August 27, 2018 Weather and Climate Report - We are in Transition

We have three transitions going on:

Monsoon Break and subsequent fluctuations as the Monsoon winds down.
Summer to Fall
ENSO Neutral to El Nino (October will be the key month)

If this is not interesting, I can not think of what would be.

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This was one of the last discussions issued with respect to Hurricane Lane and it is pretty interesting.

Tropical Storm Lane Discussion Number 43…Corrected NWS Central Pacific Hurricane Center Honolulu HI EP142018 500 PM HST Fri Aug 24 2018
It took awhile…but once the 35 to 40 kt of shear began to impact the core convection from Lane, the battle ended quickly. A very helpful AMSR2 89 GHz microwave pass over Lane at 2259 UTC showed the circulation center was now mainly comprised of low and mid level clouds completely detached from the remaining pockets of deep convection to the northeast of the center. Even a blend of the Dvorak final-T and current intensity estimates appeared to be too generous, based on the very rapid degradation of the cloud pattern and the WSR-88D radar velocities. Settled on 60 kt for the current intensity.
The new motion estimate is 315/3, but this is a bit uncertain until we have more time to examine this change. The low level circulation of Lane is expected to continue to weaken in the face of continued strong shear, and driven on a westward track by the low level flow. The track guidance is in better agreement than I’ve seen it in awhile. If it survives long enough, the global models show Lane may get a new lease on life as an extratropical low over the Northwest Hawaiian Islands. In any case, we will be happy to get rid of the tropical cyclone in our vicinity. Until then, people should be mindful of additional impacts that can still occur until Lane departs.

It shows how difficult it is to make a forecast. Hawaii mostly dodged a bullet. From reading the discussions, it seems that NOAA sought to prepare Hawaii for the worst by presenting information that in some cases was towards the high end of the range of forecasts re the impact on Hawaii. I did not analyze this carefully but I fully agree with that approach. It is better for people to be more prepared than needed than less prepared than needed and the level of confidence in the exact track and intensity etc of this storm was not high. Hawaii is located with latitude and longitude that seems to provide substantial protection from direct hits by hurricanes. This may make forecasting difficult when a storm approaches the area where Easterlies and Westerlies meet. This article provides some insight into the risks that Hawaii faces and this graphics presents the modern history.

But is it over for this summer?

We may have to set up a separate page to track Miriam as it is confusing when we update the Monday article when a storm is not the feature of that article and is not mentioned in the Landing Graphic or Article Title. For now, updated information can be obtained here. As of today. this looks less threatening than it did on Sunday. We will see how it evolves. And we will update this part of the article at least daily. Sometimes the NOAA graphic updates by itself and sometimes I have to update it so you may need to reload our aritcle to get the latest information and at some point we may add the NOAA discussion. Most likely this threat will fade fairly quickly but we can not be certain of that.

The below shows the transition we discussed a few weeks ago.

It is more of a muted pattern but with the warm anomaly to some extent along the Northern Tier

We reported the JAMSTEC forecast of the Nino 3.4 Index with our Seasonal Outlook Report on August 18 but JAMSTEC had not released their short discussion at that time. It was available last Monday but somehow we did not notice it and publish it so I am doing that now with their Nino 3.4 forecast. The JAMSTEC discussion is always very short and very informative.

It is a less intense El Nino than previously forecast BUT A TWO-YEAR EVENT.

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

Aug. 20, 2018
Prediction from 1st Aug., 2018
ENSO forecast:
The SINTEX-F predicts that a moderate-to-strong El Niño event may start in early fall 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:
As predicted earlier, the positive Indian Ocean Dipole (IOD) has actually emerged in July. The model continues predicting the positive IOD for the boreal 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 southern Africa and Tibet will experience a cooler-than-normal condition. In winter, most part of the globe will be in a warmer-than-normal condition, while southern Alaska, western U.S.A., northern Brazil, Botswana, northern India, Iran, Afghanistan, northeastern Russia, 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 Alaska, western/eastern Canada, central/eastern U.S.A., East Africa, West Africa, and northern Europe. In contrast, northwestern/southeastern U.S.A., eastern Brazil, eastern Europe, South Korea, India, 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 northern South American Continent, Australia, Mozambique, South Africa, southern Angola, Zambia, southeastern Europe facing the Mediterranean Sea, northern Europe, southern India, Southeast Asia, the Philippines, Indonesia and Australia. On the other hand, most parts of U.S.A, northeastern/south Brazil, northern South Africa, Botswana, western Europe, southeastern China will be wetter-than-normal.
Most part of Japan will experience warmer-than-normal condition in fall and winter as a seasonal average.

