March 5, 2018 Weather and Climate Report – Warmer and Drier

Written by Sig Silber

This past Wednesday the “update” forecast map for March showed Warmer and Wetter than climatology. We do not have a new March forecast map but when you combine the 6 – 14 Day and Week 3 – 4 Maps it looks like Warmer and Drier. What gives? We will try to explain the unexplainable and also discuss Arctic Amplification and possible impacts of reduced Arctic sea ice plus a photo of vacation homes that might be available.

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La Nina Status

Arctic Warming (Article is in the News Section of this Weekly Report)

Is this Global Warming and does it make a difference?

Because this is about the Arctic, in the U.S. a lot of research is done out of PMEL which is part of NOAA and the University of Washington both of which are in Seattle WA. In Europe, it is the Nordic nations where this kind of research is conducted. Possibly the best recent analysis is “Effects of Arctic Sea Ice Decline on Weather and Climate: a review” Timo Vihma Finnish Meteorological Institute and you can access that article here.  Other earlier but very useful references are first “Large-scale Atmospheric Circulation Changes are Associated with the Recent Loss of Arctic Ice” and then “Warm Arctic – Cold Continents, Climate Impacts of the Newly Open Arctic

From the Timo Vihma paper, there is this intriguing flow chart which is Figure 3 in that paper.  .

And the Abstract really serves as a summary of the conclusions:

The areal extent, concentration and thickness of sea ice in the Arctic Ocean and adjacent seas have strongly decreased during the recent decades, but cold, snow-rich winters have been common over mid-latitude land areas since 2005. A review is presented on studies addressing the local and remote effects of the sea ice decline on weather and climate. It is evident that the reduction of sea ice cover has increased the heat flux from the ocean to atmosphere  in  autumn and early  winter.  This has locally increased air temperature, moisture,  and  cloud  cover, and reduced  the  static  stability in the  lower  troposphere. Several  studies based  on  observations,  atmospheric  reanalyses,  and model experiments suggest that the sea ice decline,  together with increased snow cover in Eurasia, favours circulation patterns resembling the negative phase of the  North Atlantic Oscillation and Arctic Oscillation.  The suggested large -scale pressure patterns include a high over Eurasia, which favours cold winters in Europe and northeastern Eurasia. A high over the western  and a low over the eastern North America have also been suggested,  favouring advection of Arctic air masses to North America.  Midlatitude winter weather is, however, affected by several other factors, which generate a large inter-annual variability and often mask the effects of sea ice decline. In addition, the small sample of years with a large sea ice loss makes it difficult to distinguish the effects directly attributable to sea ice conditions.  Several studies suggest that, with advancing global warming, cold winters in mid-latitude continents will no longer be common during the second half  of the 21st century. Recent studies have also suggested causal links between the sea ice decline and summer precipitation in Europe, the Mediterranean, and East Asia.

I have not had a chance to digest the Bob Henson Article on the Gulf Stream. I provided a link in my News Section and will discuss it next Monday.

Let’s changes subjects.

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

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.

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

		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                          →
		The pattern is progressive: west to east.
To the right is the week 3 and 4 Forecast. There is a cool anomaly for most of Alaska, the Alaskan Panhandle and Northwest CONUS. There is a warm anomaly covering two thirds of CONUS east of a line from Mexicali to Green Bay.                                                                          →			↑ ←  The transition from the 8 -14 day forecast shown above to the week 3/4 shown to the left seems somewhat feasible.
To the right is the full month map issued on February 28			Recognizing that the first ten days of March are not shown in the three maps above, Do the 6 – 10 Day, 8 – 14 Day and Week 3 – 4 seem to add up to the full month of March? Questions about the March forecast map include the extent of the Western Cool Anomaly. The warm anomaly for Northern Alaska is questionable also.

