Positive) and both are relatively wet scenarios. To some extent they are consistent with the NOAA 6 - 10 Day and 8 - 14 Day Forecasts. But the association with periods of time when the AMO was Negative makes me less confident than NOAA in their forecast.

The seminal work on the impact of the PDO and AMO on U.S. climate can be found here. Water Planners might usefully pay attention to the low-frequency cycles such as the AMO and the PDO as the media tends to focus on the current and short-term forecasts to the exclusion of what we can reasonably anticipate over multi-decadal periods of time. One of the major reasons that I write this weather and climate column is to encourage a more long-term and World view of weather.

In color Black and White same graphics
McCabe Maps modified to include the subtitles McCabe Conditions from 2007 report with labels corrected with authors permission

 

McCabe Condition Main Characteristics
A Very Little Drought. Southern Tier and Northern Tier from Dakotas East Wet. Some drought on East Coast.
B More wet than dry but Great Plains and Northeast are dry.
C Northern Tier and Mid-Atlantic Drought
D Southwest Drought extending to the North and also the Great Lakes. This is the most drought-prone combination of Ocean Phases.

You may have to squint but the drought probabilities are shown on the map and also indicated by the color coding with shades of red indicating higher than 25% of the years are drought years (25% or less of average precipitation for that area) and shades of blue indicating less than 25% of the years are drought years. Thus drought is defined as the condition that occurs 25% of the time and this ties in nicely with each of the four pairs of two phases of the AMO and PDO.

Historical Anomaly Analysis

When I see the same dates showing up often I find it interesting to consult this list.

A Useful Read

Some might find this analysis which you need to click to read interesting as the organization which prepares it focuses on the Pacific Ocean and looks at things from a very detailed perspective and their analysis provides a lot of information on the history and evolution of ENSO events.

Recent CONUS Weather

This is provided mainly to see the pattern in the weather that has occurred recently.

And the 30 Days ending  February 2, 2018 And the 30 Days ending February 9, 2018

February 2, 2018 30 Day Temperature and Precipitation Departures

February 10, 2018 30 Day Temperature and Precipitation Departures
This is a big change. For precipitation the dry anomaly is moderated in the Southeast and for temperature, the Eastern cool anomaly is gone which is somewhat surprising

Dry anomaly more intense but wetter to the north. The Warm Anomaly has switched to a cool anomaly in the West North Central region.

Remember, these maps are a 30 average so the most distant seven days are removed and the most recent seven days are added.

 

Related to the dry conditions is the official Drought Monitor. If is issued every Thursday reflecting the conditions as agreed on as of the preceding Tuesday. I participate once a month in the discussion related to the situation in New Mexico. The drought monitor is not just based on precipitation but the condition of the land so it generally reflects more than a month's precipitation and temperature and wind. The situation right now is fairly serious as it impacts cattle forage, dust, fire hazard among other things. It is likely to get worse before it gets better. Here are two useful links. First this one to the Drought Monitor Site and this to the NOAA Site that has additional information.

Drought Monitor

Reference Forecasts Full Month and Three Months.

Below are the Temperature followed by the Precipitation Outlooks for the month and three months shown in the Legend. These map are issued on the Third Thursday of the Month. The maps for the following month (but not the three-month maps) are updated on the last day of the month. The 6 - 10 day and 8 - 14 Day update daily and the Week 3/4 Map Updates every Friday so usually these are more up to date. Also the three shorter-term maps will generally cover a slightly different time period since they update daily as the month progresses. But these reference maps are sometimes useful if one wants to understand how the current month was originally forecast to play out.

 
February Temperature Outlook Updated on January 31, 2018 To the left is the full month Temperature Outlook. To the right is the three-month Temperature outlook FMA Temperature  Issued on January 18,2018
February 2018 Precipitation Outlook Updated on January 31, 2018 To the left is the full month Precipitation outlook. To the right is the three-month Precipitation outlook. FMA 2018 Precipitation Outlook Issued on January 18,  2018

B. Beyond Alaska and CONUS Let's Look at the World which of Course also includes Alaska and CONUS

It is Useful to Understand the Semipermanent Pattern that Control our Weather and Consider how These Change from Winter to Summer. These two graphics (click on each one to enlarge) are from a much larger set available from the Weather Channel.  They highlight the position of the Bermuda High which they are calling the Azores High in the January graphic and is often called NASH and it has a very big impact on CONUS Southeast weather and also the Southwest. You also see the north/south migration of the Pacific High which also has many names and which is extremely important for CONUS weather and it also shows the change of location of the ITCZ which I think is key to understanding the Indian Monsoon. A lot of things become much clearer when you understand these semi-permanent features some of which have cycles within the year, longer period cycles and may be impacted by Global Warming. We are now in Mid-February and should be returning to the set of positions shown below for July. For CONUS, the seasonal repositioning of the Bermuda High and the Pacific High are very significant. Notice the Winter position of the Pacific High. It is further north than usual right now for this time of the year.

Same as above but for July

Forecast for Today (you can click on the maps to enlarge them)

This graphic is anomalies i.e. deviations from normal not the actual temperatures. This graphic is actuals not anomalies as is the case in the temperature map.
Temperature at 2 Meters Maine Reanalyer

Notice that below the map there is a tabulation of magnitude of the current anomalies by region. The Arctic is very warm having shipped their cold air to Canada and CONUS. Only Eastern Asia is cool.

We again see the dry belt stretching from Northern Africa to Eastern Asia but not including Southeast Asia. Mexico is very dry.

Additional Maps showing different weather variables can be found here.

