POTENTIAL TROPICAL CYCLONE NINE FORECAST/ADVISORY NUMBER 1
NWS NATIONAL HURRICANE CENTER MIAMI FL AL092020
1500 UTC TUE JUL 28 2020
CHANGES IN WATCHES AND WARNINGS WITH THIS ADVISORY...
A TROPICAL STORM WARNING IS IN EFFECT FOR PUERTO RICO...INCLUDING
VIEQUES...AND CULEBRA...AND THE U.S. VIRGIN ISLANDS.
THE GOVERNMENT OF ANTIGUA HAS ISSUED A TROPICAL STORM WARNING FOR
ANTIGUA...BARBUDA...THE BRITISH VIRGIN ISLANDS...MONTSERRAT...ST.
KITTS...AND NEVIS.
THE GOVERNMENT OF FRANCE HAS ISSUED A TROPICAL STORM WARNING FOR
GUADELOUPE...MARTINIQUE...AND ST. MARTIN.
THE GOVERNMENT OF THE NETHERLANDS HAS ISSUED A TROPICAL STORM
WARNING FOR SABA AND ST. EUSTATIUS.
THE GOVERNMENT OF ST. MAARTIN HAS ISSUED A TROPICAL STORM WARNING
FOR ST. MAARTIN.
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...AND NEVIS
* GUADELOUPE...MARTINIQUE...AND ST. MARTIN
* SABA AND ST. EUSTATIUS
* ST. MAARTIN
INTERESTS ELSEWHERE IN THE LEEWARD ISLANDS AND HISPANIOLA 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.
POTENTIAL TROP CYCLONE CENTER LOCATED NEAR 13.8N 53.7W AT 28/1500Z
POSITION ACCURATE WITHIN 90 NM
PRESENT MOVEMENT TOWARD THE WEST OR 280 DEGREES AT 20 KT
ESTIMATED MINIMUM CENTRAL PRESSURE 1007 MB
MAX SUSTAINED WINDS 35 KT WITH GUSTS TO 45 KT.
34 KT.......200NE 0SE 0SW 120NW.
WINDS AND SEAS VARY GREATLY IN EACH QUADRANT. RADII IN NAUTICAL
MILES ARE THE LARGEST RADII EXPECTED ANYWHERE IN THAT QUADRANT.
REPEAT...CENTER LOCATED NEAR 13.8N 53.7W AT 28/1500Z
AT 28/1200Z CENTER WAS LOCATED NEAR 13.5N 52.8W
FORECAST VALID 29/0000Z 14.8N 56.7W
MAX WIND 35 KT...GUSTS 45 KT.
34 KT...200NE 0SE 0SW 140NW.
FORECAST VALID 29/1200Z 16.0N 60.4W
MAX WIND 40 KT...GUSTS 50 KT.
34 KT...200NE 0SE 0SW 140NW.
FORECAST VALID 30/0000Z 17.3N 64.0W
MAX WIND 45 KT...GUSTS 55 KT.
34 KT...200NE 60SE 0SW 140NW.
FORECAST VALID 30/1200Z 18.8N 67.6W
MAX WIND 50 KT...GUSTS 60 KT.
50 KT... 60NE 0SE 0SW 0NW.
34 KT...210NE 90SE 0SW 140NW.
FORECAST VALID 31/0000Z 20.1N 70.7W
MAX WIND 50 KT...GUSTS 60 KT.
50 KT... 60NE 0SE 0SW 0NW.
34 KT...210NE 90SE 0SW 140NW.
FORECAST VALID 31/1200Z 21.3N 73.5W
MAX WIND 50 KT...GUSTS 60 KT.
50 KT... 60NE 0SE 0SW 0NW.
34 KT...210NE 90SE 0SW 120NW.
EXTENDED OUTLOOK. NOTE...ERRORS FOR TRACK HAVE AVERAGED NEAR 150 NM
ON DAY 4 AND 175 NM ON DAY 5...AND FOR INTENSITY NEAR 15 KT EACH DAY
OUTLOOK VALID 01/1200Z 24.1N 77.9W
MAX WIND 50 KT...GUSTS 60 KT.
OUTLOOK VALID 02/1200Z 26.8N 80.6W...INLAND
MAX WIND 45 KT...GUSTS 55 KT.
