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Atlantic Tropical Weather Discussion

AXNT20 KNHC 251755

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
155 PM EDT Fri May 25 2018

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 
1730 UTC.


Subtropical Storm Alberto has formed in the northwest Caribbean, near
19.7N 86.8W at 25/1500 UTC or about 50 nm south of Cozumel, 
Mexico. Alberto is moving N-NE or 20 degrees at 5 kt. Estimated 
minimum central pressure is 1005 mb. Maximum sustained winds are 
35 kt with gusts to 45 kt. The storm is interacting with an upper
trough, causing it to be strongly sheared, exposing several low
level centers, and keeping scattered to numerous showers and
thunderstorms around 60 nm east of the mean low level center. The
forecast calls for gradual development as Alberto moves northward
into the south central Gulf of Mexico, as either a tropical or
subtropical storm. See latest NHC Forecast/Advisory under 
AWIPS/WMO headers MIATCMAT1/WTNT21 KNHC for more information. 


A tropical wave is analyzed near 17W/18W south of 13N. The wave 
shows up well on lower level PW imagery. Clusters of thunderstorms
are active where the tropical wave intersects the monsoon trough. 

A tropical wave is moving eastward at 10 to 15 kt through French 
Guiana with the axis extending northward to 12N. The 12Z sounding
from Cayenne showed a crisp wind shift in the lower levels
compared to the day prior. This is indicative a tropical wave
passage. The wave is in a moderate moist environment that is 
supporting isolated showers within 150 nm either side of the wave 


The monsoon trough extends from the coast of Guinea, Africa near 
11N15W and continues to 04N20W to 02N30W. The ITCZ continues from
02N30W to 01S45W. Scattered moderate is from 03N to 06N between
15W and 25W.  



Broad cyclonic turning is noted across the eastern Gulf of Mexico,
ahead of the newly formed Subtropical Storm Alberto centered over
the northwest Caribbean. A surface trough is analyzed from the
northeast Gulf through the south central Gulf. Scattered to
numerous showers and thunderstorms are noted on regional radar
displays over the far southeast Gulf and in the Straits of
Florida. Weak ridging extends from the Lower Mississippi Valley to
across the Texas coast. A ship reported just north of the Yucatan
Channel reported E winds at 25 kt. A concurrent altimeter pass
showed seas to 8 ft near the Yucatan Channel. Elsewhere buoy and 
C-MAN reports from the southeast Gulf and Florida Keys indicate 
generally moderate E to SE winds, and seas . Lighter winds and 2
to 4 ft seas are noted elsewhere. A sharp upper trough is moving
across the Lower Mississippi Valley and north central Gulf. This
is supporting scattered showers and thunderstorms from around 70
nm south of Cameron Louisiana to Mobile Bay. 

The main forecast issue remains the track and development of
Subtropical Storm Alberto. Per the latest forecast, Alberto will 
intensify while moving northward, likely transition to a fully
tropical system through 48 hours, and reach the northern Gulf 
coast near 31.0N 89.1W on Tuesday morning. See latest NHC 
Forecast/Advisory under AWIPS/WMO headers MIATCMAT1/WTNT21 KNHC 
for more information. 


An altimeter pass from 1130 UTC indicated 8 to 10 ft seas over the
far northwest Caribbean, north of 19N and west of 85W associated
with the new formed Subtropical Storm Alberto. Numerous strong
convection scattered showers and thunderstorms are also active in
two prominent lines across the western Caribbean. One line of 
thunderstorms reaches from eastern Honduras to near the Isle of 
Youth, and another extends from northeast Nicaragua to just south 
of Grand Cayman Island. Elsewhere, fresh trades are noted across
the remainder of the Caribbean, with fresh to strong winds over
the south central Caribbean observed in a 14 UTC scatterometer 
satellite pass. 

For the forecast, Alberto will move north into the
Gulf of Mexico through tonight. A  band of fresh to locally 
strong SE winds will persist in the wake of Alberto, from the
south central Caribbean toward the Yucatan Channel into Sun.
Meanwhile winds will diminish over the northwest Caribbean, with
seas subsiding shortly thereafter. Little change is expected
through mid week.


A few showers persist over the northern Bahamas, mainly in the
form of streamers emanating off the islands toward South Florida.
The remainder of the Atlantic is under the influence of a broad 
surface ridge centered by a 1027 mb high near 32N35W. This high 
is supporting moderate winds in the Bahama Bank and Atlantic 
passages to the Caribbean. SE to S winds will increase to fresh 
to locally strong W of 77W Sat night through Sun night as Alberto
moves north through the eastern Gulf of Mexico.

The high pressure near 32N35W is supporting moderate to fresh
trade winds over the central and eastern Atlantic. Little change
is expected through early next week.

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