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Atlantic Tropical Weather Discussion

AXNT20 KNHC 201158

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
758 AM EDT Sun May 20 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 0600 UTC surface analysis and satellite imagery through 
1145 UTC.


An upper-level trough extends across the eastern Gulf of Mexico
and western Caribbean, with diffluent flow aloft prevailing 
across the Florida Peninsula and 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 83W and is supporting numerous moderate and 
isolated strong convection along this corridor. This activity is 
expected to continue through early this upcoming week, with heavy
rainfall and flooding possible over the land areas affected.


A newly analyzed tropical wave has an axis that extends from
13N28W to 02N29W, moving W at around 15 kt. This wave is embedded
in a sharp 700 mb trough and is helping to enhance convection S of
4N between 25W and 31W. 

A central Atlantic tropical wave has an axis that extends from
14N54W to 03N56W, moving W at 5 to 10 kt. This wave has slowed 
down its forward motion over the past 24 hours and is expected to 
become diffuse east of the Caribbean over the next couple of days.
Numerous showers and isolated moderate convection are within 300 
nm of either side of the wave axis. 


The monsoon trough passes through the coastal sections of Guinea-
Bissau near 12N16W to 03N22W. The ITCZ continues from 03N22W to 
01N35W to the Brazil coast near 00N49W. Besides the convection 
associated with the tropical wave, isolated moderate convection 
is from 01N to 05N between 12W and 51W.



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 for 
more details. A surface trough is embedded within this convection,
extending from 27N80W to 25N82W, as indicated by an overnight 
scatterometer pass. A weak ridge axis extends across the remainder
of the basin along 30N producing mainly gentle to moderate winds.

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


An upper-level trough extends over the eastern Gulf of mexico and
western Caribbean. An overnight scatterometer pass indicated that
a surface trough has developed over the NW Caribbean, with the
trough axis extending from 21N81W to 17N82W. The combination of 
upper-level diffluence on the eastern side of the upper trough and
convergence associated with the surface trough is supporting 
scattered to numerous moderate convection across the Caribbean 
waters between 76W and 83W. 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 10 ft persist 
over the central Caribbean as confirmed by a recent satellite 
altimeter pass and current buoy data.

Over the next couple of days, the upper-level trough will remain 
in place 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 upcoming week. 


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 east-central Florida is 
supporting scattered to numerous moderate convection across 
Florida, the Bahamas, and Atlantic waters mainly west of 76W. High
pressure centered over the N Central Atlantic spans the Atlantic 
waters east of Florida to the northwest African coast. Surface
observations and latest scatterometer data indicate prevailing 
fresh to locally strong southeast winds over a portion of the 
Bahamas as well as within a few hundred miles N of Hispaniola. A 
recent altimeter pass indicates wave heights of 8 to 9 ft over 
these waters 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 north to northeast 
winds are occurring over the eastern Atlantic.

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

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