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000
AXNT20 KNHC 151747
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1247 PM EST Fri Dec 15 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.


...SPECIAL FEATURES...


...Gale Warning in the Gulf of Mexico...

A cold front is along 30N84W 27N92W 24N97W. Gale-force NW-to-N winds, and sea heights ranging from 10 feet to 14 feet, are forecast during the next 6 hours or so, from 22N to 24N to the west of the cold front. The gale-force winds are expected for the next 24 hours. Please read the latest NHC High Seas Forecast under AWIPS/WMO headers MIAHSFAT2/FZNT02 KNHC for more details.


...Gale Warning in the Caribbean Sea...

Strong high pressure will build to the north of the Caribbean Sea during the evening today. A tight pressure gradient will develop in the south central basin. The trade winds will increase to fresh- to-strong. A strong pressure gradient will persist during the weekend. Gale-force winds will be along the northwest of the Colombian coast starting tonight through early Monday. The sea heights will build to 13 feet in this area. Please read the latest NHC High Seas Forecast under AWIPS/WMO headers MIAHSFAT2/FZNT02 KNHC for more details.


...ITCZ/MONSOON TROUGH...

The monsoon trough passes through the coastal sections of Liberia near 07N11W to 06N15W. The ITCZ continues from 06N15W to 04N26W 05N31W and 04N41W. Precipitation: widely scattered moderate to isolated strong rainshowers are 240 nm to the south of the Monsoon Trough/ITCZ between 11W and 17W, and within 180 nm to the south of the ITCZ between 28W and 36W. Scattered moderate to strong is within 60 nm to 120 nm to the north of the ITCZ between 21W and 26W. widely scattered moderate to isolated strong is elsewhere within 240 nm to the north of the ITCZ between 19W and 38W. Scattered moderate to isolated strong rainshowers are from 03N southward from 47W westward.


...DISCUSSION...

THE GULF OF MEXICO...

Upper level SW wind flow moves from the eastern Pacific ocean, across the western coast of Mexico near 21N105W, and across the NW half of the Gulf of Mexico. An upper level ridge extends from N Colombia, across Central America, to El Salvador, to 15N99W in the eastern Pacific Ocean. More upper level SW wind flow is reaching and moving across the Gulf of Mexico, from the anticyclonic wind flow of the ridge. Comparatively drier air in subsidence covers the SE half of the Gulf waters.

A shallow cold front stretches from the Florida Big Bend, into the N central Gulf of Mexico, into NE Mexico near 24N98W. MVFR/VFR conditions and areas of light rain are along and to the north of the cold front. Please refer to the SPECIAL FEATURES section for more details about the gale-force winds, and seas, that are related to the cold front.

THE CARIBBEAN SEA...

Middle level-to-upper level anticyclonic wind flow spans the entire area. An upper level ridge extends from N Colombia, across Central America, to El Salvador, to 15N99W in the eastern Pacific Ocean. Comparatively drier air in subsidence also is present everywhere.

A surface trough is in the coastal waters of Central America along 82W/83W from 09N to 18N. Scattered to broken low level clouds and areas of light rain/drizzle are inland from Panama to Costa Rica to Nicaragua and Honduras.

The southernmost end of a surface trough, that originates in the Atlantic Ocean, reaches SE Cuba, and to 20N81W in the Caribbean Sea. Rainshowers are possible within 60 nm on either side of the trough.

Please refer to the SPECIAL FEATURES section for more details about the development of gale-force winds to the NW of the Colombian coast starting tonight through early Monday.


...HISPANIOLA...

A middle level-to-upper level east-to-west oriented ridge cuts across the island.

SURFACE OBSERVATIONS...HAITI, in Port-au-Prince: VFR. in the DOMINICAN REPUBLIC: VFR.

The GFS MODEL forecast for 250 mb shows that NW wind flow will move across the area during the next 48 hours, being on the eastern side of a ridge. The GFS MODEL forecast for 500 mb shows that NE wind flow will move across the area during the next 2 days, with an anticyclonic circulation center that will be between the Bahamas and Cuba. The GFS MODEL forecast for 700 mb shows that NE-to-E wind flow will move across the area, with an E-to-W Atlantic Ocean ridge.

THE ATLANTIC OCEAN...

A surface trough passes through 32N52W, to 25N60W, toward the SE Bahamas/the Turks and Caicos Islands, across SE Cuba, to 20N81W, in the Caribbean Sea. Rainshowers are possible within 30 nm on either side of the trough. The southernmost point of an upper level trough reaches 32N55W. Upper level anticyclonic wind flow is moving across the area of the surface trough.

An upper level trough extends from an 18N33W cyclonic circulation center, to 12N40W 08N51W, to the coast of Guyana near 07N58W. No deep convective precipitation is associated with this feature.

A surface trough is along 43W/44W from 20N to 25N. Rainshowers are possible within 240 nm on either side of the trough. Isolated moderate rainshowers already are within 400 nm to the SE of the surface trough, moving westward with a separate area of low level clouds.

Upper level cyclonic wind flow, with a trough, covers the area that is from 22N northward between Africa and 24W. Surface anticyclonic wind flow is present in the same area. A surface ridge extends from a 1033 mb high pressure center that is near 36N29W to the Canary Islands, into northern Mauritania.

The current Gulf of Mexico cold front will move off the northeast Florida coast this evening, reach from Bermuda to south Florida Saturday, and then will stall and gradually dissipate along 25N through early next week. High pressure from the southeast United States will build eastward across the area behind the front.

For additional information please visit http://www.hurricanes.gov/marine

$$ MT

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