AXNT20 KNHC 180538

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
138 AM EDT Fri Aug 18 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 0000 UTC surface analysis and satellite imagery through 0530 UTC.


At 18/0300 UTC, Tropical Storm Harvey is located near 13.0N 57.4W, moving west at 16 kt. Estimated minimum central pressure is 1005 mb. Maximum sustained wind speed has increased to 35 kt with gusts to 45 kt. A cluster of moderate to strong convection is noted from 11N-15N between 57W-63W. Harvey should move through the Windward Islands and entering the eastern Caribbean today. Slow strengthening is possible during the next 48 hours. Harvey is expected to produce rainfall totals of 2 to 4 inches across portions of the Windward Islands from Martinique southward to Grenada. These rains could cause life-threatening flash floods and mudslides. See see the latest NHC Intermediate Public Advisory under AWIPS/WMO headers MIATCPAT4/WTNT34 KNHC, and the full Forecast/Advisory under AWIPS/WMO headers MIATCMAT4/WTNT24 KNHC for more details.

A tropical wave extends its axis from 19N46W to a 1009 mb low near 16N46W to 10N46W. Scattered moderate convection is noted mainly on the west semicircle of the low center from 15N-19N between 46W-50W. The shower and thunderstorm activity associated with this area of low pressure has changed little in organization during the past several hours. However, only a slight increase in the organization of the shower activity could lead to the formation of a tropical depression during the next couple of days before upper-level winds become less favorable for development early next week. The low is expected to move west-northwestward at about 15-20 kt during the next few days, and interests in the northern Leeward Islands should monitor the progress of this disturbance. This system has a high change of becoming a tropical cyclone during the next 48 hours.


A tropical wave is moving across the eastern Atlantic with axis extending from 17N27W to a 1010 mb near 12N28W to 06N29W. Scattered moderate convection is from 03N-16N between 29W-34W. This wave is in a very moist area based on TPW imagery and has a well pronounced 700 mb trough. Gradual development of this system is possible through the middle of next week while the wave moves westward to westward at about 15-20 kt. Currently, this system has a low change of becoming a tropical cyclone through 5 days.

A broad tropical wave is moving westward across the Caribbean extending its axis from 22N70W to 12N71W. A cluster scattered moderate convection is noted over the northern part of the wave axis from 18N-24N between 67W-72W. This convective activity is affecting the northeastern part of Dominican Republic. The wave shows up very well in the TPW animation and 700 mb streamline analysis. Moisture associated with this wave will spread across the Turks and Caicos Islands, the southern Bahamas, and the remainder of Hispaniola tonight increasing the likelihood of rain. Fresh to locally strong northeast winds are noted over waters ahead of the wave axis.

A tropical wave extends its axis across the southern portion of the Bay of Campeche and into the EPAC from 21N92W to 08N92W. The wave is enhancing scattered showers and thunderstorms over southeast Mexico and adjacent waters south of 20N between 91W-95W. The wave coincides with a 700 mb trough, and is well depicted in TPW imagery.


The monsoon trough extends from the African coast near 13N17W to a 1010 mb low pressure 12N28W to 10N38W. Scattered moderate convection is observed south of the monsoon trough's axis between 35W-44W.



A 1018 mb surface high centered over northeast Gulf near 27N87W and extends its ridge across the region producing mainly gentle to moderate winds based on scatterometer data. The tropical wave currently moving across the Bay of Campeche will enhance the convection tonight. A broad upper-level low is centered over eastern Cuba enhancing convection in its periphery mostly affecting Southern Florida and adjacent waters. Little change in this weather pattern is expected through early next week.


A tropical wave is along 71W enhancing convection over Hispaniola. Please, see the Tropical Waves section for details. Tropical Storm Harvey should move through the Windward Islands and into the eastern Caribbean today. Refer to the Special Features section for more details. Upper-level diffluent flow between an anticyclonic circulation centered over the southeast CONUS and an upper-level low spinning over eastern Cuba supports scattered showers and thunderstorms over parts of central and western Cuba. Scatterometer data depicts moderate to fresh trades across the basin. The previously mentioned tropical wave will bring showers and thunderstorms over eastern Cuba today, and over western Cuba on Saturday. Isolated showers are also noted over the southwest Caribbean, likely associated with the eastern extent of the Pacific monsoon trough combined with a diffluent pattern aloft.


A broad tropical wave is moving across Hispaniola keeping showers and thunderstorms, and gusty winds, with the potential of locally heavy rain through today.


A pair of tropical waves and Tropical Storm Harvey are moving westward across the tropical Atlantic. The northern portion of a strong tropical wave is affecting the waters north of Hispaniola. Please, see Special Features and Tropical Wave sections above for details. The remainder of the Atlantic is under the influence of a surface ridge, with a center of 1025 mb located near 34N35W. A belt of fresh to locally strong NE-E winds is noted per scatterometer data roughly between 15N-22N due to the pressure gradient between the ridge and the tropical systems located between the coast of Africa and the Lesser Antilles.

For additional information please visit http://www.hurricanes.gov/marine