August 6, 2018 Weather and Climate Report – Near Misses but Hawaii is Concerned

Written by Sig Silber

A fairly unremarkable summertime weather pattern is predicted with some added moisture from Eastern Pacific cyclones passing to the west of CONUS and the westward expansion of the Bermuda High which may gradually dry out the Southeast in Week-2 of the NOAA forecast. There is some concern in Hawaii and we are monitoring Hurricane Hector. It looks like a near miss. Aside from the current weather, we continue to have our doubts that the forecast El Nino will amount to much.

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They are getting nervous in Hawaii. Updates can be found here.  This link will take you to the current discussion. I can not find a track forecast similar to what we get from NHC. At this point it looks like a near miss.

And then there is John and Ileana which are also are not expected to impact CONUS “directly” but which will provide moisture to the Monsoon.

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

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.	A fairly stagnant pattern. We see some west to east movement along the Northern Tier and some east to west movement along the Southern Tier.		↑ ←  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.	It is an overall wet pattern but Week-2 shows some drying in the Northwest and Southeast.		↑ ←  The transition from the 8 -14 day forecast shown above to the week 3/4 shown to the left seems feasible. But it may not happen as drawn up especially for the Southeast.

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 more activity in Mexico than CONUS.

Tonight, Monday August 6, 2018, as I am looking at the above graphic, the recent pattern continues.

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

And Now the Day One and Two CONUS Forecasts

60 Hour Forecast Animation

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

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

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

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

When I look at this Day 7 forecast, we see the Hawaiian High with surface central pressure of 1032 hPa. There is also an Aleutian Low with surface central pressure of 1000 hPa. We can locate the Bermuda High with surface central pressure of 1024 hPa. And there is a large Arctic High with surface central pressure of 1020 hPa. The Four Corners High shows here as an Inland High with surface central pressure of 1020 hPa. The exact location and shape of the Four Corners High will be critical. Notice the southwest to northeast orientation and that it is elongated. We will discuss this more later. You can see the Lows circulating around and through that High.

I provided this write up that provides a simple explanation on the importance of semipermanent Highs and Lows and another link that discussed possible changes in the patterns of these highs and lows which could be related to a Climate Shift (cycle) in the Pacific or Global Warming. Remember this is a forecast for Day 7. It is not the current situation.

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

From left to right and then down, Days 3 and 4 top row, Days 5 and 6 second row and Day 7 to the right. These are small images but you can if you want click on them and get larger images but even with the small images you can trace the evolution of the pattern. The graphics update but my commentary below does not so it is just a guide for how to read these graphics. You can track the Four Corners High in this set of graphics.
Things to look for in general are the position and strength of the Aleutian Low, the Hawaiian High and any troughs especially if they extend far to the south and are over water.

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

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

Current	Day 5
Right now it is primarily zonal but it becomes meridional by Day 5. It is useful to look at the little arrows as they will indicate the potential for movement of subtropical air into CONUS. Day 5 looks a lot different than Day 0.

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.

We have two graphics showing different forecasts and we had that last week also. Part of the explanation is that one is a surface forecast and the other is a mid latitude forecast.

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

Day 3 Above, 6 Below	Day 4 Above,7 Below	Day 5 Above.

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

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

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

First – Temperature

6 – 10 Day Temperature Outlook issued today (Note the NOAA Level of Confidence in the Forecast Released on August 6, 2018 was 4 out of 5

8 – 14 Day Temperature Outlook issued today (Note the NOAA Level of Confidence in the Forecast Released on August 6, 2018 was 2 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 August 6, 2018 was 4 out of 5)

8 – 14 Day Precipitation Outlook Issued Today (Note the NOAA Level of Confidence in the Forecast Released on August 6, 2018 was 2 out of 5)

Looking further out.

Here is the 6 – 14 Day NOAA discussion released today August 6 followed by the discussion that accompanied the Week 3 – 4 Forecast which was released on August 3, 2018.

