Tropical Weather Discussion

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Tropical Weather Discussion (NHC/TPC):
NWS National Hurricane Center Miami FL
149 PM EDT Fri Jun 22 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.

...TROPICAL WAVES...

A tropical wave is emerging off the west coast of Africa and will
likely be added to the 1800 UTC surface map. The Hovmoller Diagram
indicates the westward propagation of the wave. A large cluster 
of moderate to isolated strong convection is noted from 6N-10N 
between 11W-15W in association with this system.

The axis of a tropical wave extends from 16N32W to 04N34W. African
dust surrounds the wave limiting convection. A patch of low level
moisture is near the northern end of the wave's axis.

A tropical wave is along 50W from 6N-18N, moving W at 20 kt. A 
cluster of moderate to isolated strong convection is seen near the
southern end of the wave's axis from 06N-08N between 50W and 52W.
This wave will pass west of 55W early on Sat, and move across the
Windward Islands by Sat night. 

The axis of a tropical wave extends from 18N65W to the coast of
Venezuela near 10N66W, moving W at 10-15 knots. The wave is
generating scattered moderate convection across the basin, mainly
E of 67W, including the Lesser Antilles, where showers and 
locally heavy rain have been reported. Upper diffluent ahead of an
upper-level trough that now crosses Hispaniola is helping to 
induce this convective activity. Moisture related to this wave 
will spread out over Puerto Rico and the UK/US Virgin Islands 
today, reaching Dominican Republic tonight into Sat, increasing 
the likelihood of showers with embedded tstms. A recent scatterometer
pass clearly indicates the wind shift associated with the wave's 
axis.

A tropical wave extends from the westernmost tip of Jamaica to
eastern Panama near 09N79W. Lingering moisture from this tropical 
wave will continue to support scattered showers and isolated 
thunderstorms across Jamaica and regional waters today. Scattered
showers and isolated tstms are observed between Haiti and 
Jamaica while some shower activity is near the wave's axis from
15N-18N. Abundant tropical moisture will persist over the NW 
Caribbean and central America through at least early Sat. 
 
...MONSOON TROUGH/ITCZ...
     
The monsoon trough passes through the coastal sections of Guinea
near 10N14W to 06N26W. The ITCZ continues from 06N26W to 04N40W to
the coast of Guyana near 07N58.5W. Outside of the convection 
associated with the tropical waves, scattered moderate convection
is within about 90 nm N of the ITCZ W of 52W. Isolated moderate
convection is from 07N-09N between 38W-47W.

...DISCUSSION...

GULF OF MEXICO...

A weak ridge dominates the Gulf waters, producing gentle to 
moderate winds with seas of 3-5 ft over the western Gulf, and 
seas of 3 ft or less across the eastern Gulf. Weak ridging will 
persist from the southeast Gulf to the coast of Texas through 
early next week. SE return flow will increase slightly over the 
western Gulf between the ridge and weak low pressure over northern
Mexico starting Sat night.

A surface trough will develop in the Yucatan Peninsula each 
afternoon, then move westward across the SW Gulf during the 
overnight hours, accompanied by fresh to occasionally strong east
to southeast winds.

CARIBBEAN SEA...

A tropical wave is moving across the western Caribbean. Another 
tropical wave is over the eastern Caribbean. Please, see Tropical
Waves section for more details. Expect increasing showers and 
isolated thunderstorms in association with the passage of these 
tropical waves.

Trade winds over the south central Caribbean will strengthen and 
expand in areal coverage across the basin through early next week 
as high pressure builds across the central Atlantic. Winds could 
reach near gale force along the coast of Colombia by Sat night. 

ATLANTIC OCEAN...

An upper-level trough extends from a cyclonic circulation centered
near 22N69W across Hispaniola and the waters between eastern Cuba
and Jamaica. The low continues to generates scattered showers and
tstms mainly over the waters from 23N to 26N between 68W and 72W.
Lightning density indicates frequent lightning with some of the
observed convection.

High pressure of 1029 mb centered near 34N37W extends a ridge 
westward across the forecast area. Fresh trades are noted along 
the southern periphery of the ridge. This high pressure will 
slowly shift westward through Sat night, then remain nearly 
stationary near 30N55W through Tue night. The tightening pressure
gradient that results over the central Atlantic will support 
fresh to strong trade winds and seas of 8-9 ft E of the Lesser 
Antilles to about 45W by early Sat morning. These marine 
conditions will persist on Sun with seas building up to 10 ft.
Fresh to strong winds are also expected off Hispaniola at night.

The Saharan Air Layer (SAL) from CIMSS and visible satellite 
imagery confirm the presence of African dust between the west 
coast of Africa and the Lesser Antilles, more concentrated E of 
50W.

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

$$
Graphical representation of waves, etc. on this image (NCEP/OPC) [more].
Various tropical satellite imagery available here

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