000 AXNT20 KNHC 180006 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 806 PM EDT Sat Jun 17 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 2330 UTC. ...SPECIAL FEATURES... A tropical wave is in the central Atlantic associated with a 1008 mb low centered near 06N41W. Its axis extends from 11N41W to the low to 00N41W, moving west at 15-20 kt within the last 24 hours. The wave is in a region of favorable wind shear and is embedded in a moderate moist environment at the lower levels according to CIRA LPW imagery. However, Saharan dry air is entering to its environment, thus limiting the convection to scattered moderate from 05N to 08N between 40W and 45W. This convection is being supported by upper-level diffluence. This wave has a medium chance of becoming a tropical cyclone during the next two days. Please see the latest NHC Tropical Weather Outlook under AWIPS/WMO headers MIATWOAT/ABNT20 KNHC for more details. A 1007 mb broad area of low pressure located over the northwestern Caribbean Sea near 18N86W. This system is producing a large area of disorganized showers and thunderstorms west of 84W. Gradual development of this system is expected while it moves slowly northwestward across the Yucatan Peninsula on Sunday and over the southern or central Gulf of Mexico by early next week, where a tropical or subtropical cyclone is likely to form. This system has a medium chance of becoming a tropical cyclone during the next two days. Please see the latest NHC Tropical Weather Outlook under AWIPS/WMO headers MIATWOAT/ABNT20 KNHC for more details. ...TROPICAL WAVES... A tropical wave was introduced to this map after analyzing satellite imagery, Hovmoller diagrams and model guidance. This wave's axis extends from 13N18W to 05N18W. Scattered moderate convection is observed along and west of the wave's axis from 06N-10N between 18W-25W. A tropical wave is in the eastern Atlantic with axis extending from 11N30W to 00N30W, moving west at about 15-20 kt within the last 24 hours. The wave is in a region of favorable wind shear, however the wave lacks deep convection at the time due to Saharan dry air intrusion to its environment. A tropical wave is in the central Atlantic with axis extending from 18N50W to 07N51W, moving west at 15-20 kt within the last 24 hours. The wave lacks convection at the time due to the intrusion of Saharan dry air and dust to its environment. A tropical wave is in the west Caribbean with axis extending from 21N78W to 12N79W, moving west at 10-15 kt within the last 24 hours. Low-level moisture convergence and upper-level divergence support numerous moderate to heavy showers and tstms with possible gusty winds to near gale-force north of 15N and west of 77W. ...MONSOON TROUGH/ITCZ... The Monsoon Trough extends from the coast of west Africa near 15N17W to 07N24W to 05N43W. The ITCZ extends from 05N43W to 05N52W. Four tropical waves are embedded within the Monsoon trough/ITCZ. See the Tropical Waves section for information about convection. ...DISCUSSION... GULF OF MEXICO... A weak ridge continues to dominate the Gulf region being anchored by a 1014 mb high near 27N87W, which is forecast to dissipate within the next 24 hours. The ridge provides light to gentle variable flow east of 90W and gentle to moderate southeast winds west of 90W. Water vapor imagery indicates the presence of a broad upper-level low covering most of the basin centered near 28N91W. Very dry air also prevails across the area which is supporting clear skies and fair weather. Weather conditions will change on Sunday associated with a broad area of low pressure forecast to become better organized over the northwestern Caribbean Sea and the Yucatan Peninsula later today or early tomorrow. Conditions appear to be favorable for gradual development of this system while it moves slowly northwestward into the southern Gulf of Mexico early next week. Latest Tropical Weather Outlook gives this low pressure a high chance of development through the next 5 days. CARIBBEAN SEA... Convection continues on the increase across the western Caribbean. Satellite imagery show clusters of heavy showers and thunderstorms with possible gusty winds to near gale-force mainly west of 74W associated with the Special Features surface low centered north of Honduras and a tropical wave that is currently west of Jamaica. See the Special Features and Tropical Waves sections above for details. A diffluent pattern aloft, associated with the above mentioned upper-level low over the Gulf of Mexico is helping to induce this convective activity. Increasing winds and building seas are expected across the central and western Caribbean this weekend due to a tight pressure gradient between the low pressure area and the Atlantic ridge. Mainly gentle to moderate winds prevail elsewhere, as noted in scatterometer data. Plenty of moisture and very active weather is expected to continue this weekend over the western Caribbean as the surface low becomes better organized likely affecting Central America, most of Cuba, and the Yucatan Peninsula. Locally heavy rain and gusty winds could occur across these areas. ...HISPANIOLA... Isolated showers are across the island being supported by the broad area of diffluence in the west Caribbean and the area of low pressure mentioned above. Showers are still in the forecast on Sunday mainly in the afternoon hours due to daytime heating and orographic lifting. ATLANTIC OCEAN... Four tropical waves are moving westward between the coast of Africa and the Lesser Antilles. Please refer to the Tropical Waves section above for details. A diffluent flow aloft is keeping the western Atlantic with isolated showers and thunderstorms mainly west of 72W. A weak 1018 mb surface low is located near 30N61W with surface trough extending from the low to 26N62W. This low will dissipate during the next 24 hours. The remainder of the area is under the influence of a broad high pressure with a 1024 mb surface high centered near 31N38W. 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