6-10 DAY OUTLOOK FOR AUG 12 – 16 2018

TODAY’S ENSEMBLE MEAN SOLUTIONS ARE IN GOOD AGREEMENT ON THE OVERALL 500-HPA FLOW PATTERN OVER THE FORECAST DOMAIN DURING THE 6-10 DAY PERIOD. THE MAIN LONG WAVE TROUGHS PREDICTED DURING THIS PERIOD INCLUDE A POSITIVELY-TILTED TROUGH FROM NORTHERN ALASKA SOUTHWESTWARD ACROSS THE BERING SEA, A TROUGH NEAR THE WEST COAST OF THE CONUS, AND A WEAK TROUGH CENTERED NEAR OR OVER THE OHIO VALLEY. THE 0Z CANADIAN ENSEMBLE MEAN HAS ONLY THE SLIGHTEST HINT OF THIS LAST FEATURE. MID-LEVEL RIDGES ARE FORECAST OVER THE GULF OF ALASKA AND THE WEST-CENTRAL CONUS. THE 0Z OPERATIONAL ECMWF PREDICTS THESE SAME LONG WAVE CIRCULATION FEATURES, BUT MORE AMPLIFIED. THE 0Z AND 6Z OPERATIONAL GFS MODEL RUNS DIFFER FROM ALL OTHER RUNS PRIMARILY IN THAT THEY FORECAST A DEEP TROUGH OVER WEST-CENTRAL CANADA WHICH PROPAGATES ENERGY SOUTHEASTWARD TOWARDS THE EASTERN CONUS, RESULTING IN A SIGNIFICANT TROUGH THERE.

ABOVE NORMAL TEMPERATURES ARE FAVORED FOR MOST OF THE NORTHERN CONUS, THE EAST COAST AND GULF COAST, CALIFORNIA, NEVADA, AND UTAH. ABOVE NORMAL TEMPERATURES ARE ALSO FAVORED FOR EXTREME WESTERN ALASKA, AND THE SOUTHERN HALF OF THE PANHANDLE. BELOW NORMAL TEMPERATURES ARE FAVORED FOR NEARLY ALL OF THE REMAINDER OF ALASKA, A SMALL PORTION OF THE NORTHERN INTERMOUNTAIN REGION, AND FROM SOUTHEASTERN ARIZONA AND MOST OF NEW MEXICO EASTWARD ACROSS INTERIOR PORTIONS OF THE SOUTHERN PLAINS, INTERIOR PORTIONS OF THE LOWER MISSISSIPPI VALLEY, AND PORTIONS OF TENNESSEE AND ALABAMA. THESE PREDICTED REGIONS OF ABOVE  AND BELOW NORMAL TEMPERATURES ARE BASED ON THE AUTO TEMPERATURE AND TEMPERATURE CONSOLIDATION TOOLS, AND ON THE REFORECAST GEFS AND ECMWF TEMPERATURE TOOLS.

ABOVE NORMAL PRECIPITATION IS FAVORED OVER ALL BUT FAR NORTHWESTERN ALASKA, AND FROM THE CENTRAL AND SOUTHERN INTERMOUNTAIN REGION NORTHEASTWARD TO MINNESOTA,  AND EASTWARD ACROSS THE SOUTHERN PLAINS, AND A LARGE PORTION OF THE EASTERN CONUS. BELOW NORMAL PRECIPITATION IS FAVORED OVER PORTIONS OF THE NORTHEAST CONUS, AND EXTREME NORTHWESTERN PARTS OF ALASKA. THESE PREDICTED REGIONS OF ABOVE AND BELOW NORMAL PRECIPITATION ARE BASED ON THE AUTO PRECIPITATION AND PRECIPITATION CONSOLIDATION TOOLS, AND ON THE REFORECAST GEFS AND ECMWF PRECIPITATION TOOLS.

FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: ABOVE AVERAGE, 4 OUT OF 5, DUE TO GOOD AGREEMENT ON THE PREDICTED 500-HPA HEIGHT PATTERN, BUT OFFSET BY THE EXPECTATION OF FAIRLY MODEST HEIGHT ANOMALY VALUES OVER THE CONUS.  

8-14 DAY OUTLOOK FOR AUG 14 – 20 2018   

TODAY’S ENSEMBLE MEAN SOLUTIONS ARE IN REASONABLE AGREEMENT ON THE OVERALL 500-HPA FLOW PATTERN OVER THE FORECAST DOMAIN DURING THE WEEK-2 PERIOD. 0Z CANADIAN, GFS, AND ECMWF ENSEMBLE MEANS PREDICT A TROUGH NEAR THE WEST COAST, AND QUASI-ZONAL FLOW DOWNSTREAM OVER THE CONUS. THE 6Z GFS ENSEMBLE MEAN DEPICTS A SLIGHTLY MORE AMPLIFIED TROUGH-RIDGE-TROUGH PATTERN OVER THE CONUS AND ADJACENT OCEANIC AREAS. ANOMALY CORRELATION SCORES FOR THE PAST 60-DAYS INDICATE THE FOLLOWING RANKING, BEGINNING WITH THE BEST-SCORING MODEL DURING THIS PERIOD: THE 0Z ECMWF ENSEMBLE MEAN, THE 0Z AND 6Z GEFS, THE 0Z CANADIAN ENSEMBLE MEAN, AND THE 0Z AND 6Z OPERATIONAL GFS RUNS.

