AXNT20 KNHC 220541

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
141 AM EDT Tue Aug 22 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 0515 UTC.


A tropical wave extends from 23N86W to 12N87W moving W-NW at 15-20 kt. The remnant circulation of Harvey continues to be analyzed as a 1011 mb low pressure along the wave axis near 18N87W. Scattered moderate to strong convection is from 18N-22N between 79W-89W. Satellite images and surface observations indicate that the system has not become better organized and tropical cyclone development is not expected before the system moves inland over the Yucatan peninsula this morning. However, environmental conditions are expected to be conducive for development when the system moves over the Bay of Campeche tonight or early Wednesday, and a tropical depression is likely to form over the southwestern Gulf of Mexico on Wednesday or Thursday. Regardless of development, locally heavy rainfall and gusty winds are expected to spread westward across Belize and the Yucatan peninsula during the next day or so. There is a high chance for this system to become a tropical cyclone within 48 hours.


A tropical wave extends from 22N28W to 11N30W moving W at 15-20 kt. A 1012 mb low pressure precedes the wave centered near 13N34W. Scattered moderate convection is from 08N-12N between 28W-33W. This wave in a moist area based on TPW imagery and has a well pronounced 700 mb trough.

A tropical wave extends over the eastern Caribbean from 17N65W to 10N66W, moving W at 20-25 kt. Isolated showers are near the northern end of the wave axis. The wave is expected to move across the eastern Caribbean Sea and portions of Venezuela through Tuesday helping to induce some convective activity. Subtle troughing is noted on 700 mb streamline analysis. Some moisture is observed on either side of the wave axis based on the SSMI TPW animation. This wave will cross the central Caribbean through mid-week.


The monsoon trough extends from 14N17W to 17N23W to 13N34W to 07N43W. The Intertropical Convergence Zone axis continues from 07N43W to 06N57W. Scattered moderate convection is within about 90 nm south of trough between 31W-39W. Besides the convection mentioned in the tropical wave section, scattered moderate convection is from 09N-14N between 21W-27W, and from 06N-08N between 37W-40W.



Weak surface ridging is over the Gulf of Mexico with axis along 30N. 10-15 kt easterly surface flow is over the N Gulf. The northern extent of a tropical wave is producing scattered moderate to strong convection over the Yucatan Channel, and the N Yucatan Peninsula. Scattered showers and isolated thunderstorms are also advecting over S Florida from the Atlantic. In the upper levels, an upper level low is centered over the W Gulf near 27N91W enhancing showers. Expect over the next 24 hours for the upper level low to remain quasi-stationary and continue to produce convection. Looking ahead, the remnant low of Harvey and tropical wave, currently moving across the Caribbean Sea is expected to traverse the Yucatan Peninsula this morning and Tuesday, and then move into the Bay of Campeche Wednesday, where redevelopment to a tropical cyclone appears likely.


The remnant low of Harvey currently located over the NW Caribbean continues to be the primary area of concern across the basin. Please, see Special Features section for more details. A tropical wave is over the far eastern Caribbean. Please, see the Tropical Waves section for details. Patches of low-level moisture embedded in the trade wind flow are noted over parts of the east and central Caribbean. Fresh SE winds are observed per scatterometer data across the central Caribbean, but mainly N of 13N. These winds are the result of the pressure gradient between the Atlantic ridge and the remnant low of Harvey.


Presently, showers have full dissipated. However,daytime heating, local sea breezes and mountain upslope lifting will combined with available moisture to produce isolated to scattered showers and thunderstorms during the afternoon and evening hours Tuesday. The next tropical wave is forecast to pass just south of the island Tuesday night into Wednesday.


A trough of low pressure continues to move westward across the Bahamas and now extends from 29N77W across the N Bahamas to central Cuba near 22N79W. This system continues to produce disorganized showers and thunderstorms, with fresh to strong winds mainly on its NW side based on scatterometer data. Only slow development of this system is anticipated during the next several days while it moves west-northwestward across the Bahamas and then turns northwestward or northward near Florida and the adjacent waters. Farther east, there is another surface trough that extends 25N54W to 17N55W. This trough is likely the surface reflection of an upper-level low spinning near 27N58W. The remainder of the forecast area is under the influence of the Atlantic ridge.

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

$$ Formosa