000 AXNT20 KNHC 311805 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 205 PM EDT Mon Jul 31 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 1200 UTC surface analysis and satellite imagery through 1745 UTC. ...SPECIAL FEATURES... Tropical Storm Emily is approaching the mouth of Tampa Bay centered near 27.6N 82.8W or about 30 nm SW of Tampa, Florida and 25 nm NW of Sarasota at 31/1500 UTC moving E at 8 kt. Estimated minimum central pressure is 1005 mb. Maximum sustained wind speed is 40 kt with gusts to 50 kt. Latest satellite imagery and NWS mosaic doppler radar display reveal scattered moderate isolated strong convection within 60 nm of the center in the southeast semicircle including inland sections of west-central Florida, and also from 24N to 27N east of 84W to inland much of southern Florida. Scattered moderate convection seen within 15 nm either side of a line from 25N84W to 26N85W to 26N88W denotes outer- rain bands feeding into Emily. Emily is forecast to reach the Florida west-central coast and reach to near 27.7N 81.6W by early this evening while weakening to a depression. Emily is then forecast to track across central Florida through tonight, and offshore the east-central Florida coast Tuesday morning. The cyclone is then forecast to track northeastward while regaining strength to a minimal tropical storm near 28.9N 79.6W early on Tuesday, to near 30.5N 77.7W by Tuesday evening and to near 32.2W 75.6W early on Wednesday with maximum sustained wind speed of 40 kt gusts to 50 kt. Emily is expected to produce total rain accumulations of 2 to 4 inches through tonight along the west coast of central Florida between the Tampa Bay area and Naples, with isolated amounts up to 8 inches possible. Elsewhere across central and south Florida, 1 to 2 inches of rain is expected with localized amounts of up to 4 inches possible. See latest NHC forecast/advisory under AWIPS/WMO headers MIATCMAT1/WTNT21 for more details. ...TROPICAL WAVES... A far eastern Atlantic tropical wave has its axis extending from 19N24W to 13N23W to 07N22W, moving west 10-15 kt. First visible satellite images show what appears to be a cyclonic vortex on the northern end of the wave that tilts some to the west. This portion of the wave is embedded in an extensive area of Saharan dry air and dust. Moisture with this wave had increased during the overnight hours south of 15N in the vicinity of the monsoon trough, but has significantly diminished during the past few hours. Only scattered showers and isolated thunderstorms are seen 240 nm east of the wave from 09N-16N and within 180 nm west of the wave from 07N-11N. A central Atlantic tropical wave has its axis extending from 18N45W to 12N45W to 06N42W, moving west near 16 kt. This wave is well depicted on visible satellite imagery, and is marked by a broad envelop of low clouds that shift from a southwest motion to a northwest motion across the wave axis. The 700 mb guidance from the GFS model indicated broad troughing over this wave, and resembles the overall structure of the wave as observed on the visible imagery. The wave is also void of deep convection as it is being influenced by the intrusion of Saharan Air Layer that is present over the eastern and central regions of the Atlantic. Moisture noted with the wave is confined to where the axis crosses the monsoon trough. Scattered moderate convection is within 120 nm west of the wave from 06N-09N. Scattered showers and isolated thunderstorms are within 180 nm east of the wave from 05N-11N. This wave is forecast to move into the eastern Caribbean on Wednesday attendant by scattered showers and thunderstorms. An eastern Caribbean Sea tropical wave is along 67W/68W south of 19N, moving west at 15-20 kt. This wave is moving along the southwest periphery of the sub-tropical Atlantic high pressure ridge. The wave marks the leading edge of abundant dry Saharan air and dust from the eastern Atlantic. A patch of moisture with scattered showers and isolated thunderstorms trails the wave from 12N-15N and east to near 64W. Isolated showers and thunderstorms are elsewhere within 240 nm either side of the wave. The tropical wave will move across the remainder of the eastern Caribbean through tonight, the central Caribbean Tuesday and Tuesday night and the western Caribbean Wednesday. ...ITCZ/MONSOON TROUGH... The monsoon trough axis extends from the west coast of African coast near 19N16W to 12N25W to 11N37W to 10N52W, where scatterometer data indicates that ITCZ begins and extends to 10N52W to 10N60W. Aside from convection associated with the tropical waves as discussed above, scattered moderate to isolated strong convection is within 180 nm south of the trough axis between 30W-34W, and within 60 nm south of the ITCZ between 55W-58W. Scattered moderate convection is within 120 nm south of the trough between 40W-42W and between 47W-50W, and within 60 nm south of the ITCZ between 52W-55W. ...DISCUSSION... GULF OF MEXICO... The main feature