February 18, 2019 - Intermediate-Term Weather Report

Written by Sig Silber

Updated at 2 PM EST February 19, 2019 to include the graphics not available yesterday due to the Presidents Day Holiday

We are actually transitioning into Spring. But it will not feel that way along the Northern Tier for a few more weeks. It is also getting drier but that may not last too long. The MJO and ENSO are still fighting it out. ENSO has part of NOAA on its side but lobbying does not determine weather so we will have to see how significant this potential El Nino will be. It reminds me a bit of 2014. But I do not think the outcome will be the same. I do not believe next year will be an El Nino year but most likely Neutral and closer to La Nina. It is a confusing situation but the change of seasons will occur.

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Possibly new Kelvin wave resulting from a Westerly Wind Burst (WWB)

This could extend the warm phase of ENSO through June. NOAA claims that El Nino Conditions already exist and we think that is stretching it a bit. See our article on this here.

Some Housekeeping: On January 18, 2019 we published Part I of the 15 Month Four-Season Outlook which you can access here. Part II which compares the NOAA forecast with the JAMSTEC forecast was published on January 23 and you can access it here. We published our now weekly Weather Impacts on the Economy formerly called the Drought and Agriculture Report on February 14, 2019 and that can be accessed here. 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.

In our Monday night Weekly Intermediate-Term Weather and Climate Report, we mostly cover Days 6 – 14 and Weeks 3 – 4 which depending on when you read this article covers to about Day 25. We cover Days 1- 5 also but in most cases readers will want to consult their local NWS Office for more detailed information that impacts them in the short term. However, we also now Published “Live: Severe Weather Events” and that can be accessed here. lt continually updates and provides easy access to products from the NOAA Storm Prediction Center and other parts of NOAA. This will make it easy to see if there are special situations that need to be considered by those living in the areas covered or planning to travel there. It is not intended to replace reliance on the local NWS Offices but is be an easy way to find out if and where that is needed.

Here is the recent history of the overall pattern for North America and the North Pacific.

Troughing and associated cooling over most of the Northern Tier. Warming in the Southeast. Ridging now preventing storms arriving from the Pacific. Remember, this shows four 15 Day Periods i.e. it is history. The forecast is for continuing change in the pattern. The cold anomaly is forecast to gradually ease east.

Summary of the Forecast

We now provide our usual summary first for temperature and then for precipitation of small images of the four 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.

Sometimes it is useful to see the evolution of the forecasts from the 1 – 5 Day, 6 – 10 Day (which NOAA considers to be Week-1 of their intermediate forecast) , 8 – 14 Day (which NOAA considers to be Week-2) and Week 3 and 4 (which after being issued overlap with Week-2). I do not have comparable maps for the Day 1 – 5 forecast in the same format as the three maps we generally work with. What I am showing for temperature is the Day 3 Maximum Temperature and for precipitation the five-day precipitation: the latter being fairly similar in format to the subsequent set of the maps I present each week but showing absolute QPF (inches of precipitation) not QPF deviation from Normal.

First Temperature


This shows magnitude rather than probability of being higher or lower than Normal and shows the middle day of the five day period.	The pattern is almost stationary but starting to move east. Notice the large cool anomaly.		The transition from the 8 -14 day forecast shown above to the week 3/4 forecast seems feasible .

And then Precipitation


The five day QPF is shown above. The units are different than the other maps i.e. in units of precipitation (inches) not probabilities of exceeding or being less than climatology.	Similar to temperature, the pattern is gradually shifting to the east.		The transition from the 8 -14 day forecast shown above to the week 3/4 forecast seems feasible but not necessarily.

A. Now we will begin with our regular approach and focus on Alaska and CONUS (all U.S.. except Hawaii).

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 moisture has been arriving from the Southern branch of the Polar Jet Stream. In this graphic you can see the High over the North Central and the Low over Utah spinning.