Some housekeeping: On August 18, 2018 we published our analysis of the NOAA and JAMSTEC Seasonal Outlook and that can be accessed here. We published our now weekly Drought and Agriculture Report on August 23, 2018 and that can be accessed here. Remember if you leave this page to go to links or if you have clicked to enlarge a graphic, in order to get back you need to hit the return arrow usually located on the left of your URL box on the upper left of the screen. Also most of the small graphics are designed to become full size when you click on them. If that does not work, an alternative way to view the larger graphics is to right click and then hit “view image”. That should always work.

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.	Fairly stable pattern		↑ ← 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.

Perhaps a stable pattern but keep in mind that the NOAA level of confidence for Week-2 is fairly low.

↑

← The transition from the 8 -14 day forecast shown above to the week 3/4 shown to the left does not seem feasible.

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

Water Vapor.

This view of the past 24 hours provides a lot of insight as to what is happening.

You can see from this animation that the pattern has shifted to the east a bit.

Tonight, Monday August 27, 2018, as I am looking at the above graphic, the Monsoon looks to be less active.

his 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.

One sees moisture entering CONUS from the Western Gulf of Mexico and Mexico.

And Now the Day One and Two CONUS Forecasts

Day One CONUS Forecast	Day Two CONUS Forecast

These graphics update and can be clicked on to enlarge but my brief comments are only applicable to what I see on Monday night prior to publishing.

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 was no Aleutian Low shown in this forecast yesterday but now it is there and weak at 1008 hPa. To the north, there is an Arctic Low with surface central pressure of 996 hPa. Further east, over Greenland there is a High with surface central pressure of 1016 hPa. Further south there is a small Great Lakes Low with surface central pressure of 1004 hPa. We can locate the Bermuda High with surface central pressure of 1024 hPa and it is very far north. The Four Corners High is essentially an extension of the Hawaiian High. There is also an inverted trough entering from Mexico with surface central pressure of 1008 hPa. You can see an assortment of tropical cyclones in the Pacific. There is also a Low with surface central pressure of 1012 hPa near the Yucatan. Had not noticed that before. It is probably headed west over Central America to form another Pacific Cyclone…just a guess on my part.

NOAA is having some problems interpreting the pattern. The Bermuda High would normally preclude much precipitation but precipitation is forecast for the Eastern Half of CONUS. The Hawaiian High precludes troughs dropping down from the Gulf of Alaska but some of the models have a high level trough forming off CalIfornia. Seasonal Transitions complicate forecasting.

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.
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 and far north.

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.

What we see for Day 7 is the Four Corners High essentially non-existent. There is also a Western Trough.

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.

Surface Air Pressure	Mid Atmosphere Air Pressure

These graphics are produced by the same part of NOAA and in some cases by the same person (the author changes probably with the shifts as these graphics update frequently). So I do not think they are in error but rather show an atmosphere that is very different at the ground than in mid atmosphere. The mid-atmosphere graphic usually works best for forecasting and the surface forecast works best to describe the sensible weather at that time. Meteorologists look at many different layers of the atmosphere. I provide only a snapshot in my weekly report.

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.

The issue is how far south will the West Coast trough extend.

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

Notice that the Monsoon is almost but not totally turned off for CONUS. There is a large wet area shown.

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 27, 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 27, 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 27, 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 27, 2018 was 2 out of 5)

Looking further out.

We will see how that works out for the various areas suffering from drought.

Here is the 6 – 14 Day NOAA discussion released today August 27 followed by the discussion that accompanied the Week 3 – 4 Forecast which was released on August 24, 2018.

