[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 261755
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
155 PM EDT Wed Sep 26 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 1200 UTC surface analysis and satellite imagery through
1715 UTC.

...Special Features...

Tropical Storm Kirk is centered near 12.5N 55.0W at 1800 UTC, or
about 265 nm E of Barbados or 375 nm ESE of Martinique, moving
west at 16 kt. The estimated minimum central pressure is 998 mb.
The maximum sustained wind speed is 50 kt with gusts to 60 kt.
The deep convection associated with this tropical storm extends
outward from the center up to 180 nm in the northeast semicircle
and 60 nm in the southwest quadrant. The convection has continued
to look impressive and is gradually becoming more symmetrical
during the last several hours. The latest NHC advisory has Kirk
moving in a westward to west-northwestward motion through Fri
night. On this track, Kirk is expected to move over the Lesser
Antilles Thursday night. It will move into the eastern Caribbean
Sea by Fri morning. Little change in strength is forecast until
Kirk crosses the Lesser Antilles, followed by weakening over the
eastern Caribbean Sea. Kirk is expected to produce very heavy rain
across the northern Windward and southern Leeward Islands
Thursday through much of Friday. These rains may produce life-
threatening flash floods and mudslides, especially across
Martinique and Dominica. See latest NHC Forecast/Advisory under
AWIPS/WMO Headers MIATCMAT2/WTNT22 KNHC for more details.

A strong cold front and an associated area of gale force winds
extend southward from Post-Tropical Cyclone Leslie over the
central Atlantic. The cold front enters the forecast area near
31N37W and extends SW and W to 27N40W to 26N49W to 27N58 where it
becomes a dissipating cold front. The dissipating cold front
extends to 29N64W. The latest ASCAT data show gales are currently
occurring north of 29N and east of 37W, along the front and
extending to 90 nm east of the front to 34.5W. Winds in this area
are forecast to diminish below gale force later this afternoon.
However, winds will remain around 30 kt in the area during the
next couple of days. Scattered moderate convection is along and
within 90 nm ahead of the front for the portion of the front
that's east of 39W. Meanwhile, Post-Tropical Cyclone Leslie,
centered several hundred nm west-southwest of the Azores, is
producing gale force winds. Scattered moderate convection is from
34N-38N between 37W-42W. Leslie is expected to reacquire
subtropical or tropical characteristics on Thu or Fri while the
cyclone meanders over the north-central Atlantic. There is a
medium chance of this system becoming a tropical or subtropical
cyclone during the next 48 hours. For more information on this
system, see High Seas Forecasts issued by the National Weather
Service.

...TROPICAL WAVES...

A far eastern Atlantic tropical wave has its axis along 24/25W
from 03N to 17N, moving westward at 10 to 15 kt. Model guidance
depicts a broad 700 mb trough a few degrees ahead of this wave.
Total precipitable water (TPW) imagery clearly indicates a maximum
in TPW associated with this tropical wave. Scattered showers and
thunderstorms are located north of 13N between the wave axis and
19W.

A tropical wave has been added to the analysis along 35W between
03N-13N moving west around 10-15 kt. Model guidance shows the wave
corresponds nicely with a 700 mb trough. Scattered showers and
thunderstorms are located from 03N-09N between 30W-38W.

A tropical wave has its axis along 70W south of 19N, moving
westward at 15 kt. The Total Precipitable Water (TPW) satellite
animation shows a broad pool of moisture between 65W-71W.
Scattered showers and thunderstorms extend from 12N-15N east of
the wave axis to 64W.

...MONSOON TROUGH/ITCZ...

The monsoon trough axis extends off the coast of Africa over
Senegal at 14N17W and continues to 09N25W to 07N32W, where the
ITCZ begins and continues to 06N46W. Outside of the convection
mentioned with the two tropical waves, scattered moderate
convection is noted within 120 nm north and 90 nm south of the
ITCZ between 38W-44W.

...DISCUSSION...

GULF OF MEXICO...

Upper-level diffluence over the north-central Gulf Coast is
enhancing showers and thunderstorms over southern Louisiana and
the Gulf waters north of 27.5N between 90W-94W. This enhanced
activity has generally been moving slowly westward. A thermal
trough is analyzed over the central Bay of Campeche. Scattered
showers and thunderstorms are near the coast of Mexico between
Veracruz and Tuxpan and over the Gulf south of 21N and west of
95W.

High pressure NE of the region will support gentle to moderate E
to SE winds and seas less than 4 ft across most of the region
through Sun. The only exception is locally fresh winds each night
associated with a trough moving over the eastern Bay of Campeche.

CARIBBEAN SEA...

Convection associated with Tropical Storm Kirk and the tropical
wave in the east-central Caribbean is described above in the
Special Features and Tropical Waves Sections. The forecast for the
eastern half of the Caribbean is also described above.

Elsewhere, instability generated by the eastern Pacific monsoon
trough that protrudes into the far southwestern Caribbean, along
with upper-level divergence in the area is generating an area
containing numerous moderate and isolated strong convection from
Panama northward to 12N between 77W-84W. In the northwest
Caribbean, upper-level anticyclonic turning is helping to generate
scattered moderate convection from 16N-19N between 83W and the
coast of Belize.

Expect fresh to strong trade winds to continue over the south-
central Caribbean through Thursday.

ATLANTIC OCEAN...

Tropical Storm Kirk and two tropical waves between Africa and the
Lesser Antilles are described above in the Special Features and
Tropical Waves sections. A cold front and associated gale force
winds extending southward from Post-Tropical Cyclone Leslie has
also been described above in the Special Features section.

Elsewhere, an upper-level anticyclone is enhancing isolated
showers and thunderstorms over the southeast and central Bahamas,
northern Cuba and the Florida Straits. A high pressure ridge
extends over the northwest Bahamas and the waters east of Florida,
creating fair weather north of 25N west of 75W.

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

$$
Hagen
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