THE PREDICTED WEEK-2 TEMPERATURE PATTERN IS SIMILAR TO THAT EXPECTED FOR THE  6-10 DAY PERIOD (ESPECIALLY IN ALASKA), BUT WITH SLIGHT EASTWARD PROGRESSION OF  TEMPERATURE ANOMALIES OVER THE NORTHERN CONUS.  

THE PREDICTED WEEK-2 PRECIPITATION PATTERN IS SIMILAR TO THAT EXPECTED FOR THE 6-10 DAY PERIOD FOR ALASKA, BUT OVER THE CONUS THERE ARE DIFFERENCES. THIS IS  DUE IN PART TO A WEAK HEIGHT ANOMALY PATTERN ANTICIPATED ONCE AGAIN ACROSS THE  CONUS FOR MOST AREAS. THE EXPECTED WESTWARD EXPANSION OF THE BERMUDA HIGH  ACROSS THE SOUTHEAST AND GULF OF MEXICO IS LIKELY TO STEER GULF MOISTURE  NORTHWARD ACROSS THE SOUTHERN PLAINS BEFORE IT RECURVES NORTHEASTWARD TOWARDS  THE GREAT LAKES REGION. THIS MAY ALLOW FOR REDUCED PRECIPITATION AMOUNTS ACROSS  PORTIONS OF THE GULF COAST, THOUGH THE TILT IN THE ODDS IS CONSIDERED SLIGHT. 

AS A TROUGH MOVES ACROSS THE NORTHWEST CONUS, THERE IS A SLIGHT TILT IN THE ODDS OF BELOW NORMAL PRECIPITATION. MONSOON REGION RAINFALL IS FORECAST TO BE  ENHANCED DURING WEEK-2, DUE TO ELEVATED TROPICAL CYCLONE ACTIVITY OVER THE EASTERN PACIFIC, AND THE POSSIBILITY OF A GULF SURGE STREAMING INTO THE SOUTHWEST.

FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD: BELOW AVERAGE, 2 OUT OF 5, DUE TO PREDICTED WEAK HEIGHT ANOMALIES AND DIFFERENCES AMONG TEMPERATURE AND  PRECIPITATION GUIDANCE.

THE NEXT SET OF LONG-LEAD MONTHLY AND SEASONAL OUTLOOKS WILL BE RELEASED ON AUGUST 16.

Week 3-4 Forecast Discussion Valid Sat Aug 18 2018-Fri Aug 31 2018

ENSO-neutral conditions are present across the equatorial Pacific Ocean, although the CPC ENSO forecast is for a 65% chance of El Nino formation during Fall of this year. The RMM depiction of the MJO is weak and forecast to stay weak for a while, however it is possible that tropical convection developing over the Indian Ocean will turn into a new MJO event during the next couple of weeks. Since the signal is currently weak and there’s no clear signal of re-emergence, the MJO doesn’t play a strong role in this forecast.

The Week 3-4 temperature and precipitation outlooks rely primarily on dynamical model forecasts from the NCEP CFS, the ECMWF, and the JMA operational ensemble prediction systems, as well as forecasts from the Subseasonal Experiment (SubX), a multi-model ensemble (MME) of experimental ensemble prediction systems.

Dynamical model guidance from the CFS and ECMWF is broadly consistent, depicting weak positive height anomalies over Alaska and the western half of the CONUS. Both models depict ridging over the Northeast, but the ridge in the CFS expands further south and west than in the ECMWF. The temperature forecast issued today includes a 50-60% chance of above normal temperatures over Alaska and the Pacific Northwest as well as the Northeast, which is consistent with the aforementioned model guidance.

Model guidance also suggests that tropical activity in the Atlantic will increase during week-4, which is likely to lead to enhanced cloud cover and rainfall over the Southeast. There is a 50-60% chance of both above normal precipitation and below normal temperatures over the Southeast during the forecast period.