REQUEST FOR 3 HOURLY SHIP REPORTS WITHIN 300 MILES OF 13.8N 53.7W
INTERMEDIATE PUBLIC ADVISORY...WTNT34 KNHC/MIATCPAT4...AT 28/1800Z
NEXT ADVISORY AT 28/2100Z
$$
FORECASTER BROWN
BULLETIN
Potential Tropical Cyclone Nine Advisory Number 1
NWS National Hurricane Center Miami FL AL092020
1100 AM AST Tue Jul 28 2020
...DISTURBANCE FORECAST TO BECOME A TROPICAL STORM BEFORE REACHING
THE LEEWARD ISLANDS...
...TROPICAL STORM WARNINGS ISSUED...
SUMMARY OF 1100 AM AST...1500 UTC...INFORMATION
-----------------------------------------------
LOCATION...13.8N 53.7W
ABOUT 585 MI...940 KM ESE OF THE LEEWARD ISLANDS
MAXIMUM SUSTAINED WINDS...40 MPH...65 KM/H
PRESENT MOVEMENT...W OR 280 DEGREES AT 23 MPH...37 KM/H
MINIMUM CENTRAL PRESSURE...1007 MB...29.74 INCHES
WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY:
A Tropical Storm Warning is in effect for Puerto Rico, including
Vieques, and Culebra, and the U.S. Virgin Islands.
The government of Antigua has issued a Tropical Storm Warning for
Antigua, Barbuda, the British Virgin Islands, Montserrat,
St. Kitts, and Nevis.
The government of France has issued a Tropical Storm Warning for
Guadeloupe, Martinique, and St. Martin.
The government of the Netherlands has issued a Tropical Storm
Warning for Saba and St. Eustatius.
The government of St. Maartin has issued a Tropical Storm Warning
for St. Maartin.
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, and Nevis
* Guadeloupe, Martinique, and St. Martin
* Saba and St. Eustatius
* St. Maartin
Interests elsewhere in the Leeward Islands and Hispaniola 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.
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 1100 AM AST (1500 UTC), the disturbance was centered near
latitude 13.8 North, longitude 53.7 West. The system is moving
toward the west near 23 mph (37 km/h), and this general motion
should continue during the next few days. On the forecast track,
the system is forecast to move through the Leeward Islands on
Wednesday, and near or over the Virgin Islands and Puerto Rico
Wednesday night, and near or over Hispaniola on Thursday.
Maximum sustained winds are near 40 mph (65 km/h) with higher gusts.
Some strengthening is expected during the next 48 hours, and the
system is forecast to become a tropical storm tonight or Wednesday.
Environmental conditions are expected to be conducive for
additional development and a tropical storm tonight or Wednesday.
* Formation chance through 48 hours...high...80 percent
* Formation chance through 5 days...high...90 percent
Tropical-storm-force winds extend outward up to 230 miles (370 km)
primarily to the northeast of the center.
The estimated minimum central pressure is 1007 mb (29.74 inches).
HAZARDS AFFECTING LAND
----------------------
Key messages for Potential Tropical Cyclone Nine can be found in
the Tropical Cyclone Discussion under AWIPS header MIATCDAT4 and
WMO header WTNT44 KNHC.
WIND: Tropical storm conditions are expected to reach the Leeward
Islands on Wednesday and spread into the U.S. and British Virgin
Islands and Puerto Rico Wednesday afternoon through Thursday
morning.
RAINFALL: The potential tropical cyclone will produce total rain
accumulation of 3 to 6 inches with maximum amounts of 10 inches
across the northern Leeward Islands, British and U.S. Virgin
Islands and Puerto Rico. Rainfall accumulations of 2 to 4 inches
possible across the Windward Islands. This rainfall may produce
life threatening flash flooding and mudslides, as well as potential
riverine flooding.
NEXT ADVISORY
-------------
Next intermediate advisory at 200 PM AST.
