Tropical Weather Discussion
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AXNT20 KNHC 221040

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
639 AM EDT Tue May 22 2018

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
1030 UTC.


The southern end of a sharp upper trough over the northwest
Caribbean is supporting a surface trough reaches from central
Honduras to near Cozumel Island. Deep layer tropical moisture
continues to stream northward on the eastern edge of the upper
trough, where related upper divergence is supporting clusters of
showers and thunderstorms from just north of San Andres Island to
just south of Grand Cayman Island. While environmental conditions
are expected to be unfavorable for development low pressure along
the surface trough during the next couple of days, some gradual
subtropical or tropical development is possible later this week
while the system moves slowly northward into the central or
eastern Gulf of Mexico. Regardless of development, locally heavy
rainfall is possible across western Cuba and much of Florida
during the next several days. For more information on the heavy
rain threat, please see products issued by your local weather
office. There is a very low chance for tropical storm formation
within 48 hours.


A tropical wave is along 38W S of 10N, moving W at 10-15 kt. This
wave is embedded in a sharp 700 mb trough. No significant
convection is noted with this tropical wave.

A weak tropical wave is over the eastern Caribbean Sea south of
the Virgin Islands, moving W at 10-15 kt. No significant
convection is noted with this tropical wave, and it will likely
become diffuse through late today.


The monsoon trough passes through the coastal sections of Sierra
Leone near 07N12W to 04N15W. The intertropical convergence zone
continues from 04N15W to 04N27W to near the tropical wave along
38W, then continuing west to 00N50W near the coast of Brazil.
From 00N to 05N between 15W and 35W.



A sharp upper trough persists over the eastern Gulf this morning
from the western Florida Panhandle to near the Yucatan Channel.
An associated surface trough is analyzed directly beneath the
near stationary trough. Divergent flow aloft is supporting a few
showers and thunderstorms along 23N/24N east of 90W to the
Straits of Florida. The trough interrupts a broad surface ridge
reaching across the northern Gulf and Deep South states. Gentle
to moderate E to SE winds are evident across the Gulf as noted in
buoy observations and scatterometer satellite data. Buoys and
altimeter satellite data show generally 2 to 4 ft seas. No other
showers or thunderstorms are noted.

The ridge over the northern Gulf coast will shift east through
mid week ahead of a developing low pressure area expected to
emerge off the coast of Yucatan Thu. The low pressure will
continue to move northward into the north central Gulf through
Sat, bringing fresh to strong winds and building seas to the
eastern Gulf, then diminish Sun as the low moves north of the


Please read the Special Features section for more details about
the upper level trough and related surface weather features over
the NW Caribbean Sea.

Atlantic ridging north of the area is supporting
moderate to fresh trade winds from the tropical north Atlantic
west of 55W to the central Caribbean, except for fresh to strong
winds funneling along the higher coastal terrain of northeast
Colombia and northwest Venezuela. Trade wind convergence,
possibly aided by the upper trough is supporting scattered
convection from the central coast of Colombia to near 13N77W.
Meanwhile a weak tropical wave over the far eastern Caribbean is
starting to lose definition as it drifts west, and will likely
dissipate. A line of showers and thunderstorms is active from
near Guadeloupe to 18N55W, at the base of broad upper low
centered north of the area. Buoy observations and altimeter data
show5 to 7 ft seas in the northwest Caribbean, 6 to 8 ft seas
over the central Caribbean, and 4 to 6 ft seas in the eastern
Caribbean, and 5 to 7 ft seas elsewhere.

The Atlantic ridge will maintain fresh to locally strong trades
over the central Caribbean through Fri. Strong winds and seas to
9 ft will affect the NW coast of Colombia. Low pressure may form
along the trough in the northwest Caribbean and near the Yucatan
Peninsula through mid week, then move north into the Gulf of
Mexico late Thu. Fresh to strong winds will develop between the
trough and the Atlantic high pressure south of Cuba Fri,
persisting through Sat.


A recent scatterometer satellite pass indicated fresh to strong
trade winds pulsing off the north coast of Haiti. The stronger
winds are due to localized overnight land breezes off the coast,
and relatively tight gradient south of the subtropical ridge,
reaching east to west along 30N. Otherwise, the ridge is
supporting gentle to moderate SE winds north of 22N and moderate
to fresh trade winds south of 22N. Seas are 4 to 6 ft in open

The ridge will shift eastward from mid to late week, as developing
low pressure moves through the Gulf of Mexico west of the
region. This change in the pattern will result in slightly
stronger winds over the Cay Sal Bank area, and SE to S winds
increasing over the northern Bahamas and off northeast Florida
Sat. Winds and seas will diminish elsewhere due to a weakened and
displaced Atlantic ridge.

Farther east, a 1025 mb high is centered over the central
Atlantic near 30N53W producing mostly fair weather, with moderate
trade winds over tropical Atlantic. Recent altimeter satellite
passes indicate seas to 8 ft over the deep tropics between 45W and
55W, likely in NE swell. This should diminish below 8 ft through
late today.

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