Forecast for Day 6 (Currently Set for Day 6 but the reader can change that)

World Weather Forecast produced by the Australian Bureau of Meteorology. Unfortunately I do not know how to extract the control panel and embed it into my report so that you could use the tool within my report. But if you visit it Click Here and you will be able to use the tool to view temperature or many other things for THE WORLD. It can forecast out for a week. Pretty cool. Return to this report by using the "Back Arrow" usually found top left corner of your screen to the left of the URL Box. It may require hitting it a few times depending on how deep you are into the BOM tool. Below are the current worldwide precipitation and temperature forecasts for six days out. They will auto-update and be current for Day 6 whenever you view them. If you want the forecast for a different day Click Here

Temperature

Precipitation

BOM Current Temperature Wedensday

BOM World Preciptation  Wednesday

Please remember this graphic updates every six hours so the diurnal pattern can confuse the reader.  This shows how La Nina tends to make the Southern Hemisphere wet.

And now we have experimental forecasts from the U.S. NAEFS Model. They are difficult to read without first enlarging them.

Temperature Precipitation

NAEFS 8 - 14 Day Temperature

NAEFS Experimental World Precipitation

We are hearing that the Winter Olympics are very cold and this shows why. You have click on this to read it. It shows the pattern where Eastern Siberia and Alaska are wet.

Looking Out a Few Months

Here is the precipitation forecast from Queensland Australia:

Rapidly rising SOI  forecast for February to April 2018

It is kind of amazing that you can make a worldwide forecast based on just one parameter the SOI and changes in the SOI. Western CONUS looks fairly wet, Eastern Australia is dry. 

JAMSTEC Forecasts

One can always find the latest JAMSTEC maps by clicking this link. You will find additional maps that I do not general cover in my monthly Update Report. Remember if you leave this page to visit links provided in this article, you can return by hitting your "Back Arrow", usually top left corner of your screen just to the left of the URL box.

Sea Surface Temperature (SST) Departures from Normal for this Time of the Year i.e. Anomalies

My focus here is sea surface temperature anomalies as they are one of the two largest factors determining weather around the World. If we want to have a good feel for future weather we need to look at the oceans as our weather mostly comes from oceans and we need to look at

  • Surface temperature anomalies (weather develops from the ocean surface  and
  • the changes in the temperature anomalies since that may provide clues as to how the surface anomalies will change based on the current trend of changes. This is not that easy to do since the oceans are deep, there are many currents, winds have an impact etc. Two ways that are available to use are to look at the change in the situation today compared to the average over a period of time and NOAA also produces a graphic of monthly changes. I use both. The first set of graphics is simply looking at the average compared to today and that is below.
Three Month Average Anomaly Current Anomaly
Three month average anomaly Daily SST Anomaly
La Nina shows up It now looks fairly similar to the three-month average except that the western part of the cool anomaly no longer exists. .

And when we look in more detail at the current Sea Surface anomalies below, we see a lot of them not just along the Equator related to ENSO.

                              First the categorization of the current daily SST anomalies.

Mediterranean, Black Sea and Caspian Sea Western Pacific West of North America North and East of North America North Atlantic
Neutral

Fairly Neutral

Warm off of Baja

Slightly Warm in Davis Strait and off Nova Scotia

Fairly Neutral but warm north of Scandinavia.

Equator

Pacific cool east of Dateline. But dark blues are turning to light blues. Large gap off of Ecuador and Peru. Cooling off of Maritime Continent

SST Daily Anomalies
Africa West of Australia North, South and East of Australia

West of South America

East of South America

Cool west of North Africa

Warm west of Gulf of Guinea and further south..

Cool offshore of Africa south of Madagascar

cool

Warm south and southeast all the way to and beyond New Zealand

Cool but now mostly offshore

Cool off of 30S

Warm anomaly way offshore at 40S.

Fairly Neutral close to shore.

Then we look at the change in the anomalies.  The SST  anomaly is sort of like the first derivative and the change in the anomaly is somewhat like a second derivative. It tells us if the anomaly is becoming more or less intense.

Here it gets a little tricky as for this graphic red does not mean a warm anomaly but a warming of the anomaly which could mean more warm or less cool and blue does not mean cool but more cool or less warm.

Mediterranean, Black Sea and Caspian Sea Western North Pacific West of North America East of North America North Atlantic

Mediterranean slightly warming. Caspian Sea cooling

Cooling off of Southeast Asia

Cooling in the Bering Sea

Slight cooling from the Equator to Baja

The changes are definitely in the direction of a more negative PDO.

.

Slight warming off of Nova Scotia

Slight cooling in the Gulf of Mexico

Mostly Neutral.  .

Equator Eastern Pacific warming.  Extreme cooling near the Maritime Continent. Cooling east of South America
Change in weekly anomalies February 12, 2018
Africa West of Australia North, South and East of Australia West of South America East of South America

Cooling off North Africa

Warming west of Angola

Warming between Mozambique and Madagascar

Cooling south of Africa.

Slight cooling

Cooling North, East and Southeast

Warming South

Warming offshore of 20S

Cooling offshore of 30S

Warming off of 50S

Cooling off entire Northeast

Cooling off 20S

Warming 40S

Cooling east of Cape Horn

This may be a good time to show the recent values to the indices most commonly used to describe the overall spacial pattern of temperatures in the (Northern Hemisphere) Pacific and the (Northern Hemisphere) Atlantic and the Dipole Pattern in the Indian Ocean. Notice the change in the PDO in July of 2017 and the stability of the AMO index.

Most Recent Six Months of Index Values   PDO Click for full list

AMO click for full list.

Indian Ocean Dipole (Values read off graph)
October   -0.67 +0.39 -0.3
November   +0.84 +0.40 0.0
December   +0.56 +0.34 -0.1
January   +0.12 +0.23 0.0
February   +0.05 +0.23 +0.2
March   +0.14 +0.17 +0.0
April   +0.53 +0.29 +0.2
May   +0.29 +0.32 +0.2
June   +0.21 +0.31 0.0
July   -0.50 +0.31 0.0
August   -0.62 +0.31 +0.4
September   -0.25 +0.35 +0.2
October   -0.61 +0.44  0.0
November   -0.46 +0.35  0.0
December 2017   -0.18 +0.36 -0.4
January 2018   -0.24 NA -0.3 Est

Switching gears, below is an analysis of projected tropical hazards and benefits over an approximately two-week period.

