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. Similarly to last month, the temperature and precipitation forecasts are quite different even though the ENSO forecasts are very similar as measured by the NINO 3.4 Index. But JAMSTEC sees some Modoki characteristics in 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 Mid-November 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.
Looking beyond Alasaka and CONUS, another factor for this Winter (Summer in the Southern Hemisphere) is this very strong Indian Ocean Dipole (IOD) which is beginning to return to normal.
Here is the JAMSTEC forecast for the IOD.
Here is a little bit more explanation.
The Indian Ocean Dipole (IOD) is a coupled ocean-atmosphere phenomenon in the Indian Ocean. It is normally characterized by anomalous cooling of SST in the south eastern equatorial Indian Ocean and anomalous warming of SST in the western equatorial Indian Ocean. Associated with these changes the normal convection situated over the eastern Indian Ocean warm pool shifts to the west and brings heavy rainfall over the east Africa and severe droughts/forest fires over the Indonesian region.
Schematic of a positive IOD event | Schematic of a negative IOD event. |
SST anomalies are shaded (red color is for warm anomalies and blue is for cold). White patches indicate increased convective activities and arrows indicate anomalous wind directions during IOD events.
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 Winter, Spring and then Summer. 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 November 15, 2019 so we have that for our Report tonight.
Nov. 15, 2019
Prediction from 1st Nov., 2019ENSO 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 early winter. 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 late winter through year 2020.Indian Ocean forecast:
The positive Indian Ocean Dipole is now fully established reaching a level similar to that of the extremely strong events of 1994 and 1997. The model predicts that the positive Indian Ocean Dipole will persist in late autumn, and then decay in winter. We may observe co-occurrence of a positive Indian Ocean Dipole and an El Niño Modoki-like state in autumn and winter; this is as we observed in 1994 and 2018.
Regional forecast:
On a seasonal scale, the SINTEX-F predicts that most part of the globe, particularly Australia, will experience a warmer-than-normal condition in boreal winter, except for most part of eastern U.S.A, northeastern Brazil, U.K., central Russia, northern part of the Indian subcontinent, and some parts of China. In boreal spring of year 2020, almost all part of the globe will still experience a warmer-than-normal condition, except for U.K. and some parts of western Europe.
As regards to the seasonally averaged rainfall in boreal winter, a wetter-than-normal condition is predicted for Alaska, northeastern Brazil, East Africa, and northern part of Europe, and eastern China. In contrast, some parts of western U.S.A., northern part of the South American continent, southeastern Brazil, Australia, southern Africa, southern part of Europe, some parts of Southeast Asia, Indonesia, Sri Lanka and Philippines will experience a drier-than-normal condition. In boreal spring of year 2020, a wetter-than-normal condition is predicted for northeastern U.S.A., northwestern part of the South American continent, South Africa, and eastern China. In contrast, most part of Brazil, Australia, western part of West Africa, some parts of Southeast Asia, Philippines, and southern China will experience a drier-than-normal condition.
The model predicts most part of Japan will experience warmer and slightly drier-than-normal condition in the coming winter and spring as a seasonal average.
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.
Two Months ago | One Month ago |
The Current Month. (Updates can be obtained here)
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.
Last Month | This 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 seasons 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. So for one out of three months, the first season lines up perfectly and this is that month. So for JAMSTEC, we have Winter(DJF), Spring (MAM) and Summer (JJA) and for NOAA we have the same.
This is a good time to comment on the timing associated with the preparation of the forecasts. For JAMSTEC, it is clear that their forecasts are said to be based on a Nino 3.4 forecast dated November 1, 2019. And yet the discussion comes out much later this time on November 15, 2019, The forecast maps come out a few days earlier. So we do not know if everything is based on November 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 (Early Outlook) forecast for December 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. The December Early Outlook will be updated on November 30, 2019 which is only nine days later than the Early Outlook was released but we expect it to be quite different.
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
Temperature
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
And here is the DJF 2019-2020 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 but 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. It also appears east of 120W so that combination is fairly unusual.
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. On the other hand, the dynamic methods of JAMSTEC build errors over time. So we have two less than perfect 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 or misinterpreting the impact of the Modoki-like conditions in their forecast. It is the same problem as last month and the prior 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. There is also the question of the impact of the Negative North Atlantic Oscillation and the Positive Indian Ocean Dipole.