Tonight, Monday February 18, 2019, as I am looking at the above graphic, you see moisture arriving slightly impacting the Northwest and the other features mentioned re the prior graphic. I show the moving and the static image both as the have different advantages.

We now discuss 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.

The graphic we had been using was not updating so for the time being we added another version which is updating. It does not cover all of CONUS but it does provide a very good view of what is happening in the Pacific and the North American West Coast. But the original graphic we were using is not working so we are using both.

We see some storms but hard to figure out where they are headed.

And this graphic is also now working again.

You can see moisture starting to move off the Southeast Coast.

I have decided to include the IWT information for Europe.

This is not only useful for Europe but it puts the East Coast and the Antilles into better perspective. The AR as it leaves CONUS appears to be forming a storm off the East Coast.

And Now the Day One and Two CONUS Forecasts

Day One CONUS Forecast	Day Two CONUS Forecast

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.

We see snow and freezing rain impacting the Southern Rockies and the moisture then impacting ares further east.

Additional useful forecasts are available from our Severe Weather Report which this week can be found here and always can be located via this directory.

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.

The below makes it easier to focus on a particular day. The best way to read them is from left to right on the first row and then from left to right in the row below it.

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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 forecast 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.

The Aleutian Low with surface central pressure of 980 hPa is close to Kamchatka and over the Western Aleutians. The Hawaiian High is weak and looks to be on Day 7 merged with the Western Canada High. But it has entrained a Low with surface central pressure of 1020 hPa that is likely to have impacts. There is a high over Western Canada with surface central pressure of 1032 hPa. It extends south into CONUS. There is a Low over the Maritimes with surface central pressure of 1000 hPa which may impact New England. The pattern is simple but relatively stagnant.

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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

You can see the current pattern here. Cold air is pouring into the North Central area.	Very slight shift in the pattern. But the orientation of the trough changes which may be significant.

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. Thinking about clockwise movements around High Pressure Systems and counter- clockwise movements around Low Pressure Systems provides a lot of information.

As of this evening, we see for Day 7 a somewhat zonal pattern that is moving very slowly. There is a fairly deamplified Western Trough. The 540 Line which is a best guess of where the chances of snow versus rain at sea level are about equal is deep into CONUS. Most of CONUS is above sea level so the rain/snow line is in reality even further south.

Here is the whole suite of similar maps for Days 3, 4, 5, 6 and repeated for Day 7. It is quite complicated. Read from left to right first row and then left to right on the second row.

You can see how this trough is expected to move across CONUS. It pretty well determines all the weather in CONUS. It is not moving very quickly.

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We are showing both the situation on the surface and at mid-atmosphere 500 mb and the view is different so sometimes it is useful to simply be able to compare them.

Surface 850MB	Mid Atmosphere 500 MB

For Day 7 the surface and 500 millibar views are in good agreement. It is a vertical alignment related to the very slow speed of the atmosphere moving east.

Here is the seven-day cumulative precipitation forecast. More information in how to interpret this graphic is available here.

We see moisture entering CONUS from the Northwest. And then we have the Southeastern wet pattern. At this point it looks like the Southeast Precipitation may cause flooding

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 18, 2019 was 4 out of 5

8 – 14 Day Temperature Outlook issued today (Note the NOAA Level of Confidence in the Forecast Released on February 18, 2019 was 3 out of 5).

–

Looking further out.

This is not a traditional El Nino Pattern.

Now – Precipitation

6 – 10 Day Precipitation Outlook Issued Today (Note the NOAA Level of Confidence in the Forecast Released on February 18, 2019 was 4 out of 5)

8 – 14 Day Precipitation Outlook Issued Today (Note the NOAA Level of Confidence in the Forecast Released on February 18, 2019 was 3 out of 5)

Looking further out.

Second half of months seems dry except for part of the Southeast.

