000 AXNT20 KNHC 151627 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 1227 PM EDT THU SEP 15 2016 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 1600 UTC. ...SPECIAL FEATURES... Tropical Depression Julia is centered near 31.8N 78.2W at 15/1500 UTC or about 110 nm ESE of Charleston South Carolina and about 140 nm S of Wilmington North Carolina moving E at 7 kt. Estimated minimum central pressure is 1010 mb. Maximum sustained wind speed is 30 kt with gusts to 40 kt. Scattered moderate and isolated strong convection is from 30N-34N between 72W-78W. See latest NHC forecast/advisory under AWIPS/WMO headers MIATCMAT1/WTNT21 KNHC for more details. Tropical Storm Ian is centered near 37.2N 50.5W at 15/1500 UTC or about 765 nm ENE of Bermuda and about 1115 nm W of the Azores moving NE at 21 kt. Estimated minimum central pressure is 998 mb. Maximum sustained wind speed is 45 kt with gusts to 55 kt. Scattered moderate convection is from 39N-43N between 49W-53W. Widely scattered moderate convection is elsewhere from 34N-39N between 47W-53W. See latest NHC forecast/advisory under AWIPS/WMO headers MIATCMAT5/WTNT25 KNHC for more details. Tropical Depression Twelve is centered near 17.7N 30.4W at 15/1500 UTC or about 380 nm WNW of the Cape Verde Islands moving W at 11 kt. Estimated minimum central pressure is 1009 mb. Maximum sustained wind speed is 30 kt with gusts to 40 kt. Widely scattered moderate convection is from 12N-21N between 24W- 35W. See latest NHC forecast/advisory under AWIPS/WMO headers MIATCMAT2/WTNT22 KNHC for more details. ...TROPICAL WAVES... Tropical wave extends from 11N46W to 19N46W moving W at 15 kt. The wave is likely the hybrid feature of an African easterly wave that emerged off the coast of Africa several days ago and mid- latitude energy dropping southward into the tropics associated with middle to upper level low centered near 16N48W. No significant deep convection is occurring at this time. ...ITCZ/MONSOON TROUGH... The Monsoon Trough extends from the African coast near 08N13W to 06N19W and then from 13N38W to 10N48W. The Intertropical Convergence Zone axis extends from 10N48W to 07N58W. Aside from convection associated with Tropical Depression Twelve...scattered moderate convection is from 05N-09N between 12W-18W. ...DISCUSSION... GULF OF MEXICO... Water vapor imagery indicates a weak middle to upper level low over the SW Gulf centered near 23N95W that supports a surface trough analyzed from 18N95W to 22N93W. Widely scattered showers and isolated tstms are occurring across the SW Gulf S of 21N between 92W-96W. This is likely weakening energy that fractured northward away from a tropical wave currently along 100W in the East Pacific region. To the north...an upper level anticyclonic circulation is centered over the NW Gulf waters near 28N94W with axis extending E-SE to over the central Gulf near 26N86W. At the surface...a broad 1011 mb low is centered near 27N95W with a surface trough axis extending E-NE toward the Florida Big Bend region. The low and boundary are providing focus for scattered showers and widely scattered tstms generally N of 23N between 83W-96W. The strongest convection is currently occurring E of the low centered in the vicinity of 27N92W. Low-level moisture convergence within close proximity to the trough axis and maximum middle to upper level diffluence is likely enhancing the convection as the low drifts toward the Texas coast. Global models indicate the low will reach the coast by Friday morning and weaken. Thereafter...gentle to moderate E-SE winds are anticipated through the upcoming weekend as surface ridging re-establishes itself across the SE CONUS. CARIBBEAN SEA... Overall the Caribbean basin remains fairly tranquil this afternoon. On water vapor imagery...an upper level low and associated troughing is noted moving over the western Caribbean centered over Jamaica near 18N78W with the trough axis extending NE to over the SE Bahamas...and to the S-SE over the SW Caribbean near 12N80W. Much of the western Caribbean is under the influence of relatively dry NE flow aloft with only a few isolated showers and tstms occurring offshore of the coast of Honduras S of 17N between 83W-86W...and across inland portions of Belize and Guatemala. In the SW Caribbean...scattered showers and strong tstms are occurring S of 12N between 76W-84W due to close proximity to the Monsoon Trough along 10N. To the east of the trough axis...an upper level anticyclonic circulation is centered over Puerto Rico with water vapor imagery indicating dry conditions aloft providing for mostly clear skies N of 15N E of 75W. To the S of 15N within the southern periphery of the upper level ridging...isolated showers and tstms are occurring from 13N-15N between 62W-71W. This moisture likely originated from the southern extent of a surface trough analyzed across the central Atlc from 24N53W to 13N62W. Increased precipitation is expected across the Windward Islands through Friday as the troughing drifts slowly westward and weakens during the weekend. Otherwise...gentle to moderate trades prevail and are expected to persist through the weekend with slightly stronger trades reaching occasional fresh levels across the south-central waters S of 13N between 69W-78W. ...HISPANIOLA... An upper level low is centered WSW of the island near 18N78W with a trough axis extending NE to over the SE Bahamas. Water vapor imagery indicates dry and stable conditions to the east of this upper level low and currently skies remain clear and conditions fair. The overall fair weather is expected to continue into Friday and Saturday. ATLANTIC OCEAN... Aside from Tropical Depression Julia...the remainder of the SW North Atlc is under the influence of weak and broad ridging supported aloft by an upper level anticyclonic circulation centered near 28N74W. Water vapor imagery indicates fairly dry air aloft S of 30N W of 67W resulting in mostly clear skies and fair conditions this afternoon. Over the central Atlc...a middle to upper level trough axis extends from 35N57W S-SW to 25N62W that supports a weak 1012 mb low centered near 29N60W with an equally weak cold front extending from 32N58W through the low to 28N63W to 28N67W. A pre-frontal surface trough is analyzed to the SE of the low center from 28N59W to 25N63W. Isolated showers are occurring N of 24N between 55W-65W. While Tropical Storm Ian continues to race NE north of the discussion area in the central North Atlc...a trailing line of isolated showers is within 45 nm either side of a line from 32N48W to 24N52W. South of this convergence line a surface trough extends from 24N52W to near Martinique near 14N61W. Isolated showers and tstms are noted within 120 nm either side of the boundary. Otherwise...the remainder of the eastern Atlc is under the influence of a broad surface ridge generally N of 25N anchored by a 1027 mb high centered SE of the Azores near 36N24W. For additional information please visit http://www.hurricanes.gov/marine $$ HUFFMAN