6-10 DAY OUTLOOK FOR SEP 02 – 06 2018
TODAY’S ENSEMBLE MEAN SOLUTIONS ARE IN GOOD AGREEMENT ON THE 500-HPA FLOW PATTERN OVER THE FORECAST DOMAIN DURING THE 6-10 DAY PERIOD. THE MANUAL BLEND SHOWS TROUGHS OVER THE BERING SEA AND WESTERN NORTH AMERICA FROM EASTERN ALASKA TO THE WEST COAST OF THE CONUS. DOWNSTREAM, A RIDGE IS PREDICTED OVER THE EASTERN CONUS. ABOVE NORMAL HEIGHTS ARE PREDICTED OVER THE EASTERN CONUS AND BELOW NORMAL HEIGHTS ARE FORECAST OVER MUCH OF THE WESTERN CONUS.
A FORECAST TROUGH OVER EASTERN ALASKA AND THE WESTERN CONUS INCREASES THE LIKELIHOOD OF BELOW NORMAL TEMPERATURES FOR MUCH OF ALASKA AND PARTS OF NORTHWEST. PREDICTED ABOVE NORMAL 500-HPA HEIGHTS OVER THE EASTERN CONUS FAVOR ABOVE NORMAL TEMPERATURES OVER MUCH OF THE CENTRAL AND EASTERN CONUS. ABOVE NORMAL TEMPERATURES ARE FAVORED FOR THE SOUTHWESTERN CONUS AHEAD OF A TROUGH PREDICTED OFF THE COAST.
EXPECTED FRONTAL ACTIVITY FAVORS ABOVE NORMAL PRECIPITATION OVER THE EASTERN CONUS. MOST DYNAMICAL MODELS FAVOR BELOW NORMAL PRECIPITATION OVER PARTS OF NORTHWEST. ABOVE NORMAL PRECIPITATION PROBABILITIES ARE ENHANCED IN THE ARIZONA AND NEW MEXICO MONSOON REGION, DUE TO THE LOW-LEVEL SOUTHERLY FLOW THERE. ABOVE NORMAL PRECIPITATION IS FAVORED OVER THE WESTERN GULF COAST REGION, CONSISTENT WITH CALIBRATED PRECIPITATION FROM THE GFS AND ECMWF ENSEMBLE FORECASTS. ABOVE AVERAGE STORM SYSTEM ACTIVITY INCREASES CHANCES OF ABOVE NORMAL PRECIPITATION FOR MUCH OF ALASKA, EXCEPT FOR THE SOUTH COAST AND THE ALASKA PANHANDLE.
FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: ABOVE AVERAGE, 4 OUT OF 5, DUE TO FAIRLY GOOD AGREEMENT AMONG THE MODELS AND TOOLS.
8-14 DAY OUTLOOK FOR SEP 04 – 10 2018
DURING THE WEEK-2 PERIOD, THE 500-HPA HEIGHT PATTERN OVER THE FORECAST DOMAIN iS EXPECTED TO BE SIMILAR TO THE 6-10 DAY PERIOD. TROUGHING IS PREDICTED OVER WESTERN ALASKA AND THE WESTERN CONUS, WHILE RIDGING IS EXPECTED OVER THE EASTERN CONUS.
BELOW NORMAL TEMPERATURES ARE MOST LIKELY FOR ALASKA EXCEPT THE ALASKA PANHANDLE AND PARTS OF WESTERN MAINLAND ALASKA CONSISTENT WITH DYNAMICAL FORECAST TOOLS. PREDICTED ABOVE NORMAL 500-HPA HEIGHTS FAVOR ABOVE NORMAL TEMPERATURES OVER THE CENTRAL AND EASTERN CONUS IN ASSOCIATION WITH THE ABOVE NORMAL HEIGHTS THERE. BELOW NORMAL TEMPERATURES ARE MOST LIKELY FOR THE NORTHERN ROCKIES AND THE NORTHERN HIGH PLAINS RELATED TO POTENTIAL COLD FRONT PASSAGE, WHILE ABOVE NORMAL TEMPERATURES ARE MOST LIKELY FOR THE SOUTHWESTERN CONUS AHEAD OF THE TROUGHING OFF THE COAST.
DURING THE WEEK-2 PERIOD, STORM SYSTEM ACTIVITY IS EXPECTED TO CONTINUE OVER ALASKA, FAVORING ABOVE NORMAL PRECIPITATION FOR MUCH OF THE STATE, EXCEPT THE ALASKA PANHANDLE, WHERE NEAR TO BELOW NORMAL PRECIPITATION IS FAVORED. ABOVE NORMAL PRECIPITATION IS FAVORED OVER THE CENTRAL AND EASTERN CONUS, HOWEVER THE PROBABILITIES ARE LOW. BELOW NORMAL PRECIPITATION IS FAVORED OVER THE NORTHWESTERN CONUS, CONSISTENT WITH DYNAMICAL FORECAST TOOLS. ABOVE NORMAL PRECIPITATION IS FAVORED OVER ARIZONA AND NEW MEXICO AND ADJACENT AREAS, DUE TO FORECAST ENHANCED TROPICAL MOISTURE FLOW.
FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD: BELOW AVERAGE, 2 OUT OF 5, DUE TO ONLY FAIR AGREEMENT AMONG THE MODELS AND TOOLS, AND WEAK PRECIPITATION SIGNALS OVER THE CONUS.
THE NEXT SET OF LONG-LEAD MONTHLY AND SEASONAL OUTLOOKS WILL BE RELEASED ON SEPTEMBER 20.
Week 3-4 Forecast Discussion Valid Sat Sep 08 2018-Fri Sep 21 2018
ENSO-neutral conditions remain present across the equatorial Pacific, though there are some recent indications that ocean-atmosphere coupling may accelerate over the coming weeks. The MJO has been weak of late as the low-frequency state becomes better established. Neither ENSO nor the MJO is expected to play a leading role in the Week 3-4 period. Long-term trends and retrogression of the forecast medium-range pattern are the leading physical drivers behind the current outlook.
Dynamical models are in good agreement on the gradual westward shift of the mean 500-hPa height pattern over the next three to four weeks. Anomalous ridging is forecast to be centered over the north-central CONUS during the period, with associated above-normal temperatures centered in the interior West stretching across the northern tier of the CONUS. A weakness in the above-normal temperatures is depicted across parts of the central US, where model guidance is mixed and long-term trends are minimal. This weakness extends into the Southwest where above-median rainfall is more likely. Over Alaska, a cooler-than-trend pattern is forecast upstream of the anomalous 500-hPa trough. The combination of statistical and dynamical guidance suggests that below-normal temperatures are most likely over the northeastern part of the state, with above-normal temperatures more likely only over the southern and western coastal regions.
The Week 3-4 precipitation outlook evolves from the current Week-2 outlook based on the expected retrogression of the upper-level circulation. A large swath favoring below-median rainfall is depicted from the Great Lakes to the southern Plains, near and southeast of the forecast anomalous ridge position. A weakly enhanced cyclonic circulation is forecast near Florida that tilts the odds toward above-median rainfall; this signal is particularly strong is the current SubX guidance. The southwest monsoon is forecast to intensify during the forecast period as above-normal temperatures become more likely over the interior West. Areas favoring above- and below-median precipitation over Alaska are due to the forecast trough axis over the Gulf of Alaska.
Sea surface temperatures in the vicinity of Hawaii remain slightly above-normal, and the bulk of dynamical model guidance, including the experimental SubX models, depict enhanced chances for above-normal temperatures. This is also consistent with the low-frequency state and the seasonal forecast. Dynamical model precipitation forecasts generally favor above-normal rainfall over Hawaiian Islands, which is also consistent with the expected low-frequency pattern.