Here is the 6 – 14 Day NOAA discussion released today February 18, 2019

6-10 DAY OUTLOOK FOR FEB 24 – 28 2019
THE CANADIAN, GFS, AND ECMWF ENSEMBLE MEANS ARE IN EXCELLENT AGREEMENT WITH THE LONGWAVE PATTERN THROUGHOUT THE NORTHERN HEMISPHERE. THESE ENSEMBLE MEANS FEATURE AN AMPLIFYING UPPER-LEVEL RIDGE OVER MAINLAND ALASKA DURING THIS 5-DAY PERIOD WITH A HIGH AMPLITUDE UPPER-LEVEL TROUGH EXTENDING FROM HUDSON BAY SOUTHWEST TO THE INTERIOR WEST. A SUBTROPICAL RIDGE (500-HPA HEIGHTS OF 588 TO 590 DM) REMAINS ANCHORED OVER THE FLORIDA PENINSULA, CUBA, AND THE BAHAMAS. SINCE THE DETERMINISTIC 0Z ECMWF MODEL AGREES QUITE WELL WITH ITS ENSEMBLE MEAN, THE DETERMINISTIC 0Z ECMWF MODEL WAS USED IN CREATING THE 500-HPA BLEND.
DURING THE PAST TWO WEEKS, TEMPERATURES HAVE AVERAGED BELOW NORMAL ACROSS THE WESTERN AND NORTH-CENTRAL CONUS WITH THE LARGEST NEGATIVE ANOMALIES (-20 DEGREES F OR MORE) OBSERVED IN THE NORTHERN GREAT PLAINS. THE HIGH AMPLITUDE RIDGE UPSTREAM OVER MAINLAND ALASKA AND ARCTIC HIGH PRESSURE CENTERED IN WESTERN CANADA ARE LIKELY TO MAINTAIN THIS ANOMALOUSLY COLD PATTERN THROUGH THE FINAL WEEK OF FEBRUARY. THE HIGHEST ODDS FOR BELOW NORMAL TEMPERATURES ARE FORECAST ACROSS THE NORTHERN ROCKIES AND NORTHERN GREAT PLAINS WHERE TEMPERATURES ARE LIKELY TO AVERAGE MORE THAN 20 DEGREES F BELOW NORMAL THROUGH AT LEAST DAY 7. THE SOUTHERN EXTENT OF THE ANOMALOUS COLD IS SOMEWHAT UNCERTAIN, BUT TELECONNECTIONS UPON THE LARGE POSITIVE 500-HPA CENTER OVER EASTERN MAINLAND ALASKA FAVOR BELOW NORMAL TEMPERATURES AS FAR SOUTH AS THE RIO GRANDE. THE STRONG SUBTROPICAL RIDGE FAVORS ABOVE NORMAL TEMPERATURES FROM THE SOUTHEAST NORTH TO THE MID-ATLANTIC.
DOWNSTREAM OF THE UPPER-LEVEL TROUGH AXIS, ONE OR TWO FRONTAL PASSAGES FAVOR ABOVE NORMAL PRECIPITATION ACROSS THE GREAT LAKES, EASTERN U.S., AND ALONG THE GULF COAST. UPSLOPE FLOW TILTS THE ODDS TO ABOVE NORMAL PRECIPITATION ACROSS THE NORTHERN AND CENTRAL HIGH PLAINS. A MUCH DRIER PATTERN IS LIKELY TO DEVELOP ALONG THE WEST COAST AND SOUTHWEST AS THE UPPER-LEVEL RIDGE SHIFTS EAST OVER THE NORTHEAST PACIFIC AND THE INFLUX OF SUBTROPICAL MOISTURE ABATES.
MODEL SOLUTIONS ARE IN EXCELLENT AGREEMENT WITH A HIGHLY AMPLIFIED UPPER-LEVEL TROUGH (RIDGE) OVER THE BERING SEA (MAINLAND ALASKA). THIS LONGWAVE PATTERN FAVORS ABOVE-NORMAL PRECIPITATION AND TEMPERATURES ACROSS THE ALEUTIANS AND MUCH OF MAINLAND ALASKA, WHILE OFFSHORE FLOW INCREASES CHANCES FOR BELOW NORMAL PRECIPITATION AND TEMPERATURES ACROSS THE ALASKA PANHANDLE.
FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: ABOVE AVERAGE, 4 OUT OF 5, DUE TO GOOD AGREEMENT AMONG THE ENSEMBLE MEANS IN A HIGHLY AMPLIFIED LONGWAVE PATTERN
8-14 DAY OUTLOOK FOR FEB 26 – MAR 04, 2019
THE ENSEMBLE MEANS MAINTAIN A HIGH AMPLITUDE LONGWAVE PATTERN DURING WEEK-2 WITH A SLIGHT EASTWARD PROGRESSION OF THE UPPER-LEVEL RIDGE CLOSER TO THE WEST COAST AND A DECREASE IN 500-HPA HEIGHTS OVER THE EASTERN CONUS. ANOMALOUS COLD IS LIKELY TO SHIFT EAST FROM THE WESTERN TO THE CENTRAL U.S. BY THE BEGINNING OF MARCH. LOWER ODDS FOR BELOW NORMAL TEMPERATURES ARE FORECAST ALONG THE WEST COAST DURING WEEK-2 COMPARED TO DAYS 6-10 AS THIS REGION IS LIKELY TO EXPERIENCE A WARMING TREND. THE LOWEST CONFIDENCE IN THE TEMPERATURE OUTLOOK EXISTS ACROSS THE SOUTHEAST AS MODEL SOLUTIONS VARY ON WHEN THE PERSISTENT, ANOMALOUS RIDGE WEAKENS. GIVEN RELATIVE WARMTH LIKELY THROUGH DAY 10, NEAR TO ABOVE NORMAL TEMPERATURES ARE FAVORED FROM THE CAROLINAS SOUTH TO FLORIDA.
UNLIKE PRECIPITATION OUTLOOKS DURING THE PAST WEEK WHICH HAD RELATIVELY HIGH ODDS FOR ABOVE NORMAL PRECIPITATION ACROSS THE EASTERN U.S., TODAY’S OUTLOOK FEATURES MORE MODEST PROBABILITIES AS A TRANSITION IN THE PATTERN IS EXPECTED. A FRONTAL PASSAGE EARLY IN WEEK-2 FAVORS ABOVE NORMAL PRECIPITATION ALONG THE EAST COAST, WITH THE HIGHEST ODDS FOR ABOVE NORMAL PRECIPITATION FORECAST ALONG THE GULF COAST WHERE A FRONT IS LIKELY TO SLOW AND PERHAPS STALL DURING WEEK-2. NEAR TO BELOW NORMAL PRECIPITATION IS FAVORED THROUGHOUT MUCH OF THE WESTERN AND CENTRAL CONUS DUE TO UPSTREAM RIDGING ALOFT AND A SPRAWLING AREA OF SURFACE HIGH PRESSURE. THE SLIGHT TILT IN THE ODDS FOR ABOVE NORMAL PRECIPITATION FORECAST ACROSS THE NORTHERN GREAT PLAINS IS RELATED TO UPSLOPE FLOW.
SINCE THE PATTERN ALOFT AND AT THE SURFACE REVEALS LITTLE CHANGE FROM DAYS 6-10 TO WEEK-2 ACROSS ALASKA, THE TWO OUTLOOKS ARE SIMILAR SPATIALLY FOR THIS REGION. PROBABILITIES REMAIN RELATIVELY HIGH IN THE WEEK-2 TEMPERATURE AND PRECIPITATION OUTLOOKS DUE TO THE HIGH AMPLITUDE OF THE LONGWAVE PATTERN.
FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD: AVERAGE, 3 OUT OF 5, DUE TO REASONABLY GOOD AGREEMENT AMONG THE TOOLS OFFSET BY UNCERTAINTY ON HOW FAST THE SUBTROPICAL RIDGE OVER THE SOUTHEAST WEAKENS AND COVERAGE OF BELOW NORMAL TEMPERATURES ACROSS THE EASTERN CONUS.
THE NEXT SET OF LONG-LEAD MONTHLY AND SEASONAL OUTLOOKS WILL BE RELEASED ON FEBRUARY 21.