is Tropical Storm Emily, which formed at 1200 UTC this morning west of Tampa Bay. See the special features section above for details on this tropical cyclone. In the upper levels, a rather sharp deep layer trough stretches from along the southeastern United States coastline to central Florida and to just northeast of Emily. A large anticyclone over south-central Texas dominates the upper flow pattern with its associated anticyclonic flow covering just about the entire basin, except near Emily where the upper trough related winds are more noticeable. Water vapor imagery depicts very dry air pressing south behind the upper trough. At the surface, a weakening stationary front that earlier was attached to the low that spawned the now Tropical Storm Emily is becoming diffuse from near 26N86W to 26N93W to the coast of Texas near 28N97W. A weak pressure pattern is analyzed over the Gulf outside the radii of Emily associated winds and lower pressures. Scattered showers and isolated thunderstorms are south of the diffusing the frontal boundary to 24N between 88W-93W and within 90 nm south of the boundary west of 93W. Although Tropical Storm Emily is forecast to continue to move inland across central Florida tonight, expect the convection over the SE Gulf to continue through Tuesday, impacting much of southern Florida and the Keys through much of Tuesday. The western periphery of Atlantic high pressure is then expected to protrude westward across Florida and into the eastern Gulf Tuesday night through Wednesday allowing for the deep moisture and convection over the SE Gulf to decrease. CARIBBEAN SEA... A tropical wave is moving across the eastern Caribbean early this afternoon. See above for details on this feature. The eastern segment of the eastern Pacific monsoon trough extends east to the SW Caribbean. Large clusters of scattered moderate isolated strong convection are from 09N-14N west of 81W. Scattered showers and thunderstorms are south of 13N between the coast of NW Colombia and 81W. Some of this activity may contain strong gusty winds. Aloft, a cyclonic shear axis extends from an elongated upper low at 16N75W westward to 16N82W to inland northern Honduras. With ample moisture in place across the central and western Caribbean, instability associated with the cyclonic shear axis is producing scattered showers and isolated thunderstorms from 15N-18N between 72W-81W, including portions of Jamaica. Isolated showers and thunderstorms are elsewhere west of 69W. The shower and thunderstorm activity with the cyclonic shear axis will change little through Tuesday, then begin to shift more towards the western Caribbean Tuesday night through Wednesday as the upper low retrogrades westward. ...HISPANIOLA... Scattered showers and thunderstorms are over some locations of the south-central portion of the island early this morning. This activity is expected to move off to west-northwest through the afternoon and evening as dry air aloft filters in from the east, and the upper low to the southwest near 16N75W gradually pulls farther away from the island. A tropical wave passing just to the southwest of Puerto Rico is expected to bring a slight increase of shower and thunderstorm activity on Tuesday to mainly the southern portion of Hispaniola. This activity should be rather short-lived as additional Saharan dry air behind the wave moves in over the vicinity of the island. Afternoon widely scattered showers and thunderstorms over higher terrain areas are expected this afternoon, and Tuesday. ATLANTIC OCEAN... Two tropical waves are moving across the tropical North Atlantic. See tropical waves section above. A stationary front extends from 32N77W southwest to a 1022 mb low at 30N80W, and continues southwest to across central Florida. The sharp deep layer trough that supports the front also supports a large area of scattered moderate isolated strong convection that is confined to the waters from the cental Bahamas to 30N and between 76W-79W. Similar activity is noted from 25N-27N west of the Bahamas to across southern Florida, and also over central Florida ahead of Emily. Little change is expected with the trend of this convection being active through Wednesday as the upper trough slowly flattens out. Emily is forecast to track from central Florida to offshore the east-central Florida coast on Tuesday morning near a position of 28.9N 79.6W, to near 30.5N 77.7W by Tuesday evening and to near 32.2W 75.6W early on Wednesday with maximum sustained wind speed of 40 kt gusts to 50 kt. Winds and seas near the periphery of tropical storm force winds associated with Emily are expected to be impacted with passing squalls and thunderstorms. Otherwise, a large 1029 mb high centered over the central Atlantic near 33N43W will maintian generally stable weather conditions east of about through 68W. Abundant Saharan air and dust will continue east of 66W. For additional information please visit http://www.hurricanes.gov/marine $$ Aguirre