[Tropical] Tropical Cyclone Discussion

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WTNT45 KNHC 061446
TCDAT5

Tropical Storm Elsa Discussion Number  25
NWS National Hurricane Center Miami FL       AL052021
1100 AM EDT Tue Jul 06 2021

Elsa's overall cloud pattern has changed little in organization
since earlier today.  There continues to be minimal shower and
thunderstorm activity over the western semicircle of the
circulation, with some bursting of deep convection near and east of
the estimated center.  A slightly-elevated observing site on Sand
Key, near Key West Florida, recently reported a peak 1-minute wind
of 49 kt with a gust to 56 kt.  This supports the current intensity
estimate of 50 kt.  Recent WSR-88D Doppler velocities from the Key
West radar suggest that the storm could be a little stronger than
that.  The Air Force Hurricane Hunter mission into the storm has
been delayed due to bad weather at the Keesler base, but is
rescheduled to investigate Elsa in a few hours.  This flight should
provide updated information on the intensity of the system.

Recently, the storm has been moving a little slower toward the
north-northwest and the initial motion is about 340/9 kt.  Elsa
should move generally northward today and tonight between the
western periphery of a subtropical ridge and an area of low
pressure over the northwestern Gulf of Mexico.  A gradual
turn toward the north-northeast should occur on Wednesday as the
system moves along the northwestern periphery of the ridge.
Thereafter, the cyclone is expected to accelerate northeastward
ahead of a trough over the eastern United States and eastern Canada.
This will take the system across the southeastern United States
within the next couple of days, near the coast of New England in
about 3 days and near or over Atlantic Canada in 4 days or so.  The
official forecast is nearly the same as the previous one and,
again, very close to the model consensus.

The environment over the eastern Gulf of Mexico is not ideal for
strengthening, with moderate westerly shear and some dry mid-level
air.  However, upper-level divergence ahead of a trough over the
east-central Gulf could result in some intensification of the
system during the next 12-24 hours.  The official forecast
continues to show the cyclone nearing hurricane strength while it
approaches the north Florida Gulf coast, but this is at the high
end of the numerical intensity guidance.


Key Messages:

1. Heavy rain will impact Cuba today resulting in significant
flooding and mudslides.  As Elsa moves near or along the western
Florida Peninsula through Wednesday, heavy rainfall may result in
isolated flash, urban, and minor river flooding, with considerable
flash and urban flooding possible in southwest and western portions
of Florida.  Mid to late week, heavy rainfall across coastal
Georgia, South Carolina, North Carolina, and southeastern Virginia
may result in isolated flash and urban flooding, with considerable
flash and  urban flooding possible across coastal Georgia and the
Lowcountry of South Carolina.

2. There is a danger of life-threatening storm surge along portions
of the west coast of Florida tonight and Wednesday, and a Storm
Surge Warning is in effect for that area.

3. Hurricane conditions are possible tonight and early Wednesday
along a portion of the west coast of Florida, where a Hurricane
Watch is in effect.  Tropical storm conditions are occurring across
portions of the Florida Keys and are expected to spread northward
along much of the west coast of the state through Wednesday morning,
where a Tropical Storm Warning is in effect.

4. A Tropical Storm Watch is in effect for the Georgia coast and
portions of the South Carolina coast, where tropical storm
conditions are possible late Wednesday and early Thursday.


FORECAST POSITIONS AND MAX WINDS

INIT  06/1500Z 24.9N  82.8W   50 KT  60 MPH
 12H  07/0000Z 26.6N  82.9W   55 KT  65 MPH
 24H  07/1200Z 28.9N  83.0W   60 KT  70 MPH
 36H  08/0000Z 31.3N  82.0W   35 KT  40 MPH...INLAND
 48H  08/1200Z 33.8N  80.0W   30 KT  35 MPH...INLAND
 60H  09/0000Z 36.7N  76.4W   35 KT  40 MPH...INLAND
 72H  09/1200Z 39.5N  72.5W   40 KT  45 MPH...OVER WATER
 96H  10/1200Z 48.0N  60.0W   40 KT  45 MPH...POST-TROP/EXTRATROP
120H  11/1200Z...POST-TROP/EXTRATROP

$$
Forecaster Pasch
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