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Tropical Storm Irma Discussion Number  50
NWS National Hurricane Center Miami FL       AL112017
1100 AM EDT Mon Sep 11 2017

Irma continues to weaken while moving over extreme northern Florida
with most of the deep convection displaced well to the north and
northeast of the center due to strong shear.  In fact, global model
analyses suggest that the system has partial extratropical
characteristics, with some associated cold and warm air advection.
The current intensity is set at 55 kt which is in line with the
highest sustained winds seen in surface observations.  Since the
cyclone is very large its weakening will be fairly gradual, but the
effects of land and shear should reduce the system to a depression
in about 24 hours.  Shortly thereafter Irma will likely become a
remnant low, with complete dissipation by 72 hours as shown by the
dynamical guidance.

The initial motion continues to be north-northwestward or 340/15
kt.  Not much change has been made to the NHC track forecast.  Irma
or its remnant should continue to move along the eastern and
northeastern periphery of a broad mid-level cyclonic circulation
until dissipation.  The official track forecast is close to the
latest corrected multi-model consensus.

KEY MESSAGES:

1. There is the danger of life-threatening storm surge flooding
along portions of the coasts of Florida, Georgia and South Carolina,
where a Storm Surge Warning remains in effect.

2. Irma continues to produce very heavy rain and inland flooding
across much of the northern peninsula and eastern panhandle
of Florida, and southern Georgia, which is quickly spreading to the
rest of the southeast United States.  Intense rainfall rates of 2
inches or more per hour is leading to flash flooding and rapid rises
on creeks, streams, and rivers.  Significant river flooding is
likely over the next five days in the Florida peninsula and southern
Georgia, where average rainfall totals of 8 to 15 inches are
expected.  Significant river flooding is possible beginning Monday
and Tuesday in much of central Georgia and southern South Carolina
where average rainfall of 3 to 6 inches and isolated 10 inch amounts
are expected.  Portions of these states within the southern
Appalachians will be especially vulnerable to flash flooding.

FORECAST POSITIONS AND MAX WINDS

INIT  11/1500Z 30.3N  83.1W   55 KT  65 MPH...INLAND
 12H  12/0000Z 32.0N  84.5W   50 KT  60 MPH...INLAND
 24H  12/1200Z 33.9N  86.6W   30 KT  35 MPH...INLAND
 36H  13/0000Z 35.0N  88.4W   25 KT  30 MPH...POST-TROP/INLAND
 48H  13/1200Z 36.0N  89.0W   20 KT  25 MPH...POST-TROP/INLAND
 72H  14/1200Z...DISSIPATED

$$
Forecaster Pasch

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