And then Precipitation

		Transitioning from the 6 to 10 day outlook on the left to the 8 to 14 day outlook on the right.                                         →
		The pattern is progressive: west to east.
To the right is the week 3 and 4 Experimental Forecast.    →                Alaska is dry, a large area of the Southwest which narrows as it extends up to the Canadian Border is dry. The East Coast is dry. There is a small Mid-Mississippi wet anomaly.			↑ ←  The transition from the 8 -14 day forecast shown above to the week 3/4 shown to the left does not seem feasible.
To the right is the full month map issued on February 28.			Recognizing that the first ten days of March are not shown in the three maps above, Do the 6 – 10 Day, 8 – 14 Day and Week 3 – 4 seem to add up to the full month of March? Questions about the March forecast map include the Northern tier wetness. Also the Northern Alaska wetness. It is overall too wet relative to the three partial forecasts shown.

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.

You can see from this animation that the storm in the Pacific has not really impacted CONUS significantly. The East Coast storms are not shown here. .

Tonight, Monday evening March 5, 2018, as I am looking at the above graphic, you see a continuation of the recent pattern.                     .

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.

And Now the Day One and Two CONUS Forecasts

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.

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. You can see the next East Coast Nor’easter.

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.

When I look at this Day 7 forecast, there is a large Low in the Gulf of Alaska with surface central pressure of 984 hPa. The Aleutian Low is on Day 7 in a position to impact British Columbia. There is now a large High in the Siberian Arctic with surface central pressure of 1036hPa and it really extends over to Greenland where the local High is 1028 hPa. This explains the Negative AO. This week, the Pacific Subtropical High with surface central pressure of 1028 hPa is not as critical for the forecast. This weak High is out of position out to sea and between it and land, at least at high latitude, there is the Aleutian Low. Inland there is a High with surface central pressure of 1028 hPa. There is a weak Low over the Southeast with surface central pressure of 1000 hPa. By Day 7 it is offshore and perhaps will create another Nor’easter.

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.

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.
There is not a lot of change in the pattern over the five days shown. You can see the Low impacting Washington and Oregon  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
We still seem to have a split Polar Jet Stream with Northern and Southern Branches. It is fairly far south.

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.

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

Notice you can see the fairly rapid movement of the pattern crossing CONUS. You can see two ridges during the five day period. Most of the activity seems to be in the Northeast.

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

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 March 5 was 4 out of 5

8 – 14 Day Temperature Outlook issued today (Note the NOAA Level of Confidence in the Forecast Released on March 5, 2018 was 3 out of 5).

Looking further out.

Now – Precipitation

6 – 10 Day Precipitation Outlook Issued Today (Note the NOAA Level of Confidence in the Forecast Released on March 5, 2018 was 4 out of 5)

8 – 14 Day Precipitation Outlook Issued Today (Note the NOAA Level of Confidence in the Forecast Released on March 5, 2018 was 3 out of 5)

Looking further out.

Here is the 6 – 14 Day NOAA discussion released today March 5, 2018 and the Week 3/4 (assumption rich) discussion released Friday March 2, 2018

6-10 DAY OUTLOOK FOR MAR 11 – 15 2018

TODAY’S ENSEMBLE MEAN SOLUTIONS ARE IN GOOD AGREEMENT ON THE EXPECTED LARGE SCALE 500-HPA CIRCULATION PATTERN IN THE 6-10 DAY PERIOD. A HIGH AMPLITUDE TROUGH IS PREDICTED OVER THE GULF OF ALASKA. DOWNSTREAM, A STRONG RIDGE IS PREDICTED OVER CENTRAL NORTH AMERICA WITH A TROUGH OVER THE EASTERN CONUS. BELOW NORMAL 500-HPA HEIGHTS ARE PREDICTED OVER MAINLAND ALASKA AND THE ALASKA PANHANDLE, THE WEST COAST OF THE CONUS, AND THE EASTERN CONUS. ABOVE NORMAL 500-HPA HEIGHTS ARE FORECAST FOR THE CENTRAL CONUS AND THE ALEUTIANS.   

