Tropical Weather Discussion
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AXNT20 KNHC 150926

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
526 AM EDT Tue Aug 15 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
0915 UTC.


Hurricane Gert is centered near 31.8N 72.5W at 15/0900 UTC or
about 375 nm W of Bermuda moving N at 11 kt. Estimated minimum
central pressure is 986 mb. Maximum sustained wind speed is 65 kt
with gusts to 80 kt. Numerous moderate to strong convection is
from 30N-32N between 70W-73W. Scattered moderate convection is
elsewhere from 28N-33N between 70W-74W. See latest NHC
forecast/advisory under AWIPS/WMO headers MIATCMAT3/WTNT23 KNHC
for more details.


A tropical wave is W of the Cape Verde islands associated with a
1012 mb low pressure located near 14N28W. The wave axis extends
from 18N27W to the low to 09N28W and has been moving W at 10 kt.
The wave is in a region of low vertical wind shear, however
intrusion of Saharan dry air and dust to the wave environment
limit deep convection. Shallow moisture confined to the vicinity
of the monsoon trough and upper level diffluent wind support
scattered moderate convection SW of the low center from 10N-14N
between 28W-33W. Slow development of this system is anticipated
during the next day or two, but conditions are forecast to become
a little more conducive for tropical cyclone formation by later in
the week while the system moves westward over the tropical

A tropical wave is in the central Atlc with axis extending from
20N51W to 09N53W, moving W at 25 kt. The wave is entering a
region of moderate to strong vertical wind shear and is being
severely affected by extensive Saharan dry air and dust, which is
hindering convection at the time.

A tropical wave is in the E Caribbean with axis extending from
20N64W to 10N66W, moving W at 25 kt. The wave is in a region of
strong vertical wind shear and dry air subsidence, which is
hindering deep convection at the time. Shallow moisture observed
in CIRA LPW imagery and upper level diffluent flow ahead of the
wave axis in the N-central Caribbean support isolated showers over
northern Puerto Rico and adjacent waters as well as the Mona
Passage and E Dominican Republic.


The monsoon trough extends from the coast of W Africa near 12N16W
to 14N28W to 11N42W. The Intertropical Convergence Zone axis
extends from 11N43W to the coast of Venezuela near 09N60W.
Numerous heavy showers and scattered tstms are coming off the W
African coast associated with the next tropical wave. The
convection extends from 05N to 11N E of 18W. Scattered moderate
convection is from 06N to 15N between 34W and 46W associated with
a 1012 mb low located near 11N39W.



Weak surface ridging prevails across the basin, which along with
dry air subsidence support mainly fair weather conditions.
A broad upper level low is centered just N of the Yucatan
Peninsula, which supports isolated showers there and in the
Yucatan Channel. Diffluent flow in the NW periphery of the low
support similar shower activity off the SE coast of Louisiana and
Mississippi. Winds are gentle to moderate and from the S-SE in the
western half of the basin and light variable elsewhere. The ridge
will remain in place across the Gulf waters the next couple of
days. A surface trough will develop each evening across the
Yucatan Peninsula shifting W to the Bay of Campeche during the
overnight hours. Locally higher winds can be expected west of the
trough axis.


A tropical wave is moving through the eastern Caribbean. Please
see section above. The tropical wave will continue to propagate
westward over Puerto Rico this morning, then will move over
central Caribbean waters tonight. Isolated showers are occurring
ahead of the wave axis over northern Puerto Rico and adjacent
waters, the Mona Passage and E Dominican Republic. This convection
is mainly due to shallow moisture and a diffluent wind environment
aloft associated with an upper level low over central Atlc waters.
A broad upper level low centered just N of the Yucatan Peninsula
support isolated showers in the Yucatan Channel extending to NW
Caribbean waters N of 17N W of 80W. Scattered heavy showers and
tstms are over Belize and northern Guatemala associated with the
passage of a tropical wave with axis currently moving across the
Gulf of Tehuantepec, Mexico. Otherwise, fresh to near gale force
winds are in the south-central basin forecast to continue through


An upper level low over the central Atlc will drift WSW to the north
and across the Island over the next couple of days. This low aloft
along with the passage of a tropical wave will support scattered
to isolated showers over the Island and adjacent waters through


Scattered showers and tstms are N of 28N between 70W and 74W associated
with the rainbands of Hurricane Gert centered north of the area.
See Special features for further details. Otherwise, the
remainder basin generally N of 20N is under the influence of the
Azores high, which supports fair weather. For information about
tropical waves, see section above.

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