[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT45 KNHC 080901
TCDAT5

Tropical Storm Elsa Discussion Number  33
NWS National Hurricane Center Miami FL       AL052021
500 AM EDT Thu Jul 08 2021

Doppler radar and surface observation indicate that the center of
Elsa is moving into southern South Carolina at this time.  The
organization of the storm has changed little during the past
several hours, with a complex of bands in the eastern semicircle.
The initial intensity is 35 kt, and these winds are occurring along
an area of the coast and coastal waters well southeast of the
center.

The initial motion is now 035/16.  The track guidance is in good
agreement that Elsa should accelerate northeastward during the next
few days as it becomes entrained into the mid-latitude southwesterly
flow, with the track carrying the system across the Carolinas and
the mid-Atlantic states during the next 24 hours, then near or over
southeastern New England and Atlantic Canada.  The new forecast
track is basically an update of the previous track, and it is very
close to the consensus models.

Rawinsonde data and GOES-16 RGB airmass imagery show an upper-level
shortwave trough over the southeastern United States to the west of
Elsa, and the global models forecast this system to follow the
cyclone northeastward and take on a negative tilt.  This should
result in increasing upper-level divergence over Elsa, which in turn
should lead to some strengthening as the storm moves near or over
the east coast of the United States.  The 00Z ECMWF model is not as
bullish on intensification as its previous run, but it and the 00Z
UKMET still call for strengthening, and even the weaker GFS
forecasts the favorable upper-air pattern.  Based on this, the new
intensity forecast shows a little more strengthening than the
previous forecast.

Based on the new forecast track, the tropical storm warning has
been extended northward along the United States east coast to
Massachusetts.  Non-tropical gale warnings are in effect for the
coastal areas to the north of the tropical storm warning due to the
likelihood that Elsa will become extratropical as it reaches that
area.


Key Messages:

1. As Elsa moves across the Carolinas Thursday, heavy rainfall may
result in limited flash and urban flooding. Heavy rainfall from the
Mid-Atlantic into New England Thursday and Friday could lead to
considerable flash and urban flooding.

2. Tropical storm conditions are expected along portions of the
coasts of Georgia and South Carolina this morning.  Tropical storm
conditions are also expected along the coasts of North Carolina
starting later today and the mid-Atlantic by this afternoon or
tonight.  Tropical storm conditions are expected in portions of the
southern New England states and New York by Friday.  Gale winds are
expected over the portions of the New Hampshire and Maine coasts by
late Friday or Friday night, and those conditions are possible over
portions of Atlantic Canada Friday night and Saturday.


FORECAST POSITIONS AND MAX WINDS

INIT  08/0900Z 33.4N  81.3W   35 KT  40 MPH...INLAND
 12H  08/1800Z 35.5N  79.3W   35 KT  40 MPH...INLAND
 24H  09/0600Z 38.8N  75.2W   40 KT  45 MPH...INLAND
 36H  09/1800Z 42.5N  70.1W   45 KT  50 MPH...OVER WATER
 48H  10/0600Z 46.9N  63.6W   45 KT  50 MPH...POST-TROP/EXTRATROP
 60H  10/1800Z 51.9N  54.0W   40 KT  45 MPH...POST-TROP/EXTRATROP
 72H  11/0600Z 56.6N  44.8W   35 KT  40 MPH...POST-TROP/EXTRATROP
 96H  12/0600Z...DISSIPATED

$$
Forecaster Beven
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