Tropical Weather Discussion
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AXNT20 KNHC 171755

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
155 PM EDT Thu Aug 17 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 1200 UTC surface analysis and satellite imagery through
1715 UTC.


Hurricane Gert is centered near 43.2N 50.0W at 17/1500 UTC or
about 248 nm SSE of Cape Race Newfoundland moving ENE at 35 kt.
Estimated minimum central pressure is 975 mb. Maximum sustained
wind speed is 70 kt with gusts to 85 kt. Scattered moderate to
isolated strong convection is from 43N-48N between 43W-49W.
See latest NHC Forecast/Advisory under AWIPS/WMO headers
MIATCMAT3/WTNT23 KNHC for more details.

Potential Tropical Cyclone Nine is centered near 13.1N 54.1W at
17/1500 UTC or about 317 nm E of Barbados moving W at 15 kt.
Estimated minimum central pressure is 1008 mb. Maximum sustained
wind speed is 30 kt with gusts to 40 kt. The disturbance is
expected to become a tropical cyclone later today or tonight,
and it could become a tropical storm before reaching the Windward
islands. An Air Force Reserve Hurricane Hunter aircraft is
scheduled to investigate the disturbance this afternoon. The
disturbance 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 is in the central Atlc associated with a 1009 mb
low pressure located near 15N42W. The wave axis extends from
20N42W to the low to 10N43W moving W at 15 kt. The system has
become a little better organized during the past 24 hours.
Continued gradual development of this system is possible during
the next couple of days. Upper-level winds are expected to become
less conducive for tropical cyclone formation when the
disturbance moves north of the Leeward Islands this weekend. This
system has a medium chance of becoming a tropical cyclone within
the next two days.


A tropical wave is in the E Atlc associated with a 1010 mb low
near 09N24W. The wave axis extends from 19N22W to the low center
to 05N24W. This wave in a very moist area based on SSMI TPW
imagery and has a well pronounced 700 mb trough. Widely scattered
moderate convection is over a large area from 06N-13N between
20W-30W. Environmental conditions are forecast to become more
conducive for development over the weekend while the system moves

A tropical wave is in the E Caribbean with axis extending from
24N66W to E Hispaniola to 10N71W, moving W at 15-20 kt. This wave
in a moist area based on SSMI TPW imagery and has a well
pronounced 700 mb trough. Scattered moderate to isolated strong
convection is over a large area from 15N-26N between 65W-71W to
include Puerto Rico and E Hispaniola.

A tropical wave is in the Yucatan Peninsula with axis extending
from 21N89W across Guatemala to 06N90W, moving W at 20 kt. Dry
air subsidence continues to limit convection over land. The E
Pacific in contrast has a moist SSMI TPW area, and a 700 mb
trough, that is producing widely scattered moderate convection.


The monsoon trough extends from the African coast near 15N17W to
09N24W to 08N34W. To the west, the monsoon trough and ITCZ is
disrupted due to the tropical lows and tropical waves mentioned
above. Otherwise, scattered moderate convection is from 05N-08N
between 33W-39W.



A 1019 mb high is centered over the NE Gulf of Mexico near 28N87W
with mostly fair weather. 5-10 kt anticyclonic winds are noted
around the high. 10-15 kt SE surface winds are over the W Gulf W
of 90W. Radar imagery shows scattered showers over the E Gulf,
Florida, and the Straits of Florida, E of 84W. Airmass
thunderstorms are over Louisiana. Similar thunderstorms are over
NE Florida. In the upper levels, an upper level low is centered
over the W Gulf near 22N97W producing scattered showers along the
coast of Mexico from 18N-24N between 95W-98W. An upper level high
is centered over the Florida Panhandle near 30N86W. Expect the
surface high to remain quasi- stationary over the Gulf for the
next 24 hours. Expect more airmass thunderstorms Friday during
maximum heating over Louisiana, Florida, W Cuba, S Mexico, and the
Bay of Campeche.


A tropical wave is over the E Caribbean, and another wave is over
the Yucatan Peninsula. See above. The eastern extent of the
Pacific monsoon trough is producing scattered moderate convection
over Costa Rica and Panama. Expect the E Caribbean tropical wave
to move W with convection over the next 24 hours. Also expect
continued convection the SW Caribbean.


Presently E Hispaniola has scattered moderate to isolated strong
convection spreading W. More convection is N of the island. Expect
the convection to persist beyond the next 24 hours.


Except for the SW N Atlc waters that are being impacted by the
tropical wave moving to central Caribbean waters, the Atlantic basin
N of 20N is under the influence of the mid-Atlantic subtropical
high near 32N38W with mostly fair weather. For the tropical
Atlantic S of 20N, see the special features and tropical waves
sections above.

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