152 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