SPC MD 1776


MD 1776 Image

Mesoscale Discussion 1776
NWS Storm Prediction Center Norman OK
0702 PM CST Sun Nov 08 2020

Areas affected...parts of southern Florida and the Keys

Concerning...Severe potential...Watch unlikely 

Valid 090102Z - 090330Z

Probability of Watch Issuance...20 percent

SUMMARY...Risk for a brief/weak tornado or two will gradually
increase over the next couple of hours, though potential may never
reach the point where tornado watch issuance becomes necessary.

DISCUSSION...Latest radar loop shows the center of Tropical Storm
Eta roughly 55 miles south-southeast of the Miami-Dade county
coastline.  The storm is moving slowly west-northwestward, and
should make landfall over the Keys late this evening.

Northeast of the center, a band of enhanced convection is indicated
over the Bahamas.  Several cells within this band are exhibiting
weak rotation per KMIA WSR-88D storm-relative velocity, with the
lead cell roughly 50 miles from the Broward County coastline moving
west-northwest at 25 kt.

This evening's KMFL (Miami) RAOB indicates a near moist-adiabatic
temperature profile, not particularly conducive for appreciable
updraft strength.  However, a strong increase in easterly flow with
height is indicated through the lowest km, resulting in low-level
shear favorable for updraft rotation -- as confirmed by radar within
the offshore convective band.

Given motion of Eta and the associated convective bands, an
increased threat for a brief tornado or two may spread inland over
the next couple of hours given that ample low-level shear will be
maintained across the area this evening/overnight.  However, given
the lack of thermodynamic support for strong updrafts and any
associated potential for substantial stretching, and weak
deeper-layer shear, any risk for tornadoes should be limited to
those of the weak/brief variety.

..Goss/Thompson.. 11/09/2020

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


LAT...LON   24898014 24848084 25448102 26168092 26858042 26817949
            26297894 25677902 24898014 

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