Tropical Hazards

This graphic updates on Tuesdays and I usually post on Monday which is almost a week later than when this graphic was last updated. So Week Two applies at the time I write this article on Monday but by the time you read it on Tuesday, the Week Two that I am looking at is updated and becomes Week One. So if you are reading this after Monday Night look at the Top Row, which will be the current week. 
Mostly I see as I look at this on February 12 for what is shown as Week two, the period February 14, 2018 to February 20, 2018, we see mostly a very warm area ** for Sudan and Chad. We also see some dry conditions* for part of Mozambique/Tanzania and Northern Madagascar and Northeast Australia. This is a big change for Australia from the forecast last week.

 * Moderate Confidence that the indicated anomaly will be in the upper or lower third of the historical range as indicated in the Legend. ** High Confidence that the indicated anomaly will be in the upper or lower third of the historical range as indicated in the Legend.

C. Progress of ENSO

A major driver of weather is Surface Ocean Temperatures. Evaporation only occurs from the Surface of Water. So we are very interested in the temperatures of water especially when these temperatures deviate from seasonal norms thus creating an anomaly. The geographical distribution of the anomalies is very important. To a substantial extent, the temperature anomalies along the Equator have disproportionate impact on weather so we study them intensely and that is what the ENSO (El Nino - Southern Oscillation) cycle is all about. Subsurface water can be thought of as the future surface temperatures. They may have only indirect impacts on current weather but they have major impacts on future weather by changing the temperature of the water surface. Winds and Convection (evaporation forming clouds) is weather and is a result of the Phases of ENSO and also a feedback loop that perpetuates the current Phase of ENSO or changes it. That is why we monitor winds and convection along or near the Equator especially the Equator in the Eastern Pacific.

Starting with Surface Conditions.

TAO/TRITON GRAPHIC (a good way of viewing data related to the part of the Equator and the waters close to the Equator in the Eastern Pacific where we monitor to determining the current phase of ENSO. It is probably not necessary in order to follow the discussion below, but here is a link to TAO/TRITON terminology.

And here is the current version of the TAO/TRITON Graphic. The top part shows the actual temperatures, the bottom part shows the anomalies i.e. the deviation from normal.

Current SST and wind anomalies

Location Bar for Nino 3.4 Area Above and Below

------------------------------------------------ A B C D E -----------------

 

I did not do a very neat job but this was my attempt to show the Nino 3.4 Measurement Area in context.

February 112 2018 Section including the Nino 3.4 Measurement Area

As you can see, the bulk of the cool water is at the east end and probably only the dark blue contributes to the Nino Index showing La Nina Conditions at this point. There is a lot of white showing. I have not done a perfect job of drawing this especially the +5 and -5 Latitude lines. This changes every day.

The below table only looks at the Equator (and starting this week I am including large anomalies just off the Equator also) and shows the extent of anomalies along the Equator. The ONI Measurement Area is the 50 degrees of Longitude between 170W and 120W and extends 5 degrees of Latitude North and South of the Equator so the above table is just a guide and a way of tracking the changes. The top rows show El Nino anomalies. The two rows just below that break point contribute to ENSO Neutral.

Subareas of the Anomaly

Westward Extension

 

Eastward Extension

 

Degrees of Coverage Total by ENSO Phase

Total

Portion in Nino 3.4 Measurement Area

These Rows below show the Extent of El Nino Impact on the Equator  

1C to 1.5C (strong)

NA

NA

0

0

0

+0.5C to +1C (marginal)

NA

NA

0

0

These Rows Below Show the Extent of ENSO Neutral Impacts on the Equator  
0.5C or cooler Anomaly (warmish neutral)

160E

170E

10

0

22

0C or cooler Anomaly (coolish neutral)

170E

172W

148E

150W

29

22

These Rows Below Show the Extent of La Nina Impacts on the Equator.  
-0.5C or cooler Anomaly

148W

140W

8

8

28

-1.0C or cooler Anomaly

140W

102W

118W

LAND

29

20

-1.5C or cooler Anomaly

118W

102W

16

0

-2.0C or cooler Anomaly

LAND

LAND

0

0

-2.5C or cooler Anomaly

LAND

LAND

0

0

This week only 28 degrees of longitude along the Equator in the Nino 3.4 Measurement Area registers La Nina values. The other 22 degrees register Neutral. That is not the case for the full +5N and +5S width of the Nino 3.4 Measurement Area but in this analysis we are just looking at the Equator. It is again remarkably similar to one week ago. The cool anomaly has moved a bit but is the same size.

My Calculation of the Nino 3.4 Index

I calculate the current value of the Nino 3.4 Index each Monday using a method that I have devised. To refine my calculation, I have divided the 170W to 120W Nino 3.4 measuring area into five subregions (which I have designated from west to east as A through E) with a location bar shown under the TAO/TRITON Graphic). I use a rough estimation approach to integrate what I see below and record that in the table I have constructed. Then I take the average of the anomalies I estimated for each of the five subregions.

So as of Monday February 12 in the afternoon working from the February 11 TAO/TRITON report [Although the TAO/TRITON Graphic appears to update once a day, in reality it updates more frequently.], this is what I calculated.

Calculation of Nino 3.4 from TAO/TRITON Graphic

Anomaly Segment Estimated Anomaly
  Last Week This Week
A. 170W to 160W -0.0 -0.0
B. 160W to 150W -0.3 -0.1
C. 150W to 140W -0.7 -0.5
D. 140W to 130W -1.0 -0.9
E. 130W to 120W -1.1 -1.0
Total -3.1 -2.5
Total divided by five i.e. the Daily Nino 3.4 Index (-3.1)/5 = -0.6 (-2.5)/5 = -0.5

 

My estimate of the daily Nino 3.4 SST anomaly tonight is  -0.5 which is a borderline La Nina value. NOAA has reported the weekly Nino 3.4 to be again at -0.9 which is a moderate La Nina value and we believe it is too high. Nino 4 is reported a little warmer this week at -0.3. Nino 3 is a little cooler -1.3. Nino 1 + 2 which extends from the Equator south rather than being centered on the Equator is reported warmer at -0.7. It was up there close to 3 at one time so this index has been declining quite a bit and also fluctuating quite a bit which is not surprising as it is the area most impacted by the Upwelling off the coast. So it is an indication of the interaction between surface water and rising cool water. Thus it is subject to larger changes. I am only showing the currently issued version of the NINO SST Index Table as the prior values are shown in the small graphics on the right with this graphic. The same data in graphic form but going back a couple of more years can be found here.  The full table of values can be found here.

