Tropical Storm Nestor Forecast Discussion Number 7

By | October 19, 2019

Issued at 1000 PM CDT Fri Oct 18 2019

000
WTNT41 KNHC 190235
TCDAT1
Tropical Storm Nestor Discussion Number   7
NWS National Hurricane Center Miami FL       AL162019
1000 PM CDT Fri Oct 18 2019
The Air Force and NOAA Hurricane Hunters are investigating Nestor
this evening, and they have found that the minimum pressure
has dropped to 996 mb, 3 mb lower than this afternoon, but they have
not found higher winds yet.  Based on preliminary data from both
aircraft, the initial wind speed remains 50 kt.  The Air Force also
reported that there is a lot of lightning occurring in the
thunderstorms on Nestor's east side.  Nestor remains a lopsided
tropical storm, with very intense deep convection extending well to
the east of the center with only small areas of convection near and
to the west of the center.  This asymmetric cloud pattern is due to
strong westerly wind shear associated with a nearby shortwave
trough.  Doppler radar imagery indicates that rain bands are now
spreading inland over much of the eastern portions of the Gulf
coast, and surface observations show the winds increasing near the
coast, but they are still not quite at tropical storm strength.
Water vapor satellite images show that the shortwave trough is
almost co-located with Nestor, which is likely part of the reason
why the minimum pressure has fallen.  Even though it is not
explicitly reflected in the forecast, Nestor could strengthen a
little before the storm makes landfall.  However, significant
intensification seems unlikely as the shortwave trough is expected
to bypass the cyclone soon, leaving the storm in a less favorable
environment of upper-level confluence and drier air. After landfall,
weakening is forecast and the models suggest that Nestor should lose
its tropical characteristics on Saturday when it tracks across the
southeast U.S.  The weaker extratropical cyclone is expected to
dissipate or merge with a cold front in about 4 days.
The tropical storm is moving quickly northeastward at about 20 kt.
The models are in good agreement that this general motion should
continue for the next couple of days, taking the center of the storm
inland over the Florida Panhandle on Saturday morning and across
portions of Georgia and the Carolinas later Saturday and Sunday.
The weakening system is expected to slow down and turn eastward over
the western Atlantic early next week before it merges with a cold
front.  The NHC track forecast is nudged to the west of the
previous one to be in better agreement with the latest consensus
models.
Given the structure of Nestor, dangerous storm surge and
tropical-storm-force winds will occur along a large portion of the
Florida Gulf Coast well east of the track of Nestor's center
through Saturday.
Key Messages:
1. There is a danger of life-threatening storm surge inundation of
up to 5 feet above ground level along the Florida Gulf Coast from
Indian Pass to Clearwater Beach, where a Storm Surge Warning is in
effect. Residents in these areas should follow advice given by local
officials.
2. Tropical storm force winds are spreading across portions of the
Florida Gulf Coast, where tropical storm warnings are in effect.
Regardless of the exact track and intensity of the system, these
winds will cover a large area, especially east of the center.
3. Isolated flash flooding is possible along the central and eastern
Gulf Coast and Southeast United States coast into early Sunday
morning.
4. Wind and coastal flooding hazards along the U.S. East Coast will
be covered by non-tropical watches and warnings issued by local NWS
offices, since the system is expected to lose its tropical
characteristics after it moves inland along the Gulf Coast.
FORECAST POSITIONS AND MAX WINDS
INIT  19/0300Z 28.5N  87.0W   50 KT  60 MPH
12H  19/1200Z 30.2N  85.2W   50 KT  60 MPH
24H  20/0000Z 32.7N  82.3W   35 KT  40 MPH...POST-TROPICAL
36H  20/1200Z 34.9N  78.2W   35 KT  40 MPH...POST-TROP/EXTRATROP
48H  21/0000Z 36.5N  73.7W   35 KT  40 MPH...POST-TROP/EXTRATROP
72H  22/0000Z 37.5N  67.0W   35 KT  40 MPH...POST-TROP/EXTRATROP
96H  23/0000Z...DISSIPATED
$$
Forecaster Cangialosi

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