Wednesday, October 22, 2008

IndianaWeatherOnline.com 2008-2009 Winter Forecast!

IndianaWeatherOnline.com Winter 2008-2009 Forecast
Issued by Brandon Redmond on October 22nd, 2008

So far this Autumn, except for the past several days, temperatures have continually been at or above normal while precipitation has been well below normal in most locations. The key questions is will this trend continue into the Winter?

After an amazingly cold and snowy winter last year, it will be hard even with near normal or even above normal snowfall to compare to the extremely overactive winter we experienced in 2007-2008.

Sea Surface Temperatures in the Equatorial Pacific are just one of the various indicators we use in long-range forecasting. There are three terms used to describe Temperatures in the Equatorial Pacific: El Nino, La Nina and ENSO Neutral. Typically here in the Ohio Valley, El Nino years typically result in warmer Winter Seasons, while like last year, La Nina years often provide plenty of snowfall across the Central United States.

La Nina years typically tend to provide a wealth of snowfall across our area due to several reasons. First, the Pacific Jet Stream tends to track farther North across the Central United States, often times causing storm system after storm to track Northeast across the Midwest and Ohio Valley. During ENSO Neutral/La Nina years, the Pacific Jet also tends to come onshore farther North, generally in the Pacific Northwest. At the same time, while the Polar Jet often dives Southeast out of Western and Central Canada bringing cold Arctic air down into the United States. As these two jets collide across the Central United States, the recipe is right for major winter storms. The Midwest/Ohio also tend to experience an abundance of clipper-type systems due to a strong Polar Jet, which in-turn also often times means above-normal Lake-Effect Snowfall in favored areas.

The opposite occurs during El Nino years. The Pacific Jet often tracks well South of our area, causing 90% of the storm systems to have no affect on the Ohio Valley and leaving us high and dry. The Polar jet tends to track well East of the Ohio Valley, and leaves us with above to well-above normal temperatures.

Currently Sea Surface Temperatures in the Equatorial Pacific are ENSO Neutral, but the latest trends would indicate that a weak La Nina could develop during the next several months. Over the past several months, we can already see temperatures starting to gradually fall across the Equatorial Pacific and by the beginning of 2009, it is definitely possible that a weak La Nina could be in place.

Another factor used in our seasonal and long range forecasts are our long-range forecast models. The CFS (Climate Forecast System) is a long-range forecast model that forecasts trends out to 9 months in advance. It has consistently shown near normal precipitation values through January with above normal precipitation in February and March. The CFS shows near normal temperatures for the entire Winter Season.

A third factor used in long-range and Seasonal Forecasting is Climatology and Current Trends. During the past several weeks, cold air has been building in Canada, and we have already been clipped with a semi-Arctic airmass over the past several days, and will likely experience another shot of Arctic air during the upcoming week. While snow depth and coverage across North America has been running below normal so far this year, that looks to quickly change over the next 7-14 days with several major Autumn Storms dumping several inches of snow across the Plains and well into Canada.

So after all of that Meteorological Lingo, what is my forecast for this upcoming Winter for the Ohio Valley? Here is the break down:

I generally feel that we will see a weak La Nina by January or February of 2009. With the likelihood of an active Pacific Jet and for that matter a strong/active Polar Jet, I think we will in general terms see an active Winter. Our weather systems will generally dive Southeast across the Rocky's and then move East Southeast across the Plains and into the Lower Ohio Valley. Another prominent storm track as mentioned above will be out of Central Canada (Clipper-Type Systems) that dive Southeast along the Polar Jet across the Plains and into the Midwest. Between the two, the chances for an active Winter are definitely higher than normal. Those Clipper Systems will also re-enforce the Cold Air intrusion across the Midwest and Ohio Valley.

I feel that temperatures through the Winter will be the big story, as I have above-normal confidence we will experience Below-Normal temperatures December, January and February. Needless to say, if you were hoping for a mild Winter to offset those expensive heating bills, that's not looking to likely for the upcoming Winter. Precipitation (All types included) will most likely be slightly above normal, especially in January and February. I am forecasting near normal snowfall for the Ohio Valley and Midwest.

Precipitation (All Types Included): 100 - 125% of Normal for the Entire Winter Season
Snowfall: Near Normal for the Entire Winter Season
Temperatures: 1-2 Degrees Below Normal for the Entire Winter Season



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