[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 130604
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
0605 UTC Mon Sep 13 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 0000 UTC surface analysis and satellite imagery through
0500 UTC.

...SPECIAL FEATURES...

Nicholas re-forms to the N and strengthens. At 13/0600 UTC,
Tropical Storm Nicholas is centered near 25.1N 96.5W or 60 nm SE
of mouth of The Rio Grande moving NNW at 13 kt. Estimated minimum
central pressure is 1001 mb. Maximum sustained wind speed is 50 kt
with gusts to 60 kt. Numerous moderate to strong convection is
noted within 120 nm E semicircle of center. Numerous moderate to
scattered strong convection is noted elsewhere N of 23N and W of
90W, and in the eastern Bay of Campeche. Seas 12 ft or greater are
within 60 nm NE and 30 nm SE quadrants of center. On the forecast
track, the center of Nicholas will pass near or just offshore the
coasts of northeastern Mexico and south Texas this morning, and
move onshore along the coast of south or central Texas Monday
afternoon or evening. Further strengthening is forecast until
Nicholas reaches the northwest Gulf coast later today. Nicholas is
expected to produce storm total rainfall of 8 to 16 inches, with
isolated maximum amounts of 20 inches, across portions of the
middle and upper Texas coastal areas through the middle of the
week. Across the rest of coastal Texas into southwest Louisiana
rainfall of 5 to 10 inches is expected. This rainfall may produce
areas of considerable flash and urban flooding, especially in
highly urbanized metropolitan areas. Additionally, there is the
potential for isolated minor to moderate river flooding. Over the
northeastern portions of the Mexican state of Tamaulipas, rainfall
amounts of 2 to 5 inches can be expected through today. In
addition, the combination of a dangerous storm surge and the tide
will cause normally dry areas near the coast to be flooded by
rising waters moving inland from the shoreline.

Please read the latest High Sea Forecast issued by the National
Hurricane Center at website -
https://www.nhc.noaa.gov/text/MIAHSFAT2.shtml and the latest
Nicholas NHC Forecast/Advisory and Public Advisory at
www.hurricanes.gov for more details.

...TROPICAL WAVES...

A tropical wave is expected to emerge off the west coast of Africa
today. Environmental conditions are forecast to be conducive for
some gradual development of this system thereafter, and a tropical
depression could form later this week while it moves westward at
10 to 15 kt across the eastern tropical Atlantic Ocean. The
latest Tropical Weather Outlook gives this system a medium chance
of tropical cyclone formation through 5 days. Please, see the
latest Tropical Weather Outlook at www.hurricanes.gov

An Atlantic tropical wave is along 31W from 03N to 20N, moving W
at 15 to 20 kt. Scattered moderate convection is noted near the
southern end of the wave axis.

Another Atlantic tropical wave is near 52W from 05N to 20N moving
W at 15 to 20 kt. No significant convection near the wave axis.

A Caribbean tropical wave is along 71W/72W and extends from
Hispaniola to western Venezuela moving W at 10 to 15 kt. Isolated
to scattered showers and thunderstorms are over Hispaniola and
regional waters. Isolated showers and thunderstorms are occurring
over western Venezuela.

Another tropical wave is over Central America with axis along 86W
from 16N southward. Scattered showers and thunderstorms are near
the wave axis affecting parts of Honduras, Nicaragua and Costa
Rica.

...MONSOON TROUGH/ITCZ...

A monsoon trough enters the Atlantic ocean through Guinea/Sierra
Leone border, then continues westward to near 09N28W. The ITCZ
extends from 09N32W to 06N43W to 07N51W. Other than the convection
described in the Tropical Wave section, scattered moderate convection
is evident within about 75 nm S of the monsoon trough between 24W
and 28W, and near 06N39W.

The eastern end of the E Pacific monsoon trough is triggering
scattered showers and isolated thunderstorms across parts of
northern Colombia, Panama and Costa Rica.

...GULF OF MEXICO...

Refer to the Special Features section above for details on Tropical
Storm Nicholas moving northward across the western Gulf.

Outside of T.S. Nicholas, a recent scatterometer pass provides
observations of fresh to strong E to SE winds across the western
Gulf, particularly N of 22N W of 90W where seas are in the 8-11 ft
range. Elsewhere, mainly gentle to moderate E winds prevail with
the exception of an area of fresh to locally strong NE-E winds
just N of the Yucatan peninsula. The same scatterometer pass
indicates a surface trough just to the W of the Yucatan peninsula.
This trough usually develops over the Yucatan peninsula during the
evenings hours, and moves across the SW Gulf during the overnight
and early morning hours while dissipating.

For the forecast, an area of fresh to strong winds will persist
today over the western Gulf between Nicholas and high pressure
over the SE of United States. As Nicholas moves inland tonight or
early Tuesday, a ridge will build westward across the Gulf waters.
Fresh to strong SW to W wind are expected to persist over the NW
Gulf on Tue as Nicholas continues to moves farther inland over the
N Gulf states.

...CARIBBEAN SEA...

A pair of tropical waves are moving westward across the Caribbean
Sea. Please see the Tropical Waves section for more information.

Satellite derived wind data show mainly fresh trades near the
tropical wave located along 71W/72W, and fresh to locally strong
winds in the Windward passage. Elsewhere, mainly gentle to
moderate winds are observed. Seas are generally 3-5 ft, except 4-6
ft in the Windward passage, and 6-8 ft in the Gulf of Honduras
where fresh to locally strong easterly winds are blowing.

For the forecast, moderate to fresh trades will prevail across
the basin through the forecast period. Fresh to strong winds are
expected again in the Gulf of Honduras at night Wed through Fri.

...ATLANTIC OCEAN...

A stationary front reaches from near Bermuda to Saint Augustine
Florida. Scattered showers and thunderstorms are evident near the
frontal boundary affecting mainly the waters N of 27N between 65W
and 77W. Another area of showers are thunderstorms is covering the
waters N of Puerto Rico from 20N-26N between 60W and 70W. An
upper-level low spinning just N of Hispaniola is generating this
convective activity. Fresh to strong winds are noted near the
thunderstorms located N of Puerto Rico, and N of Hispaniola,
including the approaches to the Windward passage. Farther E, a
cold front enters the forecast waters near 31N14W, then continues
SW crossing the Canary Islands to near 25N30W to 30N50W. Scattered
showers and thunderstorms are near the western end of the front.
Moderate northerly winds and 4 to 6 ft seas are noted north of
this boundary.

For the forecast west of 65W, a few showers and thunderstorms will
persist along the the frontal boundary today as it lingers over
the north waters. An area of low pressure is forecast to form by
midweek a couple of hundred miles north of the southeastern or
central Bahamas as a tropical wave interacts with an upper-level
trough. Some gradual development of this system is possible
thereafter, and a tropical depression could form later this week
while the system moves north-northwestward or northward across the
western Atlantic. This system has a medium chance of tropical
cyclone formation through the next 5 days.

For the forecast E of 65W, showers and thunderstorms are very
limited in association with a non-tropical area of low pressure
over the far northeastern Atlantic, located a few hundred miles
east of the Azores. Significant development of this system appears
unlikely during the next day or so while it moves slowly eastward.
By late Tuesday, the system is forecast to move inland over Portugal.

$$
GR
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