More Weather - Supplement to Weather Live All Week Updated As Needed Oct 13, 2019

We published the NOAA Long-Term Forecast Part I on July 15, 2021. Tonight we compare the NOAA forecast for Alaska and CONUS with the JAMSTEC forecast. We show the maps side by side in a table with a summary. Obviously, the farther out you look, the less confidence you have in the forecasts and thus also the differences in the forecasts. Also provided are the JAMSTEC World Forecasts. JAMSTEC has sent us their forecast privately as their website is still not functional. What they have sent us includes a monthly forecast for each of the first three months so we are also able to compare the NOAA and JAMSTEC August forecasts this time. As usual, there are some significant differences but also a lot of agreement. What is a bit unusal is that they differ early and agree more in subsequent seasons.

NOAA v. JAMSTEC

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An intriguing statement from the JAMSTEC Discussion.

Some parts of West Africa will also experience a wetter-than-normal condition due to the evolving Atlantic Niño.

I do not think they publish an index on that but unknown to many people the same process that we call ENSO in the Pacific also takes place in the Atlantic Ocean but it is more muted there. The dynamics are I would say almost identical. The timing does not fit real well with enhancing the hurricane season but this is something to pay attention to.

C. Comparison of the NOAA and JAMSTEC Forecasts

C1. The Comparison

Below is the comparison of the NOAA and JAMSTEC temperature and precipitation forecast maps for the month of August and then three season defined time-periods. In the Summary Table we show the NOAA forecast for Alaska and CONUS (the contiguous mid-latitude U.S) and right next to it the JAMSTEC forecast for North America (which includes Canada and part of Mexico). The NOAA forecast maps can be clicked on to enlarge. The JAMSTEC maps in the table are not set up to be clicked on to enlarge (because we do not have a larger version of them). We have concluded that these smaller images work fine for comparison purposes. Later in the article, we show the World Forecasts.

JAMSTEC normally works only with three-month seasons: Right now that is Fall: SON, Winter: DJF and Spring: MAM. Out of each three months, there is normally just one where the months in the two forecasts align perfectly for the first time period. But all of a sudden JAMSTEC has changed the process so I have forecast maps from JAMSTEC for August, September and October. I think this is an improvement. So I am now able to match up the NOAA and JAMSTEC maps exactly. It might look strange as we are comparing the NOAA SON forecast (not the ASO forecast) to the JAMSTEC SON forecast but we are also comparing the NOAA August forecast to the JAMSTEC August forecast.

It is important to remember that the NOAA forecast is dated July 15 so it was probably prepared on July 13 or 14 and the JAMSTEC forecast is dated July 1. That is important when comparing assumptions when things are changing rapidly.

In addition to the value of comparing the JAMSTEC and NOAA forecasts, the JAMSTEC forecast by showing North America provides more context for the Alaska and CONUS Forecasts as the temperature and precipitation patterns cover North America, not just Alaska and CONUS.

Map Comparisons and our Comments

Temperature*

	NOAA Alaska Plus CONUS	JAMSTEC North America
August 2021
Fall SON 2021
Winter DJF 2021-2022
Spring MAM 2022

For August: JAMSTEC is warm all over while NOAA shows a large EC area and a small cooler than climatology area. They disagree on Alaska also

For Fall: They are in pretty good agreement for Fall.

For Winter: NOAA shows a more pronounced EC area with even a small cool anomaly. JAMSTEC shows something similar but much smaller and more focused on Canada i.e. more northerly displaced.

For Spring: NOAA basically is showing a similar pattern to Winter and JAMSTEC is hinting at some less intense temperatures for the Great Lakes and on east.

Precipitation*

	NOAA Alaska Plus CONUS	JAMSTEC North America
August 2021
Fall SON 2021
Winter DJF 2021-2022
Spring MAM 2022

For August: If you removed the large dry anomaly that JAMSTEC shows, the two forecasts would be quite similar. But that dry anomaly dominates the JAMSTEC forecast.

For Fall: JAMSTEC shows basically EC everywhere and NOAA has a very dry Southwest extending into the Great Plains and a wet anomaly for the Mid-Atlantic. So these forecasts are very different.

For Winter: They come closer together for winter but NOAA shows a continuous dry southern tier which is less pronounced in the JAMSTEC forecast. The Northwest Wet anomaly is similar.

For Spring: The JAMSTEC Spring forecast is fairly similar to their Winter forecast. The both agree on a dry Southwest. But NOAA shows a large wet anomaly stretching from Eastern Texas to the Great Lakes.