Analogs to the NOAA 6 – 14 Day Outlook.

Now let us take a detailed look at the “Analogs”.

NOAA normally provides two sets of Analogs.

A. Analogs 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 the recent pattern is used to initialize the models to predict the 6 – 14 day Outlook.

B. There is a second set of analogs associated with the Outlook. It compares the forecast (rather than the prior period) to past weather patterns. I have not been regularly analyzing this second set of information. The first set applies to the 5 and 7 day observed pattern prior to today. The second set, relates to the correlation of the forecasted outlook 6 – 10 days out and 8 – 14 days out with similar patterns that have occurred in the past during a longer period that includes the dates covered by the 6 – 10 Day and 8 – 14 Day Outlook. The second set of analogs also has useful information as it indicates that the forecast is feasible in the sense that something like it has happened before. I am not very impressed with that approach. But in some ways both Approach A and B are somewhat similar. I conclude that if the Ocean Condition now are different then the analogs and if the state of ENSO now is different than the analogs that is a reason to have increased lack of confidence in the forecasts and vice versa.

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. But NOAA prefers the first set (A) as it helps them (or at least they think it does) assess the quality of the forecast.

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. It also helps the reader see the impact of the phases of the PDO and AMO which are shown. The first set (A) which is what I am using today applies to the 5 and 7 day observed pattern prior to today.

Centered Day	ENSO Phase	PDO*	AMO*	Other Comments
Mar 3, 1985	La Nina	+	–
Mar 4, 1985	La Nina	+	–
Feb 8, 2001 (2)	La Nina	–	–	Tail End
Feb 13, 2001	La Nina	–	–	Tail End
Feb 17, 2006 (2)	La Nina	+	+	Tail End
Feb 13, 2009 (2)	La Nina	+	+	Tail End
Mar 4, 2009	La Nina	+	+	Tail End

* I assign values that are consistent with the trend so I am doing some subjective smoothing with respect to the Phases of the AMO and PDO shown in this table. (t) = a month where the Ocean Cycle Index has just changed from a consistent pattern or does change the following month to a consistent pattern.

The spread among the analogs from February 8, 2019 to March 4, 2009 is 24 days which is tighter than last week.(and may suggest a pattern that is easier to forecast). 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 20. These analogs are describing historical weather that was centered on 3 days and 4 days ago (February 14 or February 15). So the analogs could be considered to be out of sync with respect to weather that we would normally be getting right now. We are now almost a week early re moving to Spring. This may be significant.

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 duplicates, there are zero Neutral analogs, zero El Nino Analog, and ten La Nina Analogs. The pre-forecast analogs this week favor all the McCabe Conditions except McCabe D “Southwest Drought extending to the Great Plains and also to the Great Lakes”. By rejecting this scenario, the forecast is consistent with the NOAA 6 – 14 Day forecast which adds to my confidence in the NOAA forecast. McCabe C “Northern Drought and Mid Atlantic Drought” is slightly favored which conflicts with the forecast which could mean that those conditions might show up in Weeks 3 and 4.

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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.

Some Indices of Possible Interest: We should always remember that the forecast is driven by many factors some of which are conflicting in terms of their impacts. Please pay more attention to the graphics than my commentary which does not update on a regular basis once the article is published. The indices will continue to update. I provide these indices as they are important guidelines to the weather. It is in a way looking at the factors that are impacting the weather. There were developed because weather forecasters found them to be useful.

