[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 300001
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
801 PM EDT Thu Jun 29 2017

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
2315 UTC.

...SPECIAL FEATURES...

Please refer to the METEO-FRANCE High Seas Forecast, that is
listed on the website: WWW.METEOFRANCE.COM/PREVISIONS-METEO-
MARINE/BULLETIN/GRANDLARGE/METAREA2. Gale-force winds are being
forecast for the areas: AGADIR and TARFAYA and for CANARIAS LATE.
The OUTLOOK, for the 24 hours that follows the forecast that is
valid until 01/0000 UTC, consists of: N or NE gale or severe gale
in AGADIR and TARFAYA, and N or NE near gale or gale in CANARIAS.
Threat of near gale east of MADEIRA.

...TROPICAL WAVES...

A far eastern Atlantic tropical wave has its axis along 21W from
02N to 20N, moving westward at 10-15 kt. This wave remains
embedded within an envelope of southwesterly monsoonal moisture
that observed in latest satellite imagery to be present just
offshore the coast of Africa. Scattered moderate to isolated
strong convection is within 60 nm east of the axis from 09N to
12N. Scattered moderate convection is within 300 nm west of the
axis from 04N to 10N.

A surface trough is along 28W/29W from 18N to 25N. This trough is
part of the energy of the northern vorticity center that is
accompanying the above tropical wave. No significant deep
convection is noted with this feature.

A central Atlantic tropical wave has its axis along 45W/46W from
02N to 16N, moving westward at about 15 knots. A large plume
of Saharan African dust is observed to the north and northeast of
this wave. This appears to be suppressing deep convection from
developing along and near the wave axis for the time being. Only
isolated showers and thunderstorms are within 150 nm either side
of the wave axis from 08N to 12N. This wave is forecast to
enter the eastern Caribbean on Saturday.

A strong tropical wave is moving through the eastern Caribbean
Sea, and has its axis along a position from near 19.5N66W to
15N67W to inland Venezuela near 10N68W. It is moving westward
at about 16 knots. This wave maintains a good track history going
back several days, and continues to mark the leading edge of an
extensive area of unsettled weather consisting of scattered
showers and thunderstorms, some of which of capable of producing
gusty winds This activity is confined to north of 13N east of the
wave axis to across the Windward Islands and portions of Puerto
Rico. Scattered showers and isolated thunderstorms are noted ahead
of the wave to near 73W and south of 15N. The wave will move
across the remainder of the central Caribbean through Friday
night, and across the western Caribbean on Saturday and Saturday
night.

The earlier western Caribbean tropical wave that was along 89W/90W
continues to move inland, and is discussed in the the eastern
Pacific Tropical Weather Discussion.

...ITCZ/MONSOON TROUGH...

The Monsoon Trough axis extends from inland Africa to the
far eastern Atlantic near 12N22W. The Intertropical Convergence
Zone then extends from 12N22W to 11N33W to just east of the
tropical wave along 45W/46W. It resumes from just west of
the same wave to 08N51W to 09N59W. Scattered moderate convection
is within 120 nm north of the axis between 51W and 55W. Similar
activity is south of the ITCZ axis within 30 nm of line from
08N30W to 07N34W.

...DISCUSSION...

...THE GULF OF MEXICO...

A mid to upper-level trough stretches from northern Louisiana
southwest to along the Texas coast and to NE Mexico. An upper
level anticyclonic circulation is centered over the eastern Gulf
near 26N85W. The associated anticyclonic flow covers just about
the entire basin, except over the far western portion south of 27N
where the flow is west to northwest south of the base of the
mid-upper trough. The area of deep moisture that affected the
NW and north-central Gulf the past few days has lifted northward
and inland the SE U.S. The western periphery of the Atlantic high
pressure ridge is the main feature across the area controlling
the wind regime throughout keeping mainly moderate to fresh
southeast to south winds throughout, except for lighter winds in
the NE Gulf through Saturday. Presently, only isolated showers and
thunderstorms are noted over some portions of the Gulf. Scattered
showers and thunderstorms are increasing over the interior
of the Florida peninsula, with some of this activity moving
westward over Gulf waters adjacent to SW Florida.

...THE CARIBBEAN SEA...

