[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 121045
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1205 UTC Sun Sep 12 2021

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 31N. The following information is based on satellite
imagery, weather observations, radar and meteorological analysis.

Based on 0600 UTC surface analysis and satellite imagery through
1020 UTC.

...SPECIAL FEATURES...

Showers and thunderstorms over the Bay of Campeche and southern
Gulf of Mexico have been increasing during the past several hours
near and east of a surface trough of low pressure.  A tropical
depression is expected to form later today or tonight while the
system moves northwestward and then northward near the coast of
northeastern Mexico. Additional development is possible through
the middle of next week if the system remains over water, and
interests along the western and northwestern Gulf coast should
monitor the progress of this disturbance. An Air Force Hurricane
Hunter aircraft is scheduled to investigate the system this
morning, and potential tropical cyclone advisories could be
initiated later today. Regardless of development, the disturbance
will continue to produce heavy rain across portions of southern
Mexico today, including the western Yucatan Peninsula, which may
lead to flash flooding and mudslides. By late today, heavy rain is
expected to reach portions of the Texas and Louisiana coasts with
a heavy rain threat continuing across those coasts through the
middle of the week. Localized significant rainfall amounts are
possible, potentially resulting in areas of flash, urban, and
isolated river flooding. The chance of tropical cyclone formation
within the next 48 hours is high.

...TROPICAL WAVES...

An Atlantic tropical wave has an axis along 25W south of 21N,
moving W at 15-20 kt. A 1010 mb low is analyzed along the wave
near 17N25W. Scattered moderate to isolated strong convection is
noted north of the low from 17N to 20N between 23W and 26W. The
National Hurricane Center is tracking this disturbance for
possible tropical development over the next few days. Currently,
it has a low chance of development over the next 48 hours.

An Atlantic tropical wave has an axis along 47W south of 22N,
moving W at 15 kt. The wave is surrounded by dry Saharan air,
which is inhibiting convection at this time.

A Caribbean tropical wave has an axis along 68W south of 21N,
moving W at 15-20 kt. This wave is moving in tandem with an upper
level trough and is producing scattered moderate to isolated
strong convection from 17N to 22N between 65W and 71W, impacting
Hispaniola, Puerto Rico, and the Virgin Islands.

A Caribbean tropical wave has an axis along 83W south of 15N,
moving W at 10 kt. A few showers are noted near the wave axis,
mainly north of Panama, but no significant convection is
associated with this feature.

...MONSOON TROUGH/ITCZ...

The monsoon trough passes through the coast of Mauritania near
20N16W to near a 1010 mb low near 17N25W to 12N31W to 06N38W. The
ITCZ continues from 06N38W to 05N45W. Outside of the convection
near the 1010 mb low, isolated convection is noted along the ITCZ
from 05N to 07N between 39W and 43W.

GULF OF MEXICO...

See the Special Features section above for details on the
disturbance over the Bay of Campeche.

A trough stretches across the western Gulf from 27N93W to 18N93W.
Scattered moderate to isolate strong convection is noted S of 27N
between 89W and 98W and moving northward toward the Texas and
Louisiana coast. Isolated thunderstorms are also moving across the
Florida Panhandle. Overnight satellite data and surface
observations show fresh to strong cyclonic winds W of 86W, with
the strongest winds noted in the north-central Gulf and within 100
nm the coast of Veracruz, Mexico. Moderate to locally fresh
easterlies are observed in the SE and NW Gulf, while gentle to
moderate winds are present in the NE Gulf. Fresh to locally strong
winds are occurring east of the trough in the Bay of Campeche.
Seas of 4-7 ft prevail in the N Gulf, while 3-6 ft are present
elsewhere in the basin, with the exception of 2-4 ft in the NE
Gulf.

For the forecast, please see the Special Features section above
for more information about the potential for tropical cyclone
development in the western Gulf. Elsewhere, quiescent conditions
are expected to prevail across the central and eastern Gulf
through midweek.

CARIBBEAN SEA...

Please see the Tropical Waves section above for details on the
tropical waves along 66W and 82W.

Scattered moderate convection is moving across the Greater
Antilles N of 17N between 66W and 84W. Scattered moderate to
isolated strong convection is noted in the SW Caribbean near the
monsoon trough, S of 13N between 74W and 84W. Fresh to strong
trade winds are continuing north of Colombia and the Gulf of
Honduras, with moderate to locally fresh winds across the rest of
the Caribbean. Seas of 5-8 ft are present in the central Caribbean
and Gulf of Honduras and 2-5 ft are prevalent elsewhere.

For the forecast, the fresh to strong winds occurring offshore
Colombia and in the Gulf of Venezuela will diminish today. The
fresh to strong winds in the Gulf of Honduras will pulse again
this evening. By tonight and into Mon morning, moderate to locally
fresh trades will prevail across the basin through Thu.

ATLANTIC OCEAN...

In the SW N Atlantic, a stationary front lingers from 31N67W to
29N78W. Scattered thunderstorms are noted along this boundary from
28N to 31N between 62W and 78W. A trough is analyzed east of the
Lesser Antilles from 16N55W to 10N56W. Scattered moderate to
isolated strong convection is noted from 12N to 23N between 55W
and 62W. In the far eastern Atlantic, a cold front stretches from
31N20W to 30N38W. Scattered showers are along this boundary. High
pressure extends across the basin anchored by a 1028 mb high near
35N45W. Moderate to locally fresh winds prevail across the basin S
of 23N with light to gentle winds north of 23N. Seas are 4 to 7 ft
with seas less than 3 ft near the Florida coast.

For the forecast west of 60W, a frontal boundary will linger
across the area through Mon which will bring showers and
thunderstorms across the area. Otherwise, quiescent conditions
will prevail through Wednesday. Meanwhile, an area of low pressure
is expected to form north of the southeastern Bahamas in a few
days resulting from the northern end of a tropical wave
interacting with an upper- level trough. Gradual development of
this system is possible, and a tropical depression could form by
the middle of the week several hundred miles southeast of the
Carolinas while it moves northwestward across the western
Atlantic. This system has a low chance of formation in the next 48
hours and a medium chance through the next 5 days.


$$
AReinhart
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