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(T. F. “Storm” Walsh III)
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The Storm Prediction Center (SPC) has designated an ENHANCED risk of Severe Thunderstorms across parts of MIDDLE TENNESSEE…FAR NORTHEAST MISSISSIPPI…NORTH-CENTRAL ALABAMA AND NORTHWEST GEORGIA…
…There is a SLIGHT risk from parts of the TENNESSEE VALLEY INTO GEORGIA AND NORTHERN FLORIDA…
There is a MARGINAL risk across parts of the MID MISSISSIPPI VALLEY…OHIO VALLEY…TENNESSEE VALLEY AND SOUTHEAST…
Probability of severe weather within 25 miles of a point.
Hatched Area: 10% or greater probability of significant severe weather within 25 miles of a point.
Tornadoes, damaging winds and hail are expected across parts of Middle Tennessee, much of northern Alabama, far northeast Mississippi and northwest Georgia. A strong tornado or two is possible during the late afternoon. Severe wind gusts are also possible into northern Florida.
Based on my afternoon analysis of forecast sounding data from F5 DATA, utilizing the NAM-WRF solution (as SPC in their report referenced the NAM model), severe indices and parameters suggest the bulk, or main portion of the severe thunderstorms, should occur approximately within the time frame of 4:00 p.m. to 7:00 p.m. CDT. As time works into later in the evening, conditions begin to weaken, however some weaker, isolated severe incidents could linger into 10:00 p.m.CDT
Based on the current forecast sounding data, the setup for tomorrow if nothing changes, appears to indicative of a VERY UNSTABLE atmosphere, with current sounding data displaying the following indices:
SBCAPE (Surface Based CAPE): 1500 – 3000 j/kg
MLCAPE (Mean Layer CAPE): 1000 – 1500 j/kg
LI (Lifted Index): -4 to -8
EHI (Energy Helicity Index): 2 – 6
STP (Significant Tornado Parameter): 4 – 9
BRN (Bulk Richardson Number): 20 – 45
Based on these values, thunderstorms should be super cell in nature. Based on CAPE values and the L.I., very large hail may be experienced, especially with stronger cells. Isolated strong tornadoes (EF2+) cannot be ruled out, especially with stronger, rotating cells, and should be more prevalent in the enhanced risk area. Once again, the current sounding data outlines I have drawn on the F5 DATA maps, do not match up with the SPC outlines. I am not sure why this discrepancy exists, as the current sounding values and outlines I have drawn, indicate where the indices show the best probability for tornadoes to occur. These outlines also match the SPC SREF STP indices outline:
NAM 4:00 P.M. CDT TOR
NAM 7:00 P.M. CDT TOR
NAM 10:00 P.M. CDT TOR
SPC SREF STP OUTLINE
Areas in both the current day 2 and day 3 outlooks will be under the influence of a strong jet max, or jet streak.
250 MB JETSTREAM WINDS
SPC has also designated an ENHANCED risk of Severe Thunderstorms for Tuesday, across parts of NORTHERN FLORIDA…
There is a SLIGHT risk across much of CENTRAL AND NORTHERN FLORIDA
There is a MARGINAL risk across FAR SOUTHERN GEORGIA INTO FLORIDA
Again, based on my afternoon analysis of forecast sounding data from F5 DATA, utilizing the NAM-WRF solution, severe thunderstorms could initiate by 11:00 a.m. EDT, with the most severe weather possibly occurring between 2:00 p.m. – 5:00 p.m. EDT. I do not have the F5 DATA maps available, as the drawing feature would not allow me to draw outlines as seen in the SPC maps. However, forecast sounding indices indicate the most severe potential, and potential for tornadic activity, to occur within the enhanced risk area. Based on the sounding data I reviewed, thunderstorms could begin as supercells early in the initial stages, and as the day wears on, information suggests either multicelluar storms or QLCS (Quasi-Linear Convective System) thunderstorms. Given the analyzed forecast sounding data, hail (some isolated large hail), isolated tornado activity, and damaging thunderstorm gusts should be on order, mainly in the enhanced risk outline. Based on the graphic displayed by the NAM F5 DATA which displays indices outlines, I cannot at this time, rule out a slight extension of the enhanced risk outline into the West Central Florida area.
I have to work tomorrow and Tuesday, so I will not be in the office to update you.
Residents within the risk areas should monitor NOAA Weather Radio and NWS statements Monday and Tuesday.
IF A TORNADO WARNING IS ISSUED FOR YOUR AREA, SEEK SAFE, STURDY SHELTER IMMEDIATELY!
Please use the following linked maps for updated severe weather and Doppler Radar information.
Have a blessed evening!
T. F. “STORM” WALSH III
GMCS, USCG (ret)
METEOROLOGIST / HURRICANE SPECIALIST /SEVERE WEATHER SPECIALIST
MEMBER WEST CENTRAL FLORIDA AMS