An upper-level trough extends from 24N73W in the Atlantic Ocean
to across Hispaniola and south to 15N73W. With the exception of
convective activity associated with the eastern Caribbean tropical
wave as described above, the other scattered shower and
thunderstorm activity is that which is confined to the far SW
Caribbean just north of the eastern extension of the Pacific
monsoon trough that extends across Costa Rica. Otherwise over the
remainder of the central and western portions of the Caribbean,
isolated showers and thunderstorms are noted there. The scattered
showers and thunderstorms over the eastern Caribbean behind the
strong tropical wave described above will spread westward to the
central Caribbean Friday night through Saturday night. In the wake
of the moisture, Saharan African dust may move across portions of
the eastern Caribbean on Saturday.

...HISPANIOLA...

Upper-level cyclonic wind flow is moving across the area. An
upper level trough extends from 24N73W in the Atlantic Ocean,
across Hispaniola and to 15N73W. Subsidence aloft and resultant
dry air over the vicinity of the trough has spread southward to
cover Hispaniola, the Windward Passage and eastern Cuba. This is
limiting the coverage of shower and thunderstorm activity across
and near Hispaniola. Latest satellite imagery shows only a few
clusters of scattered showers and thunderstorms over the interior
of northern Haiti and over the far western section of the
Dominican Republic early this evening. Model guidance suggests
that upper cyclonic flow will continue for the next 24 hours or
so. Moisture associated with the strong eastern Caribbean
tropical wave is moving across the Mona Passage, and is
approaching the southeast portion of Hispaniola. As the tropical
wave nears the island tonight and into Friday, expect for this
moisture to bring increasing shower and thunderstorm activity to
most sections of the island into late on Friday. Gusty winds can
be expected with some of the shower and thunderstorms.

...THE ATLANTIC OCEAN...

An upper-level cyclonic circulation is located near 32N37W, and
is lifting northward. A trough extends from the cyclonic center to
20N40W and to near 10N48W. Only isolated showers moving westward
are possible north of 25N and between 36W and 46W. An upper-level
cyclonic circulation center is near 28N52W, with a trough
extending from it to near 20N55W and southwest to across
Hispaniola. A small upper-level cyclonic circulation is evident
over the far northwest portion of the area at 32N75W, with a
narrow trough stretching southeastward to just east of the central
Bahamas. The eastern periphery of an eastern Gulf of Mexico upper
level anticyclone is pressing eastward into the far western
portion of the basin. Strong northwest winds within this eastern
periphery of the anticyclone have set up over the waters north of
the NW Bahamas, and also north of 27N between 73W-78W. Debris
upper cloudiness from strong convection over northern and central
Florida is spilling southward across much of the far western
portion of the basin north of 25N. West to northwest upper level
winds to the east of the narrow upper trough are advecting some of
this cloudiness eastward to near 55W and north of 28N. The tail-
end of a central Atlantic cold front reaches southwestward to near
31N71W, where it becomes a dissipating stationary front to just
east of NE Florida. The aforementioned debris high clouds cover
this frontal boundary, however, scattered showers and isolated
thunderstorms are possible along and within 120 nm south of the
boundary between 71W and 74W.

Multilayer clouds are spreading northward from the northeast
Caribbean Sea to near 24N and between 55W-66W due to southwest
winds aloft found to the east of the previously mentioned upper-
level trough. Scattered showers and thunderstorms are occurring
under these clouds, and are moving in a general northward
direction. This activity is expected to continue into Friday.

Elsewhere, surface high pressure covers the basin with the
associated ridge axis extending from 32N49W and westward to
just east of the cold portion near 31N71W. Another high pressure
ridge extends east to west to the north of 32N and west of
70W. Anticyclonic wind flow is present north of 20N between
Africa and the Bahamas. Only isolated showers and thunderstorms
are observed elsewhere to the west of 54W.

Last visible satellite imagery and satellite airmass animation
depict a large area of Saharan African dust gradually spreading
westward over the eastern Atlantic Ocean, and over portions of
the central Atlantic Ocean, especially to the north of the
tropical wave along 45W/46W. Some of this dust is likely to
spread over the Atlantic waters just north of the NE Caribbean on
Saturday.


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

$$
Aguirre
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