TROUGHING IN THE GULF OF ALASKA LEADS TO INCREASED CHANCES FOR BELOW NORMAL TEMPERATURES FOR ALASKA AND MUCH OF THE PACIFIC COAST. A RIDGE FORECAST OVER CENTRAL NORTH AMERICA LEADS TO ENHANCED CHANCES OF ABOVE NORMAL TEMPERATURES FOR THE MUCH OF SOUTHWESTERN CONUS AND THE CENTRAL PLAINS, PART OF THE GREAT LAKES REGION. ANOMALOUS TROUGHING OVER THE EASTERN CONUS AND NORTHERLY FLOW  TILT THE ODDS TO BELOW NORMAL TEMPERATURES FOR THE EASTERN CONUS AND THE LOWER MISSISSPPI VALLEY, EXCEPT FOR PARTS OF NORTHEAST.     

MOIST FLOW AHEAD OF A TROUGH IN THE EASTERN PACIFIC LEADS TO ENHANCED PROBABILITIES OF ABOVE NORMAL PRECIPITATION FOR THE WEST CONUS, AND THE ALASKA PANHANDLE. AS A TROUGH PROGRESSES TO THE EASTERN CONUS, ABOVE NORMAL PRECIPITATION IS FAVORED FOR MUCH OF THE SOUTHEASTERN CONUS AND MID-ATLANTIC REGION. RIDGING LEADS TO ENHANCED PROBABILITIES OF BELOW NORMAL PRECIPITATION FOR MUCH OF THE CENTRAL CONUS. ENHANCED EASTERLY SURFACE FLOW LEADS TO INCREASED PROBABILITIES OF BELOW NORMAL PRECIPITATION FOR MUCH OF ALASKA. THE POTENTIAL FOR SHORTWAVE ENERGY LEADS TO INCREASED PROBABILITIES OF ABOVE NORMAL PRECIPITATION FOR THE ALEUTIANS.  

FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: ABOVE AVERAGE, 4 OUT OF 5, DUE TO GOOD MODEL AGREEMENT AND THE HIGH AMPLITUDE 500-HPA PATTERNS.  

8-14 DAY OUTLOOK FOR MAR 13 – 19 2018   

THE MEAN 500-HPA FLOW PATTERN EXPECTED FOR THE WEEK-2 PERIOD FEATURES A LESS AMPLIFIED CIRCULATION AND THE OVERALL LONG WAVE PATTERN IS SHIFTED EASTWARD. BELOW NORMAL HEIGHTS ARE EXPECTED OVER MAINLAND ALASKA AND THE ALASKA PANHANDLE, AND MUCH OF THE WESTERN AND EASTERN CONUS, WHILE NEAR TO ABOVE NORMAL HEIGHTS ARE ANTICIPATED OVER THE CENTRAL CONUS AND THE ALEUTIANS.  

BELOW NORMAL TEMPERATURES ARE FAVORED FOR ALASKA, AND MUCH OF THE WESTERN AND EASTERN CONUS UNDERNEATH NEAR TO BELOW NORMAL HEIGHTS. HOWEVER, RIDGING LEADS TO ELEVATED CHANCES FOR ABOVE NORMAL TEMPERATURES FOR THE CENTRAL AND SOUTHERN PLAINS NORTHEASTWARD TO THE GREAT LAKES AND PARTS OF NEW ENGLAND.   

THERE ARE ENHANCED PROBABILITIES OF ABOVE NORMAL PRECIPITATION FOR THE WESTERN CONUS ASSOCIATED WITH ON SHARE FLOW AND TROUGHING. PROBABILITIES OF BELOW NORMAL PRECIPITATION ARE FAVORED FOR MUCH OF MAINLAND ALASKA DUE TO LOW LEVEL NORTHEASTERLY FLOW OVER THE REGION. PROBABILITIES OF BELOW NORMAL PRECIPITATION  ARE ELEVATED FOR THE SOUTHERN PLAINS AND EASTERN CONUS BEHIND THE TROUGH OVER THE ATLANTIC OFF THE EAST COAST OF THE CONUS.   

FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD: AVERAGE, 3 OUT OF 5, DUE TO FAIR AGREEMENT AMONG THE SURFACE TOOLS ACROSS MUCH OF THE FORECAST DOMAIN. 

