Tropical Weather Discussion
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AXNT20 KNHC 231722

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
122 PM EDT Tue May 23 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
1715 UTC.


A tropical wave extends from 12N21W to 04N22W, moving west about
10 kt. Scattered moderate to isolated strong convection is where
the wave meets the Monsoon Trough, mainly from 06N-08N between
20W-26W. The TPW animation shows a decent surge of moisture near
the wave axis.

A weak tropical wave extends from 13N57W to Suriname near 05N57W.
This wave was re-positioned on the 0600 UTC analysis/surface map.
The TPW animation shows a modest surge of moisture near the wave

A tropical wave is moving across the Caribbean Sea. Its axis
extends from eastern Jamaica to 10N76W, moving west at about 15
kt. A small cluster of moderate convection is near the northern
end of the wave axis. Another cluster of moderate to isolated
strong convection is near the southern end of the wave axis,
mainly south of 10N east of 78W to the coast of Colombia. This
wave shows up pretty well on the TPW animation.


The Monsoon Trough enters the tropical Atlantic through the west
coast of Africa near 11N15W and continues to 06N21W, then resumes
west of the tropical wave along 21W/22W at 06N23W to 06N29W. The
ITCZ extends from 06N29W to 07N36W to 04N51W. Outside of the
convection associated with the aforementioned tropical wave,
scattered moderate convection is within about 90 nm N of the ITCZ
between 34W and 38W.



A cold front has entered the Gulf of Mexico, and currently
extends from SE Louisiana to southern Texas. A band of showers and
thunderstorms is ahead of the front. This system is forecast to
stall over the north-central Gulf tonight. The remainder of the
Gulf region is under the influence of a weak ridge, with axis
across Cuba and the Yucatan Peninsula. The pressure gradient
between the ridge and the frontal boundary is resulting in mainly
gentle to moderate E-SE winds over the Gulf. Higher winds are
noted just ahead of the front, especially within the area of
convection. The most recent scatterometer data reveal the wind
shift associated with a thermal trough that usually develops over
the Yucatan Peninsula during the evening hours and moves across
the SW Gulf during the overnight and early morning hours. A late
season cold front will enter the NW Gulf early Wednesday followed
by fresh northerly winds. Fresh to strong SW winds are expected
ahead of the front on Wednesday. Showers and tstms are also
possible ahead of the front. Computer model indicates that these
two fronts will merge by late Wednesday.


Convection continues to flare up across the SW Caribbean in
association with a northern displacement of the monsoon trough. A
tropical wave crossing the area is also helping to induce
some convective activity in this area. According to computer model
guidance, abundant moisture will persist in the SW Caribbean and
parts of Central America the remainder of the work week. Moderate
to fresh trades are observed across most of the east and central
Caribbean based on scatterometer data. These winds are expected to
expand across the eastern and central Caribbean on Wednesday as
high pressure builds again north of the area. Patches of low
level moisture, embedded in the trade wind flow, are observed
elsewhere across the region. Aloft, an upper-level trough extends
from eastern Cuba to the coast of Nicaragua. Abundant mid-to-upper
level moisture in noted on water vapor imagery ahead of this
trough. The Saharan Air Layer from UW-CIMSS and visible satellite
imagery continue to show the presence of african dust over the
Leeward Islands, the UK/US Virgin Islands and Puerto Rico where
dry and hazy conditions are prevaling.


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 during the next two days. In fact,
computer model suggests limited moisture across the island over
the next couple of days.


A cold front has entered the forecast area and extends from 31N35W
to 25N50W to 26N60W. This front will continue to move SE across
the central Atlantic through Thursday before dissipating. High
pressure prevails across the remainder of the Atlantic Ocean. A
1025 mb high pressure located near 33N59W follows the front and
will move eastward to a postition near 33N48W in about 24 hours.
Another high pressure center of 1021 mb located near 28N25W will
remain nearly stationary. By Wednesday night, strong to near gale
force winds are expected over the SW N Atlantic ahead of the next
cold front forecast to enter the discussion area on Thursday.

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