Looks like the AO will be Positive. This normally limits the potential for cold air entering CONUS from Canada. Nevertheless the forecast is for a cold trough in the Northwest extending to the Great Lakes

It is not a surprise when the AO and NAO are positively correlated. They both have to do with Polar versus Sub-Polar pressure gradients but the AO is over CONUS and the NAO is over the Atlantic with the impacts of the NAO felt on both sides of the Atlantic. Some look at the AO as simply being the western end of the NAO but the AO is based on conditions over land and the NAO is based on conditions over the Atlantic so they are related but not the same thing. As the NAO become Negative this could impact both East Coast weather and Western Europe weather.

It looks like the AO and NAO will be mostly positively correlated as the NAO is forecast to be Neutral to Positive.

The forecast Phase of the PNA pattern is mostly Neutral. You can see the impact of the different phases in the schematics below (N.C. State). PNA Positive in on the left and PNA Negative on the right. PNA Negative is a pattern that is more westerly located than PNA Positive. This has to do with storms entering CONUS in the Northwest and then moving south either closer to the coast or further inland.

It looks like conditions favor troughs dropping down along the West Coast early in the forecast and also late in the forecast with the inland route more favored at one point. This forecast might be a bit volatile over the next two weeks.

………………………..PNA Positive…………………………….. PNA Negative……………..

We provided additional information in the introduction to this Article.

Madden Julian Oscillation (MJO)

The MJO is an area of convective activity along the Equator which circles the globe generally in 30 to 60 days. The location of the convective activity not only impacts the Equator but also the middle latitudes. Most people are not familiar with the MJO but at certain times it plays an important role Worldwide re weather and for CONUS.

There are a lot of models and I try to read the results from all of them. For access to a variety of models, I refer readers here. This weekly report summarizes things. Here is another useful source of information.

First we look at two models that I find very helpful. On the GFS graphic , the light gray shading shows the tracks which fit with 90% of the forecasts and the dark gray shading shows a smaller area that fits with 50% of the forecasts The large dot is the current location.

Looks like the MJO will again be on the move. But there is considerable uncertainty re the rate of movement.

It is sometimes useful to look at the recent history of the MJO.

You can see the movement of the MJO and changes elsewhere which may or may not be related to the MJO. The circled areas are obviously areas that NOAA believes the reader should look at. We see a direct impact on the CONUS now. Is this the MJO or El Nino?

Mostly MJO not far enough East to reinvigorate the El Nino. Interesting last week it said the connection between Hawaii and California had weakened as we awaited a Pineapple Express. Today we see it on the graphic.

Here is another way of looking at this information through time with a Hovmoeller graphic.

This is a Hovmoeller Diagram so it shows conditions through time so for our purposes we look at the bottom which is the current time. A strong Westerly Wind Burst WWB is shown. It may well have started another Kelvin wave but that wave would not arrive in the Eastern Pacific during meteorological Winter. This graphic shows the interaction of the MJO with normally westward moving Rossby Waves.

Then the first of the two graphics we typically present which shows where the MJO is now how it got there.

This shows the recent history. MJO is now in Phase 8. Will it move further east?

And then a forecast.

This suggests that the MJO will be in Phases 8 and possibly Phase 1 for this forecast period. It is moving slowly and the forecast is not intensifying (shown by distance from the origin).

The impact of this is shown in the summary graphic earlier: a shift in the cool anomaly to the east.

Remember that the MJO is one of many influences on weather. What I am normally showing here is the most reliable impacts but NOAA goes into much more depth in their analysis than I could show in this report. But the goal is to demystify weather forecasting.

Recent CONUS Weather

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

And the 30 Days ending February 9, 2019	And the 30 Days ending February 17, 2019

Less precipitation and a warmer West and Cooler Great Lakes and Northeast	Northern Tier wetter, Southeast drier, Cold Anomaly more North Central and more intense.
Remember, these maps are a 30 average so the most distant seven days are removed and the most recent seven days are added.

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 moving into late- February, early March. We should be returning from the set of positions shown below for the Winter Pattern to the Summer Pattern. For CONUS, the seasonal repositioning of the Bermuda High and the Pacific High are very significant.

