Southeast Georgia Mini Supercell - January 24

                       Southeast Georgia Mini-Supercell Event
                                         January 24, 2010



Introduction

On Sunday, January 24, 2010, a large upper trough over the central United States and
associated cold front slowly pushed towards the east coast.  A strongly sheared environment
combined with weak instability  resulted in supercell formation over Coffee county,
Georgia near Douglas. The 88D radar (KVAX) at Moody Air Force Base detected this storm
along with classic supercell signatures.


Analysis

This weather event was characterized by strong wind fields and vertical lift including a
50 knot low level jet and 100 knot upper jet.  Wind shear was impressive with a storm
relative helicity (0-3km) of 449 m^2/s^2 on the 00z/25th Tallahassee sounding (Figure 1).
 The sounding also shows elevated instability between 850 and 600 mb.  The MSAS analysis
at 2100 UTC January 24 (Figure 2) shows a southerly surface flow with weak moisture
convergence over interior southeast Georgia.  A moist and slightly unstable airmass was
indicated by surface dewpoints in the mid 60’s and surface lifted indices (LI) in the
0 to -2 range.  



Radar Data

The KVAX 88D radar is located approximately 45 miles south-southwest of Douglas which
provided a good view of the storm.  The 4 panel reflectivity at 2126 UTC shows the
strongest radar echoes of the storm.  Figure 3 indicates a hook echo at 0.5 degree
elevation with a bounded weak echo region (BWER) at 1.5 and 2.4 degrees.  A strong
reflectivity core extended through 15,000 feet with 63 dBZ detected on the 3.4 degree
slice. The storm top was only around 20,000 feet which is usually considered a low
topped ‘mini’ storm.    

The 4 panel storm relative motion(SRM) at 2126 UTC showed strong gate to gate
rotation (Vr~33 knots) at the lowest elevation slice. This rotation extended in
height with a rotational couplet extending up through 2.4 degrees or around 11,000
feet above ground level (Figure 4).       
 

Conclusion

A significant weather alert (SWA) for the possibility of strong winds and funnel clouds
was issued by the National Weather Service(NWS).   No severe weather was reported to
the NWS associated with this storm.  Only brief heavy rain was observed by the nearby
911 center.  This short lived storm never did  produce cloud to ground lightning
according to the lightning detection  network.  The lack of  lightning strikes would be  
consistent with the relatively low storm  top.  The elevated (850 to 600 mb) instability
and inversion below 850 mb likely caused this strong circulation to remain aloft
resulting in no severe weather reports.


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Written by Matt Zibura



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