The cool anomaly pretty much remained in the same location this week and again records as La Nina. The stronger Easterlies most likely related to the Inactive Phase of the MJO has caused cooler water to surface thus raising the Nino values while speeding up the demise of the La Nina as the cool pool gets depleted.

February 12, 2018 Nino Readings

This graphic brings the Nino 3.4 up to date and is easy to read.

BOM Nino 3.4

You can see that this is a double dip La Nina (with the second dip being deeper than the first hence the Southern Tier drought). You can also see that it is turning up. These are weekly values and thus not as volatile as the CDAS graphic we show elsewhere. There is no guarantee that we have passed the low point (max La Nina). If this was a stock chart one might conclude that this is a possible Head and Shoulders formation and that there was a breakdown and we might rebound to the neckline which is at about -0.5C. But this is not a stock but the NOAA CFSv2 model is pretty much predicting a return to -0.5C and then staying there more or less indefinitely. Perhaps I should run the date through a candlestick application. I hope everyone realizes I am joking since this is a State of the Weather Report this week.

This is probably the best place to AGAIN express the thought that this way of measuring an ENSO event leaves a lot to be desired. Only the surface interacts with the atmosphere and is able to influence weather. The subsurface tells us how long the surface will remain cool (or warm). Anomalies are deviations from "Normal". NOAA calculates and determines what is "Normal" which changes due to long ocean cycles and Global Warming. So to some extent, the system is "rigged". Hopefully it is rigged to assist in providing improved weather forecasts. But to assume that any numbers reported can be assumed to be accurate to a high level of precision is foolhardy.

This overlaps with the next topic but I will show it here.

February 12, 2018 Upper Ocean Heat anamaly

The discussion in this slide says it better than I could. One might compare the current reading to Oct/Nov 2016. I was planning to try to graph the slope of the decline to make a prediction as to when it reaches -0.5C.  The best laid plans oft go astray. The temperature anomaly has reversed and is colder. It explains why the models have added a month or half month to when the La Nina will be gone. The CDAS graphic which we also show is another way to do the same thing as is the BOM SOI graphic. The weather may already be reflecting the transition but this La Nina is saying "not so fast".

A side by side comparison can be useful

Comparison Week Probably Third Week of December 2017 Current Week

Equatorial (0 - 300) meter heat content As reported December 18, 2017

February 12, 2018 Upper Ocean Heat anamaly

 

You can see the relentless decline in the Eastern Pacific cool-water anomaly. It is now basically neutral but the cool water is still on the surface with the warmer anomalies sub-surface. That will change. There was a slight reported increase in coolness this week but insignificant. It might be real or artifact. I have not shown the curves on what is consider normal by month so small deviations can be caused by variations between the changed normal for the date and the actual temperature. I am not suggesting that is what has happened but just mentioning as an example of the many variables involved. Either way the Eastern Pacific is dead neutral if you average it out between the surface and deeper water.

Sea Surface Temperature and Anomalies

It is the ocean surface that interacts with the atmosphere and causes convection and also the warming and cooling of the atmosphere. So we are interested in the actual ocean surface temperatures and the departure from seasonal normal temperatures which is called "departures" or "anomalies". Since warm water facilitates evaporation which results in cloud convection, the pattern of SST anomalies suggests how the weather pattern east of the anomalies will be different than normal.

February 12, 2018 Equatorial Pacific SST Anomalies

A major advantage of the Hovmoeller method of displaying information is that it shows the history so I do not need to show a sequence of snapshots of the conditions at different points in time. This Hovmoeller provides a good way to visually see the evolution of this ENSO event. I have decided to use the prettied-up version that comes out on Mondays rather that the version that auto-updates daily because the SST Departures on the Equator do not change rapidly and the prettied-up version is so much easier to read. The bottom of the Hovmoeller shows the current readings. Remember the +5, -5 degree strip around the Equator that is being reported in this graphic. So it is the surface but not just the Equator.

Not much change from last week. The only really cool area west of 130W is now gone and it is also less cool off the coast of Ecuador. But the cool water has expanded a bit to the west.

This next graphic is more focused on the Equator and looks down to 300 meters rather than just being the surface.

February 12,  2018 Upper Ocean Heat Anoma

The Kelvin Wave that would have put a quick end to this La Nina has faded and we now have actually an upwelling wave. It is hard to assess it from the limited about of visual evidence here and  it looks like it might be followed by another Kevin wave soon. Also notice there really is no cool water west of 100W meaning the La Nina is over even if not yet so reported. But we can see why the models added a half month or so to the expected duration of this La Nina.

 Let us look in more detail at the Equatorial Water Temperatures.

We are now going to look at a three-dimensional view of the Equator and move from the surface view and an average of the subsurface heat content to a more detailed view from the surface down This graphic provides both a summary perspective and a history (small images on the right).

.February 12, 2018 Kelvin Wave Analysis.

Significant change since last week. There is hardly any cold water at the surface but a bit more in the subsurface. The La Nina is gone but still being reported. But at the same time the IndoPacific Warm Pool is showing to be a lot more robust. So we are headed for an extended period of being either borderline La Nina or Neutral.

Anomalies are strange. You can not really tell for sure if the blue area is colder or warmer than the water above or below. All you know is that it is cooler than usual for this time of the year. A later graphic will provide more information. Aside from buoyancy the currents tend to bring water from that depth up to the surface mostly farther east.