World Forecasts

1. Today (Source: University of Maine)

2. Short-term set for day six but can be adjusted (BOM – Australia)

3. 8 – 14 Day (NOAA/Canada/Mexico Experimental NAEFS))

4 Tropical Activity

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

Australia again looks hot. So does Equatorial Africa.

And now precipitation

It is still the general pattern of a wet Equator and dry North Africa extending to the Eastern Asia and even Southern Asia. South of the Equatorial the wet belt has now become very wet. You also see a wet Eastern Mediterranean.

Additional Maps showing different weather variables can be found here.

2. 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

Australia is no longer forecast to be excessively warm. But parts of South America are.

Please remember this graphic updates every six hours so the diurnal pattern can confuse the reader.

Now Precipitation

This is a forecast for one particular day (Day 6). But it shows the surface Highs and the Lows which is useful information.

3. And now we have experimental 8 – 14 Day World forecasts from the NAEFS Model.

First Temperature

Canada and the Western CONUS look cool. East Asia is warm. So is Europe.

Then Precipitation

I mostly rely on the reader to interpret world maps that update frequently. But I can’t help notice that Eastern Europe looks very wet and Australia looks dry..

4. 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 normally Week 2 applies at the time I write this article on Monday. Mostly, as I review this now on February 18, 2019 for what is shown as Week – 2, the period February 20 to February 26, 2019, we see a dry** anomaly impacting the Maritime Continent. There is a risk of high temperatures* for Northwest Australia. There is a wet area* impacting Angola i.e. Western Africa south of the Equator.

* means moderate confidence and ** means high confidence.

C. ENSO SUMMARY of Current Status.

This section is organized into three parts.

1. Current Sea Surface Temperatures (SST)

2. Current Nino 3.4 Readings

3. The Surface Air Pressure Pattern that confirms the state of ENSO.

1. Current and Recent Sea Surface Temperatures (SST)

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.

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

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.

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

We have our daily map which updates back.

First the categorization of the current Monthly Average SST anomalies.
Mediterranean, Black Sea and Caspian Sea	Western Pacific	West of North America	North and East of North America	North Atlantic
Mediterranean, Black Sea, Caspian Sea, Red Sea and Persian Gulf slightly warm.	Slightly warm	Waters around Alaska slightly warm Warm area offshore of Baja Mexico	Great Lakes cool Waters offshore of East Coast warm. Davis Strait warm.	Slightly warm around Scandinavia Cool far south of Greenland.
Equator	Fairly close to neutral, Offshore of Ecuador cool.

Africa	West of Australia	North, South and East of Australia	West of South America	East of South America
Warm south of South Africa Cool east of South Africa buy mostly offshore	Cool	Warm SE and beyond New Zealand	Cool just off Ecuador Slightly warm 10S to 30S Cool south of Cape Horn	No ENSO pattern along Equator in the Atlantic. Slightly warm off East Coast.

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. I used to interpret this graphic but really my interpretation was no more than characterizing the graphic by geographical region as per the above graphic and the reader can do this for themselves.

But I can not help mentioning the cooling along the Equator in the Eastern Pacific where an El Nino is supposed to be forming. The ocean surfaces in general are cooling.

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. NOAA considers Nino 3.4 shown in the graphic as the best indicator of Equatorial Surface Temperature Anomalies associated with different phases of ENSO. There is a duration requirement to be a recorded El Nino or La Nina but to have El Nino Conditions the Nino 3.4 index needs to be +0.5C or warmer and to have La Nina Conditions the Nino 3.4 Index needs to be -0.5C or cooler.

The Nino 3.4 Index which is most used by NOAA has now been updated. It shows the Nino 3.4 Index back in El Nino Territory. I am leaving the added graphic below in….it updates daily I think.

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

Recently has become warmer than the 0.5C NOAA threshold for El Nino. But for the moment it looks like it has peaked.

Here is a daily version

Back in El Nino territory. It had gone sky high but now is barely in El Nino territory. It changes daily.

