Tuesday, August 19, 2014

Perfect-Scoring Winter Analog Paints Ominous Picture for Upcoming Season

For the first time, an analog year has matched all five of my parameters for the upcoming winter season, and is now indicating that the upcoming winter could be another rough one.

The analog year that matched all five parameters was the winter of 1958-1959.  The image above shows 500mb height anomalies during the December-January-February period of that winter season. In this graphic, blues and purples depict stormy and cold weather, while yellows and reds indicate warm and quiet weather. The winter of 1958-1959 saw strong ridging/high pressure positioned over the north-central and northwest Pacific regions, with some stormier weather observed near the Gulf of Alaska. This Pacific ridging extended well into the Arctic, helping to dismantle the mid-level polar vortex, sending it to lower latitudes like we saw last winter.
In North America, we observed what appears to be the polar vortex centered in the Canadian Maritimes, spreading its influence across Canada and into the North US. Some slight ridging was recorded in the West US, especially into the Southwest, as well as the Southeast.

Let's push on to the temperature composite for the winter of 1958-1959.

During the winter of 1958-1959, much of the nation was locked into a rather brutal winter, with temperature anomalies in the North US dropping below -6.0 degrees Fahrenheit, anomalies not too far off from what we saw this past winter, in 2013-2014. The core of the cold was placed from the Upper Midwest into the Great Lakes, but below-normal temperatures snaked their way through the entirety of the Central and East US, save for Florida, which saw weak ridging. The West US saw a very warm winter in December-January-February of 1958-1959, again a similar story to what was seen in 2013-2014.

Lastly, let's go ahead and check out precipitation anomalies from this analog.

During the winter of 1958-1959, very dry conditions plagued the Southern Plains, Gulf Coast, and southern Ohio Valley all the way into the Northeast and Mid-Atlantic regions. Precipitation anomalies below -5.0 inches were recorded in Mississippi, Alabama, Louisiana and Oklahoma, just to name a few. The dry conditions extended north into the Midwest and Upper Midwest, but wetter than average conditions prevailed in the upper Ohio Valley, along the eastern Great Lakes. This was also the scene in Florida, and coastal Texas. The Pacific Northwest experienced a rather wet winter in 1958-1959, while some parts of the Southwest dealt with dry conditions.

Let's break this all down.

The winter of 1958-1959 matched five out of five parameters I set forth that indicate what this winter will look like. For instance, it is expected that the winter of 2014-2015 will see a positive PDO, and the winter of 1958-1959 had that as well. Such a comparison happened, successfully, four other times. It's quite rare to find an analog as similar to projected conditions as this one, and we can only hope that the similarities stick as we head into fall.

Analog forecasting gives us a general idea of what the upcoming winter may be like. It's not a set-in-stone picture of what we will experience. While I cannot confirm that we will see a very dry or cold winter, the chances of both are considered to be elevated, if this analog year is to be believed.