August 13, 2018 Weather and Climate Report – Northern Exposure

Written by Sig Silber

It looks like the more or less stagnant current pattern is going to shift to the east at least for a short time.The Aleutian Low, Arctic High, and Hudson Bay Low all figure in importantly in the forecast as well as the inverted Trough entering CONUS from Mexico.  It is almost as if Fall is approaching early – But it may be the El Nino.

Please share this article – Go to very top of page, right hand side for social media buttons.

Here is the forecast.

This has been the recent pattern

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.	The Mid-Central to Great Lakes Trough is the dominant feature.		↑ ←  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.	A slow eastern drift in the pattern.		↑ ←  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 exactly as drawn up.

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 still more activity in Mexico than CONUS. Also we see cold air triggering convection.

Tonight, Monday August 13, 2018, as I am looking at the above graphic, the recent pattern continues. But more moisture is entering CONUS.

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 1024 hPa. There is also an Aleutian Low centered more over by Kamchatka than the Aleutians with surface central pressure of 1000 hPa. To the north, there is an Arctic High with surface central pressure of 1024 hPa. Further east there is a Hudson Bay low with surface central pressure of 1004 hPa and it extends all the way south to Texas. We can locate the Bermuda High but the highest pressure may be further east than what is shown but the surface central pressure is at least 1020 hPa. The Four Corners High shows here as an Inland High extending to the north with surface central pressure of 1020 hPa. The exact location and shape of the Four Corners High will be critical. There is also an inverted trough entering from Mexico with surface central pressure of 1012 hPa.

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.

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 and the week before that 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 13, 2018 was 3 out of 5

8 – 14 Day Temperature Outlook issued today (Note the NOAA Level of Confidence in the Forecast Released on August 13, 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 13, 2018 was 3 out of 5)

8 – 14 Day Precipitation Outlook Issued Today (Note the NOAA Level of Confidence in the Forecast Released on August 13, 2018 was 2 out of 5)

Looking further out.

Here is the 6 – 14 Day NOAA discussion released today August 13 followed by the discussion that accompanied the Week 3 – 4 Forecast which was released on August 10, 2018.

6-10 DAY OUTLOOK FOR AUG 19 – 23 2018

TODAY’S ENSEMBLE MEAN SOLUTIONS ARE IN FAIR AGREEMENT ON THE 500-HPA FLOW PATTERN OVER THE FORECAST DOMAIN. A TROUGH IS FORECAST OVER THE BERING SEA WHILE RIDGING IS PREDICTED DOWNSTREAM OVER MUCH OF CENTRAL AND EASTERN ALASKA. MODELS ARE TRENDING TOWARD A STRONGER RIDGE OVER CENTRAL AND EASTERN ALASKA  WHICH TELECONNECTS WELL WITH PREDICTED CYCLONIC FLOW AND BELOW NORMAL HEIGHTS ACROSS MUCH OF THE NORTH-CENTRAL CONUS. THE 0Z ECMWF ENSEMBLE MEAN FORECASTS A BROAD, FAIRLY AMPLIFIED TROUGH OVER MUCH OF THE EAST-CENTRAL CONUS WHILE THE 0Z GEFS DEPICTS THE TROUGH AXIS FARTHER TO THE WEST OVER THE NORTH-CENTRAL CONUS. A SECOND, WEAKER TROUGH IS FORECAST BY ALL OF THE ENSEMBLE MEANS NEAR THE PACIFIC NORTHWEST. FARTHER TO THE SOUTH, SUBTROPICAL RIDGING IS FORECAST OVER SOUTHWESTERN CONUS AS WELL AS NEAR OR OVER FLORIDA. SUCCESSIVE RUNS OF THE DETERMINISTIC GFS SHOW WIDE DIFFERENCES OVER MUCH OF THE FORECAST DOMAIN. THEREFORE, TODAY’S MANUAL, 500-HPA HEIGHT BLEND FOR THE 6-10 DAY PERIOD IS BASED PRIMARILY ON THE ENSEMBLE MEAN SOLUTIONS FROM THE 0Z ECMWF AND 0Z GEFS ENSEMBLE MEANS.

