000 AXNT20 KNHC 170605 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 104 AM EST Sat Feb 17 2018 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 0000 UTC surface analysis and satellite imagery through 0545 UTC. ...SPECIAL FEATURES... Caribbean Sea Gale Warning: A tight surface pressure gradient between a high pressure system over the western Atlantic and lower pressure over northern South America should continue to support winds pulsing to minimal gale-force near the coast of Colombia through Sun. The resultant waveheights with the gale force winds are forecast to range from 10 to 14 feet. Please read the latest NHC High Seas Forecast under AWIPS/WMO headers MIAHSFAT2/FZNT02 KNHC for more details. ...MONSOON TROUGH/ITCZ... The monsoon trough axis enters the eastern Atlantic near 07N12W and continues to 01N20W, where latest scatterometer data indicates the ITCZ begins and dips to S of the Equator at 23W. Scattered moderate isolated strong convection is within 120 nm S of the axis between 20W-23W. Scattered moderate convection is S of the axis within 30 nm of 02N14W, and also N of the axis within 30 nm of line from 02N25W to 03N30W to 04N34W. ...DISCUSSION... GULF OF MEXICO... The western extension of Atlantic high pressure across the area is maintaining pretty tranquil weather conditions throughout the basin. At the surface, a 1022 mb high center is analyzed at 27N88W. In addition, satellite water vapor imagery depicts abundant dry air in the mid and upper-levels of the atmosphere. Surface observations and scatterometer data indicate that the winds are light and generally southeast or southerly across much of the area. Observed waveheights are in the 3 to 5 ft range throughout, and little change is expected through Sun. A weak surface trough extends from northern Florida southwestward to over the far NE Gulf at 29N84W and to near 27.5N87W. Only isolated showers are near this trough. Other isolated showers are noted over some portions of the far SE waters of the gulf. Areas of dense fog are expected over portions of the gulf mainly N of about 27N during the morning hours producing sharply reduced visibilities. Little change in the present synoptic pattern is expected through Sun, however, winds and seas are forecast to increase by early next week when high pressure strengthens over the western Atlantic. CARIBBEAN SEA... Please read the SPECIAL FEATURES section for details regarding the Gale Warning near the coast of Colombia. Only patches of clouds and embedded quick moving isolated showers are seen across the Caribbean within patches of low-level moisture. The trade winds in the area are fresh to strong, and they are even stronger near the coast of Colombia as discussed above. These winds are occurring due to the tight pressure gradient between a 1025 mb high over the western Atlantic and the typical lower pressures found over northern S America. No significant changes are expected to occur today, however, winds and seas will likely increase over the eastern and central Caribbean on Sun and into early next week due to a tighter pressure gradient attributed to stronger high pressure forecast to build N of the area. ATLANTIC OCEAN... Tranquil conditions and fairly light winds are occurring across the western Atlantic supported by a surface ridge and dry and stable air aloft. Over the central Atlantic, an upper-level low and accompanying surface trough is producing scattered showers and isolated thunderstorms from 25N-28N between 42W-45W. Scattered moderate convection, decreasing in coverage, is observed over the deep tropics from 03N-09N between 43W-48W as this activity developed from low-level convergence in that area. The activity is being further aided aloft by a nearby upper jet stream branch. No significant weather is occurring over the eastern Atlantic as atmospheric conditions are rather stable. Isolated to scattered showers moving quickly westward are present S of 25N W of 59W. This activity is affecting the Lesser Antilles, Puerto Rico and immediate surrounding islands. A steady stream of mid and upper level moisture in the form of broken mid and upper level clouds is seen streaming northeastward from northeastern S America to within 220 nm either side of line from 05N50W to 11N37W to 14N26W and to inland the African coast at 17N16W. Isolated showers are possible elsewhere from 02N-10N between 40W and the coast of S America, and also from 10N-18N between 20W-35W. For additional information please visit http://www.hurricanes.gov/marine $$ Aguirre