MINI SEVERE WEATHER SEASON, EL NINO & WINTER

Each year around this time we notice an uptick in the number of tornadoes across the Southeast and here in Georgia. November and for that matter December have been come to be known as the Second Season for severe weather after the lull that is seen during the summer and early fall.

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The atmosphere at this time of year (just like in the spring) is going through a major transition as cold air starts to shift southward. Unfortunately the warm air hasn’t completely gone away and this leads to problems. Then if we are in an El Nino year you have to throw in a very active and powerful branch of the southern Jetstream which you would think would help to produce lots of severe weather and tornadoes. But is that really the case? Is there a correlation?

This year’s El Nino is on track to rival the last major episode that took place in 1997-1998. Since then there have been two moderate episodes (2002-2003 & 2009 & 2010) and two weak episodes (2004-2005 & 2006-2007).

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Going back and comparing the El Nino episodes with tornado activity doesn’t reveal a clear picture. In fact during the strongest El Nino (1997-1998) there were only two tornadoes in November and none in December. The one episode that yielded the greatest number was the 2002-2003 moderate El Nino. November and December of 2002 saw 12 and 13 tornadoes respectively! The other El Nino episodes resulted in the following number of tornadoes: 2004-2005 (0 in November and 0 in December); 2006-2007 (2 in November and 2 in December); 2009-2010 (0 in November and 8 in December).

So is there a correlation between El Nino and fall tornadoes. It appears not. Is there a correlation between El Nino and wetter, cooler weather in the months of November and December? Absolutely! In fact looking back at the last five El Nino episodes and the ten corresponding months of November and December, there have only been two drier than normal months (Nov. 1997 & Dec. 2006) and two warmer than normal months (Nov. 2004 & Dec. 2006).

With all of this being said where are we so far this November? As of today Georgia has seen 2 tornadoes. They occurred at the beginning of the month in Telfair County in south Georgia. There is a possibility that a few more could occur this Wednesday primarily in the southern tier of the state. Rain so far this month has been abundant. Here in Atlanta we have recorded 6.94″ which as today is 5.05″ above normal. The normal rain total for the entire month of November is just 4.10″! In keeping with the strong El Nino you would expect the temperatures to be slightly below normal, but that has not been the case. In fact as of today we are 3 degrees above average so far this November.

So what should we expect going down the road through the winter? All indications are for the El Nino to stay strong if not strengthen some. Therefore expect cooler than normal temperatures

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and above normal precipitation.

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What about snow? Below normal temperatures and above normal precipitation…..sounds promising for snow. Right? Wrong! The below normal temperatures are factoring in the increase amount of cloud cover that comes along with an increase in storm systems rolling through. Actually in El Nino years we often have a wedge type setup with cold air sliding in out of the Carolinas at the surface in advance of the storms coming in from the west. This in fact is more conducive to ice events than snow. I personally would rather have the snow!!! As they say stay tuned, I’m sure it will be an interesting if not memorable winter!