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

Week 3-4 Forecast Discussion Valid Sat Mar 17 2018-Fri Mar 30 2018

The Madden-Julian Oscillation (MJO) has remained active over the past week, however, dynamical model guidance consistently forecasts a weakening signal over the Indian Ocean during the next 7-10 days. The ongoing La Nina event continues as well, despite some erosion of anomalously cold water at depth due to oceanic Kelvin wave activity. In the extratropics, the Arctic Oscillation has been substantially negative in recent days, with blocking highs situated over southern Greenland and the Gulf of Alaska helping to suppress flow across North America. Given the background climate perspective leading into the present Week 3-4 outlook, dynamical model guidance from the CFS, ECMWF, and JMA ensembles is the primary basis of this outlook with some adjustment made based on empirical guidance related to La Nina, the MJO, and decadal trends. The current outlook also represents a logical progression from the current forecast for the Week-2 period.

Ensemble guidance is in good agreement on the forecast 500-hPa height circulation throughout the outlook period. The most drastic change forecast by the models is a breakdown of the block over Greenland currently present, with guidance anticipating this feature will be substantially weaker by the Week-2 period. Consistent with this, models support rising heights across the southern U.S. relative to Week-2, with anomalous ridging replacing the anomalous troughing over the eastern seaboard beyond Week-2. The block currently over the Gulf of Alaska is forecast to retrograde by Week-2, with models amplifying it during Week 3-4. Anomalous troughing is anticipated across Alaska during Week-2, that is maintained into Week 3-4, with some differences among model guidance in how far south into the CONUS this feature extends during the latter period.

Given model consistency on near- to above-normal heights during the outlook period, above-normal temperatures are generally favored across the lower-48 states. The best odds for above-normal temperatures are across the Southern Plains, where dynamical models exhibit the greatest height anomalies and both the La Nina footprint and decadal trends further support anomalous warmth. Probabilities for above-normal temperatures decay with northward extent across the CONUS, further away from the anticipated anomalous ridging. The CFS and JMA extend this ridging into the Northeast, while empirical guidance also portrays this area as having increased odds for above-normal temperatures supporting some extension of higher probabilities for anomalous warmth into the Mid-Atlantic. Troughing across the Pacific Northwest from Week-2 may linger into this outlook period, with model guidance supporting below-normal temperatures across the West in Week-3 followed by some moderation in Week-4. The greatest signal for below-normal temperatures from dynamical model guidance is consistently over the Pacific Northwest, also in line with historical La Nina and decadal trends. California receives equal chances in this outlook given the disparate temperature signals between a cold Week-3 and warm Week-4 projected by model guidance as heights are forecast to rise along the Pacific coast. Below-normal temperatures are favored across Alaska in association with anomalous troughing, with the exception being along the western coast of the state due to the well below-normal sea ice situation this year.

Rising heights forecast out West and anomalous ridging across the southern U.S. each support below-normal precipitation across much of the western half of the CONUS. The exception is northern portions of the Pacific Northwest, where anomalous troughing would bring anomalous precipitation predominantly into British Columbia, but potentially above-normal precipitation for portions of Washington and Oregon. Guidance is consistent on signals for above-normal precipitation from the Lower Mississippi Valley through Ohio Valley, consistent with enhanced flow out of the Gulf of Mexico into the region. Below-normal precipitation signals also exist up the eastern seaboard, with the greatest probabilities for dry being across Florida that are also coincident with La Nina expectations. With anomalous troughing anticipated over Alaska during the outlook period this suggests dry, anomalous northerly flow and likely below-normal precipitation for the state.

Sea surface temperatures are above-normal surrounding Hawaii, with the exception of Kauai and the north shore of Oahu. Anomalous troughing forecast to the west of the islands by the CFS and ECMWF would support above-normal temperatures in association with warm, southerly flow. This troughing to the west also supports relatively high probabilities for above-normal precipitation across the entire island chain.

Some Indices of Possible Interest:

NCEP-NEFS	CFSv2

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.

