000 AXNT20 KNHC 040950 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 550 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 0600 UTC surface analysis and satellite imagery through 0945 UTC. ...SPECIAL FEATURES... Hurricane Irma is centered near 16.9N 52.3W at 04/0900 UTC or about 545 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 15N to 19N between 50W and 54W. Scattered moderate convection is elsewhere from 13N to 20N between 47W and 56W. The center of Irma is expected to approach the northern Leeward Islands late Tuesday. Some strengthening is forecast during the next 48 hours. 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 came off the W African coast earlier today. Its axis extends from 18N18W to 07N16W and is forecast to move W at 10 kt within the next 24 hours. The wave is in a region of low vertical wind shear and CIRA LPW imagery show patches of dry air in the northern wave environment N of the monsoon trough. Shallow moisture along middle to upper level diffluence support scattered moderate convection from 05N to 12N E of 18W. A tropical wave is in the central Atlc associated with a 1011 mb low located near 10N33W. The wave axis extends from 17N33W to the low to 08N33W 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 04N to 14N between 30W and 41W. Environmental conditions are expected to be conducive for gradual development, and a tropical depression will likely form later this week while the system moves west-northwestward over the tropical Atlantic Ocean. 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 17N where upper level diffluence support scattered showers and tstms across Western Haiti, the Windward Passage and Cuba adjacent waters. ...ITCZ/MONSOON TROUGH... The monsoon trough extends from the African coast near 12N16W to 12N28W to 09N39W to 12N42W. Aside from the convection associated with the tropical waves, scattered moderate convection is from 04N to 10N between 20W and 30W. ...DISCUSSION... GULF OF MEXICO... Water vapor imagery show an upper level trough extending over the far NW Atlc waters 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 27N. A surface trough continues in the SW Gulf, extending from 25N96W to 18N94W, which is generating scattered heavy showers and tstms W of 91W. This feature is expected to dampen out by late tonight into early Tuesday. Elsewhere, gentle to moderate easterly winds prevail with isolated showers occurring across the NW waters W of 90W. 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... Former isolated showers and tstms over the Gulf of Honduras are moving inland southern Belize. In the SW basin, the E extension of the EPAC monsoon trough continue to support scattered showers and tstms S of 12N. Otherwise, upper diffluence above a tropical wave that moves across central Caribbean waters supports scattered heavy showers and tstms N of 17N between 68W and 83W, including the Windward Passage and Cuba adjacent waters. 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 locally fresh trades are basin-wide. Looking beyond today, major Hurricane Irma is expected to approach the northern Leeward Islands Tuesday evening and will continue to affect the NE Caribbean through late Thursday. ...HISPANIOLA... Isolated showers are across the Island as a tropical wave continue to move W over central Caribbean waters. Upper level diffluence over the northern wave environment support scattered showers and tstms over NE Dominican Republic adjacent waters and the Windward Passage. Conditions will gradually improve on Tuesday as the way continues to move away. Looking ahead, Hurricane Irma is forecast to pass N of the Island early Thursday through early Friday. See Special Feature for further details. ATLANTIC OCEAN... Major Hurricane Irma continue to represent a threat for the NE Caribbean Tue through early Thursday. See special features for further details. A middle to upper level trough progressing over far NW Atlc waters supports isolated showers over the SW North Atlc W of 75W. Farther east, an upper level low supports a surface trough extending from 29N66W to 24N68W. Scattered showers and tstms are E of the surface trough from 22N to 29N between 60W and 66W. Surface ridging prevails elsewhere N of 24N. For additional information please visit http://www.hurricanes.gov/marine $$ Ramos