Tropical Report

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
800 AM EDT Sat Sep 30 2017

For the North Atlantic…Caribbean Sea and the Gulf of Mexico:

The National Hurricane Center is issuing advisories on Tropical
Storm Maria, located several hundred miles south-southeast of Cape
Race, Newfoundland, and has issued the last advisory on Post-
Tropical Cyclone Lee, located almost 800 miles north-northwest
of the Azores.

1. The combination of a broad trough of low pressure over Florida and
an upper-level low over the Gulf of Mexico is producing disorganized
cloudiness and showers that extend from the northwestern Caribbean
Sea northward across much of the Florida peninsula and the adjacent
waters. Environmental conditions have become less conducive for
development and the chance of tropical cyclone formation has
decreased. Nevertheless, locally heavy rainfall will likely
continue over portions of western Cuba, the Florida Keys, and the
Florida peninsula during the next several days while the system
moves slowly northward and then westward near northern Florida and
the northeastern Gulf of Mexico.
* Formation chance through 48 hours…low…20 percent.
* Formation chance through 5 days…low…20 percent.

2. A tropical wave interacting with an upper-level low is producing
a large but disorganized area of cloudiness and showers extending
from the eastern Caribbean Sea northeastward across the Lesser
Antilles to the nearby Atlantic waters. Environmental conditions
have become unfavorable for development and tropical cyclone
formation is not anticipated. This system is forecast to move
west-northwestward to westward at 10 to 15 mph during the next few
days bringing locally heavy rainfall over portions of the northern
Leeward Islands and the Greater Antilles during the next several
days. A Flash Flood Watch in effect for Puerto Rico and the
U.S. Virgin Islands through late Sunday night.
* Formation chance through 48 hours…low…near 0 percent.
* Formation chance through 5 days…low…near 0 percent.

Forecaster Avila

MARIA BEGINNING EXTRATROPICAL TRANSITION… …EXPECTED TO BECOME FULLY EXTRATROPICAL LATER TODAY OR TONIGHT

Tropical Storm Maria Discussion Number 57
NWS National Hurricane Center Miami FL AL152017
500 AM AST Sat Sep 30 2017

Despite now being over sea surface temperatures of around 25
degrees Celsius, Maria is producing a persistent cluster of deep
convection that is displaced to the east of the center due to 15 kt
of west-northwesterly shear. Satellite imagery shows cold
advection occurring within the western part of the cyclone’s
circulation behind an approaching cold front, heralding the
beginning of Maria’s extratropical transition. Based on global
model guidance, this transition should be complete within 24 hours,
and Maria’s intensity is unlikely to change much up until that time
due to baroclinic forcing. The extratropical low is likely to
gradually weaken after 24 hours and become absorbed within a
frontal zone by day 3, if not sooner.

Maria is accelerating east-northeastward in the flow ahead of a
positively tilted trough moving off the northeastern coast of North
America, and the initial motion estimate is 070/28 kt. The trough
should continue steering Maria even faster toward the east-northeast
for the next couple of days. The GFS is significantly faster than
the ECMWF, UKMET, and Canadian models since it shows Maria becoming
absorbed by the front much sooner. The NHC track forecast remains
close to the latter models and is relatively unchanged from the
previous forecast.

Guidance from the NOAA Ocean Prediction Center was used for the
track, intensity, and wind radii forecasts during Maria’s
post-tropical stages.

FORECAST POSITIONS AND MAX WINDS

INIT 30/0900Z 39.6N 50.5W 50 KT 60 MPH
12H 30/1800Z 41.3N 45.4W 50 KT 60 MPH
24H 01/0600Z 43.8N 38.3W 50 KT 60 MPH…POST-TROP/EXTRATROP
36H 01/1800Z 46.6N 30.0W 45 KT 50 MPH…POST-TROP/EXTRATROP
48H 02/0600Z 48.9N 20.5W 40 KT 45 MPH…POST-TROP/EXTRATROP
72H 03/0600Z…ABSORBED WITHIN A FRONTAL ZONE

$$
Forecaster Berg