September 17, 2019 – Intermediate-Term Weather Report – North Fall, South Summer

Written by Sig Silber

The level of confidence by NOAA in their 6 to 14 Day Forecast was lower than usual and the pre-forecast analogs did not agree well with the forecast suggesting that a transition to Fall is coming. The MJO adds to the uncertainty. Although it is not surprising that it gets cooler sooner to the north, the climatology adjustment, if correct, would make the Normal-Adjusted temperatures tend to be normal for every latitude. So what we see is a real anomaly. One should expect that the South will get the hint soon enough. 

Please share this article – Go to the very top of the page, right-hand side for social media buttons. Also, feel free to send this article to anyone you feel will benefit from it. For those who are interested in the short-term situation, we refer you to our Severe Weather Report which is republished nightly and you can find the latest version by consulting the Directory by clicking here and then clicking on the latest version of the Severe Weather Report which will be near the top of the Directory.

Status of ENSO

It is kind of a confusing situation.

Monsoon

Let’s go back to our discussion of the typical configurations of the Monsoon especially with regards to severe weather.

I prefer to use the graphics provided by Arizona but you can extrapolate the interpretation to beyond Arizona. I show the four maps and the discussion of each map can be found here.

I prepared a little table to provide some information on when the different types might occur during the Monsoon. The full information is in the referenced document.

Notice that during the Monsoon the location of the Four Corners High Migrates not always in a predictable way but there is a pattern to it and you can see that in the graphics above.

So which type of positioning is this?

Let’s look at the MId-Atmosphere pattern.

It looks somewhat like the first (or is it the second) Fall Pacific Storm has pushed the Monsoon High out of range. We have had a few days of enhanced Monsoon activity but it is not forecast to continue except for extreme southern Arizona and New Mexico in the near term but may be part of a wetter pattern in Days 8 – 14. 

This is Monsoon Pattern Type IV.

Performance of the Monsoon this Year.

I  usually leave it to readers to go to this link and look at the graphics but last week I displayed the graphic. Readers who are interested can go to that link and view them but the changes are small week to week this late in the season as they are cumulative over the Monsoon Season.

I have data by city for Arizona in a nice format that auto-updates.  I do not have it for New Mexico but you can get it from the link used to access the above graphics namely Here   You can drill down and find the data by city in both New Mexico and Arizona but I have not yet found a graphic as convenient as the below for New Mexico. It may exist, but I have not found it yet.

Shifting Gears Let’s Take a Look at Tropical Activity

You can click on the above to enlarge them. If we thought they were of great interest we would have shown them full size. The graphics should update on their own but updates on individual named storms handled by the NHC can be obtained here. And here is the link for storms in the Western Pacific. We provide additional information on an updated basis in our Severe Weather Report. To find the most recent edition of our Servere Water Report, go to the Directory and find the most recent edition which will be near the top and click on it.

Recent CONUS Weather

Here is the recent history of the overall atmospheric pattern for North America and the North Pacific. (Not yet updated)

And now looking at the recent weather.

The 30 Days ending a week ago Saturday	The 30 Days ending last Saturday (not updated yet)
Not a lot of change. The wam anomaly is more intense and the dry anomaly is a bit less intense.	A little wetter  in the North Central and the warm anomaly has spread east.
Remember this is a 30-Day Average so one week is added and one week is pushed out of a 30-day average.

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 at the 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

And then Precipitation

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 there is a a Pacific Storm and enhance Monsoon activity.

Tonight, Monday, September 16, 2019, as I am looking at the above graphic, you see some significant Monsoon activity (mostly in New Mexico) and a storm approaching British Columbia which may ease over to the U.S. Northwest.

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.

This graphic 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.

And this graphic provides a better view of all of CONUS.

This graphic shows the Atlantic.

And Now the Day One and Two CONUS Forecasts (These graphics have recently been revised by NOAA and I think greatly improved).

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.
You can easily see the convective activity.

Additional useful forecasts are available from our Severe Weather Report which this week can always 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 centered on the Eastern Aleutians with surface central pressue of 980 hPa and furthe west there is a High east of Kamchatka with surface central pressure of 1024 hPa. There is an Arctic High with surface central pressure of 1016 hPa and a Hudson Bay Low with surface central  pressure of 1000 hPa. The dominant feature on this map is an East Coast High with surface central pressure of 1016 hPa but it appears to be moving offshore in the days following Day 7. The Hawaiian High has surface central pressure of 1024 hPa. And again there is an inverted Trough in the Sea of Cortez extending into the Southwest like what we often see during the Monsoon. We even see what looks like the Four Corners High which is the signature of the North American Monsoon (NAM) and at the surface the air pressure is 1016 hPa. The mid-level high seen on a different graphic is farther east and south.

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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. A Pacific storm has brought the Jet Stream further south,	The pattern is forecast to shift east.

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.

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Here is the seven-day cumulative precipitation forecast. More information on 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 Septermber 16, 2019 was 3 out of 5

8 – 14 Day Temperature Outlook issued today (Note the NOAA Level of Confidence in the Forecast Released on September 16, 2019 was 2 out of 5).

