Tropical Weather Discussion
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AXNT20 KNHC 210513

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
113 AM EDT Mon May 21 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 0000 UTC surface analysis and satellite imagery through
0400 UTC.


An upper-level trough extends across the eastern Gulf of Mexico
and western Caribbean, with diffluent flow aloft prevailing
across the Florida Peninsula, the western Atlantic, and
Caribbean, to the east of the upper trough`s axis. This pattern is
drawing deep tropical moisture northward from the SW Caribbean
between 76W and 84W and is supporting scattered to numerous
moderate convection along this corridor. This activity is expected
to continue through at least Tuesday, with heavy rainfall and
flooding possible over the land areas affected.


An eastern central Atlantic tropical wave has an axis that
extends from 13N31W to 00N33W, moving W at 10 to 15 kt. This wave
is embedded in a sharp 700 mb trough. Although deep moisture
accompanies the wave, subsidence from aloft is inhibiting
convection except over the southern portion. Scattered moderate
convection is from 00N to 04N between 29W and 35W.

A central Atlantic tropical wave has an axis that extends from
17N56W to 05N57W, moving W at 5 to 10 kt. This wave continues to
appear as a 700 mb trough and has a poleward surge in moisture
associated with it. Scattered showers and isolated thunderstorms
are within 300 nm of either side of the trough axis. This trough
will enter the E Caribbean by Tuesday and then will become ill


The monsoon trough passes through coastal Africa near 11N15W to
05N20W. The ITCZ extends from 05N20W to 03N31W, then resumes west
of a tropical wave from 01N35W to 00N51W. Besides the convection
associated with the wave, isolated moderate convection is from 01N
to 07N between 11W and 28W.



An upper-level trough prevails across the eastern Gulf, with an
axis along 85W. Diffluent flow aloft east of the trough is
bringing tropical moisture over the far east Gulf and western
Atlantic waters affecting the Florida Peninsula and Florida
Straits/Keys. Please refer to the Special Features section above for
more details. A surface trough is embedded underneath the upper
trough, and as of 0300 UTC has an axis that extends from 30N84W
to near 23N85W. A weak ridge axis extends across the remainder of
the basin along 30N producing mainly gentle to moderate winds. A
weakening line of thunderstorms has emerged within 120 nm E of the
SE Texas coast as of 0300 UTC and will likely affect those waters
until sunrise.

The surface trough is expected move NW across the eastern Gulf
through today. The upper-level trough over the eastern Gulf will
remain nearly stationary through the first half of this week,
supporting ongoing convection over the eastern Gulf.


An upper-level trough extends over the eastern Gulf of Mexico and
western Caribbean. A surface trough is over the western Caribbean
and as of 0300 UTC had an axis extending from 21N85W to 11N83W.
The combination of upper- level diffluence on the eastern side of
the upper-level trough and convergence associated with the surface
trough is supporting scattered to numerous moderate convection
across the Caribbean waters between 78W and 84W. Broad high
pressure over the subtropical Atlantic continues to support
moderate to fresh tradewinds over most of the basin, except fresh
to strong winds over the central Caribbean. Wave heights of 8 to 9
ft persist over the central Caribbean as confirmed by both satellite
altimeters and current buoy data.

Over the next day or so, the upper-level trough and surface
trough will remain nearly stationary enhancing shower and
thunderstorm activity over the western Caribbean. The surface
ridging pattern over the Atlantic will persist, keeping a similar
wind profile in place across the basin into the middle of this


Diffluent flow aloft to the east of an upper-level trough
currently over the eastern Gulf of Mexico, combined with a surface
trough extending just offshore of northern Florida is supporting
scattered to numerous moderate convection across Florida, the
Bahamas, and Atlantic waters mainly west of 76W. To the east, high
pressure centered over the central Atlantic spans across the basin.
Surface observations and latest scatterometer data indicate
prevailing fresh to locally strong southeast winds over the
Bahamas as well as within a few hundred miles north of Hispaniola
and Cuba. A recent altimeter pass indicates wave heights of 8 to
9 ft over these waters as far N as 26N outside of the Bahamas.
Moderate to fresh tradewinds are occurring elsewhere across the
central and western Atlantic south of 27N. Gentle to moderate
winds cover the central Atlantic north of 27N. Moderate to
occasionally fresh northeast winds are occurring over the eastern

The overall pattern will change little through the next 24 hours.
Therefore, the chances for heavy rainfall over the Florida
Peninsula, Bahamas, and western Atlantic will continue.

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