Tropical cyclone activity in the East Pacific has been high recently and is expected to remain high through the forecast period. Model guidance strongly favors enhanced rainfall in the Southwest, especially over the Four Corners Region where a 60% chance forecast of above normal precipitation has been posted. Tropical wave activity and the potential re-emergence of the MJO also support this forecast.

SSTs around the west coast of Alaska are anomalously warm and dynamical guidance agrees on weak ridging over the Aleutian Islands during Week-3 that will shift north and strengthen during Week-4. Meanwhile, height anomalies over eastern Alaska should stay fairly close to normal. A 50-60% chance of above normal temperatures has been posted over Alaska. A 50-60% chance of above normal precipitation is forecast over western Alaska and a 50-60% chance of below normal precipitation is forecast over the northeastern part of the state.

Sea surface temperatures in the vicinity of Hawaii remain mostly above normal, except for the most northwestern islands. The majority of dynamical model guidance depicts enhanced chances for above-normal temperatures, especially over the southeastern islands. Dynamical model precipitation forecasts are mixed across the island chain, but generally favor above-median precipitation for eastern points.

Some Indices of Possible Interest:

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.

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.

Now we look at two models that I find very helpful. On the graphic on the left, 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.

NCEP-NEFS Dynamic Model	Statistical Models

Analogs to the 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.

(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.

* This storm may have been similar to what JAMSTEC has been predicting namely starting as a Modoki and changing to a Traditional El Nino in the second year. But we do not see a two-year event happening.

The spread among the analogs from July 16 to Aug 20 is 35 days which is a bit wide. 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 August 3. These analogs are centered on 3 days and 4 days ago (August 2 or August 3). So the analogs could be considered to be 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 Neutral Analogs, three La Nina analogs and two El Nino Analogs. The pre-forecast analogs this week favor McCabe D and disfavor McCabe Condition B. The cheat sheet below the McCabe graphics summarizes McCabe B  and D and the favoring of one and the disfavoring of the other result in a pattern that is not consistent with the forecast. But the McCabe analysis may be more useful in the winter and NOAA is not very confident about Week-2.

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

In color	Black and White same graphics

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

Historical Anomaly Analysis

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

A Useful Read

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

Recent CONUS Weather

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

And the 30 Days ending July 21, 2018	And the 30 Days ending July 26, 2018
Notice the Monsoon was mostly an Arizona event. We see a diagonal dry swath from Mexico to the Great Lakes. The Temperature Pattern has not changed very much.	You can see some changes in the precipitation pattern especially in the Northwest and Southeast and the temperature pattern is very different with a cool down east and as slight increase in warm intensity west.
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 into Mid-August and we should be starting to return from the set of positions shown below for July back slowly to the Winter Pattern. For CONUS, the seasonal repositioning of the Bermuda High and the Pacific High are very significant.

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

Temperature.	Precipitation.
Not a lot of surprises here.  But Equatorial Africa is again very warm. So is India	The pattern is changing. We no longer see the well defined dry belt. The wet belt is what stands out.

Additional Maps showing different weather variables can be found here.

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

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

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

Looking Out a Few Months

Here is the precipitation forecast from Queensland Australia:

It is kind of amazing that you can make a worldwide forecast based on just one parameter the SOI and changes in the SOI. This graphic has been updated and now is in line with the actual SOI. Of interest is wet western CONUS and the two belts of wet in the mid Asian Continent and dry for Equatorial Africa and the Middle East.

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

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

• Surface temperature anomalies (weather develops from the ocean surface and
• The changes in the temperature anomalies since that may provide clues as to how the surface anomalies will change based on the current trend of changes. This is not that easy to do since the oceans are deep, there are many currents, winds have an impact etc. Two ways that are available to use are to look at the change in the situation today compared to the average over a period of time and NOAA also produces a graphic of monthly changes. I use both. The first set of graphics is simply looking at the average compared to today and that is below.

Three Month Average Anomaly	Current Anomaly
By this point La Nina is gone	Traces of El Nino but the Indo-Pacific Warm Pool is cool. I am not convinced an El Nino will materialize.

And when we look in more detail at the current Sea Surface anomalies below, we see a lot of them not just along the Equator related to ENSO. Currently this graphic is not updating so the discussion remains as per last week. If NOAA updates this graphic in the next day or so I might update the discussion. 

