[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 101759
TWDAT

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
1700 UTC.

...SPECIAL FEATURES...

Hurricane Larry is centered near 41.8N 59.5W at 10/1800 UTC or
405 nm SW of Cape Race, Newfoundland moving NNE at 25 kt.
Estimated minimum central pressure is 971 mb. Maximum sustained
wind speed is 70 kt with gusts to 85 kt. Numerous moderate with
embedded isolated strong convection extends outward for 240 nm
from the center, except to 120 nm in the SW quadrant. On the
forecast track, Larry will pass well southeast of Nova Scotia
today, and move over southeastern Newfoundland tonight. Little
change in strength is expected before landfall in Newfoundland.
After landfall, Larry should weaken and become an extratropical
cyclone on Saturday before it merges with another low over the
Labrador Sea on Sunday. Swells generated by Larry will affect
the Bahamas through today. Significant swells from Larry will
continue affecting Bermuda, the east coast of the United States,
and Atlantic Canada through Saturday night. These swells are
likely to cause life-threatening surf and rip current
conditions. 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.

A tropical wave extends its axis along 89/90W from the central
Yucatan Peninsula southward through eastern Guatemala and
western El Salvador to the Pacific Ocean, moving W at 10 kt.
Enhanced by upper-level diffluence, scattered moderate to strong
convection is occurring from 17N-22N between 82W-89W, including
along the east coasts of Yucatan and Belize. Similar convection
is seen from 08.5N-16N between 80.5W-84.5W, including along the
Caribbean coasts of western Panama, Costa Rica, Nicaragua and
eastern Honduras. This system is forecast to move into the Bay
of Campeche and merge with a pre-existing surface trough by
Sunday. Environmental conditions are conducive to support
gradual development thereafter, and a tropical depression is
likely to form Sunday or Monday before the system moves onshore
along the western Gulf of Mexico coast. The chance of tropical
cyclone formation within the next 48 hours is medium. Regardless
of development, this disturbance is expected to produce heavy
rains across portions of Central America and the Yucatan
Peninsula through Saturday. Heavy rains are likely to reach
portions of the western Gulf coast late this weekend.

A strong tropical wave is inland over west Africa along 14W
moving W around 15 kt. Scattered moderate and isolated strong
convection is seen from 08N-19N between 10W-19W, and from
04N-08N between 18W-25W. The tropical wave will move off the
coast by this evening, and gradual development is expected
thereafter. A tropical depression is likely to form late this
weekend or early next week as the system moves west-
northwestward over the far eastern Atlantic near the Cabo Verde
Islands. Interests in the Cabo Verde Islands should monitor the
progress of this system. The disturbance has a medium chance of
development over the next 48 hours.

...TROPICAL WAVES...

An Atlantic tropical wave has an axis along 35/36W from 06N-22N,
moving W at 15 kt. Scattered moderate showers are noted along
the wave south of 08N.

An Atlantic tropical wave has an axis along 50W from 05N-21N,
moving W at 10-15 kt. No significant convection is noted with
the wave at this time.

A Caribbean tropical wave has an axis along 73W from 16N
southward to central Colombia, moving W at 10-15 kt. Scattered
showers and tstorms are near the wave axis inland over Colombia,
south of 08N.

...MONSOON TROUGH/ITCZ...

The monsoon trough passes through the coast of Mauritania near
19N16W to 15N23W to 09N30W to a 1012 mb low pressure near 12.5N
46.5W. Aside from the convection mentioned in the sections
above, scattered moderate and isolated strong convection is
noted near the low pressure from 13N-17N between 45W-48W.

GULF OF MEXICO...

A cold front extends from Cedar Key Florida near 29N83W to
27N90W to 28N95W to near Corpus Christi Texas. A sharp surface
trough extends from Tabasco Mexico near 18N 92.5W to near South
Padre Island Texas near 26N97W. Abundant moisture is present
over the south-central Gulf of Mexico, shown in Total
Precipitable Water imagery, due to a combination of the tropical
wave mentioned in the Special Features section and mid to
upper-level southwesterly flow. In addition to the
aforementioned features and the moisture, strong upper-level
diffluence is enhancing scattered to numerous moderate with
embedded isolated strong convection over most of the Gulf of
Mexico, south of the cold front. A recent ASCAT pass shows
moderate to locally fresh NE winds to the north of the cold
front. Moderate to locally fresh NW to N winds are noted in the
southwest Gulf, west of the surface trough. Mainly gentle wind
speeds prevail elsewhere, due to weak surface ridging, which
extends from the western Atlantic into the southeastern and
central Gulf, south of the cold front. Recent buoy and altimeter
data show seas of 1 to 3 ft across the basin.

For the forecast, see the Special Features section above for
information on the tropical wave that has potential to develop
into a tropical cyclone over the southwest Gulf of Mexico Sunday
or Monday. Elsewhere, the frontal boundary over the northern
Gulf will remain nearly stationary through Sunday, bringing
showers and thunderstorms across the region.

CARIBBEAN SEA...

Please see the Special Features section above for details on the
tropical wave over Central America that is inducing convection
west of 80W. Also, please see the Tropical Waves section for
details on the tropical wave that is currently along 73W.

Little to no shower or thunderstorm activity is noted east of
80W, other than isolated tstorms seen near southern Puerto Rico.
A recent ASCAT pass shows fresh trades across the south-central
Caribbean south of 16N between 67W-79W, where seas are likely 5
to 8 ft. Locally strong winds are near the tropical wave axis,
south of 15N between 73W-76W. Fresh to locally strong SE winds
are seen between Honduras and the Yucatan Channel, west of
83.5W. Moderate trades are noted elsewhere with 3 to 5 ft seas.

For the forecast, the Atlantic ridge will build westward across
the Caribbean, bringing an increase in the trade wind flow
through the weekend. Fresh to strong winds will occur offshore
Colombia and in the Gulf of Venezuela, mainly at night through
Sun. Fresh to strong winds are also likely in the late evening
in the Gulf of Honduras starting on Sat. Scattered showers and
thunderstorms are expected to continue across the NW Caribbean
today and then decrease in coverage by Sat.

ATLANTIC OCEAN...

Please see the Special Features section above for details on
Hurricane Larry over the NW Atