[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 292352
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
752 PM EDT Fri Sep 29 2017

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 1800 UTC surface analysis and satellite imagery through
2315 UTC.

...SPECIAL FEATURES...

Tropical Storm Maria centered near 37.8N 57.4W at 2100 UTC has
accelerated toward the east-northeast at 27 kt this afternoon.
Minimum central pressure remains 988 mb. Maximum sustained winds
are 50 kt with gusts to 60 kt. See the latest NHC Forecast/
Advisory under AWIPS/WMO headers MIATCMAT5/WTNT25 KNHC for more
details.

Tropical Storm Lee centered near 42.2N 46.0W at 2100 UTC is
racing northeast at 31 kt. Estimated minimum central pressure is
996 mb. Maximum sustained winds are 55 kt with gusts to 75 kt.
See the latest NHC Forecast/Advisory under AWIPS/WMO headers
MIATCMAT4/WTNT24 KNHC for more details.

A broad surface trough extending from western Cuba northeastward
across south central Florida then eastward into the Atlantic is
interacting with an upper-level low pressure system aligned north
to south across the east-central Gulf of Mexico. The interaction
is producing a large disorganized area of clouds and showers from
the NW Caribbean across Cuba to south central Florida. A weak
surface low may form from this system on either side of the
Florida Peninsula this weekend as the surface trough drifts
northward. Environmental conditions appear conducive for some
development of the low during the next 2-3 days. Regardless, this
system will produce areas of heavy rain from western Cuba
northeastward across the Florida peninsula and adjacent waters
during the next few days. This system has a moderate chance for
tropical cyclone development in the next 48 hours.

...TROPICAL WAVES...

A tropical wave in the E Atlantic along 32W-33w, moving west at
10-15 kt. Ample low level moisture accompanies this wave this
evening as evident in TPW animations. An broad upper level trough
is N of 14N to the NW of the wave axis an is currently enhancing
showers and thunderstorms along the leading edge of the wave
related moisture, from 13.5N to 15.5N between 32W and 36W. However
the associated strong westerly wind shear being induced by the
upper trough will begin to diminish convection across the northern
part of the wave, and active convection will likely shift S of 12N
and behind the wave axis later tonight and Saturday.

A tropical wave is moving across the E Caribbean along about
64W-65W S of 19N and moving west at 10-15 kt. An upper level low
center is developing just to the W of the wave, centered over the
Mona Passage and far eastern Dominican Republic, and is
interacting favorably with the wave to produce scattered moderate
to strong thunderstorms across the east and northeast Caribbean
extending NE into the Atlantic waters offshore of the Leeward
Islands, or front 14N to 21N between 59W and 67W. The upper low
will retrograde westward through early Sunday and remain in a
favorable position to continue to induce and enhance active
convection across the NE Caribbean Islands and adjacent Caribbean
and Atlantic waters.

...ITCZ/MONSOON TROUGH...

The monsoon trough extends from the coast of Africa near
09.5N14.5W to 09N23.5W to 06N36W. The ITCZ extends from 06N36W to
07.5N53W to 11N64W. A West African Squall Line is nearing the W
coast of Africa from coastal Senegal to southern Liberia, ahead of
an approaching tropical wave over Africa. Scattered moderate
to strong convection is occurring behind the tropical wave along
32W-33W from 06N-12N between 20W-30W.

...DISCUSSION...

GULF OF MEXICO...

The tail end of a quasistationary front extends from the Florida
Panhandle near 30N84W to 27.5N96W near the Texas coast, and has
actually drifted slightly S during the afternoon hours across the
NW Gulf. The front is becoming ill defined and is expected to
dissipate during the next 24 hours. To the south, a stationary
1008 mb surface low is analyzed over the Bay of Campeche near
20.5N93.5W, embedded within an area of broad cyclonic turning
across the entire Bay of Campeche extending southward into SE
Mexico. Scattered moderate convection surrounding the low earlier
today has shifted inland across Mexico. A sharp N to S aligned upper
level low is centered over the NE Gulf near 28N86.5W and is producing
subsidence across much of N central portions of the Gulf. Upper
level diffluence SE of the center continues to enhance convection
over SE Gulf as described above.

CARIBBEAN SEA...

Active convection will continue with the tropical wave across the
E Caribbean as the upper low described above moves W and generally
in tandem with the wave during the next 24-36 hours. The crux of wave
related moisture is expected to shift NW across the NE Caribbean
and into the Atlantic by late Saturday. Elongated low pressure
also extends across the Yucatan Channel SW across the Gulf of
Honduras, and is acting to force active convection across much of
the NW Caribbean to Honduras. The upper level low across the NE
Gulf extends weakly to the Yucatan Channel and is providing upper
level divergence across the area that is acting to enhance and
sustain the convection. The trough and associated convection is
expected to drift slowly northwestward and across the Yucatan
Peninsula through the weekend. Farther S, the eastern extent of
the east Pacific monsoon trough extends into the SW Caribbean with
isolated moderate convection over Panama and northern Colombia.
Little change is expected through Sat.

...PUERTO RICO and U.S. Virgin Islands...

Afternoon thunderstorms have moved NW and away from the NW coast
of Puerto Rico from Arecibo to Aguadilla in the past few hour
with gradual clearing expected there in the short term. The
tropical wave moving across the Eastern Caribbean has begun to
spread widely scattered moderate convection across the U.S. and
British Virgin Islands and across NE portions of Puerto Rico this
evening. Cells are currently moving WNW around 15 mph with SSW
upper level wind shear weakening them eventually. Clusters of
strong convection are seen across the open Caribbean SSE of St
Croix where the best low level moisture currently resides. Global
models forecast the moisture associated with the tropical wave to
move WNW to NW overnight and Saturday and interact with the upper
low to the west to produce scattered heavy showers and occasional
thunderstorms. This weather will shift across all of the Virgin
Islands and eastern Puerto Rico during the next several hours and
may maximize in the early morning hours of Saturday. This majority
of this moisture is forecast to shift NW of the islands Saturday
afternoon.

...HISPANIOLA...

Widely scattered evening showers and thunderstorms are seen in
satellite photos across the interior mountains of the island, from
north of Santo Domingo to interior NW Haiti, moving WNW near 15
mph. The upper low across the area is enhancing evening convection,
and isolated areas of heavy rainfall should be expected during
the few hours. Expect gradual clearing from east to west by
around midnight before isolated showers and thunderstorms begin
to move into E and NE portions of the island late tonight.

ATLANTIC OCEAN...

A broad plume of moisture is being pulled northward across the
northern Bahamas and surrounding waters by a middle to upper-
level low over the NE Gulf of Mexico, and supports scattered
showers and isolated strong thunderstorms west of 75W. Elsewhere,
surface ridging prevails across much of the remainder of the
central and the eastern Atlantic, anchored by 1025 mb high
pressure centered near 34N29W.

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

$$
Stripling
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