National Hurricane Center's Tropical Weather Discussion

North America - Central America - Gulf of Mexico - Caribbean - Atlantic Ocean

305 AXNT20 KNHC 181804 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 204 PM EDT Sat Aug 18 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 1200 UTC surface analysis and satellite imagery through 1745 UTC. ...TROPICAL WAVES... A tropical wave is in the E Atlc with axis extending from 07N-18N along 23W, moving W at 10 kt. The wave is in a strong deep layer environment and is being affected by dry and dust air intrusion in the lower levels as depicted in GOES-16 water vapor and enhanced IR imagery. These factors are hindering the development of convection at the time. A tropical wave is in the central Atlc with axis extending from 08N-20N along 39W, moving W at 15 kt. The wave is entering a low deep layer wind shear environment, however is being severely affected by Saharan dry air and dust, which hinder convection at the time. A tropical wave is in the E Caribbean with axis extending from 07N-18N along 62W, moving W at 15 kt. Both CIRA LPW and GOES-16 water vapor imagery show the northern wave environment being affected by low level dry air, which is limiting the convection to scattered moderate across the Windward Islands and SE Caribbean S of 14N E of 65W. A tropical wave is in the western Caribbean with axis extending from 09N-20N along 79W, moving W at 15 kt. The wave is in a moderate to strong deep layer wind shear environment and mostly a dry enviromnent. Shallow moisture in the northern wave environment and diffluent wind aloft support scattered showers and tstms from 18N-21N between 76W-81W. ...MONSOON TROUGH/ITCZ... The monsoon trough extends from the coast of W Africa near 09N13W to 06N26W to 10N40W. The ITCZ begins near 10N40W and continues to 08N50W to 10N58W. Besides the convection mentioned in the tropical waves section, scattered heavy showers and tstms are off the W coast of Africa from 06N-14N E of 20W. ...DISCUSSION... GULF OF MEXICO... The Bermuda high extends a ridge axis SW across Florida and the entire Gulf reaching also eastern Mexico. The ridge is providing return flow in the range of 5-10 kt across the region except in the north-central Gulf where scattered heavy showers and tstms enhance the wind to fresh. The area of convection is N of 27N between 85W and 93W and is being supported by inflow of shallow moisture from the Caribbean by southeasterly wind and middle level diffluent flow. Surface ridging will prevail across the basin through Wed. Showers over the N-central and NE basin are forecast to continue through Sun morning. CARIBBEAN SEA... GOES-16 water vapor imagery at the lower levels show generally dry, stable air across the basin. Besides dry air, moderate to strong deep layer wind shear cover the western half of the Caribbean, thus limiting the areas of convection. A tropical wave moving S of eastern Cuba support scattered showers over central and eastern Cuba adjacent waters. Another tropical wave moves across the E Caribbean supporting showers in the SE basin. See the tropical waves section for further details. CIRA LPW imagery show regions of abundant shallow moisture in the basin that support isolated showers in the Gulf of Honduras and N of 14N between 69W-73W, including Hispaniola. Otherwise, surface ridging extending from the Atlantic to the northern half of the basin, continues to support fresh to strong winds in the south-central Caribbean. The center of high pressure SW of the Bahamas will stall the next several days, which will allow the continuation of these winds in the south-central basin. Showers will prevail in the SE Caribbean through Sunday. ATLANTIC OCEAN... The Bermuda high and the Azores high covers most of the Atlc ocean mainly supporting fair weather. A weakness in the ridge is analyzed as a surface trough that extends from 30N54W SW to 27N60W. Scattered showers and tstms are within 120 nm either side of the trough. Isolated showers are across the Bahamas. For further information associated with the tropical waves, see section above. For additional information please visit http://www.hurricanes.gov/marine $$ Ramos