SPC MD 1789



MD 1789 CONCERNING SEVERE POTENTIAL…WATCH POSSIBLE FOR PARTS OF THE SOUTHWESTERN FLORIDA PENINSULA AND LOWER KEYS

MD 1789 Image


Mesoscale Discussion 1789
NWS Storm Prediction Center Norman OK
0336 AM CST Wed Nov 11 2020

Areas affected...Parts of the southwestern Florida Peninsula and
lower Keys

Concerning...Severe potential...Watch possible 

Valid 110936Z - 111200Z

Probability of Watch Issuance...40 percent

SUMMARY...Potential for waterspouts might not be completely
negligible with ongoing convection near southwestern Florida
Peninsula coastal areas through daybreak.  By 9-11 AM EST, it is
possible that the potential for a tornado or two could begin to
increase around the Fort Myers and Port Charlotte areas.  While it
is not yet certain that this will require a watch, trends will
continue to be monitored for this possibility.

DISCUSSION...As Eta migrates north-northeastward around 10 kts, VWP
data indicate strengthening  wind fields in the 1-3 KM AGL layer
contributing to enlarging, clockwise-curved low-level hodographs
across the lower Florida Keys into southwestern Peninsula coastal
areas.  This includes flow up to 50 kts as far east as Key West,
dropping off to 30-40 kts at Miami.

In the presence of a tropically moist boundary layer (including
surface dew points in the mid 70s F) to the northeast and east of
the circulation center, this has contributed to weak to modest
sustained low-level mesocyclones within discrete ongoing convective
development near Marathon into the Gulf waters near/northwest of the
Everglades.  Given their current strength, and the probable presence
of at least a shallow near-surface stable layer inland of the coast,
the risk for tornadoes seems likely to remain low through daybreak. 
Thereafter, with the onset of at least weak boundary-layer warming,
some of these low-level mesocyclones could begin to pose increasing
risk for producing a tornado.  

Stronger low-level wind fields, associated potential low-level
mesocyclone development, and boundary-layer destabilization could
begin impacting coastal areas around Fort Myers and Port Charlotte
as early as 14-16Z.

..Kerr/Edwards.. 11/11/2020

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...MFL...KEY...TBW...

LAT...LON   26998251 27038199 26198148 25458062 25078074 24778114
            24718151 25448183 26358252 26998251 

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