January 14, 2019 – Intermediate-Term Weather Report – Northern Exposure

Written by Sig Silber

This is a transition week. It may take a few days but the pattern is shifting north. It is also drying out but first it will be wet in advance of the trough moving across CONUS. There are many blocking features which make it difficult to estimate exactly when the trough will pass a particular part of CONUS or where the pattern might move more slowly. This can contribute to more extreme weather than might otherwise occur. The MJO is not a big contributor to the forecast this week.

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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 plan to start publishing a Report that will continually update and provide 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 will be an easy way to find out if and where that is needed. The first report may be published Wednesday night.  .

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

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 ay period.	The pattern is now mostly zonal (west to east versus meridional north to south to north). But the pattern is moving east very slowly. 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.	After Day 5, it is generally wet to the north and east but dry west and Southwest.		The transition from the 8 -14 day forecast shown above to the week 3/4 forecast seems feasible.

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 both the Northern and Southern branches of the Polar Jet Stream.

Tonight, Monday January 14, 2018, as I am looking at the above graphic, you see three places where Pacific moisture is entering CONUS. 

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.

And this graphic is now working again.

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.
Except for the Great Lakes Areas, snow looks pretty sparse for the next two days as of Monday Night.

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 is quite strong with surface central pressure of 976hPa and is mostly centered over the Western Aleutians but also extends down off the West Coast of North America but not as far as recently. The Hawaiian High has surface central pressure of 1032 hPa and is now close to shore and actually extends inland.  It interconnects with a huge Central CONUS high with surface central pressure of 1036 hPa. We see a Low for the Eastern CONUS with surface central pressure of 1008 hPa. There is an Arctic High with surface central pressure of 1020 hPa. Further to the east there is a Hudson Bay Low with surface central pressure of 1000 hPa and stretching over to Greenland.

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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.	We then see the trough that will bring modified Arctic Air across CONUS.

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.

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. 

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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.

Here is the seven-day cumulative precipitation forecast. More information in how to interpret this graphic 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 January 14, 2019 was 4 out of 5

8 – 14 Day Temperature Outlook issued today (Note the NOAA Level of Confidence in the Forecast Released on January 14, 2019 was 4 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 January 14,  2019 was 4 out of 5)

8 – 14 Day Precipitation Outlook Issued Today (Note the NOAA Level of Confidence in the Forecast Released on January 14, 2019 was 4 out of 5)

Looking further out.

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

6-10 DAY OUTLOOK FOR JAN 20 – 24 2019

THE ENSEMBLE MEANS ARE GENERALLY IN GOOD AGREEMENT IN PREDICTING MODERATELY AMPLIFIED 500-HPA FLOW ACROSS MUCH OF THE FORECAST DOMAIN. A CLOSED MID-LEVEL LOW IS FORECAST OVER THE ALEUTIANS. RIDGING IS ANTICIPATED FARTHER TO THE EAST ACROSS MUCH OF MAINLAND ALASKA EXTENDING SOUTHWARD OVER THE EASTERN PACIFIC OFF THE WEST COAST OF THE CONUS. A BROAD, 500-HPA TROUGH IS FORECAST TO DOMINATE THE EASTERN TWO-THIRDS OF THE CONUS UPSTREAM OF A STRONG RIDGE PREDICTED OVER THE NORTHERN ATLANTIC OCEAN. ENSEMBLE SPREAD IS LOW TO MODERATE ACROSS MOST OF THE FORECAST DOMAIN. THE 500-HPA MANUAL HEIGHT BLEND, BASED PRIMARILY ON THE ENSEMBLE MEAN SOLUTIONS FROM THE GEFS AND ECMWF MODELS, FAVORS BELOW NORMAL HEIGHTS FOR THE ALEUTIANS AS WELL AS MUCH OF THE EAST-CENTRAL CONUS EXTENDING TO THE SOUTHEAST. ABOVE NORMAL HEIGHTS ARE INDICATED FOR MUCH OF MAINLAND ALASKA, THE ALASKA PANHANDLE, THE WESTERN CONUS, AND NEW ENGLAND.