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.

Looks like the AO will tend to be slightly Positive initially and then become Neutral and then Negative.

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

Here is another set of graphics.

Left: Effects of the Positive Phase of the Arctic Oscillation. Right:Effects of the Negative Phase of the Arctic Oscillation. —Credit: J. Wallace, University of Washington.

I think the two sets of graphics are not incompatible and some may find one more meaningful than the other.

It is not a surprise when the AO and NAO are highly correlated. They both have to do with Polar versus Sub-Polar pressure gradients but the AO is over CONUS and the NAO is over the Atlantic. But the impacts of the NAO are felt on both sides of the Atlantic.

It looks like the AO and NAO are reasonably correlated at this time.

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.

But it gets even more complicated. With a Negative NAO the position of the pattern more east than west or vice versa changes the impacts.

The two graphics on the right are easier to interpret. They show that the variations in the position of the NAO changes the impacts as shown.

The Phase of the PNA pattern is Negative but perhaps tending towards Neutral. You can see the impact of the different phases in the schematics below (N.C. State). PNA Positive in on the left and PNA Negative on the right.

PNA Positive PNA Negative

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

The above graphics auto-update daily. The below is from the weekly NOAA MJO Report so it is frozen but comes with interpretation.

The forecast seems indicate the MJO will not have a major impact short term. We can ignore it.

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.

Centered Day	ENSO Phase	PDO	AMO	Other Comments
Aug 29, 1952 (2)	El Nino	–	+
Aug 24, 1962	Neutral	–	–
Aug 26, 1962	Neutral	–	–
Aug 29, 1962	Neutral	–	–
Aug 10, 1985	La Nina	+	–	Tail End
Aug 11, 1985	La Nina	+	–	Tail End
Aug 28, 2000 (2)	La Nina	–	N	Following 97/98 MegaNino
Sep 8, 2007	La Nina	-(t)	+

