October, 2019 Seasonal Forecasts. Part II, NOAA Comparison with JAMSTEC

Written by Sig Silber

We published the NOAA Long-Term Forecast Thursday Night (here).  Now we compare the NOAA forecast for Alaska and CONUS with the JAMSTEC forecast. They are very different even though the ENSO forecasts are very similar as measured by the NINO 3.4 Index. But JAMSTEC sees some Modoki characteristics to the Sea Surface Temperature pattern along the Equator in the Pacific. We also provide the JAMSTEC World Forecasts with special emphasis on Europe.

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Because of the importance of the ENSO Phase to the weather forecast, we start by comparing the two NOAA forecasts for ENSO (specifically the Nino 3.4 Index) with the JAMSTEC forecast. The first image is the Early-October IRI-CDC ENSO probabilities. The second image is the JAMSTEC proprietary forecast model for the Nino 3.4 Index. The third is the NOAA proprietary model CFSv2.

The forecast maps do not extend beyond three seasons but for those with curiosity, here is the JAMSTEC two-year forecast for the NINO 3.4 Index.

C. Now to our full report. (Sections A and B were covered in Part I which can be accessed here)

This report is organized into a summary that has two tables of graphics that show the temperature and precipitation forecasts for the upcoming three seasons, a brief discussion of the ENSO assumptions by both NOAA and JAMSTEC and then the JAMSTEC Agency discussion and then a comparison of the two forecasts which is basically an expansion of the summary table.

Summary of the NOAA and JAMSTEC Forecasts

For those who want a quick synopsis of the two forecasts, below is a summary of the temperature and precipitation forecasts for three time-periods and from left to right the NOAA forecast for Alaska and CONUS (the contiguous mid-latitude U.S), then JAMSTEC for North America (which includes Canada and Mexico), and then JAMSTEC for Europe and surrounding areas. Larger graphics are provided later in the report. (the graphics in the Summary Table are not set up to be clicked on to enlarge). The Summary Table is kind of a tease to keep you reading but you can see the evolution of the weather pattern through Fall, Winter, and then Spring. For some readers, these two sets of summary graphics may be all the information they wish to look at and that is fine.

Temperature

	NOAA Alaska Plus CONUS	JAMSTEC North America	JAMSTEC Europe
Winter DJF 2019-2020
Spring MAM 2020
Summer JJA

Precipitation

	NOAA Alaska Plus CONUS	JAMSTEC North America	JAMSTEC Europe
Winter DJF 2019-2020
Spring MAM 2020
Summer JJA 2020

We provided the full NOAA Discussion in Part I. The much shorter JAMSTEC Discussion was published on October 18, 2019 so we have that for our Report tonight.

ENSO forecast:

As predicted earlier, the El Niño Modoki-like state is observed now. The SINTEX-F predicts the El Niño Modoki-like state will persist at least until the autumn [Editor’s Note we are already in Autumn]. We need to be careful of its impact, as it may be different from that of the canonical El Niño. Then, the model predicts that the tropical Pacific will return to a neutral-state from the winter through the first half of year 2020. [Editor’s Note: Then why are the forecasts so different?>

Indian Ocean forecast:

As predicted earlier, a positive Indian Ocean Dipole quickly emerged in May, and now reached a level similar to that of the strong events of 1994, 1997, and 2006. The model predicts that the positive Indian Ocean Dipole will persist in the autumn, and then quickly decay in the winter. We may observe co-occurrence of a positive Indian Ocean Dipole and an El Niño Modoki-like state in the autumn; this is as we observed in 1994 and 2018.

[Editor’s Note: It appears that the above two sections were not updated which may or not be significant as JAMSTEC may have concluded that they apply as written even though I have pointed out above some inconsistancies in that assumption. The  below sections were updated.]

Regional forecast:

On a seasonal scale, the SINTEX-F predicts that most part of the globe will experience a warmer-than-normal condition in the boreal winter, except for most part of U.S.A, West Africa, Western Europe and some parts of East Africa. In the boreal spring of year 2020, most part of the globe will still experience a warmer-than-normal condition, except for some parts of western Canada, southern Africa, Australia, Iran, northwestern China, Mongolia, and central Russia.