ABOVE NORMAL TEMPERATURES ARE FAVORED FOR MUCH OF THE WESTERN CONUS AS WELL AS PARTS OF ALASKA IN ASSOCIATION WITH RIDGING AND ABOVE NORMAL HEIGHTS EXTENDING FROM THE EASTERN PACIFIC NORTHWARD TO MUCH OF MAINLAND ALASKA AND THE PANHANDLE.  MODELS HAVE TRENDED TOWARD A STRONGER RIDGE OVER MUCH OF ALASKA, RESULTING IN THE REMOVAL OF ENHANCED PROBABILITIES OF BELOW NORMAL TEMPERATURES ACROSS THE STATE RELATIVE TO YESTERDAY’S OUTLOOK. TELECONNECTIONS FROM THE STRENGTHENING RIDGE OVER THE EASTERN PACIFIC AND ALASKA SUPPORTS INCREASED PROBABILITIES OF BELOW NORMAL TEMPERATURES DOWNSTREAM FOR MUCH OF THE NORTH-CENTRAL CONUS, RESULTING IN A COOLER SOLUTION RELTIVE TO YESTERDAY’S OUTLOOK ACROSS THIS REGION. ABOVE NORMAL TEMPERATURES CONTINUE TO BE FAVORED FARTHER TO THE EAST, AHEAD OF THE MEAN TROUGH AXIS, FOR THE EASTERN SEABOARD AS WELL AS PARTS OF THE GREAT LAKES REGION. ABOVE NORMAL TEMPERATURES ARE ALSO FAVORED FOR PARTS OF SOUTHERN TEXAS IN ASSOCIATION WITH SUBTROPICAL RIDGING. 

ABOVE NORMAL PRECIPITATION IS FAVORED FOR MUCH OF THE CENTRAL AND EASTERN CONUS UNDERNEATH PREDICTED CYCLONIC FLOW. EXCEPTIONS ARE FOR PARTS OF THE FLORIDA PENINSULA AND SOUTHERN TEXAS AS SUBTROPICAL RIDGING SLIGHTLY FAVORS DRIER THAN NORMAL CONDITIONS. RIDGING AND ABOVE NORMAL HEIGHTS LEAD TO ENHANCED PROBABILITIES OF NEAR TO BELOW NORMAL PRECIPITATION FOR MUCH OF THE WESTERN CONUS AND EASTERN ALASKA. CONVERSELY, ABOVE NORMAL PRECIPITATION IS FAVORED FOR MUCH OF WESTERN AND CENTRAL ALASKA AHEAD OF THE MEAN TROUGH OVER THE BERING SEA. 

FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: AVERAGE, 3 OUT OF 5, DUE TO FAIR MODEL AGREEMENT.   

8-14 DAY OUTLOOK FOR AUG 21 – 27 2018 

THE ENSEMBLE MEAN SOLUTIONS FEATURE AN AMPLIFIED PATTERN ACROSS ALASKA WITH A TROUGH PREDICTED OVER THE BERING SEA AND ALEUTIANS AND A STRONG RIDGE PREDICTED ACROSS CENTRAL AND EASTERN ALASKA. ABOVE NORMAL HEIGHTS ASSOCIATED WITH THIS RIDGE EXTEND SOUTHEASTWARD TO THE NORTHWESTERN CONUS. CYCLONIC FLOW AND BELOW NORMAL HEIGHTS CONTINUE TO BE FORECAST DOWNSTREAM OVER THE CENTRAL CONUS WHILE ABOVE NORMAL HEIGHTS REMAIN LIKELY FOR THE NORTHEASTERN CONUS AHEAD OF THE MEAN TROUGH AXIS. THE 500-HPA MANUAL HEIGHT BLEND FOR THE WEEK-2 PERIOD IS WEIGHTED MOST HEAVILY TOWARD THE 0Z ECMWF ENSEMBLE MEAN SOLUTION, BASED ON RECENT SKILL. THE STRONGEST HEIGHT ANOMALIES IN THE RESULTANT MANUAL BLEND IS IN ASSOCIATION WITH THE RIDGE PREDICTED OVER THE EASTERN PACIFIC JUST OFF THE COAST OF THE ALASKA PANHANDLE. TELECONNECTIONS FROM THE ASSOCIATED POSITIVE HEIGHT ANOMALY CENTER WERE USED TO INFORM THE WEEK-2 OUTLOOK.