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

The spread among the analogs from February 13 to March 7 is 22 days which is fairly tight. 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, and fairly accurate if the dates are reasonably evenly distributed, is about February 24. These analogs are centered on 3 days and 4 days ago (March 1 or March 2). So the analogs could be considered to be slightly 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 three or four days earlier. 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.

Assuming the reported analogs are valid (which we could not do last Monday due to NOAA having computer issues), including the duplicates there are three Neutral Analogs, four La Nina analogs and three El Nino Analogs. Every analog is either associated with a La Nina or El Nino event or was just before or just after a La Nina or El Nino event. The phases of the analogs this week correlate to some extent with all the McCabe conditions except McCabe A which is the wettest scenario except for some East Coast drought. So we look at the opposite of McCabe A to see what would be consistent with the forecast and it is. But the fact that the are three McCabe conditions suggested by the Analogs and the association with both El Nino events and La Nina events suggests caution re the level of confidence in the 6 – 14 Day 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

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 24, 2018	And the 30 Days ending March 3, 2018
Smaller coverage of the Southwest drought. The temperature anomaly pattern is not much changed.	Some major changes with a bit of drought relief in New Mexico a lot of precipitation from NE Texas to New England. The Temperature Anomalies are also very different with a larger North Central cool anomaly and the elimination of the South Central cool anomaly among other things.
Remember, these maps are a 30 average so the most distant seven days are removed and the most recent seven days are added.

The U.S. Drought Monitor is a comprehensive way of understand the drought situation for the U.S. If is issued every Thursday and reflects the conditions as of the prior Tuesday. 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.

Because of the current drought conditions we now publish a Drought Update on Thursdays. You can access the most recent report here.

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 maps 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.

	To the left is the full month Temperature Outlook. To the right is the three-month Temperature outlook
	To the left is the full month Precipitation outlook. To the right is the three-month Precipitation outlook.

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 into Early March and should be returning to the set of positions shown below for July (and that appears to be happening at least in the Pacific).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.

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

Temperature.	Precipitation.
Not a lot of surprises here.	We again see the dry belt stretching from Northern Africa to Eastern Asia but not including Southeast Asia.

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

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

Looking Out a Few Months

Here is the precipitation forecast from Queensland Australia:

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, 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
La Nina shows up	It now looks fairly similar to the three-month average except that the cool anomaly is displaced to the west a bit.

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	Slightly warm along coast of Asia	Warm Southeast of Kamchatka	Warm off East Coast Warm Gulf of Mexico	Fairly Neutral but warm north of Scandinavia.
Equator	The La Nina cool anomaly is displaced to the west
Africa	West of Australia	North, South and East of Australia	West of South America	East of South America
Cool west of North Africa Cool west of Gulf of Guinea Cool southeast of Africa	cool	Warm southeast all the way to and beyond New Zealand	Cool but now mostly offshore Warm anomaly way offshore at 40S.	Warm off 40S

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 and Black Sea neutral.  Caspian Sea warming	Cooling between China and Japan	Warming in Bering Sea Slight cooling west of CONUS Warming east of Dateline at Midlatitudes The changes are definitely in the direction of a more negative PDO. .	Warming off East Coast Fairly extreme warming Gulf of Mexico	Cooling far south of Greenland and British Isles and west of North Africa.  .
Equator	Eastern Pacific fairly extreme warming to the east.  Warming east of Africa and Cooling west of Africa.
Africa	West of Australia	North, South and East of Australia	West of South America	East of South America
Cooling off Spain and Gulf of Guinea Cooling Southwest of Africa. Warming off of a large part of East Africa to and beyond Madagascar	Cooling	Cooling Northwest Cooling southeast and beyond New Zealand	Neutral except warming west of Ecuador as previously mentioned Warming offshore at 30S	Slight cooling in far west Caribbean Slight cooling at 60S

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.

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

 * 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.

Location Bar for Nino 3.4 Area Above and Below

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.

