000 AXNT20 KNHC 182312 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 612 PM EST Mon Dec 18 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 1800 UTC surface analysis and satellite imagery through 2315 UTC. ...SPECIAL FEATURES... ...Gale Warning in the Caribbean Sea... Pulsing nocturnal NE-to-E winds to gale-force are expected again near the coast of Colombia during the overnight tonight and early morning hours on Tuesday, particularly from 10N to 13N between 74W and 78W. Expect sea heights to range from 10 to 14 ft. Wind will diminish below gale-force by Tuesday afternoon, and are expected to reach again minimal gale force at night. Thereafter, strong to near gale force winds will persist near the coast of Colombia each night this week. Please read the latest NHC High Seas Forecast under AWIPS/WMO headers MIAHSFAT2/FZNT02 KNHC for more details. ...ITCZ/MONSOON TROUGH... The monsoon trough enters the Atlantic Ocean near 07N12W and continues to 05N20W. The ITCZ extends from 05N20W to 04N43W to NE Brazil near 02N51W. Scattered moderate convection is noted within about 30 nm on either side of the ITCZ between 20W and 27W. Similar convection is from 04N-06N between 34W-39W. ...DISCUSSION... ...GULF OF MEXICO... As of 2100 UTC, a stationary front extends across the basin from southern Lousiana to 28N96W. Mosaic Doppler Radar from the SE U.S. shows scattered showers and isolated tstms over the NW Gulf, and just north of the of the front, forecast to drift northwestward into Texas tonight. A trough is over the far western Gulf and stretches from near 28N96W to 20N95W. A recent scatterometer pass clearly indicated the wind shift associated with this trough. The remainder of the Gulf is under the influence of a ridge, with a 1023 mb high pressure located near Tampa Bay, Florida. The ridge is forecast to persist through Tuesday night. A weak cold front will reach the coast of Texas Wednesday, and stall across the N Gulf Thu before moving N as a warm front Thursday night. Looking ahead, a stronger cold front will reach the NW Gulf on Friday. Fresh southerly return flow is expected across the western Gulf ahead of the front. ...CARIBBEAN SEA... Please refer to the Special Features section for details about the gale warning near the coast of Colombia during the next two nights. The most recent scatterometer data indicated fresh to strong winds over the central Caribbean, and across the Windward Passage. Moderate to fresh winds are seen elsewhere. An altimeter pass indicated seas of 11 ft over the SW Caribbean in association with the strong trades. Patches of low level moisture embedded in the trade wind flow are observed on visible satellite imagery, more concentrated over the central Caribbean. Broad mid-level anticyclonic wind flow and strong subsidence dominates the entire Caribbean Sea. ...HISPANIOLA... A broad mid to upper-level high covering the Caribbean Sea and very dry air aloft will support mostly stable conditions across the island. However, shallow moisture embedded in the trade wind flow will move across Hispaniola producing isolated to scattered passing showers tonight and Tuesday. ...ATLANTIC OCEAN... A deep layer trough in the central Atlantic is supporting a cold front that extends from 31N40W to 22N62W. The front dissipates west of 22N62W to the north of Hispaniola. Mainly low-level clouds with isolated to scattered showers are along the frontal boundary. Strong high pressure building west of the front will prevail over the area through mid-week. This pattern will keep South Florida mostly dry and warm through the weekend. E of the front, the Azores high extends a ridge across the eastern Atlantic. For additional information please visit http://www.hurricanes.gov/marine $$ GR