THE BROAD TROUGH FORECAST OVER EASTERN NORTH AMERICA FAVORS BELOW NORMAL TEMPERATURES FOR THE EASTERN HALF OF THE CONUS EXTENDING TO PARTS OF THE SOUTHWEST. UPSTREAM RIDGING AND ASSOCIATED ABOVE NORMAL HEIGHTS LEADS TO ENHANCED PROBABILITIES FOR ABOVE NORMAL TEMPERATURES FOR THE NORTHWESTERN CONUS EXTENDING SOUTHWARD ALONG THE WEST COAST. ABOVE NORMAL TEMPERATURES ARE ALSO FAVORED FOR ALASKA DUE TO PREDICTED RIDGING AND ABOVE NORMAL HEIGHTS ACROSS MUCH OF THE MAINLAND AND THE PANHANDLE AND SOUTHERLY FLOW AHEAD OF A SURFACE LOW PREDICTED NEAR THE ALEUTIANS.  

ABOVE NORMAL PRECIPITATION IS LIKELY FOR MUCH OF THE EASTERN CONUS NEAR AND AHEAD OF A MEAN TROUGH PREDICTED OVER THE EASTERN CONUS. THE HIGHEST PROBABILITIES FOR ABOVE NORMAL PRECIPITATION ARE INDICATED FOR PARTS OF THE NORTHEAST AND MID-ATLANTIC DUE TO A POTENTIAL COASTAL STORM EARLY IN THE PERIOD. ABOVE NORMAL PRECIPITATION IS ALSO FAVORED FOR MUCH OF THE NORTHERN PLAINS, THE NORTHERN AND CENTRAL ROCKIES, AS WELL AS PARTS THE THE NORTHWESTERN CONUS DUE TO THE POTENTIAL PROGRESSION OF SHORTWAVE ENERGY AROUND THE PERIPHERY OF MEAN CYCLONIC FLOW PREDICTED OVER MUCH OF NORTH AMERICA. THERE ARE ENHANCED PROBABILITIES FOR ABOVE NORMAL PRECIPITATION EXTENDING FROM SOUTHWESTERN ALASKA SOUTHEASTWARD TO THE ALASKA PANHANDLE AHEAD OF A MEAN 500-HPA TROUGH PREDICTED NEAR THE ALEUTIANS. 

FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: ABOVE AVERAGE, 4 OUT OF 5, DUE TO GOOD AGREEMENT AMONG 500-HPA HEIGHT, TEMPERATURE, AND PRECIPITATION GUIDANCE.

8-14 DAY OUTLOOK FOR JAN 22 – 28 2019 

THE ENSEMBLE MEAN SOLUTIONS ARE GENERALLY IN GOOD AGREEMENT IN PREDICTING AN AMPLIFICATION OF A MEAN 500-HPA TROUGH SITUATED ACROSS MUCH OF THE CONUS. UPSTREAM, STRONG RIDGING IS PREDICTED OFF THE WEST COAST OF THE CONUS EXTENDING NORTHWARD TO EASTERN ALASKA. A MEAN TROUGH IS FORECAST TO PERSIST OVER THE ALEUTIANS BUT WITH REDUCED AMPLITUDE RELATIVE TO THE 6-10 DAY PERIOD. CONVERSELY, MEAN RIDGING IS PREDICTED OVER THE NORTH ATLANTIC. THE AO INDEX, AS PREDICTED BY THE GEFS ENSEMBLES IS FORECAST TO TREND NEGATIVE DURING THE WEEK-2 PERIOD CONSISTENT WITH TROUGH DEVELOPMENT ACROSS MUCH OF THE CONUS. THE MANUAL 500-HPA BLEND, BASED PRIMARILY ON THE ENSEMBLE MEANS FROM THE GEFS AND ECMWF MODELS, FEATURES BELOW NORMAL HEIGHTS ACROSS MOST OF THE CONUS EAST OF THE ROCKIES AS WELL AS FOR THE ALEUTIANS. ABOVE NORMAL HEIGHTS ARE INDICATED ACROSS MAINLAND ALASKA, THE ALASKA PANHANDLE, AND PARTS OF THE WESTERN CONUS. 