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 26 in the afternoon working from the February 25 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

My estimate of the daily Nino 3.4 SST anomaly tonight is -0.9 which is a La Nina value. NOAA has reported the weekly Nino 3.4 to be less cool at -0.8.which is still a solid La Nina value and we believe is a more realistic reading than what NOAA reported last week. Nino 4 is reported to be the same this week at -0.2. Nino 3 is less cool at  -0.6. Nino 1 + 2 which extends from the Equator south rather than being centered on the Equator is reported warmer at +0.2. It was up there close to -3.0 at one time so this index has been declining as an anomaly (rising) 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.

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

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

The discussion in this slide says it better than I could. One might compare the current reading to Oct/Nov 2016. The anomaly had returned to zero then reversed for a month and then returned to zero and now has gone positive. In retrospect it was the Kelvin Wave Activity the Upwelling Phase and the MJO which caused the brief reversal of the warming trend.

A side by side comparison can be useful

Comparison Week Probably Third Week of December 2017	Current Week

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.

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.

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

The Kelvin Wave that would have put a quick end to this La Nina has faded and then we had an upwelling wave. And now we have another looking more significant Kelvin Wave. This explains the gyrations in the forecast models first adding a month to the life of the La Nina and then recently removing that month and next time the models run the La Nina will be shown to be in its death throes. It almost looks like an El Nino is coming.

 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).

.

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 170W to 110W and it is warmer further east. At the west end of the-1C cool anomaly it is not even 100 meters deep (it was once over 200 meters deep). But we see some new cool anomalies at depth but they also now seem to be getting smaller and moving towards the surface. We now have warm water with a maximum anomaly of +4C developing west of the Dateline and crossing the Dateline at depth almost to 140W, possibly the result of another Downwelling Kelvin Wave. La Nina’s days are numbered and it does not have much longer to go.

The 28C Isotherm is at 170E, the 27C Isotherm is at 170W, 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 but the Indo-Pacific Warm Pool is gradually moving East. and the Eastern Pacific Cool Pool is gradually being forced deeper near Ecuador..

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.

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 tell us where convection has been taking place. The bottom of a Hovmoeller graphic shows the most recent readings.
Reds and browns would be suppressed easterlies or enhanced westerlies and are typical of El Nino. You see the recent change in the pattern.	We see the change in the pattern of suppressed OLR as the MJO moves through and the La Nina declines.

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

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

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.

Here is the most recent update. It is quite dramatic. We should have a new update very soon.

This is the discussion

IRI Technical ENSO Update Published: February 19, 2018

Note: The SST anomalies cited below refer to the OISSTv2 SST data set, and not ERSSTv4. OISSTv2 is often used for real-time analysis and model initialization, while ERSSTv4 is used for retrospective official ENSO diagnosis because it is more homogeneous over time, allowing for more accurate comparisons among ENSO events that are years apart. During ENSO events, OISSTv2 often shows stronger anomalies than ERSSTv4, and during very strong events the two datasets may differ by as much as 0.5 C. Additionally, the ERSSTv4 may tend to be cooler than OISSTv2, because ERSSTv4 is expressed relative to a base period that is updated every 5 years, while the base period of OISSTv2 is updated every 10 years and so, half of the time, is based on a slightly older period and does not account as much for the slow warming trend in the tropical Pacific SST.

Recent and Current Conditions

In mid-February 2018, the NINO3.4 SST anomaly was in the upper portion of the weak La Niña range. For January the SST anomaly was -0.75 C, indicating weak La Niña, and for November-January it was -0.79 C, also in that range. The IRI’s definition of El Niño, like NOAA/Climate Prediction Center’s, requires that the SST anomaly in the Nino3.4 region (5S-5N; 170W-120W) exceed 0.5 C. Similarly, for La Niña, the anomaly must be -0.5 C or less. The climatological probabilities for La Niña, neutral, and El Niño conditions vary seasonally, and are shown in a table at the bottom of this page for each 3-month season. The most recent weekly anomaly in the Nino3.4 region was -0.9, showing weak La Niña but not far from the borderline of moderate La Niña. The pertinent atmospheric variables, including the lower level zonal wind anomalies, the Southern Oscillation Index and the anomalies of outgoing longwave radiation (convection), have been showing patterns suggestive of La Niña, although the Southern Oscillation has been weak and variable and the enhanced trade winds in the western Pacific have ceased. Subsurface temperature anomalies across the eastern equatorial Pacific, while recently weakening significantly, are also still mildly negative and not inconsistent with a La Niña nearing the end of its duration. Given the current and recent SST anomalies, the subsurface profile and the La Niña patterns in most key atmospheric variables, it appears we are in the later stage of a weak (but nearly moderate) La Niña.

