000 AXNT20 KNHC 092320 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 619 PM EST FRI DEC 9 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 2300 UTC. ...SPECIAL FEATURES... ...Gulf of Mexico Gale Warning... A strong high pressure ridge has built across the north and western Gulf of Mexico today, and southward across eastern Mexico, behind a cold front that currently extends from the northwest coast of Cuba to 22N93.5W to 18N92.5W. A very strong pressure gradient between the ridge and the front is producing a large area of minimal to strong gale force winds this afternoon. Afternoon ASCAT data indicated 25-35 kt N to NE winds across much of the NW Gulf, and NW winds of 35-45 kt across the SW Gulf west of the front. This is generating a large area of high seas 12 to 20 ft NW of the front. a 1039 mb high pressure center across northern Arkansas anchors the ridge, and is forecast to shift eastward during the next 24 hours. As this occurs the front will sink slightly southward, and the pressure gradient will gradually decrease across the NW Gulf. However, gale force NW winds are expected to continue through Saturday evening offshore of Veracruz, Mexico. Please read the High Seas Forecast product under AWIPS/WMO headers MIAHSFAT2/FZNT02 KNHC for more details. ...ITCZ/MONSOON TROUGH... The Monsoon Trough extends across the African Continent reaching the Atlantic Ocean near 06N12W. The ITCZ continues from that point to 04.5N20W to 05.5N40W. A low latitude easterly wave, with a north to south aligned trough at the surface, is along 39W and southward of 10N. Active convection continues along the ITCZ, where scattered moderate to strong is observed from 03N-09N between 16W and 40W. ...DISCUSSION... GULF OF MEXICO... 1600 UTC ASCAT scatterometer data depicts gale force winds occurring over much of the western Gulf west of 90W, while strong NW gales to 45 kt prevail south of 22N and west of the front. Please refer to the section above for details. A cold front has moved southward across the Straits of Florida and extends from NW Cuba to 22.5N88W, then is stationary to 22N93.5W, then continues across the Mexican coast near 18.5N93.5W. Broken multi- layered cloudiness and isolated moderate convection is observed along and north of the front some 240 nm, with scattered moderate to strong convection along the stationary portion of the front. Fresh to strong north-northeast winds prevail across the eastern Gulf waters. The front is expected to meander across the southern Straits of Florida and northwest Cuba this weekend with northerly winds slowly diminishing below gale force late Sat in the western Gulf. CARIBBEAN SEA... A broad upper ridge generally prevail over the basin, while a TUTT low in the middle to upper levels near 15N76W continues to move westward across the central Caribbean. This TUTT low has been moving W and in synch with an easterly wave currently along 73W. Anticyclonic diffluent upper level flow to the east of the TUTT low is providing a favorable environment for persistent convection along and east of the easterly wave. Fresh to locally strong NE to E winds are occurring north of 14N both east and west of the wave axis and have built seas to 6-9 ft there. The wave will continue west across the basin and enter Central America early Sun. Elsewhere at the surface, the Monsoon Trough extends along 10N with scattered moderate convection between 78W-85W. Outside of the easterly wave, moderate to fresh NE trades prevail across the remainder of the basin, except fresh NE winds in the Yucatan Channel near the approaching cold front. Fresh to occasional strong trades are expected across the south-central Caribbean mainly north of Colombia tonight through late Saturday with trades increasing slightly through the remainder of the weekend as the strong ridge affecting the Gulf of Mexico shifts eastward into the western Atlantic. The cold front will meander across the Yucatan Channel, with associated conditions across the Gulf spreading modestly into NW portions. ...HISPANIOLA... Fair weather prevails across the island at this time as subsidence and dry air ahead of the easterly wave along 73W have dominated the island today. A modest increase in low level moisture will spread westward across the area this evening and tonight and should lead to passing tradewind showers across the area. Generally fair conditions are expected through the weekend. ATLANTIC OCEAN... A cold front extends across the western Atlantic from 31N67W through the NW Bahamas to northwestern Cuba. Broken multi- layered cloudiness and isolated convection is observed along and northwest of the front. A weak and narrow surface ridge is SE of the front and extends across the remainder of the basin, anchored on a 1020 mb surface high centered near 23N54W. A pair of weakening frontal boundaries were analyzed north of the ridge. The first is a dissipating stationary front from 27N72W to 28N58W to 27N48W to a 1017 mb surface low near 32N39W. The next dissipating cold front extends from 31N22W to 26N31W. No significant convection is related to any of these fronts. Expect the cold front in the west Atlantic to continue moving east of the Bahamas while it drifts slightly Se across the Bahamas. As mentioned above, as the surface ridge behind this cold front begins to shift eastward into the Atlantic tonight and Sat, look for increasing Ne winds and building seas behind the cold front. Little change is expected elsewhere. For additional information please visit http://www.hurricanes.gov/marine $$ Stripling