[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 032159
TWDAT

Tropical Weather Discussion...Updated
NWS National Hurricane Center Miami FL
1805 UTC Fri Sep 3 2021

Updated motion for the Caribbean Sea tropical wave along 63W

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 1200 UTC surface analysis and satellite imagery through
2145 UTC.

...SPECIAL FEATURES...
Hurricane Larry is centered near 14.8N 40.7W at 03/1500 UTC or
about 950 nm west of the southernmost Cabo Verde Islands moving
WNW at 14 kt. Estimated minimum central pressure is 981 mb.
Maximum sustained wind speed has increased to 80 kt with gusts to
100 kt. Satellite imagery depicts Larry as having a somewhat
asymmetric central dense overcast. Numerous moderate to strong
convection is noted within 150 nm of the center in the southern
semicircle. Numerous moderate to isolated strong convection is
within 60 nm of the center in the northern semicircle. Scattered
moderate to isolated strong convection is within a wide band
located south and southwest of the center from 09N to 13N between
39W-41W. Larry is forecast to continue on its present motion over
the next few days, followed by a turn to the northwest early next
week. Additional strengthening is forecast during the next few
days, and Larry is forecast to become a major hurricane this
weekend. Swells generated by Larry are expected to reach the
Lesser Antilles on Sun. 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...Updated

An eastern Atlantic tropical wave has its axis along 26W, from
04N to 19N, moving westward near 15 kt. Satellite imagery shows
only isolated showers and thunderstorms within 120 nm either
side of the wave axis from 07N to 09N. This disturbance is
expected to move westward into an environment less conducive for
development during the next couple of days, and the chances of
formation appear to be decreasing. This system could bring
showers and gusty winds to portions of the southernmost Cabo
Verde Islands for a few more hours.

A tropical wave has its axis along 63W south of 20N to inland
eastern Venezuela, moving westward at 15-20 kt. This wave is
observed to be within a very moist environment per the TPW
animation imagery. Satellite imagery shows clusters of scattered
moderate to isolated strong convection east of the wave to 60W
from just north of Trinidad and Tobago to 14N and also from 07N
to 12N between 55W-59W. During the late night overnight hours
strong east winds with very strong gusts were reported in
Grenada from convection associated with this wave. Recent ASCAT
data reveals fresh east winds to the east of the wave axis to
near 53W.

A small-amplitude western Caribbean Sea tropical wave has its
axis along 80W south of 14N, moving westward near 15 kt. No
convection is currently occurring with this weak tropical wave.

...MONSOON TROUGH/ITCZ...

The monsoon trough axis passes through the coast of Senegal near
15N17W to near 12N22W and to 12N30W. It then resumes to the
southwest of Hurricane Larry at 11N41W and continues to 10N49W.
The ITCZ extends from 10N49W to 09N60W. Aside from convection
associated with Hurricane Larry and that mentioned in the Tropical
Waves section above, scattered moderate convection is within 150
nm south of the trough and ITCZ between 45W and 50W.

GULF OF MEXICO...

As of 15Z, a stationary front extends from central Florida
westward to 29N88W and northwestward from there to inland the
Texas/Louisiana border near Sabine Pass. Weak high pressure
of 1016 mb is centered over the far southeastern Gulf just west-
southwest of the Dry Tortugas. Weak high pressure is present over
the basin. Both radar and satellite imagery show weakening
scattered showers and isolated thunderstorms over a section of the
northwestern Gulf. Outflow boundaries racing eastward from this
activity are seen north of 27N to inland the coasts of
northeastern Texas and southwestern Louisiana between 92W-93W.
Scattered showers and thunderstorms moving eastward due to the
westerly flow are increasing over the eastern Gulf waters from
26N-29N east of 86W. This activity is within a very moist
atmospheric environment. Similar activity is over the southwestern
Gulf waters.

Latest ASCAT data passes and current buoy observations indicate a
light to gentle anticyclonic wind flow pattern across the basin,
with seas in the range of 2-4 ft, with the highest being west of
the Yucatan Peninsula.

