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Potential Tropical Cyclone Nine Advisory Number 4
NWS National Hurricane Center Miami FL AL092020
500 AM AST Wed Jul 29 2020
...HEAVY RAINFALL AND GUSTY WINDS LIKELY OVER PORTIONS OF THE
LEEWARD ISLANDS THROUGH TONIGHT...
SUMMARY OF 500 AM AST...0900 UTC...INFORMATION
ABOUT 5 MI...10 KM S OF DOMINICA
ABOUT 385 MI...615 KM ESE OF SAN JUAN PUERTO RICO
MAXIMUM SUSTAINED WINDS...45 MPH...75 KM/H
PRESENT MOVEMENT...WNW OR 295 DEGREES AT 23 MPH...37 KM/H
MINIMUM CENTRAL PRESSURE...1005 MB...29.68 INCHES
WATCHES AND WARNINGS
CHANGES WITH THIS ADVISORY:
A Tropical Storm Warning has been issued for the north coast of
Haiti from Le Mole St Nicholas eastward to the northern
border with the Dominican Republic.
The government of the Bahamas has issued a Tropical Storm Watch for
the southeastern Bahamas, including the Acklins, Crooked Island,
Long Cay, the Inaguas, Mayaguana, and the Ragged Islands.
SUMMARY OF WATCHES AND WARNINGS IN EFFECT:
A Tropical Storm Warning is in effect for...
* Puerto Rico, Vieques, Culebra
* U.S. Virgin Islands
* British Virgin Islands
* Antigua, Barbuda, Montserrat, St. Kitts, Nevis, and Anguilla
* Guadeloupe, Martinique, St. Martin, and St. Barthelemy
* Saba and St. Eustatius
* St. Maarten
* Dominican Republic from Cabo Caucedo eastward to Cabo Engano and
then westward along the northern coast to the Dominican
* North coast of Haiti from Le Mole St Nicholas eastward to the
northern border with the Dominican Republic
A Tropical Storm Watch is in effect for...
* Dominican Republic from the southern Haiti border eastward to
* Turks and Caicos Islands
* Southeastern Bahamas
Interests in the central and northwestern Bahamas and Cuba should
monitor the progress of this system.
A Tropical Storm Warning means that tropical storm conditions are
expected somewhere within the warning area within 36 hours.
A Tropical Storm Watch means that tropical storm conditions are
possible within the watch area, generally within 48 hours.
For storm information specific to your area in the United
States, including possible inland watches and warnings, please
monitor products issued by your local National Weather Service
forecast office. For storm information specific to your area
outside of the United States, please monitor products issued by
your national meteorological service.
DISCUSSION AND OUTLOOK
At 500 AM AST (0900 UTC), the disturbance was centered near latitude
15.3 North, longitude 61.3 West. The system is moving toward the
west-northwest near 23 mph (37 km/h), and this general motion with
some slight reduction in forward speed is expected over the next few
days. On the forecast track, the center will move through the
southern Leeward Islands during the next few hours, near or over the
Virgin Islands and Puerto Rico tonight, near or over
Hispaniola on Thursday, and near or over the southeastern Bahamas
Maximum sustained winds remain near 45 mph (75 km/h) with higher
gusts. Some increase in strength is forecast today, with weakening
likely on Thursday due to land interaction, and some
restrengthening possible late week.
Environmental conditions are expected to be conducive for
additional development, and a tropical storm is forecast to form
* Formation chance through 48 hours...high...90 percent
* Formation chance through 5 days...high...90 percent
Tropical-storm-force winds extend outward up to 275 miles (445 km)
from the center. Antigua recently reported a wind gust of 47 mph
The estimated minimum central pressure based on Air Force Reserve
reconnaissance data and surface observations is 1005 mb (29.68
HAZARDS AFFECTING LAND
Key messages for Potential Tropical Cyclone Nine can be found in
the Tropical Cyclone Discussion under AWIPS header MIATCDAT4, WMO
header WTNT44 KNHC, and on the web at
WIND: Tropical storm conditions are moving across portions of the
Leeward Islands now and will spread across the U.S. and
British Virgin Islands and Puerto Rico this afternoon through
Thursday morning. These conditions are forecast to reach portions
of the Dominican Republic and Haiti within the warning area early
Thursday. Tropical storm conditions are possible in the watch areas
RAINFALL: The potential tropical cyclone is expected to produce the
following rain accumulations:
Across the northern Leeward Islands, British and U.S. Virgin
Islands: 3 to 6 inches.
Across Puerto Rico: 3 to 6 inches, with isolated maximum totals of
Across the Dominican Republic, northern Haiti and the Turks and
Caicos: 3 to 6 inches, with isolated maximum totals of 8 inches.
Across the Inagua Islands: 4 to 8 inches, with isolated totals of
These rainfall amounts could lead to life threatening flash flooding
and mudslides, as well as potential riverine flooding.
SURF: Swells generated by Potential Tropical Cyclone Nine will be
affecting portions of the Leeward Islands, the Virgin Islands and
Puerto Rico during the next day or two. These dangerous conditions
are forecast to reach the north coast of the Dominican Republic and
the Turks and Caicos Islands and the southeastern Bahamas on
Thursday. These swells are likely to cause life-threatening surf
and rip current conditions. Please consult products from your
local weather office.
Next intermediate advisory at 800 AM AST.
Next complete advisory at 1100 AM AST.