As regards to the seasonally averaged rainfall in the boreal winter, a wetter-than-normal condition is predicted for southern coastal area of Alaska, eastern U.S.A., most parts of Brazil, northern Australia, and most parts of southern and eastern Africa. In contrast, some parts of western U.S.A., northern part of the South American continent, Argentina, western Australia, northeastern part of South Africa, Indonesia, Sri Lanka and Philippines will experience a drier-than-normal condition. In the boreal spring of year 2020, a wetter-than-normal condition is predicted for eastern/western U.S.A., most part of the South American continent, and China. In contrast, central U.S.A., northeastern Brazil, eastern part of Australia, western part of southern Africa, most parts of West Africa, Europe, Indonesia, Philippines, and Southeast Asia will experience a drier-than-normal condition.

The model predicts most part of Japan will experience warmer-than-normal condition in the winter as a seasonal average. In the spring of year 2020, most part of Japan will be still warmer-than-normal.

Indices use a single number to convey information. Sometimes it is useful to look at the forecast Sea Surface Temperatures (SST) that correlate to the indices. I believe that the SST’s directly correlate with the JAMSTEC Nino 3.4 Index and their forecast but NOAA uses a variety of tools so it is not so easy to understand exactly how they do their forecast but there is a lot of information on that in their lengthy discussion which was presented in our Part I Report.

NOAA	JAMSTEC

Updates from JAMSTEC can be found here. Updates from NOAA can be found here. You have to look for the SST row and go to the right where it says “normalized with mask” and click on E3 which provides the latest model run.

All of these forecasts depend to a large extent on what is known about subsurface temperature anomalies. Here is the latest analysis. Updates can be obtained here.

I am showing three months: first two historical months shown side by side and then the current month.

The Current Month.

Does the SOI confirm that ENSO Neutral Conditions apply? The SOI is one measure of the extent to what the atmosphere has been impacted by the Eastern Pacific surface pattern which is measured by the Nino 3.4 Index. After all, we are more interested in the impacts to weather in the atmosphere which impacts populated areas than we are about the temperature distribution of the ocean surface along the Equator in the Pacific Ocean.

I am showing the situation this month and last month.

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

D. Now we begin our comparison of the NOAA and JAMSTEC Forecasts (Focus on next nine months i.e. three seasons)

In this Update, we compare the JAMSTEC temperature and precipitation forecast maps, which are for the World, with the NOAA temperature and precipitation forecast maps that cover only CONUS and Alaska. We do this primarily for educational purposes.

JAMSTEC works in three-month intervals which correspond to seasons and does not change the selection of months each time they update but does so every three months. At that time they drop one season and add another season further in the future. JAMSTEC provides maps for three seasons and the choice of seasons changes every three months. So for one out of three months, the first season lines up perfectly and this is not that month. So for JAMSTEC, we have Winter(DJF), Spring (MAM) and Summer (JJA) and for NOAA we have the same meaning we do not compare November. We reported on the NOAA forecast for November and we updated our report to indicate that the Week 3 – 4 forecast issued on October 18 did not support the NOAA Early Outlook issued on October 17.

This is a good time to comment on the timing associated with the preparation of the forecasts. For JAMSTEC, it is clear that that their forecasts are said to be based on an Nino 3.4 forecast dated October 1, 2019. And yet the discussion comes out much later this time on October 18, 2019, The forecast maps come out a few days earlier. So we do not know if everything is based on October 1 or if later information is utilized. We suspect that the JAMSTEC model takes a long time to run. For NOAA we have the opposite problem. The maps and discussion are always released on the Third Thursday of the month. But we do not know when they are prepared. It is our belief that the forecasts and discussion are prepared a few days prior to the release on the Third Thursday. We observed that the forecasts for November seemed to be not consistent with the Week 3 – 4 forecast released the very next day. This is a common problem in meteorology and made more difficult the larger the agency. It should not normally impact the usefulness of the forecasts beyond the immediate next month. 

