[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 211702
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1805 UTC Sat Nov 21 2020

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 over the eastern Caribbean along 62W, from 18N
southward, moving westward at 10 to 15 kt. Scattered showers are
near the wave axis.

A second tropical wave is over the central Caribbean along 75W,
from 20N southward, moving westward at 10 to 15 kt. The wave
combined with a mid-upper level trough is producing scattered
moderate convection from 18N-20N between 73W-77W, including the
Windward Passage.

Another tropical wave is along 88W, from 19N southward, moving
westward at 10 to 15 kt. The wave extends southward into the EPAC
region. Numerous moderate to isolated strong convection is seen
from 16N-19N between 86W-89W. This convective activity is
affecting the Gulf of Honduras and parts of Belize and northern
Honduras.

...MONSOON TROUGH/ITCZ...

The monsoon trough passes through the coast of Africa near 07N12W
to 07N25. The ITCZ continues from 07N25W to 05N40W to near the
coast of French Guiana. Scattered moderate to isolated strong
convection is noted from 02N-10N between 10W-25W. A diffluent
pattern aloft is helping to induce this convective activity.

GULF OF MEXICO...

A surface ridge dominates the Gulf waters producing moderate to
fresh easterly winds across the eastern half of the Gulf and
gentle to moderate winds over the western half of the basin. Seas
are in the 5-8 ft range based on buoys observations. Patches of
low level clouds are noted across the region moving westward. Low
level clouds are also banking up against the Sierra Madre
Mountains in Mexico.

Winds and seas are forecast to diminish across the Gulf region
today. A weak cold front will move across the NE Gulf Mon. Another
weak cold front may move into the northern Gulf for the middle of
next week.

CARIBBEAN SEA...

Three tropical waves are analyzed in the Caribbean Sea. Please,
see Tropical Waves section for details.

Recent scatterometer data suggest that the eastward extension of
the Pacific Ocean monsoon trough extends into the SW Caribbean.
An area of scattered moderate to isolated strong convection is
noted over the SW Caribbean just N of the monsoon trough and ahead
of a tropical wave axis with axis along 75W. This convective
activity covers the waters from 10N-13N between 75W-81W.

Mainly moderate trade winds are noted across the basin, with the
exception of moderate to fresh NE winds in the lee of eastern
Cuba. Winds and seas will diminish across the NW Caribbean through
tonight as high pressure north of the area weakens. Large northerly
swell will continue to impact the tropical Atlantic waters east
of the Lesser Antilles through Mon where fresh to locally strong
trades are seen per satellite-derived wind data. In addition, recent
altimeter data provided observations of sea heights in the 9-11 ft
range within this area. Building high pressure N of the area will
bring an increase in winds and seas across the central Caribbean
Tue night and Wed.

ATLANTIC OCEAN...

Moderate to fresh NE winds are noted across the regional waters E
of Florida, the Bahamas, and over the Straits of Florida. These
winds have been carried patches of low level moisture with
embedded showers. In fact, Mosaic Doppler Radar from the SE U.S.
shows band of showers parallel to the winds mainly over central
Florida and in the Straits of Florida.

A surface trough is analyzed from 27N67W to 20N72W. Abundant
cloudiness with embedded showers and thunderstorms is noted in
association with this trough. Moderate to fresh winds are seen on
either side of the trough axis per scatterometer data. This trough
will drift westward through late Mon. A non-tropical area of low
pressure could form near the northern end of the trough over the
western Atlantic early next week. This system would only have a
brief time period to develop subtropical characteristics before it
merges with a cold front as it accelerates northeastward by the
middle of next week. The cold front will move into the NW waters
east of northern Florida on Monday. High pressure in the wake of
the front will bring another round of fresh NE-E winds across the
SW N Atlantic Tue night into Wed.

Farther east, another surface trough extends from 30N29W to
23N27W. Recent satellite-derived wind data indicate the wind shift
related to the trough axis as well as fresh to strong NE winds
near the northern end of the trough. Visible satellite imagery
shows a well-defined swirl of low clouds in association with this
feature. High pressure dominates the remainder of the Atlantic
forecast region.

$$
GR
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