[Tropical] Tropical Cyclone Discussion

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WTNT43 KNHC 212125 CCB
TCDAT3

Tropical Storm Laura Discussion Number   8...Corrected
NWS National Hurricane Center Miami FL       AL132020
500 PM AST Fri Aug 21 2020

Corrected formatting and initial intensity

A poorly-defined convective band has become evident over the
southeastern portion of the circulation.  However, there is little
or no deep convection near the estimated center.  Overall, the
system's cloud pattern still has a ragged appearance.  Dvorak
intensity estimates range from 35 to 45 kt, and the current
intensity is held at 40 knots based on continuity from Hurricane
Hunter observations from earlier today.  There is a fairly
well-defined upper-level outflow pattern at this time, but an
upper-level trough to the west of Laura could be an impediment to
future strengthening.  The official intensity forecast is a little
below the intensity consensus mainly due to the influences of the
land masses of the Greater Antilles.  At days 4-5, the intensity
forecast is also a bit below the consensus due to uncertainties at
these longer forecast ranges.

The center is not very easy to see, even on visible or radar
images, but the best guess at an initial motion is 275/15 kt. The
track forecast reasoning has not changed much from the previous
advisory package.  Laura should move generally west-northwestward
along the southern periphery of a subtropical ridge for about the
next 72 hours.  Later in the forecast period, the cyclone is
expected to turn northwestward as it begins to move around the
western side of the ridge.  The track guidance has shifted westward
at days 4-5 and so has the official forecast, which is mostly close
to the model consensus, but not quite as far west as that guidance
in the latter part of the forecast period.

Another NOAA Hurricane Hunter Aircraft is scheduled to investigate
Laura shortly.

KEY MESSAGES:

1. Tropical storm conditions are expected across portions of the
northern Leeward Islands, the Virgin Islands, and Puerto Rico today
through Saturday, Tropical Storm conditions are also expected along
the northern coasts of the Dominican Republic and Haiti from
Saturday into Sunday.  Heavy rainfall is likely across these areas
beginning today and could cause mudslides and flash and urban
flooding through Sunday.

2. Tropical storm conditions are possible over portions of the
southeastern Bahamas and the Turks and Caicos Islands on Sunday.

3. The details of the long-range track and intensity forecasts
remain more uncertain than usual since Laura is forecast to move
near or over Portions of the Greater Antilles through Monday.
However, Laura could bring storm surge, rainfall, and wind impacts
to portions of Cuba, the Bahamas, and Florida early next week and
the northern U.S. Gulf Coast by the middle of next week.  Interests
there should monitor the progress of Laura and updates to the
forecast during the next few days.

FORECAST POSITIONS AND MAX WINDS

INIT  21/2100Z 17.1N  61.2W   40 KT  45 MPH
 12H  22/0600Z 17.7N  63.9W   40 KT  45 MPH
 24H  22/1800Z 18.6N  67.3W   45 KT  50 MPH
 36H  23/0600Z 19.6N  70.7W   50 KT  60 MPH...INLAND
 48H  23/1800Z 20.5N  74.3W   55 KT  65 MPH...OVER WATER
 60H  24/0600Z 22.0N  77.9W   55 KT  65 MPH
 72H  24/1800Z 23.5N  81.5W   55 KT  65 MPH
 96H  25/1800Z 26.3N  86.5W   65 KT  75 MPH
120H  26/1800Z 29.0N  89.0W   65 KT  75 MPH

$$
FORECASTER PASCH
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