THE AMPLIFIED TROUGH FORECAST OVER MUCH OF NORTH AMERICA LEADS TO ENHANCED PROBABILITIES OF BELOW NORMAL TEMPERATURES FOR THE MOST OF THE CONUS FROM THE GREAT BASIN EASTWARD. THE HIGHEST PROBABILITIES OF BELOW NORMAL TEMPERATURES ARE INDICATED FOR THE EAST-CENTRAL CONUS NEAR THE PREDICTED MEAN TROUGH AXIS.  ABOVE NORMAL TEMPERATURES ARE SLIGHTLY FAVORED ALONG THE IMMEDIATE WEST COAST UNDERNEATH PREDICTED ABOVE NORMAL 500-HPA HEIGHTS. RIDGING AND SOUTHERLY FLOW AHEAD OF A MEAN TROUGH NEAR THE WESTERN ALEUTIANS LEADS TO ENHANCED PROBABILITIES OF ABOVE NORMAL TEMPERATURES FOR ALASKA. 

THE PRECIPITATION PATTERN FOR THE WEEK-2 PERIOD IS SIMILAR TO THAT PREDICTED FOR THE 6-10 DAY PERIOD. ABOVE NORMAL PRECIPITATION IS FAVORED FOR MUCH OF THE EASTERN AND NORTH-CENTRAL CONUS UNDERNEATH MEAN CYCLONIC FLOW. AN AMPLIFYING RIDGE PREDICTED OFF THE WEST COAST OF THE CONUS LEADS TO INCREASED ODDS FOR BELOW NORMAL PRECIPITATION FROM THE SOUTHWESTERN CONUS NORTHWARD TO THE PACIFIC NORTHWEST. CONVERSELY, MOIST SOUTHERLY FLOW AHEAD OF A MEAN TROUGH NEAR THE ALEUTIANS LEADS TO INCREASED CHANCES FOR ABOVE NORMAL PRECIPITATION ACROSS MOST OF ALASKA. 

FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD: ABOVE AVERAGE, 4 OUT OF 5, DUE TO GOOD AGREEMENT ON A HIGH AMPLITUDE PATTERN ACROSS MUCH OF THE FORECAST DOMAIN.

THE NEXT SET OF LONG-LEAD MONTHLY AND SEASONAL OUTLOOKS WILL BE RELEASED ON  JANUARY 17.

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.

* 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 December 28 to January 23, 2019 is 26 days which is slightly tighter than last week (a  good indicator of a good 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 January 10. These analogs are describing historical weather that was centered on 3 days and 4 days ago (January 9 or January 10). So the analogs could be considered to be pretty much in sync with respect to weather that we would normally be getting right now.

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 five El Nino Analogs, two Neutral analogs and three La Nina Analogs. The pre-forecast analogs this week strongly favor McCabe Condition A which is “Very little drought Southern Tier and Northern Tier from the Dakotas east with some drought on East Coast “. This somewhat contradicts the forecast and leaves me with reduced confidence in the NOAA forecast. But the problem may be with the selection of the analogs.

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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.

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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.

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

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

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 between Phases 8 and 1 and weak (close to the origin in this graphic).

And then a forecast.

Remember we are interested in how the MJO impacts CONUS weather during mid- to late-January. So I have displayed the DJF information this week.  Over the next two weeks, Phases 2,3,4,5, and 6 may be experienced.

Temperature

Precipitation

Recent CONUS Weather

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

And the 30 Days ending January 5, 2019	And the 30 Days ending January 12, 2018
Drier in the Southwest and more intense re temperature along the Northern Tier.	You can already see the shift north of the precipitation track. We also see warming for the past 30 days.
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 January (with respect to the forecast we should be beginning to return 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)

And now precipitation

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

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

Now Precipitation

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

First Temperature

Then Precipitation

4. Tropical Hazards.

C. ENSO SUMMARY of Current Status. Our full report was published on December 13 with the  Drought Report and it can be accessed here. 

