Thursday,  Aug. 22, 2013 • Vol. 15--No. 38 • 4 of 30

(Continued from page 3)


• The highest number of total warnings issued was back in 1997 with a combination of 380 warnings.  The lowest number of warnings was issued is 169, set in 1995 and again in 2009.  The average number of warnings issued by year is about 261.  It is also important to note that in 2007, the NWS changed the warning methodology to a storm based warnings (SBWs) approach.  Prior to 2007, warnings were issued by entire counties. 
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Why has this severe weather season been so slow?
• As is usually the case, there is not one underlying reason for the lack of severe weather, but rather a combination of issues.  Recall that the basic ingredients for severe storms are moisture, instability, lift, and wind shear.  Often times this spring/summer, these ingredients tended to be out of phase.  In other words, by removing any one of these ingredients, organized severe storms become unlikely.     Several other relevant climate trends that stand out from this spring/summer include:
• -Colder than normal conditions in April and May led to a slow start to the season
• -Cooler than normal conditions  redeveloped in July and early August
• -Predominate northerly wind flow kept Gulf moisture south of the region which resulted in drier than normal conditions in mid-July through mid-August
• -There were few potent low pressure systems this severe weather season

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