000 AXNT20 KNHC 290004 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 804 PM EDT WED SEP 28 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 1800 UTC surface analysis and satellite imagery through 2345 UTC. ...SPECIAL FEATURES... Tropical Storm Matthew at 29/0000 UTC was centered near 13.9N 62.4W or about 80 NM...145 KM W of St. Lucia moving west at 14 KT. Maximum sustained winds have increased to 55 KT with gusts to 65 KT. Estimated minimum central pressure was 1004 mb. The overall cloud envelope of Matthew is quite large with scattered to numerous strong convection extending out to 180 NM in the SE semicircle. Scattered moderate isolated strong convection extended out to 240 NM elsewhere in the SE and 90 NM in the NW semicircles. Fort de France, Martinique reported wind gusts to 52 KT within the past few hours. Matthew is forecast to slowly strengthen over the next 24 hours...possibly becoming a hurricane by THU night or early FRI. Please refer to the NHC forecast/advisory under AWIPS/WMO headers WTNT24 KNHC/TCMAT4, or visit the NHC website at http://hurricanes.gov for additional details. ...TROPICAL WAVES... Tropical wave with axis along 30W/31W from 06N to 18N is moving westward at 10 to 15 KT. The wave is difficult to discern in TPW imagery and is embedded in an areas of strong SAL. As such convection is limited along the wave axis. A new low-amplitude tropical wave was analyzed along 43W from 05N to 16N. The placement of the wave was based on satellite hovmoller and easterly wave diagnostics. Scattered moderate isolated strong convection was noted within 180 NM east of the wave axis from 08N to 12N. The wave also coincided with a surge in the TPW imagery. A tropical wave extends across the western Caribbean with axis along 80W/81W from Panama to 16N, moving westward at 10 to 15 KT. The wave is moving beneath an upper- level low currently centered near 16N82W. Scattered moderate convection is observed in the area where the wave interacts with the Monsoon Trough mainly south of 12N between 78W-82W. ...ITCZ/MONSOON TROUGH... The Monsoon Trough extends over Africa reaching the east Atlantic near 14N17W through 10N24W to 08N41W. Scattered moderate to strong convection is observed from 06N-13N between 17W-26W. Isolated showers or thunderstorms prevail along the remainder of the boundary. ...DISCUSSION... GULF OF MEXICO... An expansive upper-level anticyclone is centered over eastern Mexico near 23N98W. The associated anticyclonic flow dominated almost all of the basin, except for the far northeastern portion. The base of an extensive deep-layered trough was sweeping southeast along the periphery of the anticyclone across southern Alabama and the Florida peninsula. Abundant deep layered moisture was noted over the Gulf W of 90W S of 26N. At the surface, a cold front extends from near Panama City Florida through 28.5N90W to 28N94W. A surface trough extended from 28N95W to 19N95W. Scattered moderate isolated strong convection prevailed along the surface trough affecting the waters from 20N to 24N between 92W and 94W. To the northeast, scattered showers are observed north of 26N and east 89W. Gentle to moderate southeasterly winds prevail across the basin except for light northwest winds NW of the cold front. The cold front is forecast to continue moving east with showers and thunderstorms over Florida with the surface trough over the Bay of Campeche continuing to enhance convection. CARIBBEAN SEA... An expansive upper-level anticyclone centered over eastern Mexico near 23N98W is providing northerly flow aloft over the Caribbean W of 83W. Broad troughiness prevails over the Caribbean between 70W and 83W with an embedded cyclonic circulation near 16N82W. This feature was enhancing convection from 11N- 14N and west of 82W affecting portions of Nicaragua. Another circulation was located just N of Hispaniola near 23N71W. A large anticyclone centered over the Atlantic near 18N58W and associated flow prevailed over the Caribbean E of 70W. This was providing a favorable environment in the vicinity of Tropical Storm Matthew which has entered the far eastern Caribbean. The associated mid and high level cloudiness is spreading as far west as 68W. For additional information on Matthew please refer to the special features section above. Elsewhere, tropical wave along 80W/81W S of 16N was producing scattered showers and thunderstorms over the SW Caribbean and adjacent land areas. The Monsoon Trough extends along 10N between 75W-80W with scattered moderate convection. ...HISPANIOLA... An upper-level low just northeast of the island near 23N71W was supporting isolated convection over the interior of the Dominican Republic and Haiti. Tropical Storm Matthew is forecast to pass south of Hispaniola by Friday. Cloudiness associated with Matthew is expected to spread over the island early THU with an increase in showers and thunderstorms late THU into FRI. The large envelope of Matthew may result in the potential for locally heavy rains over Hispaniola. This will greatly depend on the ultimate track of Matthew. For additional information on Matthew please refer to the special features section above. ATLANTIC OCEAN... An extensive mid-to upper level anticyclone centered near 18N58W covers the Atlantic basin between 50W and 66W with an upper level low centered near 23N71W. Downstream, a broad upper level trough dominates the tropical Atlantic between 20W and 50W with an upper level cyclone centered near 22N38W. At the surface, T.S. Matthew has moved west of the Atlantic basin. A surface trough extends across the west Atlantic from 31N75W to Andros Island. Scattered moderate convection was noted within 180 NM east of the trough. The remainder of the basin is under the influence of a surface ridge anchored by a 1034 mb high centered near 40W43W. For additional information please visit http://www.hurricanes.gov/marine $$ COBB