000 AXNT20 KNHC 070942 AAA TWDAT Tropical Weather Discussion...updated NWS National Hurricane Center Miami FL 542 AM EDT Fri Jul 7 2017 updated Special Features for convection 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 0915 UTC. ...SPECIAL FEATURES...updated Tropical Depression Four is centered near 13.4N 46.7W at 07/0300 UTC or about 855 nm east of the Lesser Antilles moving W or 20 kt. Estimated minimum central pressure is 1012 mb. The depression is poorly organized as noted in latest satellite imagery. Its convective and cloud pattern has become more symmetrical during the overnight hours. The satellite imagery shows scattered moderate to strong convection within 90 nm of the center in the north and northeast quadrants. Scattered moderate convection is within 75 nm of the center in the southeast and south quadrants. The depression is expected to continue to weaken today as dry air continues to be entrained into its circulation. The latest NHC advisory forecasts for it to degenerate to a remnant low by this evening, but it could also open up into a tropical wave at any time before that time. Please see the latest NHC Public Advisory under AWIPS/WMO headers MIATCPAT4/WTNT34 KNHC and the full Forecast/Advisory under the AWIPS/WMO headers MIATCMAT4/WTNT24 KNHC for more details. ...TROPICAL WAVES... A tropical wave is over the far eastern Atlantic with its axis extending from 16N20W to 11N21W to 05N21W, moving westward at 5-10 kt during the past 24 hours. The wave is in a region of favorable to neutral wind shear. However, extensive intrusion of Saharan dry air and dust into the wave's environment continues to presently suppress deep convection N of 08N. Observed convection is within and near the monsoon trough, and consists of the scattered moderate type within 60 nm east of the axis from 06N- 08N and also within 120 nm west of the axis from 06N-8N. A tropical wave is over the eastern Caribbean Sea with axis extending from 20N61W to 15N62W to inland northeastern Venezuela at 08N62W, moving W around 15 kt during the past 24 hours. The wave crossed the Lesser Antilles on Thursday evening as noted in the surface observations. The CIRA mid-level satellite moisture animation suggests that mid-level dry air is present across the wave's environment, and the Metosat-9 imagery confirms the presence of the dry air in showing a broken swath of eastern Atlantic Saharan African dust that protrudes into the eastern Caribbean Sea. The moisture present at the lower levels is shallow, and latest satellite imagery shows scattered showers and thunderstorms within 60 nm east and 90 nm west of the axis south of 13N. Only isolated showers and thunderstorms are within 30-60 nm of the axis north of 13N. The wave is forecast to move across the eastern Caribbean through Saturday night, and across the eastern portion of the central Caribbean on Saturday. Expect increasing moisture along with some pockets of scattered showers and thunderstorms behind the wave. A tropical wave analyzed over the western Caribbean Sea with axis extending from near 22N85W south to inland central Honduras at 16N86W, and continues southward to the eastern Pacific waters just west of northern Costa Rica. It has moved westward at about 20-25 kt during the past 24 hours. The wave is in a region of unfavorable wind shear. However, shallow moisture and upper level diffluent flow between an upper level low over the eastern Gulf of Mexico, and a broad ridge noted over the western Caribbean support scattered moderate to isolated strong convection west of the wave axis south of 18N. Isolated showers and thunderstorms are elsewhere west of the axis and within 120 nm east of the axis as the atmospheric environment remains very moist and unstable over the much of the western Caribbean Sea. A tropical wave has moved inland eastern Mexico near 98W. The flow pattern between an upper level low over central Mexico and broad upper level ridging over the SW Gulf of Mexico supports scattered moderate to isolated strong convection south of 24N and west of 91W, including the Bay of Campeche. ...ITCZ/MONSOON TROUGH... The Monsoon Trough axis extends from 13N17W to 06N23W to 04N30W. The Intertropical Convergence Zone extends from 04N30W to 03N40W to 07N47W to 09N53W to 10N58W. Aside from the convection related to the tropical wave off the coast of Africa, scattered moderate to strong convection is within 120 nm south of the axis between 37W-43W. Scattered moderate convection is within 120 nm north of the axis between 23W-27W, within 60 nm south of the axis between 27W-30W, and within 60 nm south of the axis between 33W-37W. ...DISCUSSION... GULF OF MEXICO... A tropical wave has moved inland eastern Mexico. A very moist and unstable environment east of the wave in combination with the the flow pattern set-up between an upper level low over the central Gulf and broad upper ridging over the SW Gulf is supporting scattered moderate to isolated strong convection south of 24N and west of 91W, including the Bay of Campeche. This activity is expected to continue into Saturday. A 1020 mb high is centered over the NE Gulf near 28N85W with associated light to moderate anticyclonic flow covering the eastern Gulf north of 28N and east of 87W. Isolated showers and thunderstorms are noted on mosaic national radar imagery to be present over the eastern Gulf east of 85W and south 29N. This activity is moving in a west- northwestward direction. CARIBBEAN SEA... A tropical wave is moving across the western Caribbean, while another tropical wave is over the far eastern Caribbean. See above for further details on these waves. Scattered moderate convection noted earlier over the interior of Cuba has just about dissipated, except for lingering isolated weak activity over the central portion of the island. Scattered moderate convection is along the coast of Costa Rica, southern Honduras and northern Panama. In the upper levels, broad anticyclonic flow covers the western Caribbean, while a small upper level low is centered over central Caribbean near 13N72W. Upper southerly flow over the eastern portion of the low is transporting upper moisture from northeastern Venezuela to across the eastern Caribbean, but most of it dissipates in the dry air that has moved in from the central Atlantic. The pressure gradient throughout supports 10- 25 kt trades with the strongest winds along the coast of NW Colombia. ...HISPANIOLA... Convection that occurred over the higher elevations of Haiti on Thursday afternoon and evening has dissipated. Expect Hispaniola to have a decrease in convection over the next 24 hours as the island is in between tropical waves, and dry aloft advecting from the east is settling in over the island ATLANTIC OCEAN... Tropical Depression Four and a tropical wave are analyzed over the tropical Atlantic. See above. An area of scattered showers and isolated thunderstorms moving westward is observed to the northwest of Tropical Depression Four from 18N-21N between 49W- 52W. A surface trough is over the NW Bahamas with scattered showers and isolated thunderstorms to its west. A broad 1029 mb surface high is centered north of our area near 36N35W producing fair weather. An extensive area of African Saharan dust is situated over the eastern and central Atlantic, and is gradually shifting westward as strong easterly winds aloft are present to the south of the upper level anticyclone located over those portions of the Atlantic. This synoptic pattern will change little through the next couple of days. For additional information please visit http://www.hurricanes.gov/marine $$ Aguirre