Now for a more detailed look. Below is the pair of graphics that I regularly provide. The date shown is the midpoint of a five-day period with that date as the center of the five-day period. The bottom graphic shows the absolute values, the upper graphic shows anomalies compared to what one might expect at this time of the year in the various areas both 130E to 90W Longitude and from the surface down to 450 meters. At different times I have discussed the difference between the actual values and the deviation of the actual values from what is defined as current climatology (which adjusts every ten years except along the Equator where it is adjusted every five years) and how both measures are useful for other purposes.

There is cold water from beyond the Dateline to Land. At the west end of the cool anomaly it is not consistently even 100 meters deep (it was once over 200 meters deep). But we see some new cool anomalies at depth so it is hard to know what to make of that. We now have warm water developing west of the Dateline and crossing the Dateline at depth but no longer extending all the way to 120W and beyond. La Nina's days are numbered but it looks like another month has been added to its life.
http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/ocean/weeklyenso_clim_81-10/wkteq_xz.gif
The 28C Isotherm is at 170E, the 27C Isotherm is at 175W, the 25C Isotherm is now at 150W and the 20C Isotherm no longer is reaching the surface. It has been fairly stable for a number of weeks.

The flattening of the Isotherm Pattern is an indication of ENSO Neutral just as the steepening of the pattern indicates La Nina or El Nino depending on where the slope shows the warm or cool pool to be. That flattening has occurred and we have gone to a Weak La Nina thermocline.

Tracking the change.

Sepember 15, 2017 Subsurface Water Temperatures Equatorial Ocean Subsurface as of  February 7, 2018

 

I have "frozen" the graphic on the left side above which shows the situation as reported for September 15, 2017. The one on the right which is the current situation. The situation with the cool anomaly is not much different east of the Dateline from the situation as reported for September 15, 2017 but it is a little different. West of the Dateline it looks a lot different  i.e. warmer. We use the graphic on the left as a reference to see how the current situation changes over time. The subsurface warm anomaly has progressed to the east and strengthened substantially. It is not ready to displace or dilute the Eastern Pacific Cool Anomaly just yet but it will not be long. We now see the warm anomaly appearing below the cool anomaly.

And now let us look at the atmosphere.

This graphic shows the Low-Level Wind Anomalies near the Equator.

The 850 hPa level is above the surface but close to the surface.

And now the Outgoing Long-wave Radiation (OLR) Anomalies which tells us where convection has been taking place. The bottom of a Hovmoeller graphic shows the most recent readings.
Low Level Wlind Anomalies

OLR Anomalies Along the Equator

Reds and browns would be suppressed easterlies or enhanced westerlies and are typical of El Nino. We have the opposite. We see suppressed Outgoing Long Wave Radiation (OLR) at the Dateline i.e (dry) and we  see enhanced OLR at 120E ( wet)

And Now the Air Pressure to Confirm that the Atmosphere is Reacting to the Sea Surface Temperature Pattern. The most Common way to do that is to use an Index called the SOI.

This index provides an easy way to assess the location of and the relative strength of the Convection (Low Pressure) and the Subsidence (High Pressure) near the Equator. Experience shows that the extent to which the Atmospheric Air Pressure at Tahiti exceeds the Atmospheric Pressure at Darwin Australia when normalized is substantially correlated with the Precipitation Pattern of the entire World. At this point there seems to be no need to show the daily preliminary values of the SOI but we can work with the 30 day and 90 day values.

Current SOI Readings

The 30 Day Average on February 12, 2018 was reported as 2.42 which is an ENSO Neutral value. The 90 Day Average was reported at  2.18 is also an ENSO Neutral value. Looking at both the 30 and 90 day averages is useful and right now both are in agreement with the 90 day lagging the 30 day as one would expect. The trend is down i.e. less La Nina-is So Queensland in their forecast is basing it on a declining SOI and that forecast is shown elsewhere in this report..

SOI = 10 X [ Pdiff - Pdiffav ]/ SD(Pdiff) where Pdiff = (average Tahiti MSLP for the month) - (average Darwin MSLP for the month), Pdiffav = long term average of Pdiff for the month in question, and SD(Pdiff) = long term standard deviation of Pdiff for the month in question. So really it is comparing the extent to which Tahiti is more cloudy than Darwin, Australia. During El Nino we expect Darwin Australia to have lower air pressure and more convection than Tahiti (Negative SOI especially lower than -7 correlates with El Nino Conditions). During La Nina we expect the Warm Pool to be further east resulting in Positive SOI values greater than +7).

To some extent it is the change in the SOI that is of most importance. The MJO or Madden Julian Oscillation is an important factor in regulating the SOI and Ocean Equatorial Kelvin Waves and other tropical weather characteristics. More information on the MJO can be found here. Here is another good resource.

Forecasting the Evolution of ENSO

Here is the primary NOAA model for forecasting the ENSO Cycle. The CDAS model is a legacy "frozen" NOAA system meaning the software is maintained but not updated. We find it convenient to obtain this graphic from Tropical Tidbits.com

CFSv2 spread and bias correct ENSO forecast

CDAS Legacy System

This model is still forecasting a La Nina. It probably is the most aggressive model re being so definitive about the ENSO Phase for this Fall and Winter. Click here to see a month by month version of the same model but without some of the correction methodologies applied. It gives us a better picture of the further out months as we are looking at monthly estimates versus three-month averages. Notice that since May the Nino 3.4 Index has been rising. The CDAS data It is not in conflict with the primary NOAA model but shows daily values rather then smoothing them out like the CFSv2 Model does. The CDAS data has not risen above -0.5C that seems to be a lid.

The CFS.v2 is not the only forecast tool used by NOAA. The CPC/IRI Analysis which is produced out of The International Research Institute (IRI) for Climate and Society at Columbia University is also very important to NOAA.

And now we have a recent update.

February 8, 2018 CPC/IRI ENSO Analysis.

