Wednesday, September 24, 2014

Updated JAMSTEC Model Supports Cold, Snowy Winter

The latest run of the JAMSTEC long range model came in last night, and it's still calling for a heavy-duty winter for millions across the country.

The graphic above shows the temperature anomaly forecast for the December-January-February period of 2014-2015. In this image, focusing on North America, we see an outlook very similar to what I had been pondering a handful of weeks ago. In this outlook, much of the south half of Canada is inundated with below-normal temperatures, which then intensifies and extends into the Northern US.

Interestingly enough, these below normal anomalies only hit the Plains, Great Lakes, Midwest, and eastern Rockies. For all other areas, save for the Southeast, temperature anomalies are actually above normal. The projection for the Eastern Seaboard includes a warmer than normal winter, though not a "blowtorch" winter, per se. The Western US also looks to see a warm winter, according to this outlook.

For precipitation, zooming in on North America, we do see a well-above normal precipitation trend over the Ohio Valley. This trend continues into the Northeast and Mid-Atlantic, even backtracking through the Great Lakes and Midwest. Such a wet forecast is also observed in the Southwest, where rain would certainly be welcome. The Pacific Northwest may then see slightly below normal conditions.

The piece that puzzles me (pun intended) in this forecast is the swath of above-normal precipitation anomalies across the Ohio Valley. The West US is exhibiting typical El Nino characteristics, with dry conditions in the Pacific Northwest and wet conditions in the Southwest. However, more La Nina-like conditions are observed in the East, with the above-average precipitation forecast over the Ohio Valley. It remains to be seen how reliable this outlook is, since this is the minority opinion out of the global forecast models right now.

To summarize, the new JAMSTEC is supporting a cold and snowy winter for much of the Central and East US, possibly spoiled by a warm winter in the Eastern Seaboard.