[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 282344
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
744 PM EDT Wed Jun 28 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 Warning: N winds
increasing to gale force tonight in AGADIR AND TARFAYA through
30/0000 UTC. The OUTLOOK, for the 24 hours that follow the
forecast that is valid until 01/0000 UTC, consists of: the
threat of severe N gale over AGADIR and TARFAYA. N or NE gale
increasing over eastern MADERIA and CANARIAS.

...TROPICAL WAVES...

A tropical wave over the far eastern Atlantic near the coast of
Africa has become somewhat tilted in a northwest to southeast
fashion during the day since its northern vorticity lobe moved
off the coast of Africa on Tuesday evening, with its axis
extending from 20N17.5W to near 09N16W. It is moving westward
at 10-15 kt. The wave is embedded within a rather large envelope
of deep moisture as seen in the latest satellite animation. Moist
southwesterly flow is noted across the southern extension of the
wave axis where it crosses the monsoon trough. Large clusters of
scattered moderate to strong convection are seen along and east of
the wave axis to inland the coast of Africa from 10N to 15N.
Scattered moderate isolated strong convection is within 60 nm east
of the axis from 09N to 10N.

A tropical wave over the central Atlantic has its axis extending
from 14N38W to near 02N39W, moving westward near 13 kt. Satellite
imagery and TPW data indicate that moisture around the wave is
not as deep as 24 hours ago due to a large area of Saharan dust
that intruded from the north towards the wave. The last visible
imagery showed elongated cyclonic turning of the low clouds
around the vicinity of the wave. Only isolated showers and
thunderstorms are noted within 120 nm east of the wave from 10N to
14N, and within 120 nm either side of the wave south of 14N.

A broad and rather robust tropical wave has its axis tilted in
a northeast to southwest position as it moves across the Lesser
Antilles. The axis extends from just east of Martinique through
the Windward Islands, to just west of Trinidad and Tobago and to
inland the northeast part of Venezuela. The wave moved an average
speed of about 16 kt during the past 24 hours, and is maintaining
a similar speed as of this evening. This wave continues to be
easily identifiable on satellite imagery as having the typical
configuration of those waves observed later during the season.
It is detected in the model fields, and is again further
supported by the latest diagnostic model analysis. This wave is
accompanied by scattered to moderate to isolated convection within
120 nm to its east from 12N to 16N, and within 60 nm to its west
from 12N to 14N. Some of this activity may most likely be
attendant by strong gusty winds. The wave is forecast to move
across the eastern Caribbean tonight through much of Friday,
and the eastern half of the central Caribbean Friday night.
Expect increasing showers and thunderstorms, with gusty winds,
to move across these waters.

A tropical wave over the western Caribbean Sea has its axis along
85W south of 21N, moving westward at about 10 kt. The axis of this
wave continues to mark the leading edge of a surge of deep
tropical moisture. Scattered moderate to isolated strong
convection is evident to the east of axis from 11N to 15N west of
80W to inland the eastern and central sections of Honduras and
Nicaragua. Scattered showers and isolated thunderstorms are seen
within 60 nm east of the axis from 15N to 17N. Some of the
convective activity over Honduras and Nicaragua may contain
locally heavy rainfall. The shower and thunderstorm activity
approaching those same countries from offshore may bring gusty
winds and locally heavy rainfall tonight through at least Thursday
afternoon.

The tropical wave axis earlier analyzed along 95W/96W has moved
further into the eastern Pacific, and is being discussed under
the eastern Pacific Tropical Weather Discussion.

...ITCZ/MONSOON TROUGH...

The Monsoon Trough axis extends from the coast of Africa near
14N17W to 10N23W. The Intertropical Convergence Zone then extends
from 10N22W to 10N32W to just east of the tropical wave along
38W/39W, and continues from just west of the same wave to 05N45W
to 05N51W. Other than convection associated with the tropical
waves discussed above, scattered moderate isolated strong
convection is within 120 nm north of the axis between 47W- 51W.
Scattered moderate convection is within 180 nm south of the
Monsoon Trough axis between 18W-32W.

...DISCUSSION...

