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Atlantic Tropical Weather Discussion



000
AXNT20 KNHC 220001
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
701 PM EST Sat Jan 21 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.

...SPECIAL FEATURES... 

...GULF OF MEXICO GALE WARNING...

A strong cold front is forecast to move off the Texas coast
overnight with W to NW winds increasing to 30-35 KT shortly after
sunrise Sunday with seas building to 11 FT. By Sunday afternoon W
to NW winds of 30-40 KT spread over the northern half of the Gulf
with seas building to 16 FT. By late Sunday night the broad fetch
of gale force W to NW winds builds seas to 20 FT.  

...SW N ATLANTIC GALE WARNING...

The same cold front noted above will sweep eastward into the
southwest N Atlantic with SW winds increasing to 30-35 KT N of 31N
W of 77W by Sunday evening with seas building to 13 FT. 

Please read the latest High Seas Forecast under AWIPS/WMO headers
MIAHSFAT2/FZNT02 KNHC for more details.

...ITCZ/MONSOON TROUGH...

The Monsoon Trough passes through Liberia near 07N11W and
immediately transitions the ITCZ near 07N12W which continues 
through 03N20W to 01N30W to the equator along 41W. Scattered 
moderate isolated strong convection was noted from 01S to 05N 
between 05W and 15W...and along the equator between 15W and 23W. 

...DISCUSSION...

...THE GULF OF MEXICO...

Broad complex mid-to upper level troughing over the southern 
Plains extends into the NW half of the Gulf of Mexico. Several 
well defined cyclonic circulations were noted within the area, one
over the Texas Panhandle and the other in the vicinity of the 
ARKLATEX. Satellite derived winds at 250 MB were on the order of 
65-80 KT along the northern Gulf. Strong subsidence prevailed over
most of the Gulf. Further east, a mid-to upper level ridge axis
along 76W was retreating away from the eastern Gulf. 

At the surface, a weakening stationary front was along the Gulf
coast with increasing S winds noted over most of the Gulf E of
95W. These winds were confirmed by an earlier ASCAT pass in the
central Gulf. Scattered thunderstorms were developing along the
Gulf coast in the vicinity of the stationary front. Mostly clear
skies prevailed over the Gulf itself with skies becoming 
scattered to broken toward and within 90 NM of the coast.
Deepening low pressure over the Tennessee valley will drag a 
strong cold front off the Texas coast overnight with W to NW 
winds increasing to 30-35 KT shortly after sunrise Sunday with 
seas building to 11 FT. The front will sweep rapidly E and extend 
from the Florida Big Bend into the SW corner of the Gulf of Mexico
by SUN afternoon. Gale- force winds of 30-40 KT behind the front 
by late SUN over the northern half of the Gulf will allow seas to 
build to 15 to 20 FT. Conditions will improve gradually from west 
to east Monday night through Tuesday night as high pressure builds
in behind the front.

...THE CARIBBEAN SEA...

Broad middle-to-upper level anticyclonic flow covers the Caribbean
W of 70W with winds primarily from the W to NW. A downstream
trough was digging along 63W. Strong deep layered subsidence
dominated the entire basin. 

At the surface, the tail end of a dissipating cold front extended
into Puerto Rico with otherwise sub-normal trade winds noted. 
Earlier scatterometer passes indicated NE to E winds of 10-15 KT 
over the basin. The only exception was fresh to strong E to SE 
winds over the Gulf of Honduras. 

...HISPANIOLA...

Upper level NW winds and comparatively drier air in subsidence
prevailed over Hispaniola. The 12Z rawindsonde from Santo Domingo
showed a strong capping trade wind inversion at 780 MB with sub-
normal precipitable water values of 0.73 inches. Visible
satellite imagery indicated patches of low clouds in otherwise 
fair conditions. Little change is expected over the next few days. 

...THE ATLANTIC OCEAN...

A deep layered central Atlantic trough N of 20N between 50W and
60W. This trough is supporting a cold front that passes through 
32N42W to 28N46W which became stationary to a 1014 MB surface low
near 25N52W then continued as a weakening cold front through
20N60W to Puerto Rico. Scattered moderate to strong convection was 
developing within 120 Nm E of the cold front N of 28N.  

A surface ridge, to the east of the central Atlantic cold front, 
extends from a 1026 mb high pressure center near 33N26W through 
25N35W to 18N45W. 

A 1017 mb high pressure center near 24N69W to the northeast of 
the Bahamas. Surface anticyclonic flow covers the area from 18N 
to 30N between 60W and the southeast coast. 

For additional information please visit 
http://www.hurricanes.gov/marine

$$
Cobb