[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 270005
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
805 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 1800 UTC surface analysis and satellite imagery through
2345 UTC.

...Special Features...

Tropical Storm Kirk is centered near 12.5N 55.0W at 2100 UTC, or
about 230 nm E of Barbados or 300 nm ESE of Martinique, moving
westward 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 cyclone's cloud pattern has become comma shape during the
afternoon, with convection of the scattered moderate to strong
type within 180 nm of the center in the SE quadrant. Scattered
moderate convection is within 240 nm of the center in the NE
quadrant. Scattered moderate isolated strong convection is
elsewhere within 240 nm in the SE quadrant, and also within
30 nm of line from 11N55W to 11N57W. 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 within the Tropical Storm Warning area Thu afternoon.
Kirk is expected to produce very heavy rain across the northern
Windward and southern Leeward Islands Thu through much of Fri.
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.

Post-Tropical Cyclone Leslie, located over the central Atlantic
Ocean several hundred miles west-southwest of the Azores, has
intensified into a potent non-tropical low with hurricane-force
winds. The associated shower activity is becoming more organized,
and the low is showing signs of taking on more subtropical
characteristics. Latest satellite imagery shows a large shield
rain with embedded scattered to numerous showers between 90 and
480 nm of the low in the NW quadrant. Post-Tropical Cyclone Leslie
is expected to again become a subtropical storm, or possibly a
tropical storm, on Thursday or Friday while it moves west-
southwestward at about 10 mph over the north-central Atlantic.
There is a high 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 25W from
03N to 18N, 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. The wave is void of
deep convection, except for scattered showers and thunderstorms
from 15N to 18N between 23W and 26W.

A tropical wave has been added to the analysis along 35W between
03N to 15N moving westward at 10 to 15 kt. Model guidance shows
the wave corresponds nicely with a 700 mb trough. Scattered
showers and thunderstorms are within 60 nm either side of the
wave from 08N to 12N.

A tropical wave has its axis along 71W 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 are within 120 nm of the wave
from 15N to 18N.

...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 scattered showers and thunderstorms over the
northwestern Gulf north of about 26N and west of 89W. Scattered
showers and thunderstorms are elsewhere west of 90W, and just
inland and along the coast of Florida from Naples to 29N.

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 to the northeast of the region will support gentle
to moderate east to southeast 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...

Instability generated by the eastern Pacific monsoon trough that
protrudes into the far southwestern Caribbean, along pretty decent
upper-level ventilation continues to allow for scattered moderate
convection in clusters to remain active over much of the
southwestern Caribbean south of 13N and west of 77W. Scattered
showers and isolated thunderstorms are over much of the
northwestern Caribbean, and also south of 16N east of 70W.
Stronger activity, in the form of scattered moderate isolated
strong convection, is over the far southeastern Caribbean,
including the vicinity of Trinidad and Tobago.

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

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 strong cold front and an associated area of gale force winds
extend southward from Post-Tropical Cyclone Leslie low, which is
currently a gale center, over the central Atlantic well north of
the area near 36N39W with a pressure of 978 mb. The cold front
enters the forecast area near 31N34W and extends southwestward to
25N41W to 24N50W to 26N60W and to 28N65W. Scatterometer data from
Wed afternoon showed and area of strong to near gale force south
to southwest winds north of 27N east of the front. Satellite
imagery shows scattered moderate convection along and within 30 nm
east of the front from 26N to 28N. The front is forecast to
become stationary from near 29N35W to 23N44W and to near 21N51W
by Thu afternoon and dissipate by early Fri afternoon. The strong
to near gale force winds are forecast to diminish to strong winds
on Thu and continue through Fri. The post-tropical cyclone low,
gale center, is forecast to again become a subtropical or tropical
storm during the next couple of days. More details are described
above under the Special Features section.

Elsewhere, an upper-level anticyclone, in combination with a very
moist low-level easterly flow, is enhancing isolated showers and
thunderstorms over the southeastern 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

$$
Aguirre
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