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Atlantic Tropical Weather Discussion

AXNT20 KNHC 251201

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
801 AM EDT Tue Sep 25 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 0600 UTC surface analysis and satellite imagery through 
1115 UTC.

...Special Features...

Subtropical Depression Leslie was centered near 31.9N 46.2W at 
0900 UTC, or about 1015 nm WSW of the Azores, moving SE at 7 kt. 
A faster east to northeast motion is expected later today and 
Wednesday, followed by a turn to the north by Wednesday night. 
Estimated minimum central pressure is 1007 mb. Maximum sustained 
winds are 30 kt with gusts to 40 kt. Scattered moderate convection
is limited to the eastern semicircle but extends outward up to 
330 nm from the center. Leslie is expected to lose its subtropical
characteristics by tonight. Strengthening as a post-tropical 
cyclone is expected, and Leslie is forecast to become a large and 
powerful post-tropical cyclone by Wednesday with winds approaching
hurricane force. After that time, Leslie is expected to reacquire 
subtropical or tropical characteristics by the end of the week as 
it meanders over the central Atlantic. See the latest NHC 
forecast/advisory under AWIPS/WMO headers MIATCMAT3/WTNT23 KNHC 
for more details.

A broad 1014 mb low is centered about 230 nm south of Cape 
Hatteras near 31N75W. A surface trough extends SW from the low to 
28N76W. Scattered moderate isolated strong convection is NE of the
center from 30N-34N between 70W-76W. Satellite data indicate that
the circulation of the low is elongated and not well organized. 
However, this system could still become a tropical depression 
later today while it moves northwestward. By tonight and 
Wednesday, additional development appears unlikely, due to strong 
upper-level winds, while the system moves northward and north- 
northeastward near the southeastern United States coast. There is 
a medium chance of tropical cyclone formation within 48 hours.

The remnants of Kirk are analyzed as a tropical wave along 45W 
from 04N to 16N, moving W at 20 kt. Scattered moderate to isolated
strong convection is associated with the wave from 09N-14N between
42W-49W. Winds to gale force are in the northern portion of the 
wave. This system could redevelop into a tropical cyclone during 
the next two days before it encounters unfavorable upper-level 
winds east of the the Caribbean Sea. Interests in the Windward and
Leeward Islands should monitor the progress of this disturbance as
gusty winds and locally heavy rains are likely by Thursday, even 
if the system does not redevelop into a tropical cyclone. For more
information on this system, see High Seas Forecasts issued by the
National Weather Service.


An eastern Atlantic tropical wave is along 20W/21W from 03N-17N, 
moving west at 15 kt. A 700 mb trough associated with this wave is
well depicted in model guidance, and there is evidence of 
cyclonic curvature in the winds near the surface. Deep convection 
is limited due to the presence of Saharan air, although a small
area of isolated moderate convection is present from 11N-14N
between the coast of Africa and the wave axis.

A tropical wave is along 57W from 03N-17N, moving west at 15 kt. 
The wave corresponds with a moisture maximum in TPW imagery. 
Scattered showers are located from 08N-12N between 52W-59W. 


The monsoon trough extends from the African coast near 12N16W to 
06N24W. The ITCZ continues from 06N24W to 06N35W to 11N43W, then 
resumes west of the remnants of Kirk near 08N47W to the coast of 
South America near 06N54W. Scattered showers and thunderstorms
are from 02N to 08N between 27W-36W.



A stationary front over the NW Gulf has dissipated. A thermal 
trough is over the eastern Bay of Campeche, with isolated showers
within 60 nm of the trough axis. This trough will drift westward 
across the Bay of Campeche this morning. Gentle to moderate E to 
SE winds and seas 3 ft or less will prevail across most of the 
basin through the middle of this week. Winds will increase to 
between moderate and fresh during the second half of this week.


A surface trough moving slowly westward over the eastern 
Caribbean extends from 18N62W to 12N63W. Scattered showers and
isolated thunderstorms are in the vicinity of the Leeward Islands.
The eastern Pacific monsoon trough combined with diffluence aloft
continues to enhance scattered moderate and isolated strong
convection in the SW Caribbean from 10N-14N between 77W-83W. 
Elsewhere, scattered showers are over Belize and the NW Caribbean
to the east of Belize. Expect fresh to strong winds over the 
central Caribbean through midweek, with moderate to fresh winds
thereafter through Friday.


Currently, there are three tropical waves, and a subtropical 
depression in the Atlantic. There is also a low with development
potential off the southeast coast of the U.S. See the sections 
above for details.

Elsewhere, GOES-16 split-window satellite imagery shows a large 
area of Saharan dust over the tropical Atlantic from 11N-25N 
between 30W-55W, moving W, and partially surrounds the remnants 
of Kirk on the north side.

The remainder of the basin is under the influence of a surface 
ridge, anchored by high pressure centered well north of the area
over the far northeast Atlantic.

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