First the categorization of the current daily SST anomalies.
Mediterranean, Black Sea and Caspian Sea	Western Pacific	West of North America	North and East of North America	North Atlantic
The  Black Sea and Caspian Sea are warm. The Mediterranean is warm. The Gulf of Aden and the Arabian Sea are  cool	Slightly cool east of  southern Asia Warm east of Japan and between Japan and Mainland. Warm swath from Japan to south of Alaska	Warm Bristol Bay and Chukchi Seas Cool offshore of British Columbia Slightly warm for Baja and off Mexico	Hudson Bay mixed Great Lakes Warm Cool Labrador Sea and south of Greenland Warm offshore of Nova Scotia	Scandinavia warm
Equator	Looks like El Nino but barely. May be closer to Neutral
Africa	West of Australia	North, South and East of Australia	West of South America	East of South America
Cool off of Northern Africa Slightly warm south of Africa	Cool	Cool to the northwest but closer to Maritime Continent Cool to the south and southwest	Cool off 30S	Cool offshore along the Equator Slightly warm off 30S 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.

Here it gets a little tricky as for this graphic red does not mean a warm anomaly but a warming of the anomaly which could mean more warm or less cool and blue does not mean cool but more cool or less warm.
Mediterranean, Black Sea and Caspian Sea	Western North Pacific	West of North America	East of North America	North Atlantic
Eastern Mediterranean and Black Sea mixed. Caspian Sea is cooling. Red Sea is warming	Warming around Japan and south of Kamchatka.	Cooling Bering Straits and Anadyr Warming off shore in a swath towards Asia. Cooling near the coast of British Columbia which then extends out to sea.  Cooling west of Baja and Mexico due to tropical activity   .	Warming Hudson Bay Warming off Nova Scotia Cooling off the U.S. Southeast.	Warming east of British Isles.
Equator	Eastern Pacific showing cooling i.e. a reduction in the El Nino bias.
Africa	West of Australia	North, South and East of Australia	West of South America	East of South America
Warming of southern end of Africa	Cooling Southwest	fairly neutral	fairly neutral	Warming off 40S to 50S

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

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

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

Tropical Activity Possibly Impacting CONUS.

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

Now let us look at the Western Pacific in Motion.

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

In the above graphic, it is difficult to reference the storms to geography. If you are patient and look closely you can see bodies of land under the storms. Mostly I am interested in

1. How much of the tropical activity gets caught up in the westerlies and returns to CONUS and
2. How much of the Asian storms return along the northern route to Alaska and British Columbia.

C. Progress of ENSO

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

Starting with Surface Conditions.

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

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

Location Bar for Nino 3.4 Area Above and Below

My Calculation of the Nino 3.4 Index

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

So as of Monday August 6, in the afternoon working from the August 5 TAO/TRITON report [Although the TAO/TRITON Graphic appears to update once a day, in reality it updates more frequently.], this is what I calculated.

Calculation of Nino 3.4 from TAO/TRITON Graphic

My estimate of the daily Nino 3.4 SST anomaly tonight is lower at +0.2 which is an ENSO Neutral value. NOAA has reported the weekly Nino 3.4 to be +0.1 which is an ENSO Neutral value. Nino 4 is reported to be a little warmer than last week at +0.4. Nino 3 is reported to be cooler at 0.0. Nino 1 + 2 which extends from the Equator south rather than being centered on the Equator is reported much warmer at +0.1. It was up there close to -3.0 at one time so this index has been declining as an anomaly (rising) quite a bit and also fluctuating quite a bit which is not surprising as it is the area most impacted by the Upwelling off the coast. So it is an indication of the interaction between surface water and rising cool water. Thus it is subject to larger changes. I am only showing the currently issued version of the NINO SST Index Table as the prior values are shown in the small graphics on the right with this graphic. The same data in graphic form but going back a couple of more years can be found here.  The full table of values can be found here.

This graphic brings the Nino 3.4 up to date and is easy to read. It may be more reliable than the NOAA readings. And Memorial Day is not a Holiday in Australia.

Here is another way of looking at the TAO/TRITON Graphic. It is a fast way to assess the strength of an ENSO Event and provides a way to track it.  

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

The next graphic overlaps with the subsequent topic but I will show it here.

