Tropical Weather Discussion
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AXNT20 KNHC 221030

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
630 AM EDT Mon May 22 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 0600 UTC surface analysis and satellite imagery through
1030 UTC.


A tropical wave came off the west African coast earlier this
morning. The wave axis extends from 12N18W to 04N18W and is
embedded in a neutral to favorable wind shear environment and
abundant low level moisture is present according to CIRA LPW
imagery. Water vapor imagery show the way is under a col or
divergent environment aloft that supports scattered moderate
convection from 04N-15N between 16W-24W.

A tropical wave is in the central Atlantic with axis extending
from 12N35W to 04N36W, moving west at 10 kt within the last 24
hours. The wave is in a region of unfavorable wind shear and most
of the wave environment is covered by Saharan dry air and dust,
which is hindering convection at the time.

A tropical wave is in the central Caribbean with axis extending
from 18N67W to inland Venezuela near 11N69W, moving west at 15-20
kt within the last 24 hours. Similar to the wave in the central
Atlantic, the wave environment is characterized by unfavorable
wind shear, which support the lack of deep convection at the time.


The Monsoon Trough enters the tropical Atlantic near 09N13W and
continues to 07N16W. The ITCZ extends from 06N23W to 05N33W, then
resumes west of a tropical wave at 06N38W to the coast of Guyana
near 07N58W. Scattered moderate convection is from 03N-07N
between 07W-14W and from 04N-13N between 43W-60W.



Mosaic Doppler Radar and satellite imagery show numerous heavy
showers and tstms are in the north-central and northwest Gulf
ahead of a stationary front that extends along the coast of
Texas. Moisture inflow from the Caribbean by SE wind flow and
upper level diffluence between a ridge covering the western Gulf
and the trough that support the front support this convection N of
23N W of 90W. Gusty winds to near 30 kt are seen per buoy
observations near the convective activity over the NW Gulf. A
thermal trough is over the Bay of Campeche extending 24N92W to
17N93W lacking convection, however it supports fresh E-SE winds
within 90 nm off the western Yucatan Peninsula. Otherwise,
scatterometer data show mainly gentle to moderate return flow in
the basin, except for the NE gulf where variable gentle to light
winds are observed. The front will continue to stall through
tonight when it will transition to a weak cold front to merge
with a stronger cold front that will exit the coast of Texas early
Wednesday morning.


Convection in the SW Caribbean has significantly reduced due in
part to unfavorable wind shear across the region, however upper
level divergence prevails and along with shallow moisture support
scattered to isolated showers S of 12N and within 90 nm off the
coast of Nicaragua. The pressure gradient between strong high
pressure in the Atlantic and lower pressure across the southern
basin continue to support fresh to strong winds off the Colombia
coast S of 13.5N between 70W and 76W. Latest scatterometer data
indicate the presence of moderate trades across the remainder
basin and fresh easterlies in the Gulf of Honduras. Otherwise, a
tropical wave lacking convection is entering the central Caribbean.
For further details see the tropical waves section. The wave will
move into the SW Caribbean Monday night and Tuesday while a new
tropical wave enters the eastern basin Wednesday.


Daytime heating, local sea breezes and mountain upslope lifting
will combine with available moisture to produce scattered
showers and isolated thunderstorms mainly during the afternoon
and early evening hours the next two days.


Surface high pressure prevails in the SW N Atlc being anchored by
a 1021 mb high near 30N70W that is forecast dissipate tonight. In
the central Atlc, a surface trough extends from 26N52W to 20N63W.
Isolated showers are within 60 nm either side of the trough N of
25N. A broad surface ridge covers the remainder central and
eastern Atlc with the center of high pressure being located near
28N31W, which is forecast to dissipate tonight. A cold front will
enter the north central Atlc waters this evening. Otherwise,
surface high pressure will dominate elsewhere.

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