THE RIDGE OVER THE EASTERN PACIFIC SUPPORTS ENHANCED PROBABILITIES OF NEAR TO ABOVE NORMAL TEMPERATURES FOR THE WESTERN CONUS AND ALASKA. CYCLONIC FLOW AND  BELOW NORMAL HEIGHTS LEAD TO ENHANCED PROBABILTIES OF BELOW NORMAL TEMPERATURES  FOR MUCH OF THE CENTRAL CONUS. FARTHER TO THE EAST, ABOVE NORMAL TEMPERATURES ARE FAVORED ALONG THE EASTERN SEABOARD AND FOR MUCH OF THE GREAT LAKES UNDERNEATH NEAR TO ABOVE NORMAL HEIGHTS. ABOVE NORMAL TEMPERATURES ARE ALSO SLIGHTLY FAVORED ALONG THE GULF COAST DUE TO PREDICTED SUBTROPICAL RIDGING.

ANOMALOUS SOUTHERLY FLOW AHEAD OF A TROUGH OVER THE BERING SEA LEADS TO ENHANCED PROBABILITIES OF ABOVE NORMAL PRECIPITATION FOR SOUTHWESTERN ALASKA. BELOW NORMAL PRECIPITATION IS FAVORED FOR THE NORTHWESTERN CONUS AS WELL AS THE ALASKA PANHANDLE IN ASSOCIATION WITH A STRONG RIDGE PREDICTED JUST OFF THE COAST. ABOVE NORMAL PRECIPITATION IS FAVORED FOR MUCH OF THE EASTERN HALF OF THE CONUS IN ASSOCIATION WITH PREDICTED CYCLONIC FLOW. SUBTROPICAL RIDGING LEADS TO SLIGHTLY INCREASED ODDS OF BELOW NORMAL PRECIPITATION FOR PARTS OF THE FLORIDA PENINSULA AND EXTREME SOUTHERN TEXAS. ABOVE NORMAL PRECIPITATION IS SLIGHTLY FAVORED FOR PARTS OF THE SOUTHWESTERN CONUS CONSISTENT WITH CALIBRATED PRECIPITATION GUIDANCE FROM THE GEFS AND ECMWF ENSEMBLES. 

FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD: SLIGHTLY BELOW AVERAGE, 2 OUT OF 5, DUE TO LARGE DIFFERRENCES AMONG SUCCESSIVE DETERMINISTIC GFS RUNS AS WELL AS LARGE DISAGREEMENTS AMONG THE PRECIPITATION TOOLS ACROSS MUCH OF THE WESTERN CONUS.

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

Week 3-4 Forecast Discussion Valid Sat Aug 25 2018-Fri Sep 07 2018

ENSO-neutral conditions remain over the central Pacific. The latest CPC forecast, released August 9 2018, is for a 60% chance of an El Nino forming between September and November. The MJO remains weak – the ECMWF model forecasts the MJO to stay weak through the next couple of weeks while others, including the GEFS and CFS, suggest that the MJO will re-emerge over the Indian Ocean during Week-2. Since there is considerable uncertainty and there isn’t a strong reason to prefer any one model over another, the MJO was not a significant component in making this Week 3-4 forecast.

There are other important distinctions between the Week 3-4 forecasts from the CFS and ECMWF models. The CFS forecasts a much more amplified upper-level flow over the CONUS during Week-3 than the ECMWF does. This leads to differences in their temperature and precipitation forecasts. Although the models agree on anomalous warmth over Alaska and the Northwest as well as anomalous cold over the Southwest monsoon region, the CFS indicates that the East Coast is more likely to average below normal than the ECMWF. Our statistically calibrated tools reduce the CFS anomalous cold probabilities, suggesting that the model is historically biased towards cold forecasts in that region. However, the CFS is still significantly colder through the Ohio Valley than the ECMWF is.

The final forecast is for probabilities of anomalous warmth between 50-55% in eastern Alaska and 55-60% in western Alaska. The same anomalous ridge is likely to keep Northwest CONUS warmer than normal with probabilities greater than 70% in most of Washington and Oregon. The JMA and SubX models suggest some lingering warmth for the Northeast, so a 50-55% chance of above normal temperatures has been posted for most of New England with a higher 55-60% chance over coastal Massachusetts and all of Maine. Below normal temperatures are likely in the Southwest associated with the enhanced monsoon rains as well as over Florida and parts of the Southeast.

