[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 060512
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
0605 UTC Mon Sep 6 2021

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 31N. The following information is based on satellite
imagery, weather observations, radar and meteorological analysis.

Based on 0000 UTC surface analysis and satellite imagery through
0500 UTC.

...SPECIAL FEATURES...

Hurricane Larry is centered near 21.0N 51.4W at 06/0300 UTC or
685 nm ENE of the northern Leeward Islands, moving NW at 10 kt.
Estimated minimum central pressure is 955 mb. Maximum sustained
wind speed is 110 kt with gusts to 135 kt. The eye diameter is
40 nm on IR satellite imagery. Numerous moderate to strong
convection is within 180 nm of the center. The most recent ASCAT
pass from Sunday evening around 07/0000 UTC shows that the area
of winds over 20 kt associated with Larry's circulation extends
outward 300 nm from the center, except only 210 nm in the SW
quadrant. This encompasses most of the area from 17N-26N between
45W-56W. Seas of 12 ft or higher extend 300 nm in the N
semicircle and 240 nm in the S semicircle, with seas peaking at
46 ft. On the forecast track, a northwest motion with a slight
decrease in forward speed is expected during the next few days.
Little change in strength is forecast during the next day or so,
followed by very gradual weakening. Swells generated by Larry
are reaching the Lesser Antilles and are expected to spread
westward to portions of the Greater Antilles, the Bahamas, and
Bermuda later today and Tuesday. Significant swells should reach
the east coast of the United States and Atlantic Canada by
midweek. These swells are likely to cause life-threatening surf
and rip currents. Please read the latest High Seas Forecast
issued by the National Hurricane Center at website
https://www.nhc.noaa.gov/text/MIAHSFAT2.shtml and the latest NHC
Forecast/Advisory and Public Advisory at www.hurricanes.gov for
more details.

...TROPICAL WAVES...

An eastern Atlantic tropical wave has an axis along 23/24W from
19N southward, moving W at 15 kt. Isolated moderate convection
is noted near the wave axis over portions of the Cabo Verde
Islands. Scattered moderate convection is seen from 06N-09N
within 180 nm of the wave axis.

A central Atlantic Ocean tropical wave has an axis along 39/40W
from 17N southward, moving W at 10 kt. The wave is situated at
the leading edge of a Saharan dust plume. As a result, only
isolated moderate convection is noted along and within 150 nm E
of the wave axis from 04N-06N.

A Caribbean Sea tropical wave has an axis along 78W from 19N
southward through eastern Panama, moving W at 10 kt. Isolated to
scattered moderate convection is within 150 nm either side of
the wave axis south of 14N. Convection farther north near
eastern Cuba is more related to upper-level diffluence than to
the tropical wave.

...MONSOON TROUGH/ITCZ...

The monsoon trough extends into the Atlantic Ocean off the coast
of northern Senegal near 16N17W to 06N32W. The ITCZ extends from
06N32W to 05N38W, then continues W of a tropical wave from
04N42W to 06N52W to 09N61W. Aside from the convection mentioned
above, scattered moderate and isolated strong convection is
noted from 03N-06N between 29W-33W. Isolated to scattered
moderate convection is from 04N-08N between 46W-51W.

GULF OF MEXICO...

A weak 1010 mb low along a surface trough is analyzed just off
the west coast of the Yucatan Peninsula near 20N91W. The surface
trough extends NNE from the low to near 24N89W. A recent ASCAT
pass shows fresh to strong SE winds on the NE side of the low
from 20N-23N between 89W-91W. Scattered moderate convection is
noted from 19N to 25.5N between 85.5W and 91W, including over
the Yucatan Peninsula. Numerous moderate and scattered strong
convection is seen mainly inland over the Mexican states of
Veracruz, Oaxaca and Puebla due to unstable conditions and a
divergent pattern aloft in the area, but scattered tstorms
extend over the SW Bay of Campeche, mainly south of 22N and west
of 95W. Weak surface high pressure ridging prevails elsewhere
across the Gulf of Mexico, anchored by a 1014 mb high pressure
near 28N94W and a 1016 mb high pressure near Key West Florida. A
recent ASCAT pass shows light to gentle winds over most of the
area north of 24N. Seas of 1 to 3 ft prevail across the basin,
except locally up to 4 ft off the NW coast of Yucatan.

For the forecast, the weak low pressure in the southwest Gulf is
forecast to move slowly N or NE over the central and NE Gulf of
Mexico over the next few days. Upper-level winds could become
marginally conducive for tropical cyclone formation by late Tue,
before the system moves inland over the SE U.S. mid-week. The
chance of formation in the Gulf is low with this system. Aside
from the small low pressure system, high pressure will dominate
the remainder of the basin early this week.

CARIBBEAN SEA...

See the Tropical Waves section above for details on the tropical
wave along 78W.

A diffluent pattern aloft is inducing scattered moderate and
isolated strong convection over eastern Cuba and the waters just
south of eastern Cuba. Scattered moderate showers are seen
across other portions of the western Caribbean Sea, including
the Yucatan Channel and the area just east of northern Nicaragua
and E Honduras. The eastern Caribbean is drier, although
isolated showers and tstorms are seen in the waters near
Guadeloupe, Antigua and Montserrat. A recent ASCAT pass shows
fresh trades in the central Caribbean between 67W-78W, from
12N-17N, where seas are 4 to 6 ft. Gentle to moderate winds
prevail elsewhere with 2 to 4 ft seas.

For the forecast, major Hurricane Larry will remain well to the
northeast of the Leeward Islands through tonight, then move
farther north of the area through mid week. Large swell
affecting the Atlantic side of the Leeward Islands, Virgin
Islands, Puerto Rico, Dominican Republic and the NE Caribbean
passages will peak through tonight, then gradually subside into
mid-week. Elsewhere, gentle to moderate trade winds will
persist, pulsing to fresh off Colombia mainly at night.

ATLANTIC OCEAN...

Attention remains focused of Major Hurricane Larry. Please see
the Special Features section for details.

A weak pressure pattern prevails over the western Atlantic,
leading to light to gentle winds across much of the area west of
72W. A diffluent pattern aloft is inducing scattered moderate
and isolated strong convection over eastern Cuba and the Old
Bahama Channel from 21N-24N between 76W-80W. Surface high
pressure of 1020 mb is analyzed at 27N61W. To the west of this
high pressure, an upper-level divergent pattern is inducing
scattered moderate rain showers from 25N-29N between 67W-71W. To
the northeast of Hurricane Larry, another 1020 mb surface high
pressure is analyzed at 27N40W. In the NE Atlantic, a weak cold
front extends from 31N20W to 28N28W to 31N37W, but no
significant rain or winds accompany the front. Aside from the
circulation of Hurricane Larry, gentle to moderate winds prevail
across the remainder of the Atlantic.

For the forecast, Hurricane Larry will move to near 23N54W this
evening, near 26N57W Tue evening, and to near 29N60W Wed
evening. Larry will then turn northward, remaining east of
Bermuda. Large swell generated by Larry will continue to
propagate across waters northeast of the Leeward Islands and
spread west of 65W early today. Swell from Larry will reach the
Bahamas Tue and the east coast of the U.S. by Wed.

$$
Hagen
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