–

Probably most do not get that far in my article where I usually have this graphic (I have data on the average time on the page of readers) but this graphic is interesting so I am showing it earlier than usual. Remember this is an experimental model not the official 6 – 10  day and 8 – 14 day forecast. But it puts the CONUS and Alaska forecasts into context.

Looking further out.

Now – Precipitation

6 – 10 Day Precipitation Outlook Issued Today (Note the NOAA Level of Confidence in the Forecast Released on September 16, 2019 was 3 out of 5)

8 – 14 Day Precipitation Outlook Issued Today (Note the NOAA Level of Confidence in the Forecast Released on September 16, 2019 was 2 out of 5)

Probably most do not get that far in my article where I usually have this graphic (I have data on the average time on the page of readers) but this graphic is interesting so I am showing it earlier than usual. Remember this is an experimental model not the official 6 – 10  day and 8 – 14 day precipitation forecast. But it puts the CONUS and Alaska forecasts into contex

Then Precipitation

Looking further out.

Here is the 6 – 14 Day NOAA discussion released today September 16, 2019

6-10 DAY OUTLOOK FOR SEP 22 – 26 2019

Today’s model solutions are in fair agreement in depicting a somewhat amplified 500-hPa geopotential height pattern across much of the forecast domain. Early in the period, above normal 500-hPa heights are favored in the eastern CONUS, with near normal heights forecast toward the end of the period.  Troughing over Alaska, and weak ridging in the East Pacific favors an increase in Pacific flow over the Pacific Northwest. Positive 500-hPa height anomalies are forecast for parts of California and adjacent areas of Oregon and Nevada, along with parts of the Lower Mississippi Valley. Negative 500-hPa height anomalies are forecast over Alaska.

Near to above normal temperatures are favored across the CONUS. Temperatures in the Northeast could be upwards of 10 deg F above normal early in the period with some moderation possible late. The ECMWF maintains higher 500-hPa heights and therefore warmer temperatures throughout the period compared to the GEFS and Canadian models. Over the Pacific Northwest and the Great Basin, near normal temperatures are forecast. The ECMWF reforecast tool shows higher probabilities of below normal temperatures over these areas than the GEFS tool.  For now near normal temperatures are favored, but if trends continue,  probabilities for below normal temperatures may be increased in future outlooks. Near to below normal temperature probabilities are favored over mainland Alaska in association with negative 500-hPa height anomalies. Above normal temperatures are favored for parts of southeast mainland Alaska and the Panhandle as a result of increased Pacific flow.

The biggest change relative to yesterday is the increased probabilities for above normal precipitation over the Pacific Northwest and into the Northern Inter-mountain region. This is the result of the 500-hPa isohyspes depicting increased Pacific flow into the region. Guidance also suggests the potential for one or more atmospheric river events which would result in increased chances for heavy rainfall. Further east over the Rockies, below normal precipitation is favored due to forecast surface high pressure. Weak troughing and subsequent lowering of the 500-hPa heights over parts of the Plains, Mississippi Valley, and Great Lakes favors increased frontal activity and enhanced chances of rainfall. Therefore, probabilities for above normal precipitation are increased over these areas. Below normal precipitation is forecast along the East Coast from Southern New England through Florida, and also for southern Texas, as these area are anticipated to be far enough displaced from significant upper level dynamics.

FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: Average, 3 out of 5, due to decent model agreement across the domain, but with some disagreement in terms of the amplification.

8-14 DAY OUTLOOK FOR SEP 24 – 30 2019 

For week-2, models show a strengthening ridge in the East Pacific. This results  in a weakening of the trough over Alaska. As a result, near normal 500-hPa heights are favored over Alaska. Downstream, a more amplified pattern is depicted in week-2, with troughing in the West and ridging in the East. The ECMWF ensembles are more amplified than the GEFS and are favored in today’s forecast. Above normal 500-hPa heights remain favored for most of the CONUS. The only exception is over parts of the Pacific Northwest, Inter-mountain region, and Northern Plains where some below normal 500-hPa heights are forecast.

Above normal temperatures are forecast across much of the CONUS, with the highest probabilities over the eastern third of the CONUS, and extending back through the Lower Mississippi Valley and the Southern Plains. Increased probabilities of below normal temperatures are shown over the Pacific Northwest and Inter-mountain region underneath negative 500-hPa height anomalies. Near to above normal temperature probabilities are favored over Alaska due to forecast higher 500-hPa heights and weaker troughing relative to the 6-10 day period.

Above normal precipitation remains favored for the Pacific Northwest due to continued indications for Pacific flow and enhanced moisture transport into the region, especially early in the period. These above normal probabilities are extended eastward through the Plains and Mississippi Valley. These areas are favored to see enhanced frontal activity on the front-side of the broad trough to the west. Below normal precipitation is forecast over Florida, as it is too far south to be significantly impacted by the aforementioned frontal activity.