The precipitation forecast aligns well with the temperature forecast. Above normal precipitation is likely in western Alaska due to troughing over the Bering Sea. Above normal precipitation is also likely over the monsoon region of the Southwest, although the models are split about how far east the enhanced precipitation will spread. The current forecast is essentially a blend of all of our dynamical models, and the strongest probabilities are over southeastern Arizona and southwestern New Mexico. There is a threat of atmospheric Kelvin wave activity in the eastern Pacific during the later part of Week-2 (see our GTH product, which was updated on Friday, August 10), which could lead to enhanced probabilities of tropical cyclogenesis in that area. If this forecast holds true then the threat of continuing monsoon rains will be even greater.

Sea surface temperatures in the vicinity of Hawaii remain mostly above normal, except for the most northwestern islands where they are slightly colder than last week. Most 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 parts.

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.

Below is a graphical explanation of the Arctic Oscillation

AO Positive	AO Negative
There are more impacts than shown here but these are important. Basically the AO+ means the Polar Vortex is blocked from leaving its normal locations	Again there are more impacts than shown here. A0- means Low Pressure allows the Polar Vortex to wander south.

* These graphics are from National Geographic Magazine, March 2000; Sources: Doug Martinson, Wieslaw Maslowski, David Thompson, and John M. Wallace

NAO Positive	NAO Negative
Notice the strong Icelandic Low and strong Bermuda High but located east of where it is usually found	Notice the weak Icelandic Low and Bermuda High.
There are many variations on a theme when talking about the NAO.	Some use Lisbon or Gibraltar as the sub-arctic reference point. And there appears to be a low-frequency cycle related to the AMO to some extent. Thus the NAO is a lot more complicated than I am able to show here.  I like this explanation better than the graphics I have shown. It better captures the impact of the changing relative strength of the two control factors in the Atlantic namely the Northern and Southern semi-permanent Highs and Lows.

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.   http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/mjo.shtml

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.

The spread among the analogs from July 25 to Aug 26 is 32 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 10. These analogs are centered on 3 days and 4 days ago (August 9 or August 10). 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 four Neutral Analogs, one La Nina analog and five El Nino Analogs. The pre-forecast analogs this week favor McCabe D and McCabe A. These are about as opposite as can be and reduces confidence in the forecast but the NOAA level of confidence was not high especial for Week-2 of their forecast. There are a lot of transitions taking place so forecasting right now is very difficult.

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 August 4, 2018	And the 30 Days ending August 11, 2018
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.	Not much change in precipitation. The cool anomaly is further 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 late August and we should be returning 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 Equatorial 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 for June and July. Of interest is generally dry CONUS and belt of wet in the mid Asian Continent and belt of dry for Equatorial Africa and the Middle East. Eastern Asia and Australia are wet.

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 Mediterranean and Red Sea are warm. The Gulf of Aden and the Arabian Sea are  slightly cool	Mostly neutral east of  southern Asia Warm between Japan and Mainland. Warm around Kamchatka Warm swath from Japan to south of Alaska	Warm Bristol Bay and Chukchi Seas Slightly warm offshore of British Columbia Warm for Baja and off Mexico	Hudson Bay mixed Great Lakes Warm Cool Davis Strait and south of Greenland Warm offshore of Nova Scotia down to Cape Hatteras	Scandinavia warm
Equator	Looks like Neutral
Africa	West of Australia	North, South and East of Australia	West of South America	East of South America
Cool off of Northern Africa Cool west coast of  Africa south of Equator. Cool southeast of Africa south of Madagascar	Cool	Cool to the northwest Cool to the southwest	Cool off 10S Cool off 30S	Cool 10S in a swath running ESE 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
Western Mediterranean warm Black Sea and Caspian Sea is cooling.	Warming east of Asia but cooling east of Japan. Warmng south of Kamchatka.	Cooling Bering Straits and Anadyr Cooling west of Baja due to tropical activity   .	Warming Hudson Bay Warming off Nova Scotia and  Labrador Sea Cooling off Florida	Warming east of British Isles. Cooling west 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
Cooling offshore of Africa both west, south and east	Cooling	Warming northeast	fairly neutral	Cooling along Equator pretty much all the way to Africa. Warming off 40S

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 13, in the afternoon working from the August 12 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 again at +0.2 which is an ENSO Neutral value. NOAA has reported the weekly Nino 3.4 to also be +0.2 which is an ENSO Neutral value. Nino 4 is reported to be a little warmer than last week at +0.5. Nino 3 is reported to be a little cooler at -0.1. Nino 1 + 2 which extends from the Equator south rather than being centered on the Equator is reported a little cooler 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 at 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

Here is the discussion released with the forecast.

