[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 260004
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
804 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 1800 UTC surface analysis and satellite imagery through
2300 UTC.

...SPECIAL FEATURES...

The center of Subtropical Storm Alberto, at 25/2100 UTC, is near
19.4N 86.3W, or about 160 km SSE of COZUMEL MEXICO, and about
315 km SSW of the western tip of Cuba. The estimated minimum
central pressure is 1005 mb. The maximum sustained wind speeds are
35 knots with gusts to 45 knots. It is moving eastward or 90
degrees 2 knots. 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. The PUBLIC ADVISORIES about Subtropical Storm
Alberto are being listed under the WMO header WTNT31 KNHC, and
under the AWIPS header MIATCPAT1. The FORECAST/ADVISORIES about
Subtropical Storm Alberto are being listed under the WMO header
WTNT21 KNHC, and under the AWIPS header MIATCMAT1.

...TROPICAL WAVES...

An Atlantic Ocean tropical wave is along 17W/18W from 13N
southward. The wave shows up well on lower level PW imagery.
Clusters of thunderstorms are active where the tropical wave
intersects the monsoon trough.

An Atlantic Ocean tropical wave is along 53W/54W, moving across
Suriname. The 25/12Z 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.

Alberto will intensify while moving northward, reaching 22.5N
85.7W Sat afternoon with wind speeds of 45 kt gusting to 55 kt.
Alberto will transition to a tropical cyclone Sun afternoon
centered near 26.8N 86.2W with wind speeds of 55 kt gusting to 65
kt, near 29.0N 87.8W Mon afternoon with wind speeds of 55 kt
gusting to 65 kt, then inland near 31.7N 88.6W Tuesday afternoon.

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.

Alberto will move into the Gulf of Mexico Sat, with winds and
seas decreasing over the western Caribbean thereafter. Elsewhere,
high pressure in the central Atlc will maintain fresh to strong
trade winds in the central Caribbean through early next week with
strongest winds along the coast of Colombia and in the Gulf of
Venezuela.

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.
Moderate to fresh tradewinds are expected S of 25N through Monday,
pulsing to fresh to strong offshore of northern Hispaniola during
the afternoon through evening hours each day. SE to S winds will
increase to fresh to locally strong W of 77W Sat night through Sun
night as the pressure gradient tightens between Subtropical Storm
Alberto in the Gulf of Mexico and high pressure over the area.
Those conditions should improve by Tue as the pres gradient
slackens.

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

$$
MT
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