AXNT20 KNHC 151724
Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1805 UTC Thu Apr 15 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 1200 UTC surface analysis and satellite imagery through
Eastern Caribbean Ashfall Advisory: An Ashfall Advisory has been
reissued for La Soufriere Volcano on the island of St. Vincent
near 13.3N 61.2W. Winds are blowing this new plume of volcanic
ash toward the NNW from St. Vincent over the eastern Caribbean
Sea, from 13.3N-15.5N between 61.2W-62.0. The ash cloud could
potentially affect the island of Dominica this afternoon. The
volcano remains in a state of unrest. Additional eruptions and
ash plumes are possible. Mariners within the ashfall advisory
area over the extreme eastern Caribbean are advised to exercise
caution. Mariners who encounter volcanic ash or floating
volcanic debris are urged to report the observation to the
National Hurricane Center, by calling 305-229-4424.
The monsoon trough enters the Atlantic ocean through the coast
of west Africa near 12N17W and continues SW to 08N18W. The ITCZ
continues from 08N18W to 02N30W to the coast of South America
near 02N51W. Scattered moderate and isolated strong convection
is seen from 04N-05N between 07W-15W, from 02N-06N between
20W-28W, from 04S-01N between 32W-39W and from 00N-05N between
43W-52W, including over NE Brazil and French Guiana. Isolated
moderate convection is elsewhere within 90 nm either side of the
GULF OF MEXICO...
Strong to severe thunderstorms have been occurring all morning
long in the northern Gulf waters from the Florida Panhandle to
the mid-Louisiana coast in association with a cold front that is
moving southward in the northern Gulf of Mexico. A few of the
thunderstorms contained winds gusts over 50 kt earlier, but have
since begun to weaken. The storms should continue to weaken as
the afternoon progresses. As of 1500 UTC, the cold front extends
from Destin Florida to a 1012 mb low near 30N87W to Grand Isle
Louisiana to near Rockport Texas. A recent ASCAT pass shows
strong NE winds north of the front, and mainly gentle to
moderate winds south of the front. Fresh SE winds are seen west
of the Yucatan Peninsula. Seas are 3-5 ft across the basin, but
locally higher seas are possible in thunderstorms. The cold
front will stall and weaken along 27N tonight. A stronger cold
front will move into the NW Gulf on Sat, with strong northerly
winds and building seas expected across the western Gulf this
weekend. Gale force winds are possible near the central coast of
Mexico Sat night. The front will stall from central Florida to
the Bay of Campeche Sun night and Mon.
An Ashfall Advisory is in effect for La Soufriere volcano on the
island of St. Vincent. See the special features section above
Weak ridging dominates Cuba and the NW Caribbean, with mainly
fair weather and moderate E trades. Scattered moderate and
isolated strong convection seen over Costa Rica and Panama
extends into the far SW Caribbean, south of 11N and west of 80W.
Farther east, the tail end of an Atlantic stationary front
reaches the Lesser Antilles over Guadeloupe, where a thin line
of clouds contains isolated showers and tstorms. Due to the
orientation of high pressure over the west Atlantic, strong NE
winds are noted south of the Dominican Republic on the latest
ASCAT pass. Fresh trades cover the remainder of the central
Caribbean, with moderate trades east of 67W. Seas are 4-6 ft
over the central Caribbean and 2-4 ft over the eastern and NW
The stationary front northeast of the Windward Islands will
shift eastward and weaken today. Moderate to fresh trade winds,
locally strong, will prevail across the Caribbean through Sun.
Fresh to strong SE winds are expected in the NW Caribbean this
weekend. Fresh to strong trade winds will prevail across the
central Caribbean Sun night through Mon night.
West of 65W: A 1017 mb high pressure is centered near 29N70W.
The latest ASCAT pass shows fresh to strong SW winds to the east
of northern Florida, mainly north of 29N between 76W-81W.
Scattered showers are seen mainly north of 30N between 72W and
the coast of Georgia. Gentle winds prevail elsewhere closer to
the high pressure. Seas are generally in the 4-7 ft range. For
the forecast, a cold front will move east of northern Florida
into the west Atlantic by early Fri, then stall north of the
Bahamas this weekend into early next week.
East of 65W: A cold front extends from 32N59W to Bermuda. Strong
W winds and scattered showers are north of the front. Farther
east, a pair of cold fronts extend over the central Atlantic.
The trailing front is from 32N48W to 25N53W to 21N60W,
dissipating to 19N69W. The leading cold front is from 32N43W to
25N48W to 21N52W. It continues SW as a stationary front to near
the island of Guadeloupe. Scattered moderate showers and
isolated tstorms are along and within 120 nm ahead of the
leading front. Similar convection is along the trailing front
north of 29N east of 49W. Fresh S-SW winds precede the leading
front north of 24N and west of 37W, shown by a recent ASCAT
pass. Moderate W winds are near and behind the trailing front.
Seas are mainly in the 6-9 ft range over the central Atlantic,
north of 23N. Both cold fronts will move eastward today while
weakening. The trailing front will dissipate during the next 12-
18 hours, and the leading front will become stationary on Fri
and dissipate through Sat morning. East of the fronts, surface
ridging and fair weather prevail, anchored by a 1025 mb high
pressure near 33N28W. Fresh NE trades are occurring from 10N-20N
between 17W-38W and will continue in this area through Fri.