* It is important to keep in mind that NOAA reports probabilities of being warmer or cooler than Climatology and JAMSTEC reports the degrees of temperature and millimeters of precipitation variation from Climatology (Normal). So they are not exactly comparable. Also please keep in mind that NOAA is now using a redefinition of Climatology which is the mean of the most recent three decades of weather namely 1991 to 2020. We do not believe that JAMSTEC has updated their definition of Climatology, They may have but there has been no announcement from JAMSTEC that they have updated their Climate Normals. This makes the comparisons a bit more difficult.

JAMSTEC World Forecasts

This month our comments for Summer and Fall (Northern Hemisphere Seasons) are taken directly from the JAMSTEC discussion. We do not have a JAMSTEC discussion for the July forecast.

Aug 2021

Temperature

http://www.jamstec.go.jp/aplinfo/sintexf/2017/forecast/temp2.glob.SON2020.1jul2020.F23DVAR.gif

Precipitation

We do not have a JAMSTEC interpretation of their August forecast. But you can see the two maps just as well as I can. The Maritime Continent and India and Southern and Southeast Asia are complicated.

Fall which is SON

Temperature

Precipitation

JAMSTEC says: "On a seasonal scale, the SINTEX-F predicts that most parts of the globe will experience a hotter-than-normal condition in boreal autumn (austral spring) except for northern parts of the South American Continent. " "As regards to the seasonally averaged rainfall in boreal autumn (austral spring), a drier-than-normal condition is predicted for California, southern parts of the South American Continent, most parts of southern Africa, some parts of West Africa, some parts of Europe, some parts of Indochina, and most parts of China. In contrast, most parts of Alaska, the western coastal area of Canada, Central America, northern parts of the South American Continent, some parts of Central Africa, India, Philippines, and Indonesia will experience a wetter-than-normal condition. Some parts of West Africa will also experience a wetter-than-normal condition due to the evolving Atlantic Niño. Extremely wetter-than-normal conditions in Indonesia will be mostly due to the evolving negative Indian Ocean Dipole." "The model predicts most parts of Japan will experience a warmer-than-normal condition in autumn as a seasonal average. As regards to the seasonally averaged rainfall, the model predicts almost neutral conditions over most parts of Japan in autumn."

Winter which is DJF 2021-2022

http://www.jamstec.go.jp/aplinfo/sintexf/2017/forecast/temp2.glob.DJF2021.1jul2020.F23DVAR.gif

Precipitation

JAMSTEC says: "In boreal winter (austral summer), the model still predicts most parts of the globe will experience a warmer-than-normal condition, except for northern parts of the South American Continent and some parts of Europe." "In boreal winter (austral summer), a wetter-than-normal condition is predicted for Alaska, northern parts of the South American Continent, Philippines, and Indonesia. In contrast, most parts of Australia, some parts of southern Africa, and some parts of Europe will experience a drier-than-normal condition." "The model predicts most parts of Japan will experience a warmer-than-normal condition in winter as a seasonal average. As regards to the seasonally averaged rainfall, the model predicts that in winter, Okinawa and southern parts of Japan will experience a drier-than-normal condition".

Spring which is MAM 2022

Precipitation

JAMSTEC does not comment on the third period in their discussion. We assume this represents the lower level of confidence that far out. But you can see what it shows on the maps. For temperature the Middle East up through Scandinavia looks warm. For precipitation, there is not a lot of variation from climatology.

I do not usually present this and I am doing it in a way that you have three large images but I think you can see some things.

In SON you can see the La Nina along the Equator. I am not sure why this is described as somewhat Modokiish. It does extend pretty far west. You can also see the warm water off West Africa. You can also see the warm water hugging the west coast of CONUS. The warm water withdraws from the west coast of CONUS in Winter and Spring. If I studied the pressure charts I might understand why. I can't imagine it is because of offshore winds. If I had the formula memorized I might be able to describe how that warm pattern in the Indian ocean is the IOD. BTW there is a similar set of graphics for NOAA but they do not go out this far. I used to show them. I am trying not to bury my readers in details.

Here is the JAMSTEC Discussion

We provided the full JAMSTEC Discussion in Part I. We repeat it here.

ENSO forecast:

Observation shows that the tropical Pacific is in a neutral state. The SINTEX-F predicts that a weak La Niña Modoki-like state will appear in boreal autumn.

Indian Ocean forecast:

As predicted earlier, observation shows occurrence of a negative Indian Ocean Dipole. The SINTEX-F ensemble mean predicts that the Indian Ocean will return to a neutral state in boreal autumn. However, there is a large uncertainty in the predictions, and the SINTEX-F2-3DVAR, which predicted most recent IOD events, predicts that a weakly negative Indian Ocean Dipole will persist in boreal autumn.