For the forecast, a surface trough currently over the western
Gulf of Honduras and Belize is expected to move west-northwestward
across the Yucatan Peninsula, and possibly into the southwestern
Gulf by late Sat or Sun. Unfavorable upper-level winds are likely
to limit significant development while the system moves NW or N
over the western Gulf of Mexico early next week. Elsewhere, a
stationary front over the far northeast Gulf will gradually
dissipate through early Sun, while weak high pressure dominates
much of the remainder of the basin.

CARIBBEAN SEA...

See the tropical waves section above for details on a convectively
active tropical wave that is presently over the eastern Caribbean.

A surface trough over the Gulf of Honduras and portions of
Central America is producing disorganized scattered moderate
to isolated strong convection over the far western Caribbean from
16N to 20N and west of 82W to inland Belize and the Yucatan
Peninsula. This activity is also being aided by a westward small
upper-level low that is centered over Belize. The surface trough
is expected to move west-northwestward across Central America and
the Yucatan Peninsula, bringing heavy rains to that area during
the next couple of days. The disturbance is expected to move over
the southwestern Gulf of Mexico late this weekend,

Fresh to locally strong trades are occurring in the south-
central Caribbean. Moderate to fresh trades are over and near
the Gulf of Honduras. These conditions are expected to change
little over the next few days. Elsewhere, gentle to moderate
mainly east trades prevail. Fresh to occasionally strong
trades are forecast to pulse off Colombia through late Sat.
Observed seas are in the 4-6 ft range in the areas of fresh
winds, and 2 to 4 ft elsewhere.

Although Hurricane Larry is forecast to stay well north and east
of the basin, swell from Larry may propagate through northeast
Caribbean passages early next week.

ATLANTIC OCEAN...

Please see the Special Features section for details on Hurricane
Larry.

As of 15Z, a cold front extends from 31N77W to inland central
Florida in the vicinity of New Smyrna Beach. A trough extends
from just south of the front from 29N79W, south-southwest to
25N80W. Latest ASCAT data passes shows moderate northeast winds
behind the front, while mainly gentle south to southwest winds are
ahead of it. Water vapor imagery depicts an upper-level low near
27N66W. This low is contributing to instability to the already
in place very moist environment ahead of the front. As a result,
scattered moderate convection is occurring ahead of this front
from 28N to 31N between 70W-73W. Another upper-level low is noted
to the southeast of the aforementioned low near 25N55W. Increasing
scattered moderate convection is from 22N to 26N between 57W-62W.
Similar activity is from 28N-30N between 63W-68W.

Over the eastern part of the discussion area, high pressure
prevails, with the center of a 1021 mb high pressure near 31N45W.
Over the eastern Atlantic, a trough extends from 31N23W to 28N26W
and to near 25N31W. Scattered showers and isolated thunderstorms
are within 180 nm east of the trough north of 29N. This activity
is quickly shifting eastward.

Latest ASCAT data passes indicate gentle winds throughout, except
for moderate to fresh winds elsewhere outside the winds
associated with Larry south of 26N between 32W-48W. Latest
altimeter data reveals seas in the general range of 4-6 feet
across most of the Atlantic.

For the forecast, Hurricane Larry is well east of the area in the
central Atlantic near 14.8N 40.7W 981 mb at 11 AM EDT moving WNW
at 14 kt. Maximum sustained winds 80 kt gusts 100 kt. Larry will
continue to move west-northwest through Sun, and will pass well
northeast of the Leeward Islands near 20.2N 51.8W by Sun evening,
reaching 21.4N 53.6W Mon morning. Larry will change little in
intensity as it moves more northwestward thereafter well to the
north of Leeward Islands. Large swells generated by Hurricane
Larry are expected to propagate across the waters east of the
Leeward Islands on Sun, likely spreading beyond 65W Mon and Mon
night.

$$
Aguirre
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