Tropical Weather Discussion
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000
AXNT20 KNHC 251802
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
202 PM 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 1200 UTC surface analysis and satellite imagery through
1715 UTC.

...Special Features...

Leslie has become a post-tropical cyclone as of 1500 UTC, and the
final advisory has been issued. Leslie is centered near 31.6N
44.4W, or about 940 nm WSW of the Azores, moving E at 10 kt. A
faster northeastward motion is expected on Wednesday, followed by
a northward turn 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 and extends outward up to 330 nm from the center.
Strengthening is expected, and Leslie is forecast to become a
large and powerful post-tropical cyclone by Wednesday with winds
increasing to hurricane force on Thursday. By Thursday or Friday,
Leslie is expected to reacquire subtropical or tropical
characteristics while the cyclone moves slowly eastward to east-
northeastward over the north-central Atlantic. See the final NHC
forecast/advisory under AWIPS/WMO headers MIATCMAT3/WTNT23 KNHC
for more details.

A broad 1014 mb low is centered about 175 nm south of Cape
Hatteras, North Carolina. A surface trough extends SW from the
low to 29N77W. Scattered moderate convection is in the
northeastern semicircle of the low from 30N-35N and west of 70W.
Satellite and surface data indicate that the circulation of the
low remains elongated and not well defined. However, this system
could still become a tropical depression this afternoon or tonight
while it moves slowly northwestward to northward. By Wednesday,
additional development appears unlikely due to strong upper-level
winds while the system moves northward and north-northeastward
near the eastern United States coast. Regardless of development, this
system is likely to bring scattered showers and thunderstorms across
portions of northeastern South Carolina and eastern North Carolina
this afternoon and tonight. In addition, dangerous surf conditions
and rip currents are expected along portions of the North
Carolina coast today. For more information, please see products
from your local National Weather Service office. There is a medium
chance of tropical cyclone formation within 48 hours.

The remnant of Kirk is analyzed as a 1007 mb low near 10.5N47W or
about 825 nm east of the Windward Islands. A tropical wave runs
through the low along 47W from 04N-16N. Movement is W near 20 kt.
This system continues to produce a large area of showers and
thunderstorms, along with winds to near gale force on its north
side. Scattered moderate convection is seen from 08N-14N between
44W-51W. Although satellite data indicate that the system still
lacks a closed circulation, this disturbance could still redevelop
into a tropical cyclone during the next day or two before it
moves into an area of highly unfavorable upper-level winds as it
approaches 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. There is
a medium chance of redevelopment within the next 48 hours. For
more information on this system, see High Seas Forecasts issued by
the National Weather Service.

...TROPICAL WAVES...

An eastern Atlantic tropical wave is along 21W/22W from 03N-17N,
moving west at 10-15 kt. A 700 mb trough associated with this
wave is well depicted in model guidance. Saharan air is not as
prevalent near the wave as it was yesterday. The SAL has moved out
ahead of the wave and is not as dense, as suggested by GOES-16
geocolor imagery and split-window imagery. Isolated showers and
storms extend up to 60 nm west of the wave axis from 08N-13N.
Scattered moderate convection is between the wave axis and the
coast of Africa from 11N-14N.

A tropical wave is along 58W from 03N-17N, moving west at 15 kt.
The wave corresponds with a moisture maximum in TPW imagery.
Scattered moderate convection is located from 06N-15N between
53W-59W. This tropical wave could enhance showers and
thunderstorms over the Windward Islands this afternoon through
tonight.

...MONSOON TROUGH/ITCZ...

The monsoon trough extends from the African coast near the
Senegal/Guinea-Bissau border to 07N21W to 07N25W. The ITCZ begins
at 06N27W and continues to 07N36W to 10N44W, then resumes west of
the remnants of Kirk near 08N48W to near the coast of Suriname
near 06N57W. Outside of the convection mentioned with the two
tropical waves and the remnants of Kirk, scattered showers and
thunderstorms are located from 02N-09N between 26W-37W.

...DISCUSSION...

GULF OF MEXICO...

Upper-level diffluence over the north-central Gulf Coast is
enhancing scattered showers and thunderstorms north of 27N between
84W-90W. A thermal trough over the east-central Bay of Campeche is
weakening and is no longer producing any significant shower
activity. A surface trough will develop over the Yucatan
peninsula each evening, shift W over the SW Gulf each night, then
dissipate each morning. Elsewhere across the Gulf, gentle to
moderate winds will increase to between moderate and fresh during
the second half of this week as high pressure builds N of the
region.

CARIBBEAN SEA...

A surface trough moving slowly westward over the eastern
Caribbean extends from 20N64W to 15N65W. Scattered showers and
isolated thunderstorms are in the vicinity of the Virgin Islands,
Puerto Rico and the adjacent waters from 18N-22N between 61W-66W.
The eastern Pacific monsoon trough combined with diffluence aloft
continues to enhance scattered moderate and isolated strong
convection in the SW Caribbean from 11N-15N, between 78W and the
coasts of Nicaragua and eastern Honduras. Puerto Cabezas is
currently reporting thunderstorms, and satellite imagery shows
deep convection over extreme eastern Honduras and northeastern
Nicaragua. Expect fresh to strong winds over the central Caribbean
through midweek, with moderate to fresh winds thereafter through
Friday.

ATLANTIC OCEAN...

Currently, there are three tropical waves in the tropical Atlantic
between Africa and the Lesser Antilles. There is also a low with
development potential off the southeast coast of the U.S. For
information on those features as well as post tropical cyclone
Leslie, please read the Special Features and Tropical Waves
sections above.

A cold front is located on the northern border of the forecast
area from 32N53W to 31N57W, where it becomes a dissipating
stationary front. The dissipating stationary front extends
westward to 32N64W and continues WNW out of the forecast area.
Little to no shower activity is observed with the front at this
time.

Elsewhere, ridging over the northeast Atlantic is helping to
create fair weather north of 20N and east of 35W.

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

$$
Hagen


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