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Atlantic Tropical Weather Discussion

AXNT20 KNHC 201646

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1246 PM EDT Wed Jun 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 1200 UTC surface analysis and satellite imagery through 
1715 UTC.


There are four tropical waves between the west coast of Africa 
and the Lesser Antilles.

A tropical wave is added to the 1200 UTC analysis/surface map 
along 18W from 03N-11N. The Hovmoller Diagram shows the westward
propagation of the wave, that coincides with a modest surge of
moistened air based on the TPW product. A cluster of moderate
convection's just ahead of the wave's axis from 5N-8N between

A tropical wave is along 27W from 3N-11N, moving W at 20 knots. 
This wave shows up well as a low amplitude moisture surge on the
TPW animation. Scattered moderate convection is noted where the 
wave meets the ITCZ.

A tropical wave is along 38W from 3N-11N, moving W at about 15 
knots. African dust surrounds the wave limiting convection. the
wave is well depicted in the moisture product. Scattered moderate
convection is also noted where the wave meets the ITCZ.

Another tropical wave is along 55W/56W from 5N-14N, moving W 
at about 10 knots. The TPW animation shows a surge of moistened
air near the wave's axis. A cluster of moderate convection is 
along the wave's axis from 9.5N-11.5N between 55W-57W. Moisture 
associated with this wave will reach the Windward Islands by Thu
morning. The wave will move across the eastern Caribbean Thu
afternoon through Fri night. The associated moisture is forecast
by the GFS computer model to spread out reaching Puerto Rico on 

A tropical wave is moving across the eastern Caribbean. Its axis
is along 69W, and extends from eastern Dominican Republic to the 
coast of Venezuela. The wave combined with an upper-level trough 
crossing eastern Cuba is producing scattered showers and tstms 
from eastern Dominican Republic to the Virgin Islands, including 
the Mona Passage. Lingering moisture from this tropical wave will 
continue to support showers and isolated thunderstorms across most
of Puerto Rico today. Moisture and instability related to this 
wave will affect Hispaniola today and Thu, reaching eastern Cuba 
by late Thu.


The monsoon trough passes through the coastal sections of Sierra
Leone near 08N13W to 06N26W. The ITCZ continues from 06N26W to 
05N40W to 04N48W to 07N55W. Scattered moderate convection is 
roughly noted from 3N-7N between 18W-40W.



A 1005 mb low pressure centered inland in the Deep South of Texas
near 27N98W continues to produce a large area of showers and tstms
over the western Gulf coast. Similar convective activity is flared
up over the west-central Gulf, particularly N of 21N W of 95W.
This slow moving system will continue to deliver heavy rainfall
and flooding along the coast of Texas into Louisiana. A widespread
3 to 5 inches of rainfall is possible over this region through 
Thu morning with isolated pockets of heavier amounts expected. A
1016 mb high pressure is analyzed over the eastern Gulf near
27N86W. The pressure gradient between the high pressure and the
low over southern Texas will support fresh SE winds in the NW 
Gulf through this evening. Abundant tropical moisture will persist
from Texas to Florida across the northern Gulf through late Thu.

A typical pattern, with a ridge, and a surface trough developing 
over the Yucatan Peninsula each afternoon, then moving westward 
across the SW Gulf during overnight hours, accompanied by fresh 
east to southeast winds, is expected to persist Thu through the 


A tropical wave is moving across the eastern Caribbean. Another
tropical wave is forecast to reach the Windward Islands by Thu
morning. Please, see Tropical Waves section for details. Expect
increasing showers and isolated thunderstorms in association with
the passage of these waves.

High pressure N of area is forecast to strengthen over the next
couple of days while moving westward. As a result, the trade winds 
across the south-central Caribbean will strengthen on Thursday, 
then expand in coverage across the basin this weekend. Strong 
winds will affect the Gulf of Honduras tonight, then return Fri 
night through Sun night. 

An upper-level trough extends from a cyclonic circulation located
over the western Atlantic near 27N65W to another cyclonic
circulation over the NW Caribbean. This feature is a TUTT 
(Tropical Upper-Tropospheric Trough) that extends from the 
Atlantic into the Caribbean during May to October. They are cold- 
core systems that exist mostly above 500 hPa. They are sources of 
clouds and precipitation. Currently, a SW flow on the SE side of 
this upper-level trough that also crosses eastern Cuba is helping 
to induce some shower and thunderstorm activity over the coast of 
Nicaragua and regional waters, just S of Hispaniola, and over 
Puerto Rico and the Virgin Islands.


As previously mentioned, an upper-level trough extends from a 
cyclonic circulation centered near 27N65W to eastern Cuba. 
A surface trough is analyzed from 28N60W to 27N70W to the NW 
Bahamas. Scattered showers and tstms are noted S of the trough to 
about 20N between 60W and 70W. A diffluent pattern aloft between
the upper-level trough and an anticyclonic circulation located E
of the Lesser Antilles is helping to induce this convective
activity. A ridge dominates the remainder of the Atlantic Ocean
with a 1028 mb high pressure situated near 34N30W. This system
will build westward over the region through Thu, bringing mainly
fresh trades across the Tropical N Atlantic waters, particularly S
of 19N W of 45W Fri night through Sun. A weak trough is expected 
to move into the northwest waters Fri through Sat night, with 
little effect.

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