The discussion in this slide says it better than I could. One might compare the current reading to Oct/Nov 2017. The anomaly had returned to zero then reversed for a month and then returned to zero and now has gone positive. It now seems to be declining a bit.

Side by side comparison can be useful

Comparison Week Probably Third Week of December 2017	Current Week

Sea Surface Temperature and Anomalies

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

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

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

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

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

.

Anomalies are strange. You can not really tell for sure if the blue area is colder or warmer than the water above or below. All you know is that it is cooler than usual for this time of the year. A later graphic will provide more information. Aside from buoyancy the currents tend to bring water from that depth up to the surface mostly farther east. These currents are very complicated and made even more so by the uneven nature of the ocean floor. So the exact pattern of where this warm water will erupt is beyond my level of understanding. But it will erupt to the surface in multiple different places.

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

We now have warm water with a maximum anomaly of +3C from 140W to 110W with additional warm water, but not quite as warm, extending west to Indonesia.

The 28C Isotherm is now at 170W, the 27C Isotherm is at 150W, the 25C Isotherm is now at 120W. The 20C Isotherm is now closer to reaching the surface near the coast. And the 23C Isotherm has reached the surface aat 110W as the Kelvin Wave has pretty much played out near the coast of Ecuador.

Tracking the change.

And now let us look at the atmosphere.

This graphic shows the Low-Level Wind Anomalies near the Equator. The 850 hPa level is above the surface but close to the surface.	And now the Outgoing Long-wave Radiation (OLR) Anomalies which tell us where convection has been taking place. The bottom of a Hovmoeller graphic shows the most recent readings.
Reds and browns would be suppressed easterlies or enhanced westerlies and are typical of El Nino. It looks pretty neutral.	We see the change in the pattern of suppressed OLR as the La Nina declines.

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

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

Current SOI Readings

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

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

Forecasting the Evolution of ENSO

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

Here is the most recent update. We expect a new update on August 9, 2018

Forecasts from Other Meteorological Agencies.

Here is the newly issued JAMSTEC Model Forecast.  It suggests a less strong El Nino than their forecast last month.  One can always find the latest JAMSTEC maps by clicking this link. You will find additional maps that I do not general cover in my monthly Update Report.  Remember if you leave this page to visit links provided in this article, you can return by hitting your “Back Arrow”, usually top left corner of your screen just to the left of the URL box.

We now have the short discussion that goes with the above ENSO Forecast.

Prediction from 1st Jul., 2018

ENSO forecast:

The SINTEX-F predicts that a moderate-to-strong El Niño event may start in summer and reach its peak in winter. This El Niño is more or less of Modoki-type and we need to be careful of its impact that may be different from that of the canonical El Niño.

Indian Ocean forecast:

Occurrence of a positive Indian Ocean Dipole is clearly predicted by the SINTEX-F seasonal prediction system; the ensemble mean prediction suggests its evolution from summer and its peak in fall. In accord to the positive IOD evolution, sea level anomalies are expected to be negative (positive) in the eastern (western) tropical Indian Ocean. We may observe co-occurrence of a positive Indian Ocean Dipole and an El Niño/El Niño Modoki-like state in the latter half of 2018; this is as we observed in 1994 (with El Niño Modoki) or 1997 and 2015 (with El Niño).

Regional forecast:

On a seasonal scale, most part of the globe will experience a warmer-than-normal condition in fall, while some parts of eastern Russia, southern U.S.A., northern Brazil, and East Africa will experience a cooler-than-normal condition. In winter, most part of the globe will be in a warmer-than-normal condition, while U.S.A., Argentine, western Europe, and Tibet will experience a relatively cold condition.

As regards to the seasonally averaged rainfall in boreal fall, a wetter-than-normal condition is predicted for most parts of western/northern Canada, southern U.S.A., northern Brazil, East Africa, southern West Africa, and western/northern Europe. In contrast, northwestern/northeastern U.S.A., southern Brazil, eastern Europe, the Far East, northeastern India, northern Southeast Asia, the Philippines, Indonesia and Australia will experience a drier-than-normal condition. In particular, we notice that Indonesia and Australia may be extremely drier than normal, owing to the expected co-occurrence of a positive Indian Ocean Dipole and an El Niño/El Niño Modoki-like state.