Next complete advisory at 500 PM AST.
$$
Forecaster Brown
Potential Tropical Cyclone Nine Discussion Number 1
NWS National Hurricane Center Miami FL AL092020
1100 AM AST Tue Jul 28 2020
Shower and thunderstorm activity has increased overnight and this
morning in association with a broad area of low pressure located
several hundred miles east of the Lesser Antilles. Recent visible
satellite imagery and ASCAT data show that the system's circulation
is quite elongated and lacks a well-defined center. Observations
from NOAA buoy 41040 and ASCAT suggest that the system is
already producing winds of 30-35 kt, and the systems's initial
intensity has been set to 35 kt. Dry air located just to the north
of the system has been hindering development over the past couple of
days, but environmental conditions are expected to be more conducive
for development over the next couple of days. Therefore, the system
is likely to become a tropical storm before it reaches the Leeward
Islands and advisories are being initiated in order to issue
Tropical Storm Warnings for a portion of the Leeward Islands, the
U.S. and British Virgin Islands, and Puerto Rico. A U.S. Air Force
Reserve reconnaissance aircraft is scheduled to investigate the
system early this afternoon, and should provide additional
information on the intensity and structure of the low pressure
area.
It cannot be stressed enough that since the system is still in the
formative stage, greater than average uncertainty exists regarding
both the short-term and longer-term track and intensity forecasts.
A subtropical ridge that extends westward from the central Atlantic
is expected to be the dominant steering mechanism over the next
several days, and the flow around this ridge should steer the low
pressure area generally west-northwestward. However, the details in
the track forecast could change depending on exactly where within
elongated circulation the center forms. Regardless of the exact
track, the system is expected to bring locally heavy rainfall to
much of the Lesser Antilles, and tropical-storm-force winds to
portions of the Leeward Islands, the Virgin Islands, and Puerto Rico
within the next 24-48 hours. After that time, a general west-
northwestward heading should continue but as mentioned before,
uncertainty exists as to how close the system tracks to
Hispaniola, Cuba, the Bahamas, and Florida. The NHC track forecast
is in best agreement with the HFIP corrected consensus model. It
should be noted that a stronger cyclone is likely to favor a more
northern track, while a weaker system is likely to remain more
equatorward. Users should remember that the long-term average NHC
track forecast errors at days 4 and 5 are 140 and 175 n mi,
respectively.
Given the current structure of the system, only gradual
strengthening is predicted during the next day or two, however the
system is expected to become a tropical storm when it is near the
Leeward Islands on Wednesday. After 48 hours, possible land
interaction with the Greater Antilles, and increasing south to
southwesterly shear from an upper-level trough could temper further
strengthening. The global models generally weaken the system due to
these negative factors and the NHC forecast calls for little change
in strength at the longer range. Interests in Hispaniola, the
Bahamas, Cuba, and Florida should continue to monitor forecasts as
changes to both track and intensity are likely.
Key Messages:
1. Potential Tropical Cyclone Nine will produce heavy rains and
potentially life-threatening flash flooding and mudslides across
the northern Leeward Islands, the Virgin Islands and Puerto Rico.
2. Tropical storm conditions are likely across portions of the
Leeward Islands, the Virgin Islands, and Puerto Rico Wednesday
through Thursday, and Tropical Storm Warnings are in effect.
Do not focus on the details of the track forecast, as rainfall and
wind hazards will extend far from the center of the system.
3. The details of the long-range track and intensity forecasts are
more uncertain than usual since the system does not have a
well-defined center and could move over portions of the Greater
Antilles later this week. However, this system could bring some
rainfall and wind impacts to portions of Hispaniola, Cuba, the
Bahamas, and Florida by the end of the week. Interests there should
monitor its progress and updates to the forecast over the next few
days.
FORECAST POSITIONS AND MAX WINDS
INIT 28/1500Z 13.8N 53.7W 35 KT 40 MPH...POTENTIAL TROP CYCLONE
12H 29/0000Z 14.8N 56.7W 35 KT 40 MPH...POTENTIAL TROP CYCLONE
24H 29/1200Z 16.0N 60.4W 40 KT 45 MPH...TROPICAL STORM
36H 30/0000Z 17.3N 64.0W 45 KT 50 MPH
48H 30/1200Z 18.8N 67.6W 50 KT 60 MPH
60H 31/0000Z 20.1N 70.7W 50 KT 60 MPH
72H 31/1200Z 21.3N 73.5W 50 KT 60 MPH
96H 01/1200Z 24.1N 77.9W 50 KT 60 MPH
120H 02/1200Z 26.8N 80.6W 45 KT 50 MPH...INLAND
$$
Forecaster Brown