February 8, 2018 CPC/IRI ENSO Analysis

Notice that the duration of this La Nina was increased by up to a month with FMA previously shown as equal changes for La Nina or Neutral and now FMA favors La Nina and MAM favors Neutral so looking at the center month in the three month period it looks like they have concluded it will be not as soon as March but not as late as April. We expect that to change back next week when the second report of the month comes out with a more complete set of model results. 

This is the discussion

IRI ENSO Forecast CPC/IRI ENSO Update Published: February 08, 2018

El Niño/Southern Oscillation (ENSO) Diagnostic Discussion issued jointly by the Climate Prediction Center/NCEP/NWS and the International Research Institute for Climate and Society

ENSO Alert System Status: La Niña Advisory

Synopsis: A transition from La Niña to ENSO-neutral is most likely during the Northern Hemisphere spring (~55% chance of ENSO-neutral during the March-May season).

During January 2018, La Niña was evident in the pattern of below-average sea surface temperatures (SSTs) across the central and eastern equatorial Pacific Ocean. The latest weekly index values were close to -1.0°C in the Niño-1+2, Niño-3, and Niño-3.4 regions, while the western-most Niño-4 region was -0.5°C . While negative anomalies were maintained near the surface, the sub-surface temperatures in the eastern Pacific Ocean returned to near average during the last month. This was due to the eastward propagation of above-average temperatures in association with a downwelling equatorial oceanic Kelvin wave, which undercut the below-average temperatures near the surface. The atmospheric conditions over the tropical Pacific Ocean also reflected La Niña, with suppressed convection near and east of the International Date Line and enhanced convection around Indonesia . Also, the low-level trade winds remained stronger than average over the western and central Pacific, while upper-level winds were anomalously westerly.  Overall, the ocean and atmosphere system remained consistent with La Niña.

Most models in the IRI/CPC plume predict La Niña will decay and return to ENSO-Neutral during the Northern Hemisphere spring 2018 . The forecast consensus also favors a transition during the spring with a continuation of ENSO-neutral conditions thereafter.  In summary, a transition from La Niña to ENSO-neutral is most likely during the Northern Hemisphere spring (~55% chance of ENSO-neutral during the March-May season) (click CPC/IRI consensus forecast for the chance of each outcome for each 3-month period).

La Niña is anticipated to continue affecting temperature and precipitation across the United States during the next few months (the 3-month seasonal temperature and precipitation outlooks will be updated on Thursday February 15th). The outlooks generally favor above-average temperatures and below-median precipitation across the southern tier of the United States, and below-average temperatures and above-median precipitation across the northern tier of the United States

This discussion is a consolidated effort of the National Oceanic and Atmospheric Administration (NOAA), NOAA’s National Weather Service, and their funded institutions. Oceanic and atmospheric conditions are updated weekly on the Climate Prediction Center web site (El Niño/La Niña Current Conditions and Expert Discussions). Forecasts are also updated monthly in the Forecast Forum section of CPC’s Climate Diagnostics Bulletin. Additional perspectives and analysis are also available in an ENSO blog.

The next ENSO Diagnostics Discussion is scheduled for 8 March 2018.

The above is based on looking at a variety of models and other information but we should not forget that NOAA has their own model.

CFSv2 spread and bias correct ENSO forecast

It is not in disagreement with the MAM assessment but suggests there is not much difference in weather impacts from ENSO after JFM as the estimate of the NINO 3.4 Index does not change very much through the end of the forecast period shown in the CFSv2 Model. If you look at the spread among different model runs which are shown on the graphic does the mean of the model runs mean anything? I think not.
It pretty much looks like this model is indicating that we remain in either borderline La Nina or ENSO Neutral with a strong La Nina Bias through the summer.

Here is a another view of the same model with on the right the forecasts of the sea surface temperatures that result from the forecast. It is the model as of January 14 and is frozen i.e. will not update.

January 15, 2018 SST Outlook and CSFv2

And here is what is called the plume of a varied of forecast models. We expect to have an updated version of this graphic next week.

January 19, 2018 Plume of ENSO Forecast Models.

This is the new version. It is difficult to find the NOAA NCEP model in the graphic but it is near the middle but lower than the mean. Notice all the models have bottomed and are rising going forward.

Forecasts from Other Meteorological Agencies.

Here is the Nino 3.4 report from the Australian BOM (it updates every two weeks)

Australia POAMA ENSO model run

And the ENSO Outlook Discussion Issued on February 13, 2018:

La Niña decline may be hastened by recent shift in trade winds

The La Niña in the Pacific Ocean continues to decline. Sea surface temperatures in the central tropical Pacific have warmed steadily since late December, with most models forecasting La Niña will end early in the southern hemisphere autumn.

El Niño–Southern Oscillation (ENSO) indicators continue to show at least some La Niña characteristics. Sea surface temperatures indicate a weak La Niña pattern, with the coolest waters concentrated in the eastern Pacific Ocean, while the Southern Oscillation Index is neutral, but weakly positive. However, a very strong pulse of the  Madden-Julian Oscillation (MJO), which drove a burst of monsoonal activity over northern Australia in late January, has caused the western Pacific trade winds to weaken considerably. The rapid weakening of the trade winds may hasten the decline of La Niña. The MJO also led to above-average cloudiness at the Date Line for the first time since early September 2017.

In order for 2017–18 to be classed as a La Niña year, thresholds need to be exceeded for at least three months. Four of the eight climate models surveyed by the Bureau suggest this event is likely to last at least until late summer, while a few continue the event into the southern hemisphere autumn of 2018.

Typically, the strength of a La Niña event reflects the strength of its impact upon Australian climate. The current event is weak, and hence climate patterns have been significantly different from those observed in the last strong La Nina of 2010–12.  Large parts of eastern Australia have been drier than average for the past two or three months, the opposite of what is typically expected during La Niña.

Here is the most recent JAMSTEC forecast issued on January 1, 2018

January 1, 2018 JAMSTEC Forecast

And here is the short discussion issued with the January forecast.

Jan. 18, 2018

Prediction from 1st Jan., 2018

ENSO forecast:

The weak La Niña-like condition will persist until late spring. Then the tropical Pacific will return to a normal state by summer.

