JAMSTEC Issues their Three-Season Weather Outlook on January 15, 2024

The Japan Agency for Marine-Earth Science and Technology, or JAMSTEC, is a Japanese national research institute for marine-earth science and technology

From the JAMSTEC Discussion:

"Recent observations show that a La Niña condition has developed. As predicted earlier, it looks more like a Modoki type than a canonical type. The SINTEX-F ensemble mean predicts that the La Niña Modoki will continue to develop through the rest of the boreal winter. The tropical Pacific will then be in a neutral state during the boreal spring and summer."

Although it is a World forecast, it includes a forecast for North America since North America is part of the World. One might try to compare it to the NOAA Outlook which we have also published today.

JAMSTEC starts by forecasting the SSTA and Nino 3.4 Index on the first day of the month and from there it usually takes their models about two weeks to produce their seasonal forecast. I received it from JAMSTEC on January 16, 2025 which is the same day that NOAA issued their four-season update this month. The JAMSTEC model runs are based on conditions as of January 1, 2025. The NOAA Seasonal Outlook is based on conditions closer to the time when it was issued.

First, we take a look at the forecasted sea surface temperature anomalies (SSTA).

This shows their forecast of sea surface temperature anomalies at three points in time. Blue is a cold anomaly and is associated with La Nina if it occurs in the Nino 3.4 measurement areas in the Pacific along the Equator. The cool anomaly along the Equator is much further west than usual in FMA which gives it the Modoki characteristics. This impacts the Walker Circulation. The La Nina cool surface anomaly is not even shown in the MAM SSTA analysis by JAMSTEC. So they are forecasting an even shorter La Nina than NOAA.

NOAA publishes a similar SSTA analysis. It can be accessed HERE.

JAMSTEC uses the same definition of Normal (climatology) as NOAA. JAMSTEC does a better job at characterizing La Ninas and El Ninos than NOAA. JAMSTEC provides me with a lot of other information that I do not include in my articles to keep them to a manageable size for readers. That material is the atmospheric pressure patterns. There is also a lot more information on their website.

This month we have the JAMSTEC three-season forecast at the same time as the NOAA four-season forecast so I published them both today.

Now we look at three forecasts. JAMSTEC tries to work with meteorological seasons and this month it does not line up perfectly since we have FMA, MAM, and JJA. MAM is Meteorological Spring and JJA is Meteorological Summer. So we have a forecast that bridges Winter and Spring and forecasts for Spring and Summer. So it is really a two-season forecast with a little extra because February is part of Meteorological Winter.

I am not sure about the way they calculate the SNR (Signal to noise ratio) but they seem to be trying to assign a confidence level to the anomalies which NOAA does more eloquently. As you can see they have more confidence in the temperature forecasts than the precipitation forecasts and so does NOAA in their work.

Their Summer forecast for the U.S. is very different than the NOAA forecast.

We also have forecast maps for February, March and April unlike NOAA which only provides a separate map for one month but they provide 13 three-month maps.

April in particular with respect to precipitation is quite different than what we would conclude from the NOAA discussion.

Here is the discussion that came with the set of maps.

ENSO forecast:
Recent observations show that a La Niña condition has developed. As predicted earlier, it looks more like a Modoki type than a canonical type. The SINTEX-F ensemble mean predicts that the La Niña Modoki will continue to develop through the rest of the boreal winter. The tropical Pacific will then be in a neutral state during the boreal spring and summer.

Indian Ocean forecast:

The SINTEX-F predicts that a negative phase of the IOD will rapidly decay through the rest of the boreal winter, and then the tropical Indian Ocean will be in a neutral state during the boreal spring and summer.
A strong positive Indian Ocean Subtropical Dipole persists. The model predicts that it will persist through the rest of the austral summer and disappear by the austral autumn.
Recent observations show that a Ningaloo Niño reached its peak. The model predicts that it will weaken but persist into the austral winter.

Regional forecast:

The model predicts warmer-than-normal conditions for most of the globe during the February-April average, particularly the signal-to-noise ratio is higher (dotted area) in the southern U.S., Mexico, eastern Brazil, New Zealand, the western coastal area of Australia, East/Central Africa, some parts of Saudi Arabia, southwestern China, East Asia, Myanmar, some parts of the Philippines, some parts of Indonesia. The model predicts colder-than-normal conditions in northern Brazil. The model also predicts a similar pattern in the boreal spring and summer.

For the February-April mean precipitation, drier-than-normal conditions are predicted for a part of the southwestern United States (including southern California and Arizona), where the signal-to-noise ratio is higher (dotted area). On the other hand, wetter-than-normal conditions are predicted for some parts of northern South America, the western Pacific Islands, and some parts of the Philippines. During the boreal spring and summer, the model does not predict a strong signal over land.

The model predicts that most of Japan will experience a higher-than-normal surface temperature during the February-April average. During the boreal spring and summer, the model also predicts that most of Japan will be warmer than normal.

Much additional information can be found at the JAMSTEC SINTEX-F website which can be accessed HERE

I hope you found this article useful and interesting.