In winter, we expect a drier-than-normal condition in U.S.A, Mexico, northern South American Continent, northern/western Australia, northern Mozambique, eastern Tanzania, a western part of southern Africa, western Europe, the Philippines, and Indonesia. On the other hand, eastern U.S.A, eastern Brazil, southeastern Australia, eastern South Africa, southern Mozambique, and central Africa will be wetter-than-normal.

Most part of Japan will experience warmer-than-normal and drier-than-normal conditions in fall as a seasonal average. However, more detailed monthly prediction suggests a rather wet condition in September. In winter, overall Japan will experience warmer-than-normal and drier-than normal conditions.

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

And the ENSO Outlook Discussion Issued on July 31, 2018

El Niño WATCH continues

The El Niño–Southern Oscillation (ENSO) remains neutral. While the central Pacific Ocean has cooled very slightly in the past fortnight, more than half of international climate models predict warming to recommence in the coming weeks, and El Niño likely to develop in spring. Therefore, the Bureau’s ENSO Outlook remains at El Niño WATCH. El Niño WATCH means there is approximately a 50% chance of El Niño forming in 2018; double the normal chance.

Oceanic ENSO indicators remain neutral. The surface of the tropical Pacific Ocean has cooled slightly in the past fortnight but remains warmer than average. Likewise, the water below the surface of the central and eastern tropical Pacific has also cooled recently, but remains warmer than average. Atmospheric indicators such as the trade winds and the Southern Oscillation Index (SOI), remain neutral.

Most international climate models surveyed by the Bureau indicate warming of the tropical Pacific is likely to recommence in the coming weeks. Five of eight models indicate El Niño levels will be reached in the southern hemisphere spring, while a sixth model reaches El Niño levels in December.

During El Niño, winter-spring rainfall in eastern Australian is typically below average while daytime temperatures are typically warmer than average in the south.

Indian Ocean IOD (It updates every two weeks)

This graphic shows a collection of models used to forecast the NINO 3.4 Index

Indian Ocean Dipole Outlook  Discussion Issued July 31, 2018

The Indian Ocean Dipole (IOD) remains neutral. The weekly index value to 29 July was −0.35 °C. Three of six international climate models indicate a positive IOD event may develop, with a fourth model close to meeting thresholds. A positive IOD event typically reduces winter–spring rainfall in central and southern Australia, and can exacerbate any El Niño driven rainfall deficiencies.

It is useful to understand where and how the IOD is measured.

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

D. Putting it all Together.

At this time, La Nina Conditions along the Equator have come to an end and we are solidly into ENSO Neutral and possibly entering El Nino Conditions. But the drivers of a transition to El Nino are not solidly in place.

Forecasting Beyond Five Years.

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

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

The odds of a climate shift for the Pacific taking place has significantly increased. It may be in progress. The AMO is pretty much neutral at this point so it may need to become a bit more negative for the “McCabe A” pattern to become established. Our assessment is that the standard time for Climate Shifts in the Pacific is likely to prevail and it most likely will be a gradual process with a speed up in less than five years but more than two years. The next El Nino may be the trigger. 

E. Relevant Recent Articles and Reports

Weather in the News  

Nothing to Report

Weather Research in the News

Nothing to Report

Global Warming in the News

Nothing to Report

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

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

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

2. Medium Frequency Cycles such as ENSO and IOD

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

4. Computer Models and Methodologies

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

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

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

1. Introduction

2. Climate Impacts of Global Warming

3. Economic Impacts of Global Warming

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

H. Useful Background Information

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

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

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

Click for Source

Interaction between the MJO and ENSO

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

History of ENSO Events as measured by the ONI

The new SON reading of +0.1 is clearly an ENSO Neutral reading. The full history of the ONI readings can be found here. The MEI index readings can be found here.

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

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

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

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

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

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

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

MJO (Madden Julian Oscillation)

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. Here is a good description of the MJO.

This is the source of the analysis of the impact of the MJO on CONUS. “A composite study of the MJO influence on the surface air temperature and precipitation over the Continental United States Shuntai Zhou • Michelle L’Heureux • Scott Weaver • Arun Kumar”

The below shows the various phases of the MJO. Where the above average convection (green) is found is described by one of 8 phases shown below. The dry part of the pattern is shown in brown and is called the Inactive or dry part of the MJO.

The below is the summary analysis for precipitation in the July to September Season. The full data set for all seasons can be found here for Temperature and here for Precipitation. My analysis of that data was that there is not much difference between the level of significance of the temperature and precipitation in the JAS three-month period.