[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 111139
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1205 UTC Sun Apr 11 2021

Tropical Weather Discussion for North America, Central America
Gulf of Mexico, Caribbean Sea, northern sections of South
America, and Atlantic Ocean to the African coast from the
Equator to 32N. The following information is based on satellite
imagery, weather observations, radar and meteorological analysis.

Based on 0600 UTC surface analysis and satellite imagery through
1115 UTC.

...SPECIAL FEATURES...

East Atlantic Gale Warning: ASCAT data from last night revealed
gale-force southwest winds from 28N- 31N between 30.5W- 33W.
These gales are occurring on the SE side of a large 990 mb low
pressure system centered near 35N43W. The low is moving NE at 20
kt. Wave heights are in the 11-17 ft range in the area of gale
force winds. The MeteoFrance forecast indicates that the winds
there will diminish below gale force soon.

Windward Islands Ashfall Advisory: La Soufriere volcano on the
island of Saint Vincent near 13.3N 61.2W is undergoing frequent
eruptions. Satellite imagery shows the volcanic ash plume
spreading well to the east and northeast of St. Vincent, roughly
in an area from 10N-18N between 40W-62W, which includes Barbados.
Violent volcanic eruptions may occur suddenly without warning.
Volcanic ash may be reaching the ocean surface east northeast of
St. Vincent. Mariners should exercise caution, and report volcanic
ash or floating debris to the National Weather Service by calling
305-229-4424.

...MONSOON TROUGH/ITCZ...

The monsoon trough axis extends southward from the coast of
Guinea-Bissau near 12N16W to 04N23W, where overnight scatterometer
data indicates that it transitions to the ITCZ to 02N32W to
01N49W. Scattered moderate to isolated strong convection is
well south of the ITCZ along the coast of Brazil between 36W-41W.

GULF OF MEXICO...

The earlier observed cluster of strong thunderstorms that was
over the southeastern Gulf has dissipated. A new and increasing
large thunderstorm complex has quickly developed over the NE
Gulf from 26N to 30N between 85W-90W. Similar activity is over
northern Florida. With a rather potent upper-level trough
located over the eastern Gulf and ample available moisture in
place at the low-levels and daytime heating later on, expect for
additional clusters of strong to severe thunderstorms to develop
over the NE Gulf and over north-central Florida during this
morning. This activity is likely to persist into the afternoon
hours. The main hazards associated with these storms are likely
to be wind gusts of 35-45 kt and frequent lightning. The storms
will propagate east-southeastward during the day.

Elsewhere over the Gulf as of 09Z, a weak cold front extends from
south-central Louisiana to 26N96W, where it becomes stationary
inland Mexico just south of Brownsville. A trough out ahead of
it extends from 28N92W to a 1003 mb low near 22N95W and to near
19N95W. Scattered moderate convection is within 30 nm of 28N90W.
Overnight ASCAT data shows fresh east-southeast winds over the
east-central Gulf, with gentle to moderate winds elsewhere. Wave
heights are in the 3-6 ft range across the basin. Fresh southerly
winds will prevail across the most of the basin this morning to
the east of the cold front. The cold front will reach from the
Florida panhandle to the central Gulf by early this evening, and
weaken further to a trough as it reaches the southeastern Gulf Mon
and dissipates late Mon. The aforementioned upper-level trough
will also aid in the development of scattered showers and
thunderstorms over the rest of the eastern Gulf waters today. Some
of this activity may contain frequent lightning and strong gusty
winds.

CARIBBEAN SEA...

See the Special Features section above for details on an Ashfall
Advisory issued for ongoing volcanic eruptions on St. Vincent.

The latest surface analysis depicts a rather weak pressure
gradient across the basin. Overnight ASCAT data shows fresh
trades over most of the basin, while fresh to strong east-
southeast winds are in the Gulf of Honduras. Wave heights are
in the 3-6 ft range, except for slightly higher wave heights
of 5-7 ft in the central Caribbean area. The earlier noted
scattered moderate thunderstorm activity over northwestern
Honduras and the Gulf of Honduras has dissipated. Isolated
showers and thunderstorms are over the northern part of South
America. Isolated showers are possible over the far eastern
Caribbean.

ATLANTIC OCEAN...

See the Special Features section above for details on an Ashfall
Advisory issued for ongoing volcanic eruptions on St. Vincent.

The earlier observed line of scattered moderate showers and
thunderstorms that was east of the Florida peninsula
dissipated. Isolated showers are possible from 25N to 32N
between 72W-78W. Isolated showers are noted over the waters
between the Bahamas Cuba and over some parts of the Straits of
Florida and Keys. Buoy observations indicate that there are
fresh southerly winds over the far western part of the area.
This in advance of a cold front that is presently moving across
the southeastern U.S. The thunderstorm complex over the NE Gulf
of Mexico will cross the Florida peninsula and move offshore to
the Atlantic waters during the day today and into this evening.
Expect wind gusts of 35-45 kt and frequent lightning this
afternoon, especially in the waters extending offshore between
Daytona Beach and West Palm Beach Florida. Outside of the
thunderstorms, expect for the fresh southerly winds over the NW
waters to shift eastward through Mon ahead of the aforementioned
cold front that will move off the southeastern U.S. coast
tonight. The front will reach from near 31N75W to east-central
Florida early Mon, from near 31N70W to the central Bahamas and to
east-central Cuba Mon evening and the southeast waters by late
Tue. The front will move east of the forecast waters on Wed as
weak high pressure builds in behind it. The high pressure will be
displaced southeastward through Thu night as yet another cold
front moves across the northwest and north-central waters. Fresh
to strong southwest winds are expected to precede this front.
Scattered to numerous showers and thunderstorms, some strong to
severe, are expected to push off the Florida coast today.

A large occluded gale-force low pressure system north of the
area centered near 35N43W is producing a large area of strong
westerly winds north of 26N between 30W-58W. Seas are 11-17 ft in
this area. Northerly swell from this system, with seas in excess
of 8 ft, is affecting most of the central Atlantic north of 21N
between 26W-63W. Fast-moving small cells of showers and
thunderstorms are seen rotating cyclonically in the southern
semicircle of this low. This activity is brushing the waters
north of 29N between 39W-48W. Cold air instability aloft is
helping to sustain this activity.

A trough is analyzed over the central Atlantic along a position
from near 32N30W, south-southwestward to 25N36W to 20N44W and to
near 15N54W. Upper-level diffluence to the east of the
northeastern portion of the surface trough is aiding an area of
scattered moderate convection east of the trough from about 24N to
32N between 23W-31W. A 1018 mb high is centered near the Canary
Islands, with a ridge stretching southwestard to 23N27W and to
near 17N41W. A 1017 mb high is centered near 28N68W. Associated
gentle anticyclonic winds are occurring between 61W-72W.

$$
Aguirre
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