000 AXNT20 KNHC 291754 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 155 PM EDT Wed Jul 29 2020 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 1700 UTC. ...SPECIAL FEATURES... Potential Tropical Cyclone Nine is centered near 16.2N 64.7W at 29/1800 UTC, or about 90 nm S of St. Croix, moving WNW at 20 kt. Estimated minimum central pressure is 1006 mb. Maximum sustained wind speed is 40 kt with gusts to 50 kt. Scattered strong convection extends out 240 nm from the center in the NE quadrant and 150 nm SW quadrant. Scattered moderate isolated strong convection is elsewhere within 360 nm NE, 180 nm SE, 270 nm SW and 210 nm NW of the center. Heavy rain may lead to life-threatening flash flooding over the Leeward Islands, Virgin Islands, Puerto Rico and the Dominican Republic today into Thu. A recent ASCAT pass shows that tropical storm force winds of 35-40 kt exist in the NE quadrant in the area between 150-270 nm NE of the center. These winds are likely currently affecting the northern Leeward Islands, and will be spreading to the Virgin Islands early this afternoon. The highest seas this afternoon and evening are expected on the Atlantic Ocean side of the northern Leeward and Virgin Islands, with peak seas of 18 ft. PTC Nine is forecast to remain at tropical storm strength as it interacts with Hispaniola on Thursday, and Cuba and the Bahamas on Friday. Please read the latest NHC Public Advisory at https://www.nhc.noaa.gov/text/MIATCPAT4.shtml and Forecast/ Advisory at https://www.nhc.noaa.gov/text/MIATCMAT4.shtml for more details. ...TROPICAL WAVES... A tropical wave has been added to the analysis with axis along 20W from 03N-18N, moving W at 15 kt. Numerous moderate scattered strong convection is within 120 nm W and 180 nm E of the wave axis from 09N-13.5N. An Atlantic tropical wave is along 33W from 03N-21N, moving W at 20 kt. Isolated moderate convection is seen from 12N-14N between 28W-30W and from 03N-08N between 33W-37W. A Caribbean Sea tropical wave is along 76W from 04N-20N, moving W at 20 kt. Isolated moderate convection is near eastern Panama where the wave axis meets the east Pacific monsoon trough. The northern portion of a tropical wave has moved inland over Belize along 89W from 18N southward. Scattered showers and tstorms associated with this wave over the Gulf of Honduras will end later today. ...MONSOON TROUGH/ITCZ... The monsoon trough passes through the coastal sections of Mauritania near 19N16W to 13N23WW to 07N41W to 08N45W. The ITCZ continues from 08N45W to 09N53W. Numerous moderate isolated strong convection is observed from 08N-11N between 24W-27W and from 04N-08N between 38W-45W. GULF OF MEXICO... A ridge extends across the northern Gulf supporting gentle to moderate E to SE winds and 2 to 4 ft seas across the basin, except for fresh winds and 3 to 5 ft seas off the west coast of the Yucatan peninsula. An upper-level low over NE Mexico is generating upper-level diffluence over the west-central Gulf, enhancing scattered moderate showers and tstorms over the western Gulf, west of 95W. For the forecast, surface ridging will dominate the Gulf waters through Fri, supporting mainly gentle to moderate return flow. Beyond that, much will depend on the track and intensity of Potential Tropical Cyclone Nine, currently located over the eastern Caribbean. Nine may approach the Florida Straits and far southeast Gulf by Sat and Sun. CARIBBEAN SEA... Potential Tropical Cyclone Nine is currently affecting the eastern Caribbean, east of 69W and north of 13N. See Special Features section above for the current details on Nine. Several stations on Guadeloupe and Martinique reported 24-hour rainfall amounts ending at 29/1200 UTC between 3 and 4 inches. For the forecast, seas as high as 10-15 ft are forecast through tonight for portions of the NE Caribbean in the waters south of Puerto Rico. Tropical storm force winds are forecast to be in the Mona Passage tonight, near Hispaniola Thu, and in the Windward Passage late Thu and Thu night. The NW Caribbean should monitor the progress of Nine in case the track shifts farther south. Winds and seas will largely diminish over the eastern Caribbean Fri, except for an area of swell to at least 8 ft that will penetrate through the Mona Passage. Elsewhere, scattered showers and tstorms related to the east Pacific monsoon trough are over the far SW Caribbean off the coast of Panama through southern Nicaragua. A recent ASCAT pass shows fresh trades in the central Caribbean and in the Gulf of Honduras, with moderate winds elsewhere in the western Caribbean. Fresh to strong NE winds are expected tonight through Thu night across the Windward Passage and Cuba adjacent waters. Fresh trade winds will prevail over Colombia adjacent waters and in the Gulf of Honduras through tonight. ATLANTIC OCEAN... A small upper-level trough off the SE coast of the U.S. is inducing upper-level divergence to the SE of the trough. This is enhancing scattered moderate convection east of Florida and north of the NW Bahamas, from 27N-32N between 75W-80W. A surface ridge extends across the Atlantic from a 1023 mb high near 33N28W to a 1025 mb high near 31N55W to a 1020 mb high over central Florida. Convection related to PTC Nine is currently occurring south of 23N between 58W-67W. The ASCAT pass from around 1300 UTC this morning showed that winds over 25 kt associated with the circulation of PTC Nine were confined to areas south of 24N between 56W-66W at that time. The swath of dangerous winds and seas associated with PTC Nine will occur over the waters north of Puerto Rico and Hispaniola to 25N through Thu, reaching the SE Bahamas and Windward Passage late Thu and into the central and NW Bahamas through Fri to include the adjacent offshore waters. Tropical storm force winds are also expected over the Old Bahama Channel Fri and Florida Straits Saturday. $$ Hagen