[Tropical] Tropical Cyclone Discussion

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WTNT45 KNHC 071500
TCDAT5

Tropical Storm Elsa Discussion Number  30
NWS National Hurricane Center Miami FL       AL052021
1100 AM EDT Wed Jul 07 2021

An Air Force Hurricane Hunter aircraft has made several fixes in
Elsa this morning, and recent observations from the plane indicated
that the center is now on the coast making landfall.  The aircraft
found that the central pressure remained about steady with maximum
winds of 55 kts up to landfall.  Sustained tropical-storm-force
winds are being reported from observing sites within the warning
area, with an unofficial report of a sustained wind of 54 kt gusting
to 62 kt at Horseshoe Beach in Taylor County, Florida during the
past half hour.

Center fixes indicate that Elsa has continued northward, with a
motion estimate of 360/12 kt.  Elsa should turn toward the
north-northeast today as it moves along the northwestern periphery
of an Atlantic subtropical ridge.  On Thursday, the cyclone should
begin to accelerate northeastward on the southeast side of a broad
mid-tropospheric trough over the eastern United States and Canada.
The official track forecast is on top of the latest multi-model
consensus, TVCA, solution.  This is only slightly to left of the
previous NHC track, and shows the center moving near the
northeastern U.S. coast within the next 48 hours.

Weakening will occur while the cyclone moves over land during the
next 36 hours or so, and the official intensity forecast closely
resembles the decay-SHIPS guidance.  Since winds of 35 kt are
possible near the coast well to the southeast of the center within
the next day or two, a tropical storm warning is in effect for a
portion of the southeast U.S. coast.  Some slight reintensification
is shown when the center moves near the coast in 48-60 hours.
However, since the water temperatures are rather cool near the
northeast coast, strengthening will probably be influenced by
baroclinic forcing associated with a 500 mb shortwave trough.  The
system will likely become extratropical by 72 hours if not sooner
while it moves through Atlantic Canada.


Key Messages:

1. As Elsa moves across the western and northern Florida Peninsula
today, heavy rainfall may result in considerable flash, urban, and
isolated moderate river flooding.  Heavy rainfall across southeast
Georgia, South Carolina, North Carolina, and southeastern Virginia
may result in isolated flash and urban flooding, with considerable
flash and urban flooding possible 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. There is still a danger of life-threatening storm surge along
portions of the west coast of Florida today, and a Storm Surge
Warning is in effect for that area.

3. Tropical storm conditions wile continue today across portions of
the northeast Gulf coast today within the warning area.

4. 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 much of the
coasts of Georgia and South Carolina.  Tropical storm conditions
are also possible along the coast of the mid-Atlantic states by
Thursday night or Friday.


FORECAST POSITIONS AND MAX WINDS

INIT  07/1500Z 29.9N  83.6W   55 KT  65 MPH
 12H  08/0000Z 31.7N  82.9W   35 KT  40 MPH...INLAND
 24H  08/1200Z 34.3N  80.9W   30 KT  35 MPH...INLAND
 36H  09/0000Z 37.3N  77.6W   30 KT  35 MPH...INLAND
 48H  09/1200Z 40.6N  73.3W   35 KT  40 MPH...NEAR COAST
 60H  10/0000Z 44.5N  68.0W   40 KT  45 MPH...NEAR COAST
 72H  10/1200Z 49.0N  60.9W   40 KT  45 MPH...POST-TROP/EXTRATROP
 96H  11/1200Z 58.0N  47.0W   35 KT  40 MPH...POST-TROP/EXTRATROP
120H  12/1200Z...DISSIPATED

$$
Forecaster Pasch
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