000 AXNT20 KNHC 040605 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 205 AM EDT Mon Sep 4 2017 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 0000 UTC surface analysis and satellite imagery through 0545 UTC. ...SPECIAL FEATURES... Hurricane Irma is centered near 17.2N 51.0W at 04/0300 UTC or about 615 nm E of the Leeward Islands moving W at 12 kt. Estimated minimum central pressure is 961 mb. Maximum sustained wind speed is 100 kt with gusts to 120 kt. Numerous strong convection is from 16N to 19N between 50W and 52W. Scattered moderate convection is elsewhere from 13N to 20N between 48W and 56W. See the latest NHC Intermediate Public Advisory under AWIPS/WMO headers MIATCPAT1/WTNT31 KNHC and the full Forecast/ Advisory under AWIPS/WMO headers MIATCMAT1/WTNT21 KNHC for more details. ...TROPICAL WAVES... A tropical wave is in the E Atlc associated with a 1013 mb low located near 10N33W. The wave axis extends from 17N33W to the low and it has been moving W at 10 kt. The wave is in a region of low to moderate vertical wind shear, however enhanced IR imagery continue to show some Saharan dry air and dust in the wave environment. CIRA LPW imagery at the lower levels confirm the presence of dry air in the vicinity of the wave. Shallow moisture and divergence aloft support scattered moderate convection from 06N to 14N between 32W and 40W. A tropical wave is in the central Caribbean with axis extending from 20N74W to 09N76W, moving W at 20-25 kt. The wave is in a region of low vertical wind shear, however it continues being affected by dry air subsidence from aloft, except N of 18N where upper level diffluence support scattered showers and tstms across Western Haiti and the Windward Passage. ...ITCZ/MONSOON TROUGH... The monsoon trough extends from the African coast near 12N16W to 11N30W to 09N37W. Aside from the convection associated with the tropical wave in the E Atlc, scattered moderate convection is from 04N to 11N E of 30W. ...DISCUSSION... GULF OF MEXICO... Water vapor imagery indicates a middle to upper level trough extending over the far NW Atlc to a broad base over S Florida. Middle to upper level diffluent flow prevails in the SE basin, thus supporting the continuation of scattered to isolated showers S of 26N. A surface trough continues in the SW Gulf, extending from 24N92W to 18N93W, which is generating scattered heavy showers and tstms. Fresh to strong winds are observed in the area of strongest convection or the E Bay of Campeche E of the trough axis. This feature is expected to dampen out by late Monday night into early Tuesday. Elsewhere, gentle to moderate easterly winds prevail with isolated showers occurring across the NW waters W of 93W. A surface ridge axis is expected to anchor along 30N Tuesday, gradually slide southward, and weaken by Wednesday as a weak frontal boundary moves off the Texas and Louisiana coasts. CARIBBEAN SEA... Middle level diffluent flow supports isolated showers and tstms in the Gulf of Honduras. In the SW basin, the E extension of the EPAC monsoon trough support scattered showers and tstms S of 12N. Otherwise, upper diffluence underneath a tropical wave that moves across central Caribbean waters supports scattered heavy showers N of 18N between 67W and 79W, including the Windward Passage. For further details on the wave, see section above. Water vapor imagery show dry air aloft across the remainder basin, which subsidence is supporting fair weather conditions. Otherwise, moderate to fresh trades are basin-wide. Looking beyond today, major Hurricane Irma looms across the central tropical Atlc and is forecast to approach 60W Tuesday evening into the overnight hours. ...HISPANIOLA... Scattered showers and tstms are expected to continue through Monday as a tropical wave continues to move westward away from the Island. Conditions will gradually improve on Tuesday. Looking ahead, Hurricane Irma is forecast to approach from the east and likely be centered N-NE of the island Thursday afternoon. ATLANTIC OCEAN... Major Hurricane Irma continue to represent a threat for the NE Caribbean Tue through late Wednesday. See special features for further details. A middle to upper level trough is progressing over far NW Atlc waters supporting isolated showers over the SW North Atlc. Farther east, an upper level low supports a dissipating stationary front extending from 30N62W SW to 27N67W. Scattered showers and tstms are from 24N to 29N between 60W and 64W. Surface ridging prevails elsewhere N of 24N. For additional information please visit http://www.hurricanes.gov/marine $$ Ramos