Current Status of ENSO

This section is organized into three parts.

But first: NOAA  did not declare El Nino Conditions in their Status Report on January 10. 2018

EL NINO/SOUTHERN OSCILLATION (ENSO) DIAGNOSTIC DISCUSSION issued by CLIMATE PREDICTION CENTER/NCEP/NWS and the International Research Institute for Climate and Society 10 January 2019

ENSO Alert System Status: [Editor’s Note: Remains] El Nino Watch

Synopsis: El Nino is expected to form and continue through the Northern Hemisphere spring 2019 (~65% chance).

ENSO-neutral continued during December 2018, despite widespread above-average sea surface temperatures (SSTs) across the equatorial Pacific Ocean. In the last couple of weeks, all four Nino indices decreased, with the latest weekly values at +0.2 degC in the Nino-1+2 region and near +0.7 degC in the other regions. Positive subsurface temperature anomalies (averaged across 180 deg-100 degW) also weakened, but above-average temperatures continued at depth across most of the equatorial Pacific Ocean. The atmospheric anomalies largely reflected intra-seasonal variability related to the Madden-Julian Oscillation, and have not yet shown a clear coupling to the above-average ocean temperatures. Equatorial convection was generally enhanced west of the Date Line and suppressed east of the Date Line, while anomalies were weak or near average over Indonesia. Low-level winds were near average, while upper-level wind anomalies were westerly over the eastern Pacific. The traditional Southern Oscillation index was positive, while the equatorial Southern Oscillation index was slightly negative. Despite the above-average ocean temperatures across the equatorial Pacific Ocean, the overall coupled ocean-atmosphere system continued to reflect ENSO-neutral.

The majority of models in the IRI/CPC plume predict a Nino3.4 index of +0.5 degC or greater to continue through at least the Northern Hemisphere spring 2019. Regardless of the above-average SSTs, the atmospheric circulation over the tropical Pacific has not yet shown clear evidence of coupling to the ocean. The late winter and early spring tend to be the most favorable months for coupling, so forecasters still believe weak El Nino conditions will emerge shortly. However, given the timing and that a weak event is favored, significant global impacts are not anticipated during the remainder of winter, even if conditions were to form. In summary, El Nino is expected to form and continue through the Northern Hemisphere spring 2019 (~65% chance; click CPC/IRI consensus forecast for the chance of each outcome for each 3-month period).

This discussion is a consolidated effort of the National Oceanic and Atmospheric Administration (NOAA), NOAA’s National Weather Service, and their funded institutions. Oceanic and atmospheric conditions are updated weekly on the Climate Prediction Center web site (El Nino/La Nina Current Conditions and Expert Discussions). Forecasts are also updated monthly in the Forecast Forum of CPCs Climate Diagnostics Bulletin. Additional perspectives and analysis are also available in an ENSO blog. The next ENSO Diagnostics Discussion is scheduled for 14 February 2019.

Here is the new probability forecast from the CPC/IRI

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

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 and Black Sea warm, Caspian Sea cool	Warm	Warm especially in Gulf of Alaska but also down along the West Coast to a lesser degree	Great Lakes cool Cool north of Cape Hatteras Warm around Florida and the Greater Antilles	Not shown in this map other than the North Atlantic which is Neutral
Equator	Looks like El Nino but Barely
Africa	West of Australia	North, South and East of Australia	West of South America	East of South America
Warm off Kenya extending beyond Madagascar Warm off Angola	Cool	Cool NE Warm SE and beyond New Zealand	Neutral except cool off 40S	Warm 20S extending to Africa. Warm 40S to 50S.

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.

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.

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

Here is a daily version

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.

This may help put the above graphics in focus.

Updated ONI History

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.

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.

E. Relevant Recent Articles and Reports

Weather in the News

Nothing to Report

Global Warming in the News

Nothing to Report

F. Useful Reference Information

Understand How the Jet Stream Impacts Weather

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Standard Pressure Levels

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