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000
AXNT20 KNHC 251755
TWDAT

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.


...SPECIAL FEATURES...

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.


...TROPICAL WAVES...

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 axis.


...MONSOON TROUGH/ITCZ...

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.


...DISCUSSION

GULF OF MEXICO...

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.

CARIBBEAN SEA...

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.

ATLANTIC OCEAN...

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.

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

$$ Christensen

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