...THE GULF OF MEXICO...

A mid to upper level trough is evident on water vapor imagery to
be just inland the Texas and southwest Louisiana coasts. A jet
stream branch with strong southwest to west winds is seen just
east of this trough, and stretches northeastward over the western
Gulf, and eastward over the north-central and northeastern Gulf.
A dissipating stationary boundary has drifted northward to inland
Louisiana and to just along the Florida panhandle coastline. A
surface trough over the far western Gulf waters is supported by
the aforementioned mid to upper level trough. Visible satellite
imagery from this afternoon along with observations from buoys
indicated that weak surface low of 1011 mb formed along the far
western Gulf surface trough that extends from just southwest of
Galveston to just northeast of Brownsville. The surface analysis
reveals a weak pressure pattern present elsewhere across the Gulf.
A large area of scattered moderate to isolated strong convection
is confined to the much of the NW Gulf north of about 25N and west
of 90W. This activity increased quite impressively during today,
and is gradually spreading towards the north-central Gulf waters.
This activity is capable of producing strong gusty winds. Isolated
showers and thunderstorms are seen east of 90W, and also south of
25N west of 90W. With little changes to the present synoptic
pattern forecast through Friday, the convection described over the
NW Gulf is expected to continue through most of Friday as it
shifts to more to the north central Gulf.

...THE CARIBBEAN SEA...

The main feature presently in the basin is a strong tropical wave
just entering the southeastern Caribbean and another tropical
wave over the western Caribbean near 85W south of 21N. These
features are discussed in the section above. Aside from the
convection related to the tropical waves and isolated showers and
thunderstorms occurring elsewhere over the NW Caribbean, generally
fair weather prevails elsewhere. Scatterometer data depicts
moderate to fresh trades across the basin, except in the SW
Caribbean from 11N to 15N between 72W and 80W where a stronger
gradient present there is supporting strong northeast to east
winds. Little change is expected with these winds through Friday.
The tropical wave entering the southeastern Caribbean will be the
main feature during the next 48 hours. Scattered showers and
isolated thunderstorms are noted well ahead of the wave affecting
the waters south of 15N and east of 70W. This activity will
continue to spread westward through Thursday. The impacts of this
wave as related to marine interests will be mainly highlighted in
the offshore and high seas forecasts in the the Marine Weather
Discussion.

...HISPANIOLA...

Isolated thunderstorms are observed over the interior of the
island as some dry air has filtered in from the north. Guidance
suggests that little change is expected in the present weather
pattern through the next 24 hours, then increasing moisture along
with scattered showers and thunderstorms are expected on Friday
as a strong tropical wave approaches the island.

...THE ATLANTIC OCEAN...

A large eastern Atlantic upper-level cyclonic circulation is
located about 900 nm to the west of the western edge of the
Canary Islands. A trough extends from the cyclonic center to
near 10N41W. Isolated showers are possible within 300 nm of
the circulation. Another upper-level cyclonic circulation is
near 31N57W, and is transitioning to a trough with time. An
upper level trough extends from the cyclonic center to 24N57W
to 22N62W to 21N75W. A surface trough is analyzed from 29N59W
to 22N61W. Scattered showers and isolated thunderstorms are
noted east of the surface trough and south of the upper cyclonic
circulation from 24N to 29N between 52W and 57W.

A stationary front extends from near 32N74W to inland Florida
between Saint Augustine and Daytona Beach. The front is supported
by broad upper troughing just north of the area west of 68W. A
surface trough is southeast of the frontal boundary from near
32N71W to the NW Bahamas. Plenty of moisture and instability is
present over the this portion of the area, with all the
ingredients being conducive to the development of scattered
showers and thunderstorms to be present northwest of a line from
32N64W to 27N73W to South Florida. This activity is expected to
continue through late Thursday before central Atlantic high
pressure builds back to the west along 28N on Friday.

Otherwise, the wind flow pattern around the southern periphery
of high pressure that dominates the central and eastern portions
of the basin will continue to transport Saharan African dust
westward to the the central Atlantic by Friday.


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

$$

Aguirre
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