[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 111741
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
141 PM EDT Fri Aug 11 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 1200 UTC surface analysis and satellite imagery through
1715 UTC.

...TROPICAL WAVES...

A tropical wave is added to the 1200 UTC analysis/surface map
along 17W/18W based on visible satellite imagery and the
Hovemoller Diagram that shows the westward propagation of the
wave since August 9. In addition, the wave shows up very well on
the TPW animation and 700 mb streamline analysis. Scattered
moderate convection is where the wave meets the monsoon trough
from 10N-12N between 16W-19W.

Another tropical is midway between the coast of Africa and the
Lesser Antilles and extends from 19N38W to 10N39W moving W at
10-15 kt. The wave coincides with a well defined 700 mb trough,
and a high amplitud northward bulge of moisture is noted on the
TPW product, mainly to the east of the wave axis. African dust
surrounds the wave, which is limited the convection to only
isolated showers near the wave axis.

A tropical wave extends from 19N70W to 10N71W moving W at 10-15
kt. The wave coincides with a 700 mb trough, and is well depicted
in the moisture product. The wave is currently helping to induce
some shower activity over Dominican Republic. This wave will move
across the rest of Hispaniola and the central Caribbean today,
then slow somewhat as it continues through the western Caribbean
through Sunday night.

...ITCZ/MONSOON TROUGH...
The monsoon trough extends from the African coast near 12N16W to
10N25W to 11N34W to 09N38W. The Intertropical Convergence Zone
axis continues from 09N38W to 07N50W to 06N57W. Aside from
convection associated with the tropical waves, scattered moderate
convection is from 07N-12N between 19W-30W. Isolated moderate
convection is from 07N-10N between 30W-38W.

...DISCUSSION...

GULF OF MEXICO...
A surface ridge, with axis across the north waters, dominates the
Gulf region producing mainly light to gentle winds across the
area N of 25N, and gentle to moderate winds S of 25N, with the
exception of moderate to fresh winds near and to the NW of the
Yucatan Peninsula due to the presence of a thermal trough. A 1020
mb high pressure is along the ridge near 29N87W, and will be
nearly stationary across the NE and north-central Gulf waters
through the weekend. A surface trough is over Florida and the SE
Gulf generating some shower and tstm activity. The trough will
drift westward across Florida through Saturday as the Atlantic
ridge begins to build westward. Abundant moisture will persist
across the eastern Gulf through at least late Saturday. An upper-
level anticyclonic circulation centered over the Rio Grande River
valley near 30N100W is providing a N-NE upper level flow across
much of the basin.

CARIBBEAN SEA...
A tropical wave is along 70W/71W. Please, see Tropical Waves
section for details. The most recent scatterometer data indicate
fresh to locally strong winds across the south-central Caribbean,
in the Gulf of Honduras, and also across the Windward Passage. The
pressure gradient over the area will continue to support fresh to
locally strong nocturnal trades over the far south-central
portions of the Caribbean south of about 13N to include portions
of the coasts of Colombia and Venezuela and Gulf of Venezuela
through late Sunday night. The pressure gradient is forecast to
tighten early next week as the Atlantic ridge builds westward.
This will allow for these winds to expand northward across the
central Caribbean to near 17N by Tuesday. Expect building seas to
8-10 ft with the strongest winds.

Clusters of moderate to isolated strong convection are noted over
the SW Caribbean, just N of Costa Rica and Panama. A diffluent
pattern aloft, associated with an upper-level anticyclonic
circulation situated near 13N77W supports this convective
activity. Shallow moisture embedded in the trade wind flow is
noted elsewhere.

...HISPANIOLA...
A tropical wave moving across Hispaniola today will combined with
the local effects to produce scattered showers and thunderstorms
mainly this afternoon and evening. The tropical wave will move
away from the island on Saturday, but an upper-level trough
extending across Hispaniola will continue to favor the development
of scattered showers and tstms mainly during the afternoon and
evening hours. Moisture is forecast to diminish across the island
on Sunday.

ATLANTIC OCEAN...
A trough is N of Puerto Rico and extends from 24N63W to 19N66W. A
1013 mb low pressure is along the trough axis near 22N64W.
Scattered moderate convection is noted around the low center, and
in a band from 19N-25N between 60W and 63W. The convective
activity associated with this system has become a little better
organized since yesterday, but there are no indications of a
closed circulation. Upper-level winds are forecast to become more
favorable for development by the weekend, but dry air aloft could
limit additional development of the thunderstorm activity. This
makes the overall environment only marginally conducive for
tropical cyclone formation. The disturbance is expected to move
northwestward today, then northward over the weekend across the
western Atlantic Ocean. The latest Tropical Weather Outlook gives
this low pressure a medium change of tropical cyclone formation
through 48 hours. A recent scatterometer pass provides observations
of fresh to strong E-SE winds within about 150 nm NE semicircle
of low center.

Another weak low is over NE Florida near 29.5N81W. A trough
extends from the low center across central Florida to the SE Gulf
of Mexico near 25N84W. Mosaic Doppler Radar from the SE U.S.
indicates scattered showers and isolated thunderstorms in
association with this feature over Florida and coastal waters,
including also the Straits of Florida. This system has become
less organized and development is not anticipated, but it could
still produce locally heavy rains to portions of the Florida
peninsula as it moves northward during the next day or two.

A third low pressure of 1016 mb is near 29.5N42.5W with a trough
extending SW to near 24N48W. Isolated showers and tstms are near
the low center. The remainder of the Atlantic Ocean is under the
influence of a ridge anchored by a 1030 mb high pressure located
NE of the Azores. The ridge is forecast to build westward across
the forecast waters early next week, with the high pressure
center located SW of the Azores.

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

$$
GR
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