Tropical Weather Discussion
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AXNT20 KNHC 052355

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
705 PM EST Tue Dec 5 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 1800 UTC surface analysis and satellite imagery through
2315 UTC.



A cold front currently extending from the Ohio Valley through
the deep south and extending from near Lake Charles, Louisiana
to near Corpus Christi, Texas is forecast to sweep further into
the Gulf of Mexico as strong high pressure building behind the
front will tighten the pressure gradient in the western Gulf,
thus supporting gale force winds beginning tonight over the
northwest Gulf then spreading southward to the southwest Gulf
by late Thursday. Seas will build to 10 to 13 FT by Thursday.
Please read the latest NWS High Seas Forecast under AWIPS/WMO
headers MIAHSFAT2/FZNT02 for more details.


Strong low pressure well N of the forecast waters with
associated cold front extending from 31N45W to 28N50W to 27N62W.
Earlier scatterometer data indicated W to NW winds of 30 to 35
KT N of 29N west of the front to 54W. Seas of 17 to 24 Ft were
noted in the area. The front will continue to drift ESE during
the next 24 hours when the winds are expected to decrease below
gale force. Please read the latest NWS High Seas Forecast under
AWIPS/WMO headers MIAHSFAT2/FZNT02 for more details.


The monsoon trough extends from the African coast near 08N13W
then immediately transitions to the Intertropical Convergence
Zone near 07N16W then continues through 05N30W to 04N47W to
07N57W. Scattered moderate convection is within 90 nm of the
ITCZ W of 23W.



A strong cold front has emerged off the Gulf coast and extends
from Lake Charles, Louisiana to Corpus Christi, Texas as of 2100
UTC. Light to locally moderate return flow was noted in advance
of the front over the remainder of the Gulf N of 25N. Mosaic
radar imagery indicated scattered showers and thunderstorms
along and to the north of the front from southern Mississippi,
Louisiana to the middle and upper Texas coastal waters.
Generally fair conditions prevail elsewhere over the basin
within a ridge of high pressure along 26N. Strong high pressure
building behind the front will tighten the pressure gradient in
the NW Gulf and will support frequent gust to gale force winds
beginning tonight. Scattered showers and thunderstorms will be
associated with this front as it moves across the basin. Heavy
showers are expected in the SE Gulf Friday into Saturday as the
front moves further SE. Please see the special features section
above for information on the Gale force winds.


Deep tropical moisture over the SW Caribbean is interacting with
diffluent flow aloft to support clusters of moderate to strong
convection generally S of 13N and W of 79W. East of this area of
convection a 1007 mb surface low was embedded in the eastern
extension of the EPAC monsoon trough. A surface trough over the
eastern Caribbean extends from 19N64W to 11N66W and supports
scattered showers and isolated thunderstorms over Puerto Rico,
the Virgin Islands and the Lesser Antilles.The remainder of the
Caribbean is generally void of convection. High pressure north
of the region supports fresh to locally strong trades over the
Central Caribbean generally between 70W and 82W, and moderate
trades elsewhere. Little change is expected over the next 48


Increasing deep layered moisture from the southwest Caribbean is
advecting over Hispaniola. This was reflected in the 1200 UTC
rawinsonde from Santo Domingo which indicated moisture to about
560 millibars and TPW values of 1.8 inches. Currently multi-
layered clouds with scattered showers are occurring over the
island. Additional moisture from a surface trough over the
eastern Caribbean will support scattered showers Wed through


Strong high pressure anchored over the NW Atlc waters extends a
ridge axis SSW covering the SW N Atlc waters generally W of 58W.
In the central Atlc, a mid to upper level low with associated
trough continues to support a cold front extending from 31N45W
SW to to 28N50W to 27N62W. Gale force winds are N of 29N W of
this front to 54W. See special features section for further
details. A middle level low near 47N32W supports another frontal
system analyzed as a stationary front along 31N35W SW to 23N50W
to 19N60W. Scattered showers and isolated tstms are within 180
nm east of the front and N of 25N. This front is forecast to
dissipate within the next 24 hours. High pressure centered over
Spain extends SW and covers the remainder of the eastern

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