Thursday, March 24, 2011

Putting the winter of 2010-2011 "in the books"

The winter of 2010-2011 is officially over, both meteorologically (on February 28) and astronomically (on March 20), so now is a good time to go back and review what Memphis and the Mid-South dealt with during this La Nina winter.  For this post, I'll define winter using the meteorological period of December-February.

Referring back to late last fall, I wrote a post on the expected conditions for this past winter.  Due to a consensus among many organizations that La Nina would dominate the weather pattern throughout the winter months, I predicted a warmer and wetter winter than average, with an increased risk of a severe weather outbreak not unlike to the La Nina winter of 2008.  How did it turn out? Well, La Nina existed, but was overshadowed by a fairly strongly negative North Atlantic Oscillation (NAO), which allowed colder than normal weather to exist across eastern North America.

The balance between La Nina and the negative NAO resulted in temperatures that started off very cold in December, but warmed some in January and February, thus an average winter temperature of 42.1 degrees, which is slightly below the average of 42.7 degrees.  In terms of precipitation, despite some significant snowfall (more on that in a minute), drought conditions from late fall persisted into winter and Memphis ended up with just over 50% of normal winter precipitation. The total was 7.37" of liquid precip versus an average of 14.23", ranking this winter as the 8th driest on record.  The severe weather threat never really materialized this winter, other than on February 24th when strong wind ripped through the metro area with a line of thunderstorms, causing damage in parts of the region.

While a great deal of snowfall was not expected, the Memphis area experienced a third straight snowy winter. The total snowfall at Memphis International Airport was 9.7", which was the most since 1987-88, with six days of measurable snowfall, the most since 1984-85.  This is 6.1" above the normal of 3.6".  Below is a graphic courtesy of NWS-Memphis showing winter snowfall totals across the Mid-South.
2010-2011 Winter Snowfall Totals, from NWS-Memphis
More details on the recently completed winter season can be found in a National Weather Service review.

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