Tropical Weather Discussion
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AXNT20 KNHC 200604

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
105 AM EST Fri Jan 20 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
0530 UTC.


A cold front is over the W Atlantic from 32N59W to 25.5N66W to
28N76W moving east. Gale force winds S to SW winds of 30 to 35 kt
are noted N of 27N within 90 NM east of the front. W to NW winds
of 25 to 35 KT were noted N of 29N west of the front to 67W. Seas
were 8 to 12 FT. Gale force winds are forecast to persist E of
front for the next 48 hours. See latest NWS High Seas Forecast
under AWIPS/WMO headers HSFAT2/FZNT02 KNHC for more details.


The Monsoon Trough extends from the African coast near 07N11W to
04N11W. The Intertropical Convergence Zone continues from 04N11W
to 02N30W to the coast of South America near 02S43W. Scattered
moderate isolated strong convection is from 02S-03N between 35W-
44W...and from 01S-05N between 25W-33W.



As of 2100 UTC a dissipating cold front extended from near Lake
Charles Louisiana to 25N97W with scattered moderate convection
within 90 NM of the front. A prefrontal squall line with numerous
showers and thunderstorms extended from Biloxi Mississippi to
27N91W. Scattered showers and isolated thunderstorms were noted
within 60 NM east of the front. Generally fair conditions
prevailed over the remainder of the Gulf. Fresh to strong S to SW
winds were noted ahead of the prefrontal squall line with light
and variable winds behind the dissipating front. Winds along the
immediate coast of Texas were turning more to the southeast in
advance of a stronger area of low pressure over northern Texas. In
the upper levels, a sharpening negatively-tilted mid-to upper
level trough extends from a cyclonic circulation over Kansas SSE
into the far NW Gulf. Strong upper level subsidence was sweeping
around the base of the trough along the upper Texas coast.
Strongly diffluent flow was noted ahead of the trough axis over
the northern Gulf which aided in maintaining the pre-frontal
squall line.


A 1422 UTC ASCAT scatterometer pass indicated 20-25 KT trade
winds over the Caribbean Sea S of 17N between 70W and 80W
with stronger winds of 25-30 KT within 90 NM of the coast of
Colombia. Moderate to locally fresh winds were noted elsewhere
over the basin. Scattered low-topped showers were noted inland
over Nicaragua, Honduras, and Guatemala. Otherwise mostly fair
conditions prevailed. In the upper levels, an upper level ridge
is over the W Caribbean W of 72W with a downstream upper level
trough over the E Caribbean. Very strong subsidence dominated the
entire Caribbean.


Strong upper level subsidence prevailed in the vicinity of the
island with moderate NW flow aloft. The 12Z rawindsondes from San
Juan, Puerto Rico and Santo Domingo both verified the existence of
very dry air above 800 MB. Precipitable water values of 0.92 and
0.65 inches were noted at the respective locations. Little change
is expected over the next 24 hours.


A weak 1017 mb high is centered over the Bahamas near 25N77W. A
cold front is presently over the W Atlantic from 32N59W to 25N66.5W
to 28N76W moving east. Scattered showers and isolated
thunderstorms were noted within 90-120 NM east of the front.
Strong winds were noted either side of the front with gale force
winds occuring N of 27N within 90 NM east of the front and N of
29N to 67W. Refer to the special features section above for
additional information. A dissipating stationary front is over
the far E Atlantic extending from 32N26W to 28N43W. 1025 MB high
pressure centered near 33N31W was bridging through the front and
dominated the flow over the Atlantic from the ITCZ between the
coast of Africa and 45W.

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