Tropical Weather Discussion
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807
AXNT20 KNHC 190000
TWDAT

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

...SPECIAL FEATURES...

The persistent upper-level trough located over the NW Caribbean
the past few days has begun to fracture with the southern portion
of the trough beginning to fill and drift westward. The upper
level flow over Hispaniola is gradually becoming more zonal which
has partially resulted in an abatement of deep convection over
the island this evening. The large area of deep convection noted
earlier across the central Caribbean has propagated southward
toward the extreme southern Caribbean. Additional convection was
developing near western Jamaica. The associated surface trough and
a tropical wave have moved well west of the area with the surface
trough over western Cuba/Florida straits and the tropical wave
along 80W. The 1200 UTC Kingston rawinsonde still indicated deep
layered moisture with precipitable water values of 2.27". Some
drying between 800 and 500 mb was noted on the 1200 UTC Santo
Domingo rawinsonde suggesting some dry air was advecting into
Hispaniola/Haiti. Per NWP model guidance and recent trends, the
heavy rainfall threat appears to be shifting to Jamaica and the
NW Caribbean over the next 24 hours or so. Please monitor
advisories and bulletins from local meteorology offices, emergency
management services, and other governmental agencies.

Please refer to the METEO-FRANCE High Seas Forecast, listed on
the website: WWW.METEOFRANCE.COM/PREVISIONS-METEO-MARINE/BULLETIN/
GRANDLARGE/METAREA2. Gale-force winds are forecast for the areas
of AGADIR and CANARIAS. These conditions will dissipate during
the next 24 hours.

...TROPICAL WAVES...

Tropical wave axis extends from 11N44W to 01N45W, moving west at
15-20 KT. Moisture within the wave environment has decreased
some over the last six hours as noted in TPW imagery. Scattered
showers are observed from 04N-08N between 47W-50W.

A tropical wave is moving across central Venezuela with axis from
11N65W to 01N65W, moving westward at 10 knots. No significant
convection is related to this wave at this time.

A tropical axis extends from 15N80W across central America into
the EPAC near 05N81W, moving west at 10 kt. Abundant moisture
prevails in the wave`s environment, as noted in TPW imagery.
Scattered moderate convection is observed within this wave
affecting the south-central Caribbean from 13N-18N between
73W-79W.

...ITCZ/MONSOON TROUGH...

The Monsoon Trough extends from 18N16W to 09N27W. The ITCZ
extends from 05N33W to 01S47W. Scattered moderate to strong
convection was noted from 04N-09N between 17W-21W. Scattered
moderate covection was noted within 180-240 NM of the coast of
Liberia.

...DISCUSSION...

GULF OF MEXICO...

Upper-level westerly flow covers the Gulf of Mexico with water
vapor imagery depicting deep layered subsidence over the
southeastern half of the Gulf. A band of upper level moisture
swept across the far NW Gulf. Satellite derived winds indiacted
the axis of the subtropical jet along the Texas coast. At the
surface, a ridge extends along 29N/30N anchored across the western
Atlantic near 33N64W. Lower pressures prevail across Mexico and
the far west Gulf waters. The resulting pressure gradient is
supporting moderate to fresh SE winds across the northern half of
the basin. Light to gentle winds prevail elsewhere. Little change
is expected during the next 24 hours.

CARIBBEAN SEA...

A tropical wave is moving across the south-central portion of the
basin along 80W. Please refer to the SPECIAL FEATURES section
above for details. A deep-layered trough extends its axis across
the western Caribbean and western Atlantic and was in the process
of fracturing. A surface trough was analyzed from 22N80W to
19N82W. Some diffluence prevailed to the east of the trough over
the southern Caribbean with waning support for scattered showers
and thunderstorms within 90 NM of 12N77W. Despite the fact that
the convection has moved south of the island of Jamaica, Cuba and
Hispaniola, re-development could occur tonight and Friday mainly
over Jamaica and Cuba. Please monitor advisories and bulletins
from local meteorology offices and other governmental agencies.
1500 UTC ASCAT passes depicted fresh to locally strong trades
over the central portion fo the basin between 70W-77W with
subnormal trades over the far western portion of the basin.
The surfrace trough and tropical wave should move further west
with stronger trades spreading westward in their wake.

...HISPANIOLA...

Upper-level flow has become more zonal across the island with a
break in the heavy rainfall from the past few days. As noted
above, mid-level drying was noted on the 1200 UTC Santo Domingo
rawindsonde from 800-500 mb. NWP model guidance and the recent
trend of mid-level srying suggests the threat of heavy rainfall
should lessen over the next 24 to 48 hours. Please monitor advisories
and bulletins from local meteorology offices, emergency
management services, and other governmental agencies.

...ATLANTIC OCEAN...

A Gale Warning is in effect for the far east Atlantic waters.
Please refer to the SPECIAL FEATURES section above for details. A
1025 mb surface high is centered near 33N64W. Its associated
ridge extends across the western Atlantic W of 50W. Another
surface ridge extends across the remainder of the basin, anchored
by a 1030 mb high centered near 41N23W.

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

$$
Cobb



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