Tropical Weather Discussion
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AXNT20 KNHC 150604

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
204 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 0000 UTC surface analysis and satellite imagery through
0545 UTC.


Hurricane Gert is centered near 31.2N 72.3W at 15/0300 UTC or
about 385 nm W of Bermuda moving N at 7 kt. Estimated minimum
central pressure is 986 mb. Maximum sustained wind speed is 65 kt
with gusts to 80 kt. Numerous moderate convection is from 30N-
32N between 71W-74W. Scattered moderate convection is elsewhere
from 28N-34N between 71W-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 with axis extending
from 24N24W to 11N27W, 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 the convection. Shallow
moisture confined to the vicinity of the monsoon trough and upper
level diffluent wind support scattered moderate convection from
10N to 14N between 28W and 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 Atlantic.

A tropical wave is in the central Atlc with axis extending from
23N45W to 08N49W, 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
21N63W 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.


The monsoon trough extends from the coast of W Africa near 15N16W
to 12N37W to 08N49W. The Intertropical Convergence Zone axis
extends from 08N52W to the coast of Venezuela near 08N60W.
Numerous heavy showers and scattered tstms are coming off the W
African coast associated with the next tropical wave. The
convection extends from 06N to 13N E of 21W. Scattered moderate
convection is from 07N to 16N between 30W and 46W associated with
a 1011 mb low located near 12N37W.



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,
Mississippi and Alabama. 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 propagate westward
across Puerto Rico early this morning, then will move over central
Caribbean waters early on Wednesday. Isolated showers are
occurring ahead of the wave over northern Puerto Rico and
adjacent waters, the Mona Passage and Hispaniola, but mainly due
to shallow moisture and a diffluent wind environment aloft. 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 81W. Otherwise, fresh to near gale
force winds are in the south-central basin forecast to continue
through Thursday.


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 are NE of the Bahamas between 70W-76W associated
with the rainbands of Hurricane Gert centered north of the area.
See Special features. Otherwise, the remainder basin generally N
of 20N is under the influence of the Azores high. For information
about tropical waves, see section above.

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