Here is the NOAA proprietary Nino 3.4 forecast model. The forecast spread is enormous. The blue lines are the most recent model runs.

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 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.

Notice in the bottom graphic the big difference between temperature anomalies south of the Equator and north of the Equator. This creates a dynamic situation.

*Location Bar for Nino 3.4 Area Above and Below*
————————————————	A	B	C	D	E	—————–

Looks like a Modoki. See the warm water (the yellow) near the Dateline. It is somewhat warm close to shore. But totally neutral in between.

I see much less tan and more yellow at the bottom of the Hovmoeller Diagram meaning current conditions i.e. less El Nino-ish. A month ago it looked more like an El Nino. Not now. But that might change. But not immediately.

This is a Hovmoeller Diagram so we read it from the bottom (current situation) up (prior times as per the Y Axis. Over at the Dateline we see the start of another Kelvin Wave but it will not impact this meteorological winter. Some are beginning to think we may have a two-year warm event. I notice that in this graphic NOAA is calling this an El Nino pattern. It is not the surface shown here.

This may help put the above graphics in focus.

You can see the gap that has formed between the current subsurface warm anomaly which is barely in El Nino Territory and the next warm anomaly which trails by a month or so. You also see the cold water coming up from below. This is why the meteorologists and models are backing off of their El Nino forecast. It is not going to happen at least not soon. On the right you see the history.

Since the above graphic had not been updated at the time we went to press, the following is useful as it is updated. The date shown is the midpoint for the five day average. But now the above image has also been updated but I am leaving in the additional image as it is also useful but it is not frozen and will update every five days.

The top graphic is of most interest. There used to be two warm anomalies. One has played out. The other has not yet reached the area were it is forced to surface. It will but is not there yet. It may be sufficient to generate true El Nino Conditions which do not exist now to a point that it is clear cut.

The bottom graphic shows the “thermocline” is not of an El Nino nature. It is more like La Nina actually. The warm water is to the west not the east. With El Nino this thermocline flattens out. We should not be seeing cool anomalies so close to the surface in the Eastern Pacific.

3. The Surface Air Pressure that Confirms the Nino 3.4 Index

And of course Queensland Australia is the official keeper of the SOI measurements.

The SOI Index is essentially showing ENSO Neutral at this point in time. But it may be rapidly moving into El Nino territory.

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).

D. Putting it all Together.

At this time, La Nina Conditions along the Equator have come to an end and we are solidly into ENSO Neutral and possibly entering into El Nino Conditions. But the drivers of a transition to El Nino are not solidly in place. In fact this is almost unprecedented in terms of the lateness of the arrival of a potential El Nino. If an El Nino it will be where the Peak Value of the Nino 3.4 Index will be achieved early on and will be in decline the rest of the time which has different impacts than an El Nino with a stable Nino 3.4 Index.

There is some thought now that we might have a sub-El Nino situation that extends into next Winter. JAMSTEC ruled that out but there are some signs that this could happen.

E. Relevant Recent Articles and Reports

Weather in the News

Failed El Nino of 2014

Global Warming in the News

Nothing to report

Useful Reference Information

Understand How the Jet Stream Impacts Weather

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This is particularly useful for locations at the base of the trough but it works wherever the jet stream is involved and when one can forecast where the jet stream will be. This is the general model but local offices of the NWS will be interpreting this very specifically for the various part of their County Warning Area (CWA). Do not be intimidated by the graphics. It is not that complicated. The idea is that if you are facing the Jet Stream (on the ground of course) and are more or less below the center of the Jet Stream, there will be different impacts to your right than to your left and it makes a difference if you are where the jet stream is dis

charging the wind (Exit Region) or where the wind is converging into the Jet stream (Entrance Region). This terminology is a bit confusing until you get used to it.

include(“/home4/aleta/public_html/pages/weather/modules/MJO_and_ENSO_Interaction_Matrix.htm”); ?>

Standard Pressure Levels

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February 18, 2019 – Intermediate-Term Weather Report

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