[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 040536
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
136 AM EDT Fri May 4 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 0000 UTC surface analysis and satellite imagery through
0600 UTC.

...MONSOON TROUGH/ITCZ...

The monsoon trough extends from 08N13W to 00N35W. The intertropical
convergence zone continues from 00N35W to 00N50W. Scattered
moderate convection is ongoing from 02S to 04N between 20W and
25W.

...DISCUSSION...

GULF OF MEXICO...

A ridge extends east to west from the western Atlantic along the
northern Gulf coast to Texas. Strong peak winds reported by CMAN
observations in the Florida Keys are evidence of fresh to strong
easterly winds persisting across the Straits of Florida, between
the ridge to the north, a weak trough over the far southeast Gulf,
and a more developed trough to the east. Seas are likely reaching
8 ft in the Straits accordingly, reaching as far west as the
approaches to the Yucatan Channel. Convergence of the fresh to
strong easterly flow out of the Bahamas is supporting scattered
showers across the Straits, as noted in regional radar. Fresh SE
return flow and seas to 6 ft are noted over the far northwest
Gulf, between the ridge and lower pressure over south Texas. A
couple of platforms in the Texas coastal waters are report fog in
the moist SE flow, but widespread fog or significant restriction
to visibility are not anticipated overnight.

Farther south, a thermal trough will develop over the northwest
coast of Yucatan during the evening, and drift westward across the
SW Gulf before dissipating later in the morning. A surge of fresh
to occasionally strong NE to E winds will accompany this trough.
This pattern will repeat each evening through the period.

For the forecast, winds over the southeast Gulf will diminish and
back more to the NE through early Sat ahead of the trough moving
from the western Atlc across Florida. Scattered showers and
thunderstorms will accompany the trough as it moves into the
eastern Gulf early Sun before stalling and weakening. The ridge
will weaken as well and high pressure will shift west through the
lower Mississippi Valley, allowing moderate northerly flow and 2
to 4 ft seas through mid week.

CARIBBEAN SEA...

A surface trough is developing from north of Hispaniola into the
north central Caribbean. E to SE winds will increase slightly from
the Tropical North Atlantic through the central Caribbean as high
pressure builds westward over the Atlantic in the wake of the
trough. This is already starting to happen as winds off Colombia
diminish slightly, as they increase through the Windward and
Leeward Islands. Strong NE winds are also noted in the lee of Cuba
on a recent scatterometer pass from 02 UTC. Scattered
thunderstorms are popping up in the Windward Passage as well, on
the southeast side of a prominent mid/upper low centered north of
the area. Seas will build over tropical north Atlantic and the
eastern Caribbean to 6 to 9 ft through Sun.

This pattern will persist through Sun, then start to subside into
early next week as the trough moves farther westward and the ridge
weakens. Instability associated with the mid/upper level low will
provide more thunderstorm potential to the north central Caribbean
through late Sat.

ATLANTIC OCEAN...

The main weather maker remains a prominent cold-core, mid/upper
level low centered over Cat Island in the central Bahamas.
Divergence of the southeast side of this feature is supporting a
broad area of scattered showers and thunderstorms over the
southern Bahamas, Turks/Caicos Islands, and north of Hispaniola
and Puerto Rico. This is also supporting the development of a
amplifying surface trough extending from 27N68W through Haiti and
into the north central Caribbean. Strong NE to E winds are ahead
of the trough east and across the Bahamas, as noted in a 02 UTC
scatterometer satellite pass, with seas in excess of 8 ft noted in
a concurrent altimeter satellite pass. Moderate to fresh easterly
winds are noted north of 27N, closer to the subtropical ridge
axis. Buoy and scatterometer data also show strong SE winds off
the Leeward Islands in the Atlantic, with buoys showing seas to 9
ft. This is related to ridging building in the wake of the trough.

The trough will sharpen and elongate as it moves westward,
eventually moving into Florida Sat. Strong to near gale force
winds will accompany the trough, as well numerous showers and
scattered thunderstorms across the Bahamas through Sat. Scattered
thunderstorms are possible across the Bahamas and adjacent waters
into Sun as the upper low slowly drifts south-southwestward.
Winds and seas will start to diminish Sun through early next week
as through lifts northward to off the northeast coast of Florida
through Mon, and the ridge weakens, but hold in place along
roughly 28N/29N.

Farther east, the remainder of the Atlantic is under the
influence of a 1029 mb high pressure located near the Azores.
This system is producing moderate to fresh trade winds across the
deep tropics, where seas are reaching 6 to 8 ft in NE to E swell.

For additional information please visit
http://www.hurricanes.gov/marine

$$
Christensen
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