FROM THE KATC TV3 WEATHER BLOG:
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While I’m not a big fan of making long-term seasonal outlooks (reasons to be explained below), based on the data from the Climate Prediction Center (CPC) and the National Oceanic and Atmospheric Administration (NOAA) it does appear that Acadiana will see a drier than normal winter with temperatures expected to be at or above normal.
While there is high confidence in the precipitation forecast, there is below normal confidence by this author on the temperature forecast.
Cooler than normal equatorial Pacific water temperatures have been developing over the last several months indicating that a “La Nina” pattern has re-developed.
This pattern is similar to the last two winters for Louisiana/Acadiana which was characterized by below normal rains and well below normal temperatures.
The winter of 2009/2010 (December through February) averaged more than 4 degrees below normal with 17 days of freezing temperatures in Lafayette while the winter of 2010/2011 averaged 2.5 degrees below normal with 27 days of freezing of temperatures.
Last winter would have been considered just as cold as the winter before if it were not for a dramatic swing in the second half of February where temperatures soared consistently into the 70s and 80s.
Interestingly enough there is enormous variability in the number of freezes Acadiana will see in any given winter with some years experiencing just a handful of freezes and other winters more than two dozen. Last year may have been close to a record for the number of freezes, but these statistics are not readily available.
In addition, when forecasting winter temperatures we must understand that even in an above normal winter, Acadiana can experience an arctic outbreak that could bring temperatures into the teens or lower. So perception versus reality also becomes an issue with these type of forecasts.
The real wildcard for winter forecasting, especially for temperatures, is the Arctic Oscillation, which per the last two winters trumped our La Nina influenced weather pattern ushering strong cold fronts to the area.
Per NOAA, “The Arctic Oscillation is always present and fluctuates between positive and negative phases. The negative phase of the Arctic Oscillation pushes cold air into the U.S. from Canada. The Arctic Oscillation went strongly negative at times the last two winters, causing outbreaks of cold and snowy conditions in the U.S. such as the “Snowmaggedon” storm of 2009. Strong Arctic Oscillation episodes typically last a few weeks and are difficult to predict more than one to two weeks in advance.”
With all of the above being said, it is with much consternation that we make the long-term outlooks.
Based on the current information supplied by NOAA and the CPC and given La Nina has kicked back in across the Pacific, Acadiana will likely see drought conditions perpetuating and/or worsening through the spring.
We will buy into above normal temperatures for now, but I would expected several very strong cold fronts nonetheless thanks to a more unpredictable Arctic Oscillation.
Another key to nailing the temperature forecast is where will the upper level trough axis be most prevalent this winter.
If the upper “troughing” is similar to the last two years, we will adjust our temperature forecast downward, but just a subtle shift of average trough a few hundred miles to the east will translate to much above normal temperatures.
So there here it is: a low confidence forecast for above normal temperatures and a high confidence forecast of below normal precipitation this winter for Acadiana.
Based on our late October pattern it would also be a fair prediction that November through early January could actually be below normal in Acadiana with the latter part of January into February possibly more dramatically warmer than normal skewing the numbers for the entire winter.
And based on the last two winters I would also expect a dozen or more freezes and the possibility of one or two events that may bring temperatures down into the mid-20s or slightly lower.
As for predicting any snow or ice events, your guess will be as good as mine. If the aforementioned forecast pans out, I wouldn’t be too excited for a winter storm…but if the pattern plays out closer to the last two winters we may indeed get one or two shots at the frozen stuff.
And per usual chances for a White Christmas in Acadiana will remain an abysmal 1 in 1000 year chance…here’s to “wish-casting”!
Rob Perillo
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LONG TERM WINTER FORECAST FOR ACADIANA (LOUISIANA)
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