Hail Storms over Southeast Georgia and a Long-lived Supercell over Northeast Florida

March 23, 2013
A. Enyedi, NWS Jacksonville

Synopsis

Severe thunderstorms produced large hail (golf ball size) over southeast Georgia during the morning hours, while a long-lived supercell storm moved inland from the northeast Gulf of Mexico near Pensacola, and tracked eastward near the Interstate 10 corridor toward Lake City before taking a more southeast track. Along the supercells route, it produced large hail from golf ball to baseball size and caused widespread wind damage, especially just southeast of Lake City where strong winds flipped an airplane and caused significant damage to homes in the area. A State of Emergency would later be declared for areas southeast of Lake City due to such widespread and catastrophic wind damage.

Image 1: Composite Image of Storm Tracks and Damage Reports Within Jacksonville County Warning Area (CWA)

Morning Environment & Southeast Georgia Hail Storms

A warm front was lifting northward over central Florida, while a surface low was over Texas. Morning storms over the southeast region were firing in an area of elevated instability (not surface based) as evidenced by the 12Z 3/23/13 Jacksonville sounding.

 

Image 2: Surface and Upper Air Analysis. HPC surface analysis with 12Z observations and the 12Z Jacksonville RAOB from 3/23/2013.  

The morning sounding from JAX showed southwest to west winds rapidly increasing above 850 mb (about 5,000 ft above ground level). The soundings from both Jacksonville and Tallahassee depicted 60-75 kt west winds in the hail growth zone (which is generally between the -10 ̊  C level and -30 ̊ C level in the atmosphere).  Note in Image 2, the sounding where the hail growth zone was analyzed. Also present in the hail growth zone was elevated instability, above an inversion near 700 mb (about 10,000 ft agl).  Thus, environmental analysis supported hail storms.

Afternoon Environment & Northeast Florida Supercell

As the warm front approached northeast Florida from the south later in the day, low level shear increased as did low level instability. Environmental analysis around 1 pm indicates that the surface warm front shifted northward toward the Florida-Georgia state line, while strong influx of Gulf of Mexico moisture increased in the mid levels as did shear with the 850 mb analysis (Image 3 below), showing SW winds near 40 kts from the Gulf of  Mexico. Also impressive around this time was the amount of upper level divergence, which is depicted in the 300 mb analysis of Image 3, likely due to the amount of speed shear present. All of these ingredients support the potential for severe, rotating storms, especially along the warm front axis.

 

This is exactly what transpired as one long-lived true supercell track just along the warm front all the way from near Pensacola, Florida eastward through the day near the Interstate 10 corridor until it exited the Atlantic coast near St. Augustine Beach around 3 pm.

 

 

 Spotter and Social Media Reports Were VERY Beneficial

A huge
assest to the NWS meteorologists working this severe weather event were the real-time weather reports, photos, even videos, that the general public, emergency responders and Skywarn Storm Spotters reported to the NWS during the event. The NWS was able to provide real-time information in our warning products and to our customers which helped provided credibility and validity to the warnings. Keep the reports coming!

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