[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 031759
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
159 PM EDT Fri Nov 3 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
1745 UTC.

..ITCZ/MONSOON TROUGH...

The monsoon trough axis extends from the African coast near
10N14W to 08N19W. The Intertropical Convergence Zone extends from
08N19W to 07N28W to 09N38W where it is bisected by the trough
along the position from 14N37W to 09N40W to 04N41W. It resumes
to the W of the trough at 08N41W to 08N49W to near 10N55W.
Scattered moderate convection is within 120 nm N of the ITCZ
between 25W and 30W, within 120 nm S of the axis between 29W and
34W and within 30 nm of the monsoon trough axis between 15W and
22W. Scattered moderate moderate to isolated strong convection is
observed to the S of the ITCZ within 60 nm of line from 06N13W to
04N16W, and within 30 nm of line from 03N25W to 03N30W.

...DISCUSSION...

GULF OF MEXICO...

Strong upper zonal flow prevails throughout the SE United States
and Gulf of Mexico. A jetstream branch is across the central part
of the basin is advecting broken high clouds ESE from 21N to 28N
and to the E of Texas. At the surface, a 1023 mb high is analyzed
over the border between western S Carolina and NE Georgia. A well
entrenched ridge extends from this high center southwestward to
across southern Louisiana and to the northern part of the SW Gulf.
The associated pressure gradient is allowing for generally gentle
to moderate NE to E winds over the basin, except in the far
western section where winds are gentle to moderate, SE to S in
direction. The Gulf is void of deep convection as very limited
low-level moisture in combination with the subsidence aloft and
the strong zonal winds are not conducive this type for this type
of convection to develop. Latest satellite imagery shows small
patches of low-level moisture moving quickly SW over the
southeastern Gulf. Isolated showers are possible with these
clouds. Little overall changes are expected with the current
weather pattern over the area through Sunday.

CARIBBEAN SEA...

In the upper levels, a small anticyclone is centered near 16N74W,
with a ridge stretching WNW to across Belize and the southern
Yucatan Peninsula, and another ridge extending southeastward to
far NE Venezuela. Water vapor imagery shows associated strong
subsidence covering just about the entire sea, except the far
western section S of 18N and W of 77W, and over the extreme
southeastern portion of the sea. The dry air resulting from the
subsidence is inhibiting deep convection from developing across
the open waters of the basin. Only patches of low-level moisture
with isolated showers and thunderstorms moving westward are seen
over these waters, including the waters just SW of the Windward
passage. In the western portion S of 18N and W of 77W scattered
moderate isolated strong convection in clusters are observed
where low-level convergence exists along with the additional
factor of a surface trough that is just along the coasts of
southern Honduras to that of Costa Rica. This activity should
remain active into Saturday night.

Low-level moisture related to a surface trough nearing the Windward
Islands from the Atlantic basin is noted S of 14N and E of 63W.
Isolated showers are occurring with this moisture. This moisture
will gradually increase through Saturday, with the possibility of
some scattered shower and thunderstorm activity moving over this
part of the sea. Presently, it appears most of this activity
should remain just to the E of the islands as upper level winds
shear off the tops of the deeper convection.

...HISPANIOLA...

Patches of low-level moisture with scattered showers are moving
quickly westward just offshore the northern and southern coasts of
Hispaniola. Some showers are affecting portions of these coasts.
With abundant dry sinking air aloft over and near the island, the
shower activity is expected to be rather shallow as it continues
in a westward motion over the next couple of days.

ATLANTIC OCEAN...

A well-defined surface trough is analyzed over the western Atlantic
from near 30N74W to a small and weak low-level swirl at 26N75W and
to the SE Bahamas. A shortwave trough embedded in the westerly
flow aloft has triggered off scattered moderate isolated strong
convection to the NE of the trough N of 29N between 71W and 75W.
The shortwave trough will shift eastward through Sunday as a
longwave trough develops over the far western portion of the area.
The surface trough will continue westward to near 78W to include
the vicinity of the NW Bahamas on Sunday.

To the E of the upper mentioned features, an upper-level low is
located over the central Atlantic near 32N54W, with a sharp upper
trough stretching S to 28N54W and southeastward to near 18N52W to
near 13N51W. At the surface a weak trough extends from 32N52W to
a dissipating low at 27N56W and to near 25N59W. Only isolated
showers are along and within about 60-90 nm of the trough. A broad
upper-level diffluent flow pattern is present to the E of the
upper-level low and trough. Latest satellite imagery shows
abundant moisture in the form of multilayer clouds with numerous
showers and scattered thunderstorms to the N of 19N between 45W
and 53W. The majority of this moisture along with shower and
thunderstorms is advecting northward. Broken to scattered mid
and high level clouds are streaming eastward from the abundant
moisture area towards 20W, while at the surface and low-levels
scattered to broken low clouds with isolated showers are noted.
The aforementioned shower and thunderstorm activity is forecast
to remain quite active during the next 24 to 48 hours. A surface
trough is analyzed over the deep tropics along a position from
14N37W to 09N40W to 04N41W. This trough is moving westward
around 15 kt. Scattered moderate convection is seen to its NW
within 30 nm of line from 13N42W to 14N37W, and is being aided
by upper-level divergence occurring E of the upper level trough
axis that is along 28N54W to 18N52W to 13N51W. Other scattered
moderate convection is southeast of the trough within 30 nm of a
line from 05N32W to 05N40W.

To the W of the upper trough described in above paragraph, a
surface trough is analyzed from near 22N54W to 16N58W to near
09N60W. Although the upper air over this trough is very dry as
noted in the latest water vapor imagery depicting abundant
moderate to strong subsidence over the trough, an upper level
disturbance riding southeastward in the upper NW flow is helping
to produce an area of scattered moderate isolated strong
convection along and within 120 nm E of this trough from 09N to
13N. The trough will move across most of the Lesser Antilles
tonight into Saturday and across the eastern Caribbean Sea
Saturday. The trough should bring scattered shower and
thunderstorm activity to mainly the Windward Islands, and
isolated showers to the rest of the Lesser Antilles through
Saturday.

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

$$
Aguirre
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