000
AXNT20 KNHC 131253
TWDAT 

Tropical Weather Discussion...Update
NWS National Hurricane Center Miami FL
1205 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 0900 UTC surface analysis and satellite imagery through 
1210 UTC.

Updated Special Features Below

...SPECIAL FEATURES...

Tropical Storm Nicholas is centered near 25.4N 96.9W at 13/1200 
UTC or 35 nm SSE of mouth of The Rio Grande moving NNW at 4 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 200 nm E semicircle of center 
AND 30 nm W semicircle. Numerous moderate to scattered strong 
convection is noted elsewhere N of 21N and E of 90W, and in the 
eastern Bay of Campeche. Seas 13 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 
high 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, south of 9N between 28W to 33W. 

Another Atlantic tropical wave is near 52W from 05N to 19N moving
W at 15 to 20 kt. No significant convection near the wave axis.

A Caribbean tropical wave is along 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 and Colombia. 

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 07N34W to 06N52W. 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 8-15 
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 move 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 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 31N11W, then continues
SW crossing the Canary Islands to near 24N30W 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 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.

$$

Chan