2009-10 Winter Outlook, The Comparisons

As you are aware, I released my initial winter outlook on September 1, 2009 (you can read the full post here) and I followed that up with some specific details for key locations with this post. On October 14, 2009, one of the nation's largest private weather companies, AccuWeather, released their 2009-10 Winter Outlook (viewable by clicking provided link) and today, October 15, 2009, the National Oceanic and Atmospheric Administration (NOAA) released the official U.S. Government 2009-10 Winter Outlook. I would like to compare my forecast with the other two and to see if we are thinking in similar ways heading in different directions.

Let's first take a look at a quick review of my forecast for this winter. My forecast is for below normal temperatures for much of the Eastern U.S. with the emphasis of the largest anomalies in the Tennessee and Ohio Valleys. A second area of below normal temperatures is expected across Nevada, Utah and Arizona. Above normal temperatures are forecast across much of the Rockies with near normal conditions expected elsewhere. Now, what is below normal, much below normal and near normal mean? My forecast categorizes these items as such:

• Near Normal: Temperatures +/- 2 of seasonal normal values (DEC-JAN-FEB)
  
• Above Normal: Temperatures 2 to 4 degrees above normal values
  
• Much Above Normal: Temperatures greater than 4 degrees above normal values
  
• Below Normal: Temperatures 2 to 4 degrees below normal values
  
• Much Below Normal: Temperatures great than 4 degrees below normal

My winter forecast was put together using several different variables and some of these are:

• Current & Forecast ENSO Values (El Nino)
  
• Current & Forecast PDO Values (Pacific Decadal Oscillation
• Current & Forecast AO Values (Arctic Oscillation)
  
• Current Weather 30 to 90 Day Weather Trends

Using my methods, the winter seasons I have chosen to use to help act as guidelines and past reference points are: 1951-52, 1957-58, 1963-64 and 1976-77.

Now, there is a moderate El Nino in place and I am forecasting that the El Nino will likely peak around November/December and hold steady for a month or two and then begin to taper off. By then, most of the winter will have likely passed by. This will set up a weather pattern that will provide for a quick moving, and likely controlling, southern jet stream that will move along the southern tier of the U.S. and then bend up along the East Coast. This pattern will allow for an enhancement in precipitation and allow the coldest air of the season to move into the Southeast/Ohio Valley and Mid-Atlantic.

A mix of colder than normal temperatures and an increase in moisture means the potential for above normal snow/ice for the same area mentioned above to be below normal temperature-wise. The largest above normal chances for snowfall occur along and north of the I-20 corridor from Dallas-Atlanta and along and south of the Ohio River. I am predicting the potential for this area to see in excess of 150% above normal snowfall. Cities included in this area include: Dallas, Little Rock, Shreveport, Birmingham, Huntsville, Nashville, Paducah, Lexington, Atlanta, Asheville, Richmond, and Washington D.C.

So let's look at the other winter outlooks. First, how about temperatures? AccuWeather is also predicting a large swath of below normal temperatures across the southern tier of the U.S. and from Southern California to the Southeast and then up the East Coast to New England. Inside the below normal area a well below normal area is highlighted a bit further south then my winter forecast and encompasses the Mid-South and Tennessee Valleys and into the Appalachians from Louisiana to West Virginia.

NOAA's forecast has a bit smaller below normal area than goes from Texas to the Mid-Atlantic with the largest chances of below normal temperatures running from southeast Texas to the Southeast and up into the Mid-Atlantic.

All-in-all, the three winter forecasts are in pretty close agreement with where the below normal temperatures are forecast. They are also similar in placement of above normal and well above normal temperatures. I admit my forecast may be under doing the potential forecast warmth across the northern Rockies into the Upper Midwest.

How about snowfall? Well, neither AccuWeather nor NOAA released a specific snowfall forecast for this winter; however, AccuWeather did release a graphic showing some indications of their thoughts related to snowfall and it shows similar thoughts in increasing the snow potential from Texas to the Mid-Atlantic.