000 AXNT20 KNHC 121048 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 648 AM EDT Tue Sep 12 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 1100 UTC. ...SPECIAL FEATURES... At 12/0900 UTC, the Weather Prediction Center in College Park Maryland began issuing advisories on what is now Post Tropical Cyclone Irma. The center of Post Tropical Cyclone Irma is located near 33.0N 85.2W or about 90 nm ESE of Birmingham, Alabama, moving NNW at 9 kt. The estimated minimum central pressure is 998 mb. Maximum sustained wind speeds are 15 kt with gusts to 20 kt. Irma is forecast to continue weakening and cross from Georgia into Alabama shortly, then reach the NW corner of Alabama Tuesday evening. Please refer to Public Advisories issued by the Weather Prediction Center under AWIPS/WMO headers MIATCPAT1/WTNT31 KWNH for more details. At 12/0900 UTC, the center of Hurricane Jose is near 27.5N 69.0W, or about 380 nm NNE of Grand Turk Island, moving E at 6 knots. The estimated minimum central pressure is 987 mb. The maximum sustained wind speeds are 65 kt with gusts to 80 kt. Numerous moderate and scattered strong convection is noted within 180 NM in the SE and within 120 nm in the NW semicircles. Jose is forecast to slowly make an anti-cyclonic loop northeast of the Bahamas during the next several days. Please read the latest NHC Forecast/Advisory under AWIPS/WMO headers MIATCMAT2/WTNT22 KNHC for more details. ...TROPICAL WAVES... A tropical wave over the E Atlantic has an axis extending from 18N35W to 05N39W, moving west around 15 kt. This wave is becoming displaced from troughing in initial model 700 mb wind fields due to interaction with a sharp mid to upper-level trough stretching from 32N41W to 14N50W. SSMI TPW satellite imagery indicates the wave is embedded in an area of deep-layer moisture. Scattered moderate and isolated strong convection is present from 19N to 22N between 35W and 38W. A tropical wave has crossed the Windward and Leeward Islands into the far eastern Caribbean. The wave axis extends from 19N64W to 06N64W, moving west around 15 kt. This wave coincides with modest troughing in initial model 700 mb wind fields. SSMI TPW satellite imagery indicates the wave is embedded in an area of deep-layer moisture. Isolated showers and thunderstorms have developed over the SE Caribbean from 11N to 13N between 60W and 69W during the past 6 hours. ...ITCZ/MONSOON TROUGH... The monsoon trough extends from Senegal on the west coast of Africa near 15N17W to 12N24W to 16N35W to low pressure 1011 mb centered near 13N47W to 12N53W. The ITCZ continues from 12N53W to 12N61W. Strong upper level divergence to the SE of an upper- level trough is generating scattered moderate and isolated strong convection from 14N to 19N between 39W and 48W. Scattered moderate and isolated strong convection is occurring from 12N to 14N between 48W and 56W. ...DISCUSSION... GULF OF MEXICO... Post Tropical Cyclone Irma is located on the Georgia/Alabama State Line. Irma should continue a general northwestward motion and approach the Tennessee Valley this afternoon. The large circulation of Irma is generating moderate to fresh winds over the Gulf waters N of 28N and E of 90W, where seas are subsiding but still range between 5 and 8 ft. Dry air wrapping around the south side of this system has cleared out cloud cover over the NE Gulf. Shower coverage over the NE Gulf waters is virtually nil. Moderate northerly winds generally prevail over the western half of the basin as a surface ridge builds across the area. A surface trough over the Bay of Campeche extends from 21N90W to 22N96W. South of the trough axis moderate to fresh NW winds are noted. Cloudiness and isolated showers are seen in the vicinity of the trough from 20N to 23N between 92W and 95W. CARIBBEAN SEA... A tropical wave over the far eastern Caribbean is enhancing the trades in the vicinity of southern Windward Islands but is only producing isolated showers and thunderstorms from 11N to 13N from 60W to 69W. A surge in the trades should continue accompanying the wave and affect the southern Caribbean waters as the wave continues west. Scatterometer data depicts light to moderate trades across most of the area as the sub-tropical high to the north is weakened by Jose. West of 80W moderate to fresh southerly winds prevail to the south of Irma. ...HISPANIOLA... The relatively dry weather regime over the Caribbean extends over the island. Shower coverage should be limited to the higher terrain during daytime heating, when isolated thunderstorms can be expected. ATLANTIC OCEAN... Please see the Special Features section above for information concerning Post Tropical Cyclone Irma and Hurricane Jose. Also, see the tropical waves section for information concerning the tropical waves over the basin. Aside for these areas, the remainder of the basin remains under the influence of ridging extending SW from a 1025 mb Azores high centered near 39N26W. For additional information please visit http://www.hurricanes.gov/marine $$ McElroy