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AXNT20 KNHC 222356
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
756 PM 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 1800 UTC surface analysis and satellite imagery through 2315 UTC.


...SPECIAL FEATURES... A tropical wave extends from 25N89W to 16N90W moving NW at 10-15 kt. The remnant circulation of Harvey continues to be analyzed as a 1010 mb low pressure along the wave axis, over the Yucatan Peninsula near 20N90W, with scattered to numerous showers and thunderstorms occuring from 20N-26N between 85W-91W, including the Yucatan Channel where numerous showers and tstms are currently noted. The low pressure area (remnants of Harvey) is forecast to emerge off the coast of the Yucatan Peninsula tonight. Environmental conditions are conducive for a tropical depression or tropical storm to form on Wednesday or Thursday while the low moves northwestward at about 10 mph across the western Gulf of Mexico, possibly reaching the northwestern Gulf coast on Friday. Regardless of development, this system is likely to slow down once it reaches the coast, increasing the threat of a prolonged period of heavy rainfall and flooding across portions of Texas, southwestern Louisiana, and northeastern Mexico into early next week. This system could also produce storm surge and tropical storm or hurricane force winds along portions of the Texas coast later this week, and interests from northeastern Mexico to southwestern Louisiana should continue to monitor its progress. A gale warning has been issued for the SW and west-central Gulf beginning Wednesday morning. See latest NWS High Seas Forecast under AWIPS/WMO headers MIAHSFAT2/FZNT02 KNHC and the Tropical Weather Outlook under AWIPS/WMO headers MIATWOAT/ABNT20 KNHC for more details.


...TROPICAL WAVES... A tropical wave extends from 23N29W to a 1011 mb low pressure within the monsoon trough located near 14N34W moving W at 15-20 kt. Satellite imagery indicates a large area of cloudiness in association with this wave, but convection is limited. A cyclonic turning is seen near 18N33W. This wave remains in a very moist area based on TPW imagery and has a well pronounced 700 mb trough.

A tropical wave is moving across the eastern Caribbean and extends from 17N73W across Colombia to near 08N74W moving W at 20-25 kt. An area of showers with embedded tstms is noted near the northern end of the wave axis from 15N-17N between 70W-73W. The wave is also enhancing some shower and tstm activity over northern Colombia. The wave coincides with a 700 mb trough, and is well depicted in the moisture product. This system will move across the central Caribbean through mid week, and across the western Caribbean later in the week.


...ITCZ/MONSOON TROUGH... The monsoon trough extends from the African coast near 14N17W to 17N25W, then resumes near 14N34W to 10N40W to 08N51W. The Intertropical Convergence Zone axis continues from 08N51W to 10N57W. Scattered moderate isolated strong convection is from 09N-14N E of 20W. A large cluster of moderate to strong convection is approaching the west coast of Africa likely associated with the next tropical wave. Scattered moderate convection is within about 150 nm SE of a line from 15N29W to 10N37W, and within 75 nm south of trough axis between 45W-49W.


...DISCUSSION...

GULF OF MEXICO... Attention remains focused on the remnant circulation of Harvey currently located over the Yucatan Peninsula. Please, see Special Features section for details. The large and well defined upper- level low that was affecting the Gulf waters with showers and tstms during the previous days has weakened some and now a large anticyclonic circulation has developed over the eastern Gulf. The upper-level low is still spinning over the NW Gulf near 27N93W producing isolated showers and tstms. A 1020 mb high pressure centered near Mobile, Alabama extends a ridge over the northern Gulf producing mainly gentle winds.

CARIBBEAN SEA... A tropical wave is moving across the Caribbean Sea. Please, see Tropical Waves section for details. The most recent scatterometer data provide observations of fresh to locally strong SE winds across the NW Caribbean mainly N of 20N W of 83W. Similar wind speeds are noted over the central Caribbean. Strong trade winds are forecast to pulse off the coasts of northeast Colombia and northwest Venezuela in the wake of the tropical wave currently located along 73W/74W. A surface trough over the Atlantic extends to near Martinique in the Windward Islands producing isolated showers. Moisture associated with this trough will affect mainly the Leeward Islands later tonight and Wednesday, reaching the UK/US Virgin Islands by Wednesday night. This will increase the chance for showers with isolated tstms across the islands.


...HISPANIOLA... Scattered showers with embedded tstms are observed this evening over Hispaniola, more concentrated over Haiti. Daytime heating, local sea breezes and mountain upslope lifting will continue to combine with available moisture to produce isolated to scattered showers and thunderstorms mainly during the afternnon and evening hours.

ATLANTIC OCEAN... A trough of low pressure persists between the NW Bahamas and Florida producing a large and disorganized area of showers and thunderstorms. The trough extends from 29N79W across south Florida to the Florida Keys. Any development of this system during the next few days should be slow to occur while it drifts northward over Florida and the adjacent waters. Environmental conditions could become a little more conducive for tropical or subtropical development by the weekend when the system begins to move northeastward over the western Atlantic. Regardless of development, very heavy rain and flooding is possible over portions of the Florida peninsula during the next few days. Farther east, there is another surface trough that extends 27N57W to 19N57W to near Martinique in the Windward Islands. This trough is likely the surface reflection of an upper- level low located near 27N58W. An earlier scatterometer pass showed the wind shift associated with this trough. The upper-level low is generating isolated showers and tstms mainly from 22N-31N between 53W-60W. The remainder of the Atlantic forecast area is under the influence of the subtropical ridge.

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

$$ GR

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