This is also consistent with the ECMWF reforecast tool. Although a trend toward higher 500-hPa heights is forecast over Alaska, weak troughing is projected to remain in place over the Bering Sea, favoring a continuation of an active weather pattern across the state. Therefore, probabilities of above normal precipitation are forecast for most of Alaska excluding the northern portion of the mainland.

FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD: Below average, 2 out of 5, due to uncertainty in how amplified the upper level pattern becomes, and in the exact placement and timing.

 The next set of long-lead monthly and seasonal outlooks will be released on  September 19.

Analogs to the NOAA 6 – 14 Day Outlook.

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 is 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 September 3 to September 29 is 26 days which is tighter than last week and suggests more ability to have confidence in the 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 September 16, 2019. These analogs are describing historical weather that was centered on 3 days and 4 days ago (September 12 or September 13. So the analogs could be considered to be out of sync with respect to weather that we would normally be getting right now in the sense that we getting weather that is about a half of week early. This seems a bit strange especially with regards to temperature but I do not have an easy way to assess it for precipitation.

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 three Neutral analogs, four El Nino Analogs, and three La Nina Analogs. This suggests that we are in ENSO Neutral now. The pre-forecast analogs this week are very consistent with McCabe C and D which are associated with drought. But the NOAA forecast is not that consistent with McCabe C and D which for me somewhat reduces the credibility in my mind of the NOAA forecast. One should keep in mind that the Analogs relate to conditions in the Pacific so to the extent that CONUS weather is more influenced by the Atlantic, the less the direct applicability of the Analogs. All the analogs were associated with AMO+. The dynamic models are much more reliable than the pre-forecast analogs but I use them as a double check that is all. If the forecast and the analogs do not line up, there are three major possibilites:

A. The analogs were not chosen well.

B.  The current pattern is different than what has occured in the past.

C. There are factors ouside of the area  where they look for historical analogs with such factors influncing the forecast.

“A” is unlikely as is “B” so “C” is usually the reason.

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.

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.

Here is another way of integrating all forecasts into a single graphic.  These forecasts extend out further into the future than the forecasts presented earlier. But they do not show the recent history.  Also, the set of four does not include the AO but instead the WPO so it is not the same but may be useful.

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.

This is the Summary from the weekly NOAA analysis of the MJO.

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

The MJO Index (more information can be found here) indicates where the MJO has been and this Hovmoeller Graphic shows this. The Index is shown for the parts of the Equator where the MJO is most usually found.

Forecast Models.

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.

Now the first of the three graphics we typically present which shows where the MJO is now and how it got there. 

This shows the recent history.  MJO is now in Phase 8 and just outside the circle of minimum impacts. What next?

And then a forecast.  On this 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.

And then the ECMF forecast.

Then side by side.

The new NOAA combination graphics were too difficult for me to explain so I am now showing the original graphics which do not have NOAA commentary but auto-update.

And we also look at the low-level wind anomalies.

Below is a Hovmoeller version which shows more than two time periods as above but a longer history. Along the bottom which is the current week, you can see the westerlies. The key takeaways are

A. There may have been another WWB but no sign so far of another Kelvin Wave.

B The MJO has not been active.

Remember that the MJO is one of many influences on the weather.

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 Patterns 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-September. We should now be starting to leave 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

Again, 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.

We showed these graphics earlier so I am not repeating them.

4. Tropical Hazards.

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 a disproportionate impact on the 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.
The Mediterranean, Black Sea, and Caspian Sea	Western Pacific	West of North America	North and East of North America	North Atlantic
The Mediterranean and Black Sea are slightly warm. The Caspian is neutral. The Persian Gulf is warm. .	Warm between  Japan and the mainland	Waters in Bristol Bay and the Chukchi Sea are warm and the Arctic Ocean is extremely warm. Gulf of Alaska  warm Very warm off all of the West Coast.	Hudson Bay slightly warm Davis Strait very warm Waters offshore of  East Coast are cool around Nova Scotia.	North Atlantic a bit warm.
Equator	Eastern Pacific cool.
Africa	West of Australia	North, South, and East of Australia	West of South America	East of South America
Slightly cool off West Africa. Cool southeast of Africa extending beyond Madagascar. Warm near shore in Gulf of Guinea.	Neutral	Cool to the north Slightly cool to the southeast out to New Zealand. Cool to the south	Cool  to 40S	Cool near the Equator. Warm 20S  to 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.

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.

ENSO Considerations

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.

The following graphic is somewhat similar to the graphic above but it updates every five days not once per week. The date shown is the midpoint for the five-day average. It shows a lot more detail than the above graphic. You can see some water at depth that is anomalously warm. But the depth of the warm anomaly is becoming less and there is cool water below it. This pattern might persist for a while.

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.

We are in ENSO Neutral with a La Nina bias.

E. Relevant Recent Articles and Reports

Weather in the News

Nothing to report

Weather Research in the News

Nothing to Report

Global Warming in the News

Nothing to report

Useful Reference Information

Understand How the Jet Stream Impacts Weather

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Standard Pressure Levels

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