Tropical Weather Discussion
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AXNT20 KNHC 181627

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1226 PM EDT Wed Oct 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 1200 UTC surface analysis and satellite imagery through
1745 UTC.


A tropical wave is in the central Atlc with axis extending from
13N27W to 06N29W, moving W at 10 kt. The wave came off the coast
of Africa a couple of days ago very weak, however disorganized
convection has augmented and latest scatterometer data show fresh
to strong winds associated with it. Satellite derived data
indicate the wave is in a strong vertical wind shear environment.
However, shallow moisture and middle to upper level diffluence
support scattered moderate convection and isolated tstms from
08N-13N between 22W-31W.

A tropical wave is in the E Caribbean with axis extending from
17N61W to 07N61W, moving W at 20 kt within the last 24 hours. The
wave is in a region of moderate to strong vertical wind shear.
However, shallow moisture in the E basin along with upper level
diffluent flow support scattered heavy showers and tstms from
09N-15N between 60W-65W.

A tropical wave is in the E Caribbean with axis extending from
18N66W to inland Venezuela near 08N66W, moving W at 10-15 kt. The
wave is in a region of moderate to strong vertical wind shear. The
wave is underneath an upper level low that supports scattered
heavy showers and isolated tstms from 14N to 18.5N between 65W-
68W, including eastern Puerto Rico.

A tropical wave is moving across Central America with axis
extending from 16N83W across Nicaragua to 06N83W, moving W at 15
kt. The wave is in a region of low to moderate vertical wind shear
and CIRA LPW is showing abundant moisture associated with it at
the lower levels. This environment is supporting numerous heavy
showers and scattered tstms from 08N-14N between 80W-86W,
including Nicaragua.


The monsoon trough extends from the African coast near 08N13W to
07N19W. The Intertropical Convergence Zone axis extends from
07N19W to 09N27W, then resumes near 08N32W continuing along to
06N47W to 08N57W. Aside convection associated with the tropical
wave in the central Atlc, scattered moderate convection is from
07N-14N between 52W-60W.



A stationary front extends from the southern Florida peninsula
near 26N81W westward to 25N90W then curves SW to the Bay of
Campeche near 18N94W. The front is supported aloft by a middle to
upper level trough progressing eastward over the E CONUS seaboard
and SW N Atlc waters. Scattered moderate convection is within 240
nm S of the boundary between 80W-86W and in the eastern Bay of
Campeche. Isolated showers are within 210 nm N of the boundary E
of 87W. High pressure builds behind the front supporting northerly fresh
to strong winds in the western half Bay of Campeche and in the NE
Gulf. The front is expected to weaken today and gradually become
diffuse by early Thu. Fresh to strong winds will prevail through
tonight and then decrease into moderate to occasional fresh
through the end of the week.


A middle to upper level high covers the western half of the basin
proving stability and fair weather, except S of 18N W of 80W where
a tropical weather support numerous to scattered heavy showers and
tstms. An upper level low covers a great portion of the eastern
half of the Caribbean supporting scattered heavy showers in the
vicinity of two tropical waves, one along 67W and another near
62W. See tropical waves section for further details. Convection
associated with these waves is forecast to impact the Lesser
Antilles, Puerto Rico and Hispaniola today through early Thursday. Otherwise,
moderate to fresh trades across the central and eastern basin are
expected to gradually increase through the end of the week as
high pressure N of the are strengthens.


Dry air subsidence from aloft support mainly fair weather across
the Island. However, isolated showers and tstms are starting to
enter the Dominican Republic and adjacent waters as a tropical
wave, currently moving across Puerto Rico, continue to move west.
Scattered heavy showers and tstms associated with the wave are
forecast to affect the Island this evening through Thursday


A stationary front extends from 30N72W SW to the southern Florida
peninsula near 25N80W, which is expected to meander while
gradually dissipating through early Thursday. The front is
supported aloft by a middle to upper level trough. Isolated
showers are occurring W if the front and within 75 nm E of it.
Farther east, an upper level low support a pre-frontal surface
trough from 30N65W to 25N70W as well as scattered showers from
22N-32N between 60W-70W. The remainder of the central and eastern
Atlc are under the influence of a surface ridge anchored by a
1030 mb high centered near 32N35W.

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