|Mesoscale Discussion 1691|
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Mesoscale Discussion 1691
NWS Storm Prediction Center Norman OK
0216 PM CDT Tue Sep 15 2020
Areas affected...Coastal Alabama and Florida
Concerning...Tornado Watch 489...
Valid 151916Z - 152115Z
The severe weather threat for Tornado Watch 489 continues.
SUMMARY...The tornado threat associated with several outer feeder
bands of Hurricane Sally will likely increase this afternoon and
evening. The current tornado watch will remain valid until around
23Z when a new tornado watch will likely be coordinated.
DISCUSSION...As of 2 pm CDT, the center of Hurricane Sally was
located at 29.2N 88.2W or about 105 miles southwest of Mobile,
Alabama from the latest NHC guidance. Several feeder bands are
rotating around the storm, with embedded cellular convective
elements noted. Additional small discrete cells were observed off
the coast of the Florida, near Tallahassee. The wind field around
Sally is forecast to continue to mature, and SPC mesoanalysis shows
that strong 0-1 km shear of 50-60 kts is present in Sally's
northeastern quadrant. Some dry air entertainment between the bands
should support weak destabilization this afternoon and evening given
the very moist surface conditions (TDs 75-79 degrees F). The
increase in buoyancy and strong low-level shear should support small
rotating updrafts with an attendant risk for tornadoes as the bands
move ashore. The threat for tornadoes will increase further as Sally
moves slowly to the north this evening and overnight, bringing
stronger shear and convection onshore. Tornado Watch 489 remains
valid until 2300 UTC when a new tornado watch will be coordinated.
...Please see www.spc.noaa.gov for graphic product...
LAT...LON 29838551 29988571 30148609 30238658 30228692 30128745
30088792 30168821 30378833 30648834 30838831 31138801
31218764 31238713 31138619 30958541 30728480 30298411
29758412 29668443 29568488 29598518 29838551
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