Expected Conditions

What is the outlook for the ENSO status going forward? The most recent official diagnosis and outlook was issued approximately one week ago in the NOAA/Climate Prediction Center ENSO Diagnostic Discussion, produced jointly by CPC and IRI; it stated that the La Niña is likely to transition to ENSO-neutral during spring. A La Niña Advisory was once again issued with that Discussion. The latest set of model ENSO predictions, from mid-February, now available in the IRI/CPC ENSO prediction plume, is discussed below. Those predictions suggest that the SST is likely to remain in the weak La Niña range just for the February-April season, followed by a likely return to neutral starting with the March-May season.

As of mid-February, about 60% of the dynamical or statistical models predicts La Niña conditions for the initial Feb-Apr 2018 season, dropping to only around 25% for Mar-May and Apr-Jun. At lead times of 3 or more months into the future, statistical and dynamical models that incorporate information about the ocean’s observed subsurface thermal structure generally exhibit higher predictive skill than those that do not. For the May-Jul 2018 season, among models that do use subsurface temperature information, about 75% of models predicts neutral conditions and about 15% predicts La Niña conditions. For all models, starting with the second lead time of Mar-May 2018 and lasting through most of the forecast range, predictions for ENSO-neutral conditions have more than a 50% probability, with probabilities peaking around 75-80% for May-Jul. However, near the end of the forecast range, Sep-Nov and Oct-Dec, the probability for El Niño rises to over 40% and La Niña probabilities are only about 10%, leaving only about 45% for neutral.

Note  – Only models that produce a new ENSO prediction every month are included in the above statement.

Caution is advised in interpreting the distribution of model predictions as the actual probabilities. At longer leads, the skill of the models degrades, and skill uncertainty must be convolved with the uncertainties from initial conditions and differing model physics, leading to more climatological probabilities in the long-lead ENSO Outlook than might be suggested by the suite of models. Furthermore, the expected skill of one model versus another has not been established using uniform validation procedures, which may cause a difference in the true probability distribution from that taken verbatim from the raw model predictions.

An alternative way to assess the probabilities of the three possible ENSO conditions is more quantitatively precise and less vulnerable to sampling errors than the categorical tallying method used above. This alternative method uses the mean of the predictions of all models on the plume, equally weighted, and constructs a standard error function centered on that mean. The standard error is Gaussian in shape, and has its width determined by an estimate of overall expected model skill for the season of the year and the lead time. Higher skill results in a relatively narrower error distribution, while low skill results in an error distribution with width approaching that of the historical observed distribution. This method shows probabilities for La Niña at about 55% for Feb-Apr, dropping to near 35% for Mar-May, and decreasing thereafter to less than 20% for Apr-Jun through Oct-Dec. Probabilities for neutral conditions begin around 45% for Feb-Apr, rise to a peak around 80% for Apr-Jun, after which they drop to about 50% for Jul-Sep and to about 40% or less for Aug-Oct to Oct-Dec as El Niño probabilities rise, reaching nearly 50% by Oct-Dec. A plot of the probabilities generated from this most recent IRI/CPC ENSO prediction plume using the multi-model mean and the Gaussian standard error method summarizes the model consensus out to about 10 months into the future. The same cautions mentioned above for the distributional count of model predictions apply to this Gaussian standard error method of inferring probabilities, due to differing model biases and skills. In particular, this approach considers only the mean of the predictions, and not the total range across the models, nor the ensemble range within individual models.

