Atlantic Tropical Weather Discussion (Text)

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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Page last modified: Wednesday, 18-Oct-2017 16:27:58 UTC