(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 August 10 to September 8 is 29 days which is tighter than last week. 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 24. These analogs are centered on 3 days and 4 days ago (August 23 or August 24). 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 La Nina Analogs, two El Nino Analogs and three La Nina analogs. The pre-forecast analogs this week pretty much exclude McCabe C which is associated with Northern Tier and Atlantic Drought. Since they are not in the forecast the analogs add confidence to the NOAA forecast. The NOAA forecast is not highly confident for Week-2. The over-representation of analogs associated with La Nina is strange. But most of the analogs are associated with PDO- so that then is not all that surprising. 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

McCabe Condition	Main Characteristics
A	Very Little Drought. Southern Tier and Northern Tier from Dakotas East Wet. Some drought on East Coast.
B	More wet than dry but Great Plains and Northeast are dry.
C	Northern Tier and Mid-Atlantic Drought
D	Southwest Drought extending to the North and also the Great Lakes. This is the most drought-prone combination of Ocean Phases.

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 18, 2018	And the 30 Days ending August 25, 2018

The precipitation pattern is more positive for the Southern Plains. The temperature pattern has not changed very much.	Not a lot of change but some relief from the drought is noted
Remember, these maps are a 30 average so the most distant seven days are removed and the most recent seven days are added.

B. Beyond Alaska and CONUS Let’s Look at the World which of course also includes Alaska and CONUS

It is Useful to Understand the Semipermanent Pattern that Control our Weather and Consider how These Change from Winter to Summer. These two graphics (click on each one to enlarge) are from a much larger set available from the Weather Channel. They highlight the position of the Bermuda High which they are calling the Azores High in the January graphic and is often called NASH and it has a very big impact on CONUS Southeast weather and also the Southwest. You also see the north/south migration of the Pacific High which also has many names and which is extremely important for CONUS weather and it also shows the change of location of the ITCZ which I think is key to understanding the Indian Monsoon. A lot of things become much clearer when you understand these semi-permanent features some of which have cycles within the year, longer period cycles and may be impacted by Global Warming. We are now moving into Septemberand 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)

Equatorial Africa is really hot.

And now precipitation

It is still the general pattern of a wet Equator and dry North Africa extending to the Eastern Asia but not Southern Asia. South of the Equatorial wet belt it is dry. Hawaii is wet!

I have not changed the source but it seems that the links I had before (the images were smaller and in a table) were not updating. We will see if this works better.

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

Temperature	Precipitation

Please remember this graphic updates every six hours so the diurnal pattern can confuse the reader.	Other than the Equator, it looks quite dry. For CONUS it does not agree with the NOAA forecast.

I do not see as much wet as NOAA is forecasting but this is a forecast for one day (Day 6) while the NOAA forecast is for Days 5 -10.

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

Temperature	Precipitation

You can really see that Canada is cool.	You have click on this to read it. There are a lot of extremes dry and wet shown. But CONUS looks dry.

This agrees with the NOAA 8 – 14 Day forecast which is not a surprise. Unfortunately I can not include this many large graphics in my article regularly as they load slowly.

Brazil looks dry. Will they have the soybeans they have promised to China?

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 around Kamchatka Warm blob east of Japan	Warm Chukchi Sea Slightly warm offshore of British Columbia Mixed for Baja	Hudson Bay cool Great Lakes Warm Warm quite a bit south of Greenland and off Newfoundland Warm offshore of Nova Scotia down to Long Island	Scandinavia warm
Equator	Still looks like Neutral

Africa	West of Australia	North, South and East of Australia	West of South America	East of South America
Cool west coast of Africa south of Equator. Cool southeast of Africa south of Madagascar	Cool	Cool to the northwest off shore Cool to the south and southwest	Generally cool La Nina lives	Slightly cool 10S 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 fairly neutral Black Sea and Caspian Sea is cooling.	Cooling west and east of Japan. Warming off Anadyr.	Cooling Bristol Bay. Warming offshore of CONUS Northwest Warming west of Baja .	Cooling Hudson Bay Warming off Nova Scotia and far south of Greenland Slight cooling west of Florida	Significant cooling around British Isles.
Equator	Eastern Pacific showing cooling i.e. a reduction in the El Nino bias except north of the Equator.

Africa	West of Australia	North, South and East of Australia	West of South America	East of South America
Warming west of North Africa. Cooling east of Mozambique	Fairly Neutral	Cooling northwest and southwest	Warming offshore of Ecuador Cooling 30S	Warming north of the Equator stretching to Africa. Cooling 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.