Regional forecast:

On a seasonal scale, the SINTEX-F predicts that most parts of the globe will experience a hotter-than-normal condition in boreal autumn (austral spring) except for northern parts of the South American Continent. In boreal winter (austral summer), the model still predicts most parts of the globe will experience a warmer-than-normal condition, except for northern parts of the South American Continent and some parts of Europe.

As regards to the seasonally averaged rainfall in boreal autumn (austral spring), a drier-than-normal condition is predicted for California, southern parts of the South American Continent, most parts of southern Africa, some parts of West Africa, some parts of Europe, some parts of Indochina, and most parts of China. In contrast, most parts of Alaska, the western coastal area of Canada, Central America, northern parts of the South American Continent, some parts of Central Africa, India, Philippines, and Indonesia will experience a wetter-than-normal condition. Some parts of West Africa will also experience a wetter-than-normal condition due to the evolving Atlantic Niño. Extremely wetter-than-normal conditions in Indonesia will be mostly due to the evolving negative Indian Ocean Dipole. In boreal winter (austral summer), a wetter-than-normal condition is predicted for Alaska, northern parts of the South American Continent, Philippines, and Indonesia. In contrast, most parts of Australia, some parts of southern Africa, and some parts of Europe will experience a drier-than-normal condition.

The model predicts most parts of Japan will experience a warmer-than-normal condition in autumn and winter as a seasonal average. As regards to the seasonally averaged rainfall, the model predicts almost neutral conditions over most parts of Japan in autumn. In winter, Okinawa and southern parts of Japan will experience a drier-than-normal condition

C2. ENSO Assumptions

Now let us look at the NOAA recent ENSO Update. This happens every month on the second Thursday. I show this because it is the information that NOAA works from in producing the Four-Season Forecast. We have covered some of this when we reported on the IRI/CPC analysis on July 8, 2021. I have added the JAMSTEC assumptions and also the Australian Bureau of Meteorology Assumptions.

ENSO UPDATE

NOAA seems fairly confident that there will be a La Nina this Winter.

The gray bar is the probability of ENSO Neutral and the blue bar is the probability of La Nina. So starting in SON La Nina is more likely than ENSO Neutral. The really bad news is that the probability of La Nina is high during the time of the year when the West needs to have snow. Not all La Nina's are dry but most are for the U.S. West.

Here you see the new forecast on the left with the Mid-June forecast on the right. The methodologies are not the same but still this is a big change.

This is a NOAA graphic but not part of the release of information on July 8, 2021. My interpretation of this graphic is that we are NOT in La Nina right now. It is a cross-section of the Equatorial Pacific. What counts is the surface temperature and this only shows the Equator and the actual calculation is based on the temperature anomaly from 170W to 120W but inducing 5 degrees north and south of the Equator. I have a different graphic that shows that but this one is probably more accurate for the area shown. The water is anomalously cold east of 100W. But west of 150W it is certainly not as cold as -0.5C. So we are definitely in ENSO Neutral the question being what is next and when will there be a change.

Usually I only show the top half of this graphic and if want I can let it update. If I snip a piece it will be frozen. Tonight I show the full graphic and both are useful. I now see signs of La Nina in the top graphic

But now I freeze the graphic and focus on the top part which shows the temperature anomalies.

Below is the graphic above but also one issued five days later. (I believe these images are five-day averages centered on the date shown.)

Prior Version

Updated Version

WHAT A CHANGE IN ONE WEEK!

CFSv2 spread and bias correct ENSO forecast

NOAA may not rely on this much but I include it and allow it to update so readers can notice any changes if they consult this article more than once. There are two criteria for the Phase of ENSO and Sea Surface Temperature is one and the most important and for most purposes it is measured in an area called Nino 3.4 and that measurement is shown here both the actual for overlapping three-month periods that have happened and forecast for two individual months and from there overlapping three month periods.

It is difficult to read but I interpret the above as a La Nina bias through the end of the year than an El Nino Bias for the second half of winter.

The Modoki image is slight more La Nina inclined.

The Southern Oscillation Index or SOI being above 7 confirms that the Atmosphere is in tune with the Sea Surface Temperatures in the Pacific along the Equator. This is another graphic that we have not frozen.

This is the Australian Bureau of Meteorology SOI Index and until very recently it definitely did not confirm that we were in a La Nina. But notice the recent spike in the SOI index. Some believe this index is out of date since it was developed when it was convenient to measure things on land and the two measurement points in this index are on land and not directly on the Equator. NOAA has their own index that uses two points right on the Equator. Some studies show that the slope of the curve (first derivative) may be as important as the absolute value of the index.

Here is the BOM (Australia Bureau of Meteorology) Nino3.4 tracker.

BOM Nino 3.4

It shows we are not in a La Nina. I have not frozen this graphic so it will update in the article. It is unclear how the recent change in Climate Norms impacts this graphic.

Here is their current forecast.

NINO3.4 SST plume graphs from ACCESS-S forecasts, updated daily

Their criteria are stricter than what is used by NOAA. But even with the NOAA criteria, Australia would conclude that we will be back in La Nina in August or September.

Indian Ocean Dipole

Here is the JAMSTEC index forecast.

I can not figure it out

Here is the BOM version.

It clearly shows a negative IOD event.

Here is the BOM Discussion of this event. It also mentions ENSO.

Negative IOD event likely in 2021 INACTIVE ENSO Outlook

Indian Ocean Dipole (IOD) index values continue to be negative. A negative IOD event is declared when there have been at least 8 weeks below the IOD index threshold of −0.4 °C. A negative IOD increases the chances of above average winter-spring rainfall for parts of southern Australia.

The most recent weekly IOD value is −0.27 °C, which is above the negative IOD threshold (−0.4 °C) but follows on from the IOD index being below the negative IOD threshold for the previous six weeks. Most climate models surveyed by the Bureau predict the IOD to return to below the negative IOD threshold, with a negative IOD event likely for the second half of the southern hemisphere winter and into spring.

The El Niño–Southern Oscillation (ENSO) remains neutral with most oceanic and atmospheric indicators within the neutral range. Cloudiness near the Date Line has been below average over the past fortnight, although this is weak and a localised pattern. Most climate model outlooks indicate a neutral ENSO state is likely to continue for the remainder of the southern hemisphere winter and spring despite tropical Pacific sea surface temperatures slowly cooling over the coming six months. This may be contributing to the wetter than average climate outlooks for parts of Australia.

The Southern Annular Mode (SAM) has been positive for the past four weeks. Forecasts suggest SAM will return to neutral levels over the coming week. Neutral SAM has little influence on Australian climate, while positive SAM typically means cold fronts and troughs are shifted further south than their usual winter path.

It is likely some of the wetter weather seen during June may have been a result of the developing negative IOD event, while the drier weather for parts of southern WA and western Tasmania may have been influenced by the positive SAM.

The Madden–Julian Oscillation (MJO) is currently over the Indian Ocean. Most climate models indicate the MJO will weaken approaching the Maritime Continent over the coming week. Should the MJO maintain its strength, an MJO near the Maritime Continent typically leads to stronger westerly winds over the Indian Ocean, which can reinforce the negative IOD.

Climate change continues to influence Australian and global climate. Australia's climate has warmed by 1.44 ± 0.24 °C over 1910–2019, while southern Australia has seen a reduction of 10–20% in cool season (April–October) rainfall in recent decades.

I am not sure what to do with this.

I would have to research this (I did and wrote a section on it once but I have forgotten it). I am amazed that JAMSTEC knows more about the U.S. California Coast than NOAA. The California Nino is sort of like a two-year cycle so what you observe in the prior year can help with the forecast for the current year. Since the index is not much above zero and was not mentioned in the JAMSTEC discussion, I am presenting it but will not attempt to interpret it.

D. Conclusion

As usual, there is a disagreement between NOAA and JAMSTEC. The differences are substantial especially with respect to precipitation.

It is difficult to relate the differences in the forecast to differences in assumptions on ENSO. But JAMSTEC tends to consider other factors that may not be considered by NOAA. On the other hand, the new versions of the JAMSTEC model are early in their usage and may not have been fully calibrated. I do not think I have gone into it in detail but when it comes to models we need to recognize that there are limitations and NOAA and JAMSTEC use very different approaches which I have summarized in the below table.

	Shorter Term	Intermediate-Term
NOAA	Deterministic	Statistical
JAMSTEC	Deterministic	Deterministic (may also use statistical methods)
Assessment	Generally Considered to be reliable for 14 to 28 days	Errors build up in deterministic models and statistical models generally have insufficient historical data to be reliable

So it is kind of a pick your poison choice. But both agencies have great skill at employing approaches that have inherent limitations.

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More Weather - Supplement to Weather Live All Week Updated As Needed Oct 13, 2019

Temperature*

Precipitation*