[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 222350
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
750 PM EDT Sat Sep 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 1800 UTC surface analysis and satellite imagery through
2315 UTC.

...Special Features...

Tropical Storm Kirk is centered near 8.6N 24.8W at 22/2100 UTC,
or 375 nm (690 km) S of the southernmost Cabo Verde Islands,
moving WNW at 13 kt. A westward to west-northwestward motion at a
similar forward speed is expected to continue through tonight. A
faster westward motion across the deep tropical Atlantic Ocean is
expected Sunday through Tuesday. Minimum central pressure is 1005
mb. Maximum sustained wind speed is 35 kt with gusts to 45 kt.
Some strengthening is forecast through Sunday, with little change
in intensity expected on Monday and Tuesday. Scattered moderate
convection is observed within 275 nm of the center in the western
semicircle, while scattered showers are noted within 150 nm of
the center in the eastern semicircle. See the latest NHC
forecast/advisory under AWIPS/WMO headers MIATCMAT2/WTNT22 KNHC
for more details.

Tropical Depression Eleven is centered near 13.6N 53.9W at
22/2100 UTC, or 415 nm (770 km) E of the Windward Islands, moving
NW at 3 kt. A faster west-northwestward motion is expected to
begin tonight and continue through dissipation. Estimated minimum
central pressure is 1008 mb. Maximum sustained wind speed is 25
kt with gusts to 35 kt. The depression is expected to weaken to a
remnant low tonight or Sunday and dissipate Sunday night east of
the Lesser Antilles. Scattered moderate convection is noted
between 90-240 nm from the center in the E semicircle. See the
latest NHC forecast/advisory under AWIPS/WMO headers
MIATCMAT1/WTNT21 KNHC for more details.

Satellite imagery indicates that a frontal non-tropical low
pressure system is located about 1000 nm west-southwest of the
Azores. Conditions are expected to become conducive for this low
to acquire subtropical or tropical characteristics during the next
day or so, and a subtropical or tropical cyclone is likely to
form by early next week while the low meanders over the central
Atlantic Ocean. The system has a medium chance of tropical cyclone
formation within the next 48 hours. Please refer to the latest
Tropical Weather Outlook under AWIPS/WMO headers MIATWOAT/ABNT20
KNHC for more information.

A cold front extends from a 1001 mb low pressure located N of the
area near 34.5N44W to 31N43W to 28N56W. The most recent
scatterometer data provide observations of minimal gale force
winds just ahead of the front, particularly N of 27.5N and within
60 nm east of the front. Seas of 9 to 11 ft are within the area of
these winds. A gale warning has been issued accordingly. Gale
force winds are expected ahead of the front through Sunday
morning.

...TROPICAL WAVES...

A tropical wave has its axis along 42W from 03N-16N and is moving
west at 10-15 kt. The wave corresponds nicely with a maximum in
TPW imagery. Model analyses depict an associated 700 mb trough
along 42W. Scattered showers are located near and east of the
wave axis from 10N-14N between 39W-45W.

A western Caribbean Sea tropical wave has its axis along 86W from
08N-21N, moving west around 10 kt. The 700 mb trough associated
with this wave is well depicted in model guidance, and TPW imagery
shows abundant moisture in its environment. Scattered moderate
convection is noted south of 20N between 80W-88W. Moisture
associated with this wave will continue to spread inland across
Central America through tonight, enhancing similar convection.

...MONSOON TROUGH/ITCZ...

The monsoon trough extends from the African coast near the
Mauritania/Senegal border to 15N19W. It continues from 07N24W to
06N30W to 08N38W. The ITCZ begins near 09N43W and continues to
09N52W. Aside from the convection associated with the tropical
wave and cyclones across the area, scattered showers are located
along and within 90 nm south of the monsoon trough between 26W-
31W.

...DISCUSSION...

GULF OF MEXICO...

An upper-level cyclonic circulation is centered near 27N86W. A
surface trough is analyzed over the SE Gulf along 84W from 23N-
26N. Both features are helping to enhance convection slightly
across the eastern Gulf east of 86W from 23N-29N, where scattered
showers and isolated thunderstorms are observed. A surface trough
extending from the coast of SE Louisiana to 25N91W is producing
isolated showers and thunderstorms from 24N-26N between 88W-92W.
A cold front currently over east-central Texas is expected to move
eastward, reaching the Texas coast tonight. This front is likely
to just barely reach the NW Gulf off the Texas coast tonight
before stalling and dissipating on Sunday. A surface trough
located ahead of the front is currently just inland over south
Texas. Scattered moderate convection is noted over the NW Gulf
north of 27N and west of 92W. Gentle to moderate E to SE winds and
seas 3 ft or less will prevail across most of the Gulf of Mexico
through the middle of next week. A surface trough will develop
over the Yucatan peninsula each evening, shift W over the SW Gulf
each night, then dissipate by morning. Moderate to fresh winds
will accompany the trough.

CARIBBEAN SEA...

A tropical wave is moving across the far western Caribbean, and a
portion of this wave is entering Central America. Please see the
Tropical Waves section for more details.

The eastern Pacific monsoon trough combined with diffluence aloft
continues to enhance convection over portions of Panama and the
waters of the southwest Caribbean from the coasts of Panama and
Costa Rica northward to 12N and eastward to 78W. Plenty of
moisture will persist over the extreme southwest Caribbean, Panama
and Costa Rica through tonight. Elsewhere, fresh to strong winds
prevail over the central Caribbean. These winds will diminish
across most of the basin by Sun night.

ATLANTIC OCEAN...

Currently, there are two tropical cyclones and a tropical wave
between the west coast of Africa and the Lesser Antilles. Please
see the Special Features and Tropical Waves sections for more
details.

A broad 1011 mb low is centered 200 nm south of Bermuda. A
surface trough runs through the low from 31N61W to the low near
29N65W to 28N69W. Scattered moderate convection is seen extending
out to 180 nm from the center of the low in the eastern
semicircle. Strong upper-level winds and dry air are expected to
limit development for the next day or so, but conditions could
become more conducive for some development of this system by early
next week while it moves westward and west-northwestward over the
southwestern Atlantic Ocean. By the middle of next week, upper-
level winds are likely to increase again, which would limit
additional development as the system turns northward and moves
closer to the southeastern coast of the United States. The low has
a low chance of tropical cyclone formation during the next 48
hours.

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

$$

GR/ERA
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