Most Recent Six Months of Index Values	PDO Click for full list	AMO click for full list.	Indian Ocean Dipole (Values read off graph)
October	-0.67	+0.39	-0.3
November	+0.84	+0.40	0.0
December	+0.56	+0.34	-0.1
January	+0.12	+0.23	0.0
February	+0.05	+0.23	+0.2
March	+0.14	+0.17	+0.0
April	+0.53	+0.29	+0.2
May	+0.29	+0.32	+0.2
June	+0.21	+0.31	0.0
July	-0.50	+0.31	0.0
August	-0.62	+0.31	+0.4
September	-0.25	+0.35	+0.2
October	-0.60	+0.44	0.0
November	-0.45	+0.35	0.0
December 2017	-0.13	+0.36	-0.4
January 2018	+0.29	+0.17	-0.1
February	-0.19	+0.06	0.0
March	-0.61	+0.13	-0.1
April	-0.89	+0.06	0.0
May	-0.69	-0.00	-0.1
June	-0.88	-0.01	-0.4
July	-0.23	+0.02	-0.2

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

This graphic updates on Tuesdays and I usually post on Monday which is almost a week later than when this graphic was last updated. So normally Week Two applies at the time I write this article on Monday. Mostly as I review this on August 27 for what is shown as Week Two, the period August 29 to September 4, 2018, we see a dry* southern tip of India and northern Philippines. There is a wet* anomaly just off West Africa perhaps impacting Africa close to the coast and there is both a wet** anomaly and chance of cyclonic activity* off the western coast of Central America.

* 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

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

The current forecast assumes a lot of “1” taking place.

C. Progress of ENSO

This section is organized into four parts.

1. Current and Recent Sea Surface Temperatures (SST)

2. Current and Recent Equatorial Pacific Subsurface Temperatures

3. History of the Nino 3.4 Readings and forecasts from other Meteorological Agencies.

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

1. Current and Recent Sea Surface Temperatures (SST)

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

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.

There is an increasing amount of white. It is ENSO Neutral looking less like a change to ENSO El Nino.

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

We may need KW#4 or even KW#5 to actually have a recorded El Nino. We may see KW#4 on this graphic but not yet flagged by NOAA and there may well be a WWB from a MJO in October. So we are in the early stages here at this point in time.

2. Current and Recent Equatorial Pacific Subsurface Temperatures Let us look in more detail at the Equatorial Water Temperatures.

This graphic provides both a summary perspective and a history (small images on the right).

The most intense warm anomaly east of the Dateline extends from 140W to 110W but does not extend down to even 150 meters. So that is playing out. In the other direction there is another warm anomaly at greater depth which is slowly moving to the east. We look at this again later in another graphic.

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 extending west to Indonesia.

http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/ocean/weeklyenso_clim_81-10/wkteq_xz.gif

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 22C Isotherm has reached the surface at 100W as the Kelvin Wave has pretty much played out near the coast of Ecuador.

The flattening of the Isotherm Pattern is an indication of ENSO Neutral just as the steepening of the pattern indicates La Nina or El Nino depending on where the slope shows the warm or cool pool to be. That flattening has occurred and we have gone to an ENSO Neutral thermocline.

Tracking the change.

Sepember 15, 2017 Subsurface Water Temperatures

Equatorial Ocean Subsurface as of August 21, 2018

I have “frozen” the graphic on the left side above which shows the situation as reported for September 15, 2017. The one on the right which is the current situation. The situation with the cool anomaly is now much different east of the Dateline from the situation as reported for September 15, 2017. The cool pool to the east is gone and has been replaced by a warm anomaly. We have Down-welling Kelvin Waves erupting to the surface now. This two sets of graphics provides a good feel for the duration of a weak La Nina that gets no reinforcements. The situation now is essentially the reverse of the situation in September of 2017.

The next graphic basically averages out the anomalies by longitude.

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

You can see the relentless decline in the Eastern Pacific cool-water anomaly. It is now significantly positive. But has it stabilized at this level?

3. History of the Nino 3.4 Readings and forecasts from other Meteorological Agencies.

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 27, in the afternoon working from the August 26 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

Anomaly Segment	Estimated Anomaly
	Last Week	This Week
A. 170W to 160W	+0.5	+0.5
B. 160W to 150W	+0.5	+0.5
C. 150W to 140W	+0.5	+0.6
D. 140W to 130W	+0.6	+0.6
E. 130W to 120W	+0.6	+0.5
Total	+2.7	+2.7
Total divided by five i.e. the Daily Nino 3.4 Index	(+2.7)/5 = +0.5	(+2.7)/5 = +0.5

My estimate of the daily Nino 3.4 SST anomaly tonight is again +0.5 which is a borderline El Nino value. NOAA has reported the weekly Nino 3.4 to be +0.3 which is an ENSO Neutral value. Their estimate seems too low to me if TAO/TRITON is accurate but there are other graphics that suggest that the NOAA Nino 3.4 estimate is a better estimate than I have made. Nino 4 is reported to be cooler than last week at +0.4. Nino 3 is reported to be cooler at +0.1. Nino 1 + 2 which extends from the Equator south rather than being centered on the Equator is reported cooler at -0.2 It was 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.