EL NIÑO/SOUTHERN OSCILLATION (ENSO) DIAGNOSTIC DISCUSSION issued by CLIMATE PREDICTION CENTER/NCEP/NWS and the International Research Institute for Climate and Society 9 August 2018 ENSO Alert System Status: El Niño Watch Synopsis: There is ~60% chance of El Niño in the Northern Hemisphere fall 2018 (September-November), increasing to ~70% during winter 2018-19.

               ENSO-neutral continued during July, as indicated by near-average sea surface temperatures (SSTs) across the central and eastern equatorial Pacific at the end of the month (Fig. 1). The latest weekly Niño indices were 0.0°C for the Niño-3 index, +0.1°C for the Niño-3.4 and Niño1+2 indices, and +0.4°C for the Niño-4 index (Fig. 2).  Positive subsurface temperature anomalies (averaged across 180°-100°W) continued over the past month (Fig. 3), and the volume of anomalous warmth extended to the surface in the eastern part of the basin (Fig. 4). Convection remained suppressed near the Date Line and over western Indonesia (Fig. 5).  Low-level winds were near average across most of the equatorial Pacific Ocean, while upper-level wind anomalies were westerly over the eastern Pacific and near the International Date Line. Overall, the oceanic and atmospheric conditions reflected ENSO-neutral. 

            The majority of models in the IRI/CPC plume predict ENSO-neutral to continue during the remainder of the Northern Hemisphere summer 2018, with El Niño most likely thereafter (Fig. 6). Model predictions for El Niño have not wavered despite the recent decrease in the positive SST anomalies in portions of the eastern Pacific. Because of the consistency of forecasts and the expected eventual resurgence in the low-level westerly wind anomalies, the forecasters still favor the onset of El Niño in the coming months.  In summary, there is ~60% chance of El Niño in the Northern Hemisphere fall 2018 (September-November), increasing to ~70% during winter 2018-19 (click CPC/IRI consensus forecast for the chance of each outcome for each 3-month period).

This discussion is a consolidated effort of the National Oceanic and Atmospheric Administration (NOAA), NOAA’s National Weather Service, and their funded institutions. Oceanic and atmospheric conditions are updated weekly on the Climate Prediction Center web site (El Niño/La Niña Current Conditions and Expert Discussions). Forecasts are also updated monthly in the Forecast Forum of CPC’s Climate Diagnostics Bulletin. Additional perspectives and analysis are also available in an ENSO blog. The next ENSO Diagnostics Discussion is scheduled for 13 September 2018. To receive an e-mail notification when the monthly ENSO Diagnostic Discussions are released, please send an e-mail message to: [email protected].

Climate Prediction Center
National Centers for Environmental Prediction
NOAA/National Weather Service
College Park, MD 20740

Sometimes it is useful to compare the new forecast to the old.

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 August 14, 2018

Little change in the tropical Pacific; El Niño remains possible in 2018

The El Niño–Southern Oscillation (ENSO) is currently neutral. While the tropical Pacific Ocean has cooled in the past month, most international climate models forecast warming to resume in the coming weeks, with El Niño development possible in the southern 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.

While the surface of the central to eastern tropical Pacific has cooled over the past month, the water below the surface of the western Pacific is warming again. Although atmospheric indicators such as the Southern Oscillation Index (SOI) remain neutral, tropical cyclones to the north of the equator are acting to increase the warmth in the Pacific by suppressing trade winds.

Most international climate models surveyed by the Bureau predict warming of the tropical Pacific is likely to recommence in the coming weeks. Most models suggest El Niño thresholds are likely to be reached by the end of the year, with the majority suggesting these thresholds could be met by mid to late spring.

El Niño during spring typically means below average rainfall in eastern and northern Australia while daytime temperatures are typically above average over southern Australia.

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 August 14, 2018

The Indian Ocean Dipole (IOD) is currently neutral. The weekly index value to 12 August was +0.16 °C. However, the ocean to the northwest of Australia remains cooler than normal, which is contributing to suppressed rainfall over southern and southeast Australia. Three of six international climate models suggest a short-lived positive IOD event may develop. A positive IOD during spring typically reduces 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.