[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT45 KNHC 072057
TCDAT5

Tropical Storm Elsa Discussion Number  31
NWS National Hurricane Center Miami FL       AL052021
500 PM EDT Wed Jul 07 2021

Surface synoptic data indicate that the center of Elsa has moved
into extreme southern Georgia and, assuming continued weakening
since earlier today, the maximum winds are estimated to be 40 kt.
This may be a generous estimate of the current intensity since no
surface observations of sustained tropical-storm-force winds have
been recently received.  Elsa should weaken into a tropical
depression on Thursday.  By early Friday, the dynamical models show
some restrengthening of the cyclone as it moves along the
Mid-Atlantic coastline.  However, the simulated satellite imagery
from the global models at that time depict the system resembling a
frontal cyclone, so it is dubious as to whether Elsa will be
completely tropical in 48 hours.  Due to the uncertainty as to when
extratropical transition will occur, tropical storm watches have
been issued for Long Island and portions of southern New England at
this time.

The initial motion is northward, or 010/12 kt.  Elsa is forecast to
turn north-northeastward overnight as it moves around the
northwestern periphery of an Atlantic subtropical ridge while
accelerating northeastward ahead of a broad mid-level trough over
the eastern United States and Canada on Thursday.  The official
forecast is about the same as the previous one and closely follows
the multi-model consensus.


Key Messages:

1. Heavy rainfall may result in considerable flash, urban, and
isolated moderate river flooding over northern Florida.  Heavy
rainfall across southeast Georgia, South Carolina, North Carolina,
and southeastern Virginia may result inconsiderable flash and urban
flooding across southeast Georgia and the Lowcountry of South
Carolina.  Heavy rainfall across the Northeast and New England
Thursday and Friday could lead to isolated flash and urban flooding.

2. Although the center of Elsa is expected to remain inland of the
coastline from Georgia through the Carolinas during the next day
or two, tropical storm conditions are expected along portions of the
coasts of Georgia and South Carolina tonight.  Tropical storm
conditions are also possible along the coast of the mid-Atlantic
and southern New England states by Thursday night or Friday.


FORECAST POSITIONS AND MAX WINDS

INIT  07/2100Z 30.8N  83.4W   40 KT  45 MPH...INLAND
 12H  08/0600Z 32.8N  82.1W   35 KT  40 MPH...INLAND
 24H  08/1800Z 35.6N  79.4W   30 KT  35 MPH...INLAND
 36H  09/0600Z 38.8N  75.4W   35 KT  40 MPH...INLAND
 48H  09/1800Z 42.0N  70.5W   35 KT  40 MPH...INLAND
 60H  10/0600Z 46.0N  64.5W   40 KT  45 MPH...POST-TROP/EXTRATROP
 72H  10/1800Z 50.0N  57.0W   40 KT  45 MPH...POST-TROP/EXTRATROP
 96H  11/1800Z...DISSIPATED

$$
Forecaster Pasch
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