000 AXNT20 KNHC 201804 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 205 PM EDT Mon Mar 20 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 1745 UTC. ...ITCZ/MONSOON TROUGH... The Monsoon Trough axis extends from the African coast near 07N11W to 00N18W to 01S28W. The Intertropical Convergence Zone axis extends from 01S28W to the South American coast near 03S42W. Scattered moderate to strong convection is from 03S-03N between 00W-06W. Scattered moderate/isolated strong convection is from 03S-03N between 06W-10W. Scattered moderate convection is occurring from 01N-04N between 10W-17W, and from the equator to 03N west of 45W. ...DISCUSSION... GULF OF MEXICO... As of 1500 UTC, a 1025 mb high is analyzed over the north central Gulf of Mexico near 27N91W. Buoy observations show anticyclonic flow throughout consisting of 10-15 kt, except for lighter winds of 5-10 kt near the high center. Water vapor imagery shows very strong subsidence aloft along with strong zonal flow in the wake of yesterday's cold front. This is keeping conditions very dry throughout. Mostly clear skies are north of 23N east of 92W, while scattered to broken low clouds are west of 92W, and south of 23N east of 92W. The 1025 mb high is forecast to shift slightly eastward through Tuesday, then move westward back to the north-central waters on Wednesday. Little overall change is forecast for the basin through Wednesday. CARIBBEAN SEA... A weakening frontal trough extends from eastern Cuba southwest to just offshore the coast of the border between Honduras and Nicaragua near 15N83W. Scattered showers are within 90 nm northwest and 60 nm se of trough, respectively. The trough is forecast to dissipate tonight. Buoy observations and a few ship reports show 15-20 kt northeast winds to the northwest of the trough. 10-15 kt northeast to east trades are over the remainder of the Caribbean, with the exception of within 90 nm of the coast of Colombia where trades are in the 20-25 kt range due to the pressure difference between low pressure over northwest Colombia and stronger high pressure over the northwest Caribbean. Satellite imagery depicts pockets of scattered showers moving westward over portions of the central and eastern Caribbean waters. Similar activity is observed across portions of the Leeward Islands, Puerto Rico, south-central Hispaniola, Jamaica, and eastern Cuba. Scattered showers are also over sections of northern Honduras and over the interior of Nicaragua. Isolated showers moving northwestward are over the northeast Caribbean and near the Windward Islands. Over areas not currently being affected by low-moisture and shower activity, dry condtions aloft due to strong subsidence is allowing for only scattered to locally broken clouds to generally mostly clear over those areas. A weak surface trough over the eastern Caribbean will reach the central Caribbean waters by Wednesday. This will introduce additional low-level moisture over that portion of the sea along with the possibility of increasing chances for scattered showers. Scattered showers are expected to persist along and inland the coasts of eastern Honduras and Nicaragua through Wednesday. ...HISPANIOLA... Scattered showers are presently over some sections of the central portions of the island as well as over northwest and southwest Haiti due to low level moisture lingering over much of the island in combination with ongoing daytime heating. Little change is expected during the next 24 hours, then the possibility for increasing scattered showers increases afterwards as low-level moisture increases with the approach of a surface trough. ATLANTIC OCEAN... As of 1500 UTC, a dissipating cold front is over the western Atlantic from 32N62W to 23N69W, where it becomes a dissipating stationary front to the eastern tip of Cuba. A fast moving cold front is behind this front along a position from 32N64W to 23N73W to along the northern coast of central Cuba. Strong to near gale force west to northwest winds with seas of 8-14 ft are behind this front. A narrow line of cumulus clouds defines the front on satellite imagery. Broken patches of stratocumlus clouds moving southward denoting a drier air mass are observed to the north of 25N west of 70W, and north of 26N between the front and 70W. Isolated showers are possible with these clouds. Patches of low-level moisture with scattered showers are seen northeast of Puerto Rico from 19N-22N between 63W-66W. A 1028 mb high is centered over the eastern Atlantic near 33N28W, with a ridge southwest to near 23N56W. In the upper levels, an upper level trough is noted over the western Atlantic north of about 24N between 60W-76W supporting the fast moving cold front, and producing upper level diffluence across the northern portion of the dissipating cold front. This is helping to aid scattered moderate/isolated strong convection north of 27N east of the first front to 58W. An elongated upper level low is centered over the tropical Atlantic near 22N22W. Isolated showers moving westward are noted from 17N to 22N between 22W-40W. The aforementioned cold front extending from 32N64W to 23N73W and to along the coast of central Cuba will merge with the dissipating front tonight, with the merged front forecast to become stationary from near 22N65W to the Windward Passage on Tuesday before it begins to drift to the north on Wednesday while weakening. Scattered showers and is to isolated thunderstorms are expected along and near the merged front. For additional information please visit http://www.hurricanes.gov/marine $$ Aguirre