Atlantic Tropical Weather Discussion (Text)

AXNT20 KNHC 191033

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
633 AM EDT Sat Aug 19 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 0600 UTC surface analysis and satellite imagery through 
1030 UTC.


Tropical Storm Harvey is located near 13.8N 65.9W at 19/0900 UTC,
or about 243 nm south of St. Croix, moving west at 18 kt. Estimated
minimum central pressure is 1005 mb. Maximum sustained wind speed
is 35 kt with gusts to 45 kt. The low-level center of Harvey 
remains near the eastern edge of a strong convective area that 
covers the area from 10N-17N between 65W-71W. Harvey will continue
moving through the eastern and central through the day. Interests
in the Caribbean Sea and the adjacent land areas of eastern 
Central American and northern South America should monitor the 
progress of Harvey. Locally heavy rains could occur tonight over 
portions of the Windward Islands and the offshore islands of 
northern Venezuela. Locally heavy rains could also occur over 
Aruba, Bonaire, and Curacao today. 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 is in the east Atlantic with axis extending from 
20N39W to a 1010 mb low pressure located near 13N40W to 10N40W. 
Satellite imagery indicates a large cyclonic circulation in the 
cloud field, but convection is limited in association with this 
low. Saharan dust surrounds the wave/low. This system coincides 
with a well defined 700 mb trough, and a high amplitude northward 
bulge of moisture is noted on the TPW imagery. Environmental 
conditions appear somewhat conducive for gradual development over 
the next few days while the system moves west-northwestward to 
northwestward at about 15-20 kt, but upper-level winds are 
forecast to become unfavorable by the middle of next week. This 
system has a low change of becoming a tropical cyclone within the 
next 48 hours.

A tropical wave extends across the central Atlantic with axis from
22N57W to 11N57W, moving west at 10-15 kt. The wave shows up very
well on the TPW animation and 700 mb streamline analysis. At this
time, scattered showers are noted across the northern portion of 
the wave mainly north of 18N between 53W-59W. Environmental 
conditions are expected to be only marginally conducive for 
development during the next few days. This system has a low change
of becoming a tropical cyclone within the next 48 hours.

A tropical wave extends from the northern Bahamas, across central Cuba
and west of Jamaica, then to the southwest Caribbean, moving west
at 10-15 kt. An area of moderate convection is along the wave's 
axis from 22N-28N between 74W-80W. The wave shows up very well on
the TPW animation and 700 mb streamline analysis. Moisture associated
with this wave will continue spreading over the northern Bahamas 
and central Cuba this morning, and across south Florida and 
western Cuba in the afternoon and evening, increasing the 
likelihood of showers and thunderstorms. There is a potential of 
locally heavy rain and localized flooding with this activity. 


The monsoon trough extends from the African coast near 15N17W to
the low/wave near 14N40W. No significant convection is observed at
this time.



A weak surface ridge continues to dominate the Gulf waters,
anchored by a 1017 mb high centered near 28N88W. Mainly light to 
gentle anticyclonic winds are prevailing across the basin. A 
surface trough is analyzed from 30N84W to 28N86W. Scatterometer 
and surface data indicate the wind shift associated with this 
trough. A thermal trough will develop during the evening hours 
over the Yucatan Peninsula before pushing offshore into the SW 
Gulf each night. A surge of fresh winds will accompany this 
trough. Little change in this weather pattern is expected through 
early next week. In the upper levels, a large and well-defined 
upper-level low is spinning over the Straits of Florida inducing 
some shower activity over the southeastern Gulf and the Florida 
Peninsula. The upper-low will drift westward across the eastern 
Gulf during the weekend. 


A tropical wave is over eastern Cuba along 79W. Please, see the 
Tropical Waves section above for details. Tropical Storm Harvey 
will continue moving through the eastern and central Caribbean 
through the day. Please, see the Special Features section for 
more details. An upper-level low spinning over the waters just 
north of western Cuba supports scattered showers across the 
northwest Caribbean waters and the Yucatan Channel. Scattered 
showers and thunderstorms are noted over the southwest Caribbean
mainly south of 10N associated with the eastern extent of the 
Pacific's monsoon trough combined with a diffluent pattern aloft.


Daytime heating, local sea breezes and mountain upslope lifting 
will combined with available moisture will produce scattered 
showers and thunderstorms across the island mainly during the 
afternoon and evening hours through the weekend. 


A pair of tropical waves are moving westward across the tropical 
Atlantic while the northern portion of another tropical wave is 
affecting the northern Bahamas. Please, see the 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 1026 mb located near 39N22W. A belt of fresh to locally strong
easterly winds is noted per scatterometer data roughly between 
17N-23N due to the pressure gradient between the ridge and the 
tropical waves and associated areas of low pressure between the 
coast of Africa and the Lesser Antilles. Fresh to strong northerly
winds are also noted between the coast of Africa and the 
Madeira/Canary Islands. These winds are the result of the pressure
gradient between the Atlantic ridge and lower pressures over west

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Page last modified: Saturday, 19-Aug-2017 10:34:04 UTC