You can see that this is a double dip La Nina (with the second dip being deeper than the first hence the Southern Tier drought). You can also see that has turned up and entered Neutral Territory. These are weekly values and thus not as volatile as the CDAS graphic we show elsewhere.

This is probably the best place to AGAIN express the thought that this way of measuring an ENSO event leaves a lot to be desired. Only the surface interacts with the atmosphere and is able to influence weather. The subsurface tells us how long the surface will remain cool (or warm). Anomalies are deviations from “Normal”. NOAA calculates and determines what is “Normal” which changes due to long ocean cycles and Global Warming. So to some extent, the system is “rigged” in the sense that no matter how warm the water along the Equator gets, there will always be warmer and cooler water so that one can identify the phases of ENSO. Hopefully it is “rigged” to assist in providing improved weather forecasts. But to assume that any numbers reported can be assumed to be accurate to a high level of precision is foolhardy.

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.

Subareas of the Anomaly	Westward Extension	Eastward Extension	Degrees of Coverage		Total by ENSO Phase
Subareas of the Anomaly	Westward Extension	Eastward Extension	Total	Portion in Nino 3.4 Measurement Area	Total by ENSO Phase
These Rows below show the Extent of El Nino Impact on the Equator
1C to 1.5C (strong)	165E	173E	8	0	35
+0.5C to +1C (marginal)	173E 160W	170W 125W	48	35	35
These Rows Below Show the Extent of ENSO Neutral Impacts on the Equator
0.0 to 0.5C (warmish neutral)	170W 125W	160W 120W	15	15	15
-0,5C to 0C (coolish neutral)	120W	LAND	25	0	15
These Rows Below Show the Extent of La Nina Impacts on the Equator.
-0.5C or cooler Anomaly	LAND	LAND	0	0	0
-1.0C or cooler Anomaly	LAND	LAND	0	0
-1.5C or cooler Anomaly	LAND	LAND	0	0
-2.0C or cooler Anomaly	LAND	LAND	0	0
-2.5C or cooler Anomaly	LAND	LAND	0	0
This week there are 0 degrees of longitude along the Equator in the Nino 3.4 Measurement Area which registers La Nina values. There are 35 degrees that register El Nino. The other 15 degrees register Neutral. That is not the case for the full +5N and +5S width of the Nino 3.4 Measurement Area but in this analysis we are just looking at the Equator. Roughly speaking, the ratio of the El Nino Value to 50 tells us if we are close to being in El Nino. And we are. 35/50X100% = 70%

Forecasting the Evolution of ENSO

Here is the primary NOAA model for forecasting the ENSO Cycle.	The CDAS model is a legacy “frozen” NOAA system meaning the software is maintained but not updated. We find it convenient to obtain this graphic from Tropical Tidbits.com

This model is forecasting El Nino. I am not longer showing the larger version of this graphic but if you click on it it will enlarge. Also, click here to see a month by month version of the same model but without some of the correction methodologies applied. It gives us a better picture of the further out months as we are looking at monthly estimates versus three-month averages.	Notice that since February, 2018 the Nino 3.4 Index has been rising. The CDAS data is not in conflict with the primary NOAA model but shows daily values rather then smoothing them out like the CFSv2 Model does. The CDAS data has recently risen to neutral with an El Nino trend. But it has recently returned to just plain neutral.

We thought it useful to show the CFS.v2 forecast full size. It peaks in OND, 2018 and then begins a decline but staying in El Nino territory for the duration of the forecast.

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

The discussion released with the forecast can be found here.

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

Some pay more attention to the early report as it is based mostly on the opinions of meteorologists. I pay more attention to the second model-based report. It looks like the second report is starting to look more like the JAMSTEC forecast perhaps extending the El Nino longer.

This graphic shows a collection of models used by various meteorological agencies to forecast the NINO 3.4 Index

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.

