000 AXNT20 KNHC 041733 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 1233 PM EST WED JAN 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 1200 UTC surface analysis and satellite imagery through 1715 UTC. ...ITCZ/MONSOON TROUGH... The Monsoon Trough extends across Africa reaching the Atlantic waters near 05N08W to 02.5N17W. The ITCZ begins from that point to 03N27W to 00N50W. Isolated showers and thunderstorms are observed on either side of these boundaries from the Equator to 05N between 10W-30W. ...DISCUSSION... GULF OF MEXICO... At 1200 UTC, a cold front is analyzed across the Gulf of Mexico based on visible satellite pictures, Theta-E values and surface observations. At this time, the front extends from near Tampa Bay to the central Gulf at 24N90W to the central Bay of Campeche. Mosaic Doppler Radar from the SE U.S. shows bands of showers across central and south Florida ahead of the front, which is forecast to move through south Florida tonight, causing a wind shift to the northwest. These winds will bring a cooler and drier airmass. A second cold front stretches from the western Florida Panhandle to near Brownsville, Texas. These fronts will merge later today with the merging front reaching the SE Gulf and the Yucatan Peninsula this evening. Then, the front is forecast to stall across the Straits of Florida later tonight into Thursday and gradually dissipate. A stronger cold front will enter the NW Gulf Thursday evening, reaching from the Florida Panhandle to 26N94W to near Tampico Mexico by Friday evening. Fresh to strong northerly winds and building seas will follow this front, with the potential of gale force winds across the western Gulf on Saturday. Aloft, broad mid-to upper level ridge characterized by NW flow dominated the entire Gulf of Mexico. CARIBBEAN SEA... The most recent scatterometer data provided observations of fresh to strong trade winds across the south-central Caribbean. Gentle to moderate winds are noted across the remainder of the east and central Caribbean with light to gentle winds across the NW part of the basin. Little change in the overall pattern is expected over the next 24-48 hours. The aerial extent and strength of the trades will increase by Friday night as the Atlantic high pressure intensifies and extends a ridge toward the NE Caribbean. Shallow moisture embedded in the trade wind flow will move across the region producing isolated to scattered passing showers. In the upper-levels a trough extends from Hispaniola to the SW Caribbean. Water vapor imagery shows strong subsidence in mostly moderate to strong west to northwesterly flow over the entire Caribbean basin. This flow is being induced by the trough. HISPANIOLA... Water vapor imagery depicts a shortwave trough extending across the eastern portion of Dominican Republic. Cloudiness and isolated showers are observed over this area and adjacent coastal waters... including the Mona Passage. The trough is expected to move east away from the island during the next 24 hours. A drying trend will prevail after that. ATLANTIC OCEAN... A cold front extends from 30N76W to central Florida. Fresh to strong southerly winds are ahead of the front, particularly N of 28N. Scattered showers and thunderstorms are also ahead of the front. This system will extend from Bermuda across the central Bahamas to the Straits of Florida late tonight, then stall and weaken Thursday. A dissipating cold front enters the forecast region near 31N29W and continues along 27N40W to 27N54W. This front is associated to a very complex low pressure system across the NE Atlantic. Isolated showers and thunderstorms are near the frontal boundary. A ridge dominates the remainder of the discussion area. A strong upper level jet originates near 10N60W and extends through 14N50W to 22N30W to 25N20W to the African coast at 26N with satellite derived winds indicating speeds of 100 to 120 KT. Expect fresh to locally strong trade winds and building seas across the Atlantic waters E of the Lesser Antilles Friday and Saturday as the Atlantic high pressure intensifies. For additional information please visit http://www.hurricanes.gov/marine $$ GR