000 AXNT20 KNHC 202352 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 705 PM EST TUE DEC 20 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 2315 UTC. ...SPECIAL FEATURES... .None. ...THE ITCZ/THE MONSOON TROUGH... The Monsoon Trough extends sw off the coast of Africa at 06N11W to 05N14W where scatterometer winds indicate a transition to an ITCZ axis, which continues sw to 01N27W, then turns nw to 03N42W where it loses identity. Scattered moderate isolated strong convection is noted from the equator to 05N between 20W and 37W. ...DISCUSSION... ...THE GULF OF MEXICO... Nearly zonal mid to upper level flow is observed across most of the Gulf of Mexico. To the lower levels a stationary front extends sw from Tampa Bay through 23N93W to the s-central Bay of Campeche. Strong to near gale force northwesterly winds will continue s of 25N to the sw of the decaying front this evening, then mostly strong nw winds are expected late tonight through midday Wed when the remnants of the front will become orientated from nw to se along a position from 23N97W to 19N93W where it meander for a few days. Fresh to locally strong ne winds should develop along the nw coast of the Yucatan Peninsula tonight. Otherwise broken to locally overcast low to to mid level clouds are observed to the n of the front with elevated platforms in the n-central gulf reporting reduced visibility in fog and low- level stratus. ...THE CARIBBEAN SEA... A tight pressure gradient between Atlantic high pressure and lower pressure over Colombia will support near gale force winds along the nw coast of Colombia tonight into Wed, and fresh to locally strong ne to e winds are expected elsewhere to the n of 11N between 70W and 87W. Combined seas of 8 to 13 ft are forecast in the resultant ne-e swell. An area of broken low to mid level clouds, with scattered showers and even a few thunderstorms detected by lightning data, is observed to the e of 70W. The heaviest clusters are passing w across the Mona Passage and onshore the Dominican Republic at the moment. This convective activity will likely continue to shift w with time as the supporting upper trough is forecast to shift w across the central Caribbean through Wed. Subsidence associated with an upper ridge is suppressing convection across the western Caribbean. ...HISPANIOLA... A sharp transition line between deep moisture and pronounced drying subsidence is currently orientated n to s along 69W. The line will shift w tonight into Wed allowing showers along the e coast to spread w across the central and western portions of the Dominican Republic, and possibly reach eastern Haiti late Wed. ...THE ATLANTIC OCEAN... A 1021 mb surface low is analyzed at 32.5N74W and trails a cold front sw to Central Florida. The northern segment of the cold front will continue e tonight and stall from Bermuda to Central Florida on Wed night and Thu. The front will move e again on Thu night and Fri with high pressure building in its wake. Broken to overcast low and mid level clouds with embedded accompany the front and are also noted across the Straits of Florida. An upper level trough dissects the s-central n Atlc from 32N53W to 19N70W. Upper diffluence e of the trough is supporting large areas of broken lo-mid level clouds and embedded showers and thunderstorms all within 150 nm either side of a line from 25N46W to the Mona Passage. This activity will shift w tonight and Wed as the supporting upper trough shifts w. Dense cirriform clouds are streaming ene from South America to Africa within 300 nm either side of a line from 06N55W to 20N17W. For additional information please visit http://www.hurricanes.gov/marine $$ Nelson