Aug. 20, 2018
Prediction from 1st Aug., 2018
ENSO forecast:
The SINTEX-F predicts that a moderate-to-strong El Niño event may start in early fall 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:
As predicted earlier, the positive Indian Ocean Dipole (IOD) has actually emerged in July. The model continues predicting the positive IOD for the boreal 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 southern Africa and Tibet will experience a cooler-than-normal condition. In winter, most part of the globe will be in a warmer-than-normal condition, while southern Alaska, western U.S.A., northern Brazil, Botswana, northern India, Iran, Afghanistan, northeastern Russia, 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 Alaska, western/eastern Canada, central/eastern U.S.A., East Africa, West Africa, and northern Europe. In contrast, northwestern/southeastern U.S.A., eastern Brazil, eastern Europe, South Korea, India, 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 northern South American Continent, Australia, Mozambique, South Africa, southern Angola, Zambia, southeastern Europe facing the Mediterranean Sea, northern Europe, southern India, Southeast Asia, the Philippines, Indonesia and Australia. On the other hand, most parts of U.S.A, northeastern/south Brazil, northern South Africa, Botswana, western Europe, southeastern China will be wetter-than-normal.
Most part of Japan will experience warmer-than-normal condition in fall and winter as a seasonal average.

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

And the ENSO Outlook Discussion Issued on August 28, 2018

El Niño WATCH continues
The El Niño–Southern Oscillation (ENSO) is currently neutral. However, current observations and model outlooks indicate El Niño remains possible in 2018. Therefore, the Bureau’s ENSO Outlook remains at El Niño WATCH, meaning there is approximately a 50% chance of El Niño forming in the coming months; double the normal chance.
Surface waters of the central and eastern tropical Pacific Ocean are slightly warmer than average, and water below the surface is warming. Atmospheric indicators largely remain neutral, although the Southern Oscillation Index (SOI) has become more negative (El Niño-like).
All of the surveyed international climate models predict further warming of central equatorial Pacific sea surface temperatures (SSTs) over the coming months. All of the models suggest El Niño thresholds are likely to be reached by the end of spring, with the majority suggesting values will remain at or above the threshold into early 2019.
El Niño during spring typically means below-average rainfall in eastern and northern Australia while daytime temperatures are typically above average over the southern two-thirds of Australia.

Indian Ocean IOD (It updates every two weeks)

Indian Ocean Dipole Outlook Discussion Issued August 28, 2018

The Indian Ocean Dipole (IOD) is currently neutral. The weekly index value to 26 August was −0.17 °C. Three of the six international climate models surveyed by the Bureau suggest that a short-lived positive IOD 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.

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

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.

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 along the Dateline as the La Nina declines. But we now see suppressed OLR further west.

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 have 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. And of course the next El Nino is project to occur this winter.

The potential for a near or marginal El Nino this winter could extend the period needed for a shift in the PDO. We are looking for a powerful El Nino to signal the change not a weak to moderate El Nino. But JAMSTEC which was forecasting a moderate to strong El Nino has backed off on the intensity of the forecast El Nino but not the duration. So it may be that we may not yet be moving to McCabe A and the U.S. will not have just yet get used to being wet for the next 20 to 30 years but instead have another two to five years of the current pattern. But it may also be that the Climate Shift in the Pacific is imminent. .

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

Relationship of MJO and ENSO
	El Nino	La Nina	MJO Active Phase	MJO Inactive Phase
Eastern Pacific Easterlies	Weaker	Stronger Part of Decay Process	Counteracts Easterlies	Enhances Easterlies
Western Pacific Westerlies	Stronger May Create or Stimulate the Onset of El Nino via Kelvin Waves	Weaker Part of Decay Process	Strengthens Westerlies	Weakens Westerlies
MJO Active Phase	More likely Stimulates	Less likely and weak Retards development of a new La Nina	Stimulates the Jet Stream
MJO Inactive Phase	Less Likely Suppresses	More likely but weak Accelerates development of a new La Nina and the Decline of a mature La Nina		Slows the Jet Stream and can induce a Split Stream especially during a La Nina

Table needs more work. Is intended to show the interactions. What is more difficult is determining cause and effect. This is a Work in Progress.

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)

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.

August 27, 2018 Weather and Climate Report – We are in Transition

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August 27, 2018 Weather and Climate Report – We are in Transition

Total

Portion in Nino 3.4 Measurement Area

165E

173E

8

0

35

173E

160W

170W

125W

48

35

170W

125W

160W

120W

15

15

15

120W

LAND

25

0

LAND

LAND

0

0

0

LAND

LAND

0

0

LAND

LAND

0

0

LAND

LAND

0

0

LAND

LAND

0

0

D. Putting it all Together.

E. Relevant Recent Articles and Reports

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

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

H. Useful Background Information

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Democratic Governors Are Quicker In Responding To The Coronavirus Than Republicans

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