Indian Ocean forecast:

A normal state in the tropical Indian Ocean will persist until late spring. Then we expect evolution of a moderately positive Indian Ocean Dipole in summer. However, there is a large uncertainty in the prediction at present because of the large spread in the prediction plumes of the dipole mode index.

Regional forecast:

On a seasonal scale, most part of the globe will experience a warmer-than-normal condition, while some parts of northern/eastern U.S., northwestern Canada, Europe, India, northern Brazil, central and southern Africa, and northern Australia will experience a colder-than-normal condition in boreal spring. As regards to the seasonally averaged rainfall, a wetter-than-normal condition is predicted for some parts of the Philippines, East Australia, and northern Brazil during boreal spring, whereas most parts of Indonesia, Indo-China, Southeast Asia, eastern/southern U.S, and southern Brazil will experience a drier condition during boreal spring.

In spring, most parts of Japan will experience somewhat warmer-than-normal conditions. The southern part will experience drier-than-normal conditions.

Indian Ocean IOD (It updates every two weeks)

BOM IOD Forecast.

Indian Ocean Dipole Outlook  Discussion Issued February 13, 2018

The Indian Ocean Dipole (IOD) is currently neutral. IOD events are unable to form between December and April.

The Indian Ocean Dipole (IOD) is neutral. The weekly index value to 11 February was −0.08 °C. All six of the climate models surveyed by the Bureau indicate that the IOD will remain neutral into the southern hemisphere winter of 2018.

The influence of the IOD on Australian climate is weak during December to April. This is because the monsoon trough shifts south over the tropical Indian Ocean changing wind patterns, which prevents the IOD pattern from being able to form.

The IOD Forecast is indirectly related to ENSO but in a complex way. It is important to understand how and where the IOD is measured.

IOD Measurement Regions

IOD Positive is the West Area being warmer than the East Area (with of course many adjustments/normalizations). IOD Negative is the East Area being warmer than the West Area. Notice that the Latitudinal extent of the western box is greater than that of the eastern box. This type of index is based on observing how these patterns impact weather and represent the best efforts of meteorological agencies to figure these things out. Global Warming may change the formulas probably slightly over time but it is costly and difficult to redo this sort of work because of long weather cycles.

D. Putting it all Together.

At this time it would seem that La Nina Conditions are here for this Winter and Spring with La Nina Conditions already in place. But the situation for next Summer is not yet clear. However, we are getting very close to being able to forecast the end of this La Nina event. But it may only be a temporary end for the Summer and next Fall as it may return for next Winter or Spring. But that is now looking less likely with ENSO Neutral highly likely. There is no sign of the next El Nino.

Forecasting Beyond Five Years.

So in terms of long-term forecasting, none of this is very difficult to figure out actually if you are looking at say a five-year or longer forecast.

The research on Ocean Cycles is fairly conclusive and widely available to those who seek it out. I have provided a lot of information on this in prior weeks and all of that information is preserved in Part II of my report in the Section on Low Frequency Cycles 3. Low Frequency Cycles such as PDO, AMO, IOBD, EATS. It includes decade by decade predictions through 2050. Predicting a particular year is far harder.

The odds of a climate shift for the Pacific taking place has significantly increased. It may be in progress. The AMO is pretty much neutral at this point (but more positive i.e. warm than I had expected) so it may need to become a bit more negative for the "McCabe A" pattern to become established. That seems to be slow to happen so I am thinking we need at least a couple more years for that to happen. On the other hand, AMO- is what is showing up in the pre-forecast analogs that NOAA provides and which I report on. That might mean something. So our assessment is that the standard time for Climate Shifts in the Pacific are likely to prevail and it most likely will be a gradual process with a speed up in less than five years but more than two years. The next El Nino may be the trigger.

E. Relevant Recent Articles and Reports

Weather in the News

Chicago Had a Lot of Snow

Weather Research in the News

Nothing to report

Global Warming in the News

Arctic Sea Ice Loss  Might make CONUS Northern Tier Cooler.

F. Table of Contents for Page II of this Report Which Provides a lot of Background Information on Weather and Climate Science

The links below may take you directly to the set of information that you have selected but in some Internet Browsers it may first take you to the top of Page II where there is a TABLE OF CONTENTS and take a few extra seconds to get you to the specific section selected. If you do not feel like waiting, you can click a second time within the TABLE OF CONTENTS to get to the specific part of the webpage that interests you.

1. Very High Frequency (short-term) Cycles PNA, AO,NAO (but the AO and NAO may also have a low frequency component.)

2. Medium Frequency Cycles such as ENSO and IOD

3. Low Frequency Cycles such as PDO, AMO, IOBD, EATS.

4. Computer Models and Methodologies

5. Reserved for a Future Topic (Possibly Predictable Economic Impacts)

G. Table of Contents of Contents for Page III of this Report - Global Warming Which Some Call Climate Change.

The links below may take you directly to the set of information that you have selected but in some Internet Browsers it may first take you to the top of Page III where there is a TABLE OF CONTENTS and take a few extra seconds to get you to the specific section selected. If you do not feel like waiting, you can click a second time within the TABLE OF CONTENTS to get to the specific part of the webpage that interests you.

1. Introduction

2. Climate Impacts of Global Warming

3. Economic Impacts of Global Warming

4. Reports from Around the World on Impacts of Global Warming

H. Useful Background Information

The current conditions are measured by determining the deviation of actual sea surface temperatures from seasonal norms (adjusted for Global Warming) in certain parts of the Equatorial Pacific. The below diagram shows those areas where measurements are taken.