In summary, the probabilities derived from the models on the IRI/CPC plume describe, on average, a slight preference for weak La Niña conditions for Feb-Apr 2018, followed by the period from Mar-May through Jun-Aug with neutral having more than a 50% chance. Chances for El Niño are small through May-Jul 2018, rising to near 35% for Jul-Sep and nearly 50% by the final period of Oct-Dec. A caution regarding this latest set of model-based ENSO plume predictions, is that factors such as known specific model biases and recent changes that the models may have missed will be taken into account in the next official outlook to be generated and issued early next month by CPC and IRI, which will include some human judgment in combination with the model guidance.

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.

Here is 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.

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.

Forecasts from Other Meteorological Agencies.

Here is the JAMSTEC Model Forecast

And the recently released short discussion.

Feb. 19, 2018  Prediction from 1st Feb., 2018

ENSO forecast:

The La Niña-like condition will disappear by 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 summer. Then we expect evolution of a moderately positive Indian Ocean Dipole in fall. 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.

Atlantic Ocean forecast:

The Atlantic Niño and the Benguela Niño appear to develop in 2018. [Editor’s Note: We had noticed the strange temperature pattern along the Equator in the Atlantic and will research this further]

Regional forecast:

On a seasonal scale, most part of the Eurasian Continent will experience a warmer-than-normal condition except for western Europe. Northern/eastern U.S., southern Canada, central America, northern Brazil, Peru, Ecuador, Indochina, western, 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 the Philippines, Indochina, central and southern Africa, Mexico, Ecuador, and northeastern Brazil during boreal spring, whereas most parts of Indonesia, southern China, Korea, East Africa, eastern U.S, and northern Brazil will experience a drier condition during boreal spring.

Most part of Japan will experience somewhat warmer-than-normal and drier-than-normal conditions in spring.

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

And the ENSO Outlook Discussion Issued on February 27, 2018: La Niña retreats

La Niña continues its decline, with sea surface temperatures in the central tropical Pacific Ocean warming over the past fortnight. Most models indicate a return to neutral conditions is likely early in the southern autumn.

The decline of this La Niña is evident in oceanic and atmospheric patterns, with several indicators recently returning to levels more consistent with a neutral ENSO phase. Sea surface temperatures are very close to neutral levels, cloudiness near the Date Line has increased, and trade winds are generally near normal across the equatorial Pacific. However, the current pulse of the Madden-Julian Oscillation (MJO) has been strong, and the effects of wind variations associated with it is likely to have amplified the decline. As the MJO progresses east, its effect will reverse, meaning some La Niña indicators are likely to strengthen briefly.

Four of eight international climate models surveyed by the Bureau maintain La Niña values through March. By May, only one model still exceeds La Niña thresholds. For July, all eight are within the neutral range. This ENSO event has had relatively little effect on Australian rainfall patterns over the 2017–18 summer.

Indian Ocean IOD (It updates every two weeks)

Indian Ocean Dipole Outlook  Discussion Issued February 27, 2018

The Indian Ocean Dipole (IOD) is neutral. The weekly index value to 25 February was +0.20 °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 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 along the Equator are coming to an end. The actual impacts on Worldwide weather lag the change in conditions along the Equator so we will have impacts from this La Nina for two or three more months. But the situation for next Summer is not yet totally clear.

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. 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 and it is probably three or more years out.

E. Relevant Recent Articles and Reports

Weather in the News  

Bombogenesis Nor’ester at High Tide Crushes Boston

“Bombogenesis” occurs when the central pressure of a storm drops at least 24 millibars (mb) in 24 hours

Weather Research in the News

Arctic Warming

Another Version of the Same Story or Perhaps the Source

Global Warming in the News

Is Gulf Stream Weakening a Problem for New England?

Also see above under Weather Research.

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.

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.

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

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

The new SON reading of -0.8 is the fourth 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  80:20. These are three-month averages so JFM 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? It would have to be slightly positive to have the average be above -0.5 and that is now unlikely but possible. Not all Meteorological Agencies Worldwide will necessarily accept this La Nina to be legitimately declared. 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.

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.

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.

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.

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.