Wednesday, July 30, 2014

Fall 2014 Seasonal Forecast

This is the outlook for Fall 2014.

We will begin by analyzing the temperature outlook from a trusted long-range ensemble guidance system.

For the August-September-October period, the ensemble system shows an outlook of warmer than normal temperatures across the Western US and portions of the Northeast, with darker shadings indicating higher confidence in that forecast anomaly. The warmest temperatures appear to be centered over Montana and Idaho in this outlook, as well as portions of New York and towards Maine. The big story here, however, is the anomalous cold shown in this outlook. We see below normal temperature anomalies extending from the Canada/US border, all the way down to the US/Mexico border. The core of the cold looks to be across the Plains and Midwest, with higher confidence in cold weather displayed by the dark blues. These dark blues look to be most prevalent in the Midwest, Plains, Great Lakes, Ohio Valley and Mid-Atlantic.

If we fast-forward to the October-November-December temperature forecast, we find a similar outlook as the one we just analyzed for the August-September-October period. In this forecast graphic, we see cold weather forecasted across most of the nation. The cold extends from the Pacific Coast to the Carolinas, with the deepest cold weather displayed over the North and Central Plains, as well as the Southwest US. Most of the coastal Eastern Seaboard looks to be in slightly above normal temperatures, though confidence in this is rather low.

After a cold winter, spring and summer, a cold outlook for fall is something that makes sense. We are still seeing that persistent pool of warm waters in the northeast Pacific, which has allowed these seasons to be so chilly. As a result, we should be wary of a chilly fall this year, something that could continue into the winter.

Let's now examine the precipitation outlook.

The precipitation outlook for August-September-October from this long range ensemble system has a variety of conditions across the country. We see a general dry trend over the Southwest, unfortunately worsening the already-catastrophic drought in California and other states. The Pacific Northwest is showing a variable signal. The North Plains are exhibiting above-normal precipitation anomalies in rather high confidence for this timeframe, and this trend continues into the Midwest and Great Lakes. A stark dry trend is observed in the Southern Plains with enhanced confidence, and a similar story can be found in the upper Midwest. In the East US, we see mainly variable conditions that cannot let us determine a particular forecast for this area. Beyond this forecast period, the precipitation outlook exhibits too low of confidence to determine a thorough forecast.

Because we don't know what the El Nino situation will do for this fall and winter, it's hard to see how reliable this precipitation outlook is. The drought conditions in the Southwest should allow for a general dry trend there by process of a feedback loop, unless we see a sustained El Nino arise. I do believe we see conditions in the Midwest and Great Lakes a bit drier than they are projected to be, with conditions along the East Coast averaging around normal or slightly above normal.