El Nino Zones

NOAA focuses on a combined area which is all of Region Nino 3 and part of Region Nino 4 and it is called Nino 3.4. They focus on that area as they believe it provides the best correlation with future weather for the U.S. primarily the Continental U.S. not including Alaska which is abbreviated as CONUS. The historical approach of measurement of the impact of the sea surface temperature pattern on the atmosphere is called the Southern Oscillation Index (SOI) which is the difference between the atmospheric pressure at Tahiti as compared to Darwin Australia. It was convenient to do this as weather stations already existed at those two locations and it is easier to have weather stations on land than at sea. It has proven to be quite a good measure. The best information on the SOI is produced by Queensland Australia and that information can be found here. SOI is based on Atmospheric pressure as a surrogate for Convection and Subsidence. Another approach made feasible by the use of satellites is to measure precipitation over the areas of interest and this is called the El Nino - Southern Oscillation (ENSO) Precipitation Index (ESPI). We covered that in a weekly Weather and Climate Report which can be found here. Our conclusion was that ESPI did not differentiate well between La Nina and Neutral. And there is now a newer measure not regularly used called the Multivariate ENSO Index (MEI). More information on MEI can be found here. The jury is still out on MEI and it it is not widely used.

The below diagram shows the usual location of the Indo-Pacific Warm Pool. When the warm water shifts to the east we have an El Nino; to the west a La Nina.

Western Pacific Warm Pool

Click for Source

Interaction between the MJO and ENSO

This Table is a first attempt at trying to relate the MJO to ENSO

El Nino La Nina MJO Active Phase MJO Inactive Phase Relationship of MJO and ENSO Eastern Pacific Easterlies Western Pacific Westerlies MJO Active Phase MJO Inactive Phase

  • Weaker
  • Stronger
  • Part of Decay Process
  • Counteracts Easterlies
  • Enhances Easterlies
  • Stronger
  • May Create or Stimulate the Onset of El Nino via Kelvin Waves
  • Weaker
  • Part of Decay Process
  • Strengthens Westerlies
  • Weakens Westerlies
  • More likely
  • Stimulates
  • Less likely and weak
  • Retards development of a new La Nina
  • Stimulates the Jet Stream
 
  • Less Likely
  • Suppresses
  • More likely but weak
  • Accelerates development of a new La Nina and the Decline of a mature La Nina
 
  • Slows the Jet Stream and can induce a Split Stream especially during a La Nina

 

Table needs more work. Is intended to show the interactions. What is more difficult is determining cause and effect. This is a Work in Progress.

History of ENSO Events as measured by the ONI

February 5, 2018 Revised Historical ONI Readins.

Note: Without fanfare the base climatology was recently changed from ERSST.V4 to ERSST.V5. This is done every five years and is totally proper but it does shuffle the deck re what were and were not ENSO events so it perhaps should have had more press but that is not the fault of NOAA but if they had kept me in the loop I would have covered it. I was not excluded just not included and did not notice it until after the fact. No big deal but it is important. 

The new SON reading of -1.0 is the third La Nina Reading. These would have to extend through JFM 2018 for this to be recorded as a La Nina. The chances of this are about  60:40. These are three-month averages so DJF is pretty much determined since two months are in. The key will be March. Will March be sufficiently Neutral to have the three-month average be Neutral? The full history of the ONI readings can be found here. The MEI index readings can be found here.

Four Quadrant Jet Streak Model Read more here This is very useful for guessing at weather as a trough passes through. It would apply to the states that are at the apex of the trough.

If the centripetal accelerations owing to flow curvature are small, then we can use the "straight" jet streak model. The schematic figure directly below shows a straight jet streak at the base of a trough in the height field. The core of maximum winds defining the jet streak is divided into four quadrants composed of the upstream (entrance) and downstream (exit) regions and the left and right quadrants, which are defined facing downwind.


Isotachs are shaded in blue for a westerly jet streak (single large arrow). Thick red lines denote geopotential height contours. Thick black vectors represent cross-stream (transverse) ageostrophic winds with magnitudes given by arrow length. Vertical cross sections transverse to the flow in the entrance and exit regions of the jet (J) are shown in the bottom panels along A-A' and B-B', respectively. Convergence and divergence at the jet level are denoted by "CON" and "DIV". "COLD" and "WARM" refer to the air masses defined by the green isentropes.

[Editor's Note: There are many undefined words in the above so here are some brief definitions. Isotachs are lines of equal wind speed. Convergence is when there is an inflow of air which tends to force the air higher with cooling and cloud formation. Divergence is when there is an outflow of air which tends to result in air sinking which causes drying and warming, Confluence is when two streams of air come together. Diffluence is when part of a stream of air splits off.]

Here is a time sequence animation. You may have to click on them to get the animation going.

   

Equatorial Temperature Simulation

Isotherm Simulation

   

 

When we discuss the jet stream and for other reasons, we often discuss different layers of the atmosphere. These are expressed in terms of the atmospheric pressure above that layer. It is kind of counter-intuitive to me. The below table may help the reader translate air pressure to the usual altitude and temperature one might expect at that level of air pressure. It is just an approximation but useful.

air pressure and altitude

Re the above, H8 is a frequently used abbreviation for the height of the 850 millibar level (which is intended to represent the atmosphere above the Boundary Layer most impacted by surface conditions), H7 is the 700 mb level, H5 is the 500 mb level, H3 is the 300 mb level. So if you see those abbreviations in a weather forecast you will know what they are talking about.

Tropical Activity Possibly Impacting CONUS.

Eastern Pacific Two Day Tropical Weather Outlook

When there is activity and I have not provided the specific links to the storm of "immediate" interest, one can obtain that information at this link. At this point in time, no (new) tropical events are expected to appear in this graphic during the next 48 hours. If that changes, we will provide an update.

Now let us look at the Western Pacific in Motion.

Western Pacific Tropical Activity

The above graphic which I believe covers the area from the Dateline west to 100E and from the Equator north to 45N normally shows the movement of tropical storms towards Asia in the lower latitudes (Trade Winds) and the return of storms towards CONUS in the mid-latitudes (Prevailing Westerlies). This is recent data not a forecast. But, it ties in with the Week 1 forecast in the graphic just above this graphic. Information on Western Pacific storms can be found by clicking here. This (click here to read) is an unofficial private source but one that is easy to read.

Click here for a list of Sig Silber's Weather Posts

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