[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT43 KNHC 231454
TCDAT3

Tropical Storm Laura Discussion Number  15
NWS National Hurricane Center Miami FL       AL132020
1100 AM EDT Sun Aug 23 2020

Laura continues to produce a large area of deep convection to the
south and southeast of the estimated center location.  The center
has not been easy to locate this morning, but the low-cloud motions
seen in GOES-16 one-minute visible imagery, along with surface
observations, suggest that the center is just west of the west coast
of Haiti.  Data from a NOAA P-3 aircraft that has flown a
tail-Doppler radar mission along the southern and northern coasts of
Hispaniola this morning found maximum winds of 40-45 kt, so the
initial intensity has been set at 45 kt.  Little change in strength
is expected during the next 36 hours while Laura moves near or over
Cuba.  When the center of Laura emerges over the Gulf of Mexico
Monday night, the upper-level environment is expected to be
conducive for strengthening, and once the circulation recovers from
its trek over land, deepening is anticipated.  Warm water and a very
favorable upper-level wind pattern are expected to allow for steady
intensification until Laura reaches the northern Gulf coast, and
with landfall expected between the 72 and 96 h forecast points, the
system could be somewhat stronger than explicitly indicated below.
The NHC intensity forecast is a blend of the SHIPS and HFIP
corrected consensus models.

Although the center of Laura was been difficult to track while it
passed over Hispaniola, the estimated motion is west-northwestward
at about 18 kt.  A strong deep-layer ridge over the western
Atlantic should continue to steer Laura west-northwestward for the
next couple of days.  The track guidance has continued to nudge
southward during the first 36 hours and the official forecast
has been adjusted accordingly, taking the storm closer to the
southern coast of Cuba.  After that time, the ridge is forecast to
build westward over the eastern Gulf of Mexico.  This pattern
should allow Laura to maintain a west-northwestward motion until it
approaches the central Gulf, where a northwestward motion is
expected to begin as the storm nears the western periphery of
the ridge.  The dynamical models have trended toward stronger
ridging over the eastern Gulf, resulting in a westward shift in
the guidance. The NHC track forecast has been moved westward at
72-96 hours, and lies between the GFS and ECMWF solutions. Users are
reminded to not to focus on the exact details of the track forecast
at the longer range as future adjustments will likely be required,
and storm hazards will extend far from the center.

Key Messages:

1. Tropical storm conditions are expected across portions of the
Dominican Republic and Haiti, the Turks and Caicos, the southeastern
Bahamas, and Cuba through Monday. Heavy rainfall is likely across
these areas and could cause mudslides and life-threatening flash and
urban flooding.

2. Tropical storm conditions are possible over the central Bahamas
and Andros Island tonight and Monday, and in the Florida Keys on
Monday.

3. While the details of the long-range track and intensity forecasts
remain uncertain, Laura is forecast to strengthen over the Gulf of
Mexico and there is an increasing risk of storm surge, rainfall, and
wind impacts along portions of the U.S. Gulf Coast by the middle of
the week. This could result in a prolonged period of hazardous
weather for areas that are likely to be affected by Marco earlier in
the week. Interests along the Gulf Coast should monitor the progress
of Laura and Marco and updates to the forecast during the next few
days.

FORECAST POSITIONS AND MAX WINDS

INIT  23/1500Z 19.2N  73.2W   45 KT  50 MPH
 12H  24/0000Z 20.3N  76.0W   45 KT  50 MPH...INLAND
 24H  24/1200Z 21.6N  79.9W   45 KT  50 MPH...NEAR CUBA
 36H  25/0000Z 22.9N  83.2W   45 KT  50 MPH...INLAND
 48H  25/1200Z 24.1N  86.2W   50 KT  60 MPH...OVER WATER
 60H  26/0000Z 25.3N  88.9W   65 KT  75 MPH
 72H  26/1200Z 26.8N  91.4W   80 KT  90 MPH
 96H  27/1200Z 30.9N  94.0W   85 KT 100 MPH...INLAND
120H  28/1200Z 35.7N  92.8W   30 KT  35 MPH...INLAND

$$
Forecaster Brown
This weather bulletin was brought to you by:
www.nashvilleweather.net