Presentation of the Forecast Maps.

I show the NOAA Maps first followed by the JAMSTEC maps. I extract North America from the Worldwide JAMSTEC map and use that to compare with the NOAA Maps. I also extract Europe including parts of North Africa and Western Asia from the Worldwide JAMSTEC maps and include those excerpted maps in the summary table at the beginning of this article.

Now we will compare the maps in that summary but with full-sized maps.

Winter DJF 2019 – 2020 (Notice we start with DJF which is Winter and we are not looking at November in this analysis)

Temperature DJF 2019 – 2020 for NOAA

And here is the DJF 2019 – 2020 temperature forecast for North America that I extracted from the JAMSTEC World Forecast.

And now the JAMSTEC WORLD FORECAST (I focus on areas other than Alaska and CONUS as that has already been covered)

Precipitation

NOAA (DJF 2019 – 2020)

And here is the DJF2019-2020 Precipitation Forecast for North America that I extracted from the JAMSTEC World Forecast.

And now the JAMSTEC WORLD FORECAST (My detailed comments on Alaska and CONUS appear with the larger graphics above)

Spring (MAM 2020)

Temperature

NOAA

And here is the MAM 2020 Temperature Forecast for North America that I extracted from the JAMSTEC World Forecast.

JAMSTEC WORLD FORECAST (My detailed comments on Alaska and CONUS appear with the larger graphics above)

Precipitation

NOAA

And here is the MAM 2020 Precipitation Forecast for North America that I extracted from the JAMSTEC World Forecast.

JAMSTEC WORLD FORECAST (My detailed comments on Alaska and CONUS appear with the larger graphics above)

Summer JJA 2020

Temperature

NOAA

And here is the JJA 2020 Temperature Forecast for North America that I extracted from the JAMSTEC World Forecast.

JAMSTEC WORLD FORECAST

Precipitation

NOAA

And here is the JJA 2020 NA precipitation I extracted from the JAMSTEC World Map

JAMSTEC WORLD FORECAST

D. Conclusion

Both NOAA and JAMSTEC have forecasts that in one way or another incorporate the value of Nino 3.4. Both forecast it to be positive and under +0.5C. JAMSTEC also sees Modoki characteristics in the pattern as measured by their Modoki Index which was created by Karumuri Ashoc EMI= [SSTA]A-0.5*[SSTA]B-0.5*[SSTA]C  The square  bracket  in this Equation represents  the area-averaged SSTA  over each  of  the regions A (165E-140W, 10S-10N), B (110W-70W, 15S-5N), and C (125E-145E, 10S-20N),  respectively.  The fact that this calculation yields a value greater than +0.5C probably means the warmer water along the Equator in the Pacific is a bit farther west than usual for a typical El Nino although we are not having an El Nino. But the warm anomaly is there.

This shifts the Walker circulation west a bit. NOAA may take this into account but generally does not use Japanese terminology for the condition of the Equatorial Pacific Ocean which we share. I see that as a weakness in their forecasting approach. Also though it is possible to take Modoki into consideration using statistical methods, it is not easy to do so I suspect that NOAA does not do it. One the other hand, the dynamic methods of JAMSTEC build errors over time. So we have two flawed methodologies competing and thus comparing the results of the two flawed approaches is useful. 

Slight changes in the ENSO Phase are likely to change the actuals from what has been forecast. I do not have a lot of confidence in either of the forecasts but for different reasons. NOAA may not be properly taking into account the Modoki aspect of the situation and JAMSTEC may be overestimating the impact of the Modoki-like conditions in their forecast. It is the same problem as last month.

One of the reasons for doing this comparison is it provides the ability to create our own updated forecast as we see the assumptions made by each agency be confirmed or not. That is especially true when the actuals start coming within the range of the two sets of assumptions. Weather is not linear so it is more complex than scaling the solution to where the actuals are showing up relative to the two versions of the assumptions but with a little imagination one might be able to sort it out.

It is going to be difficult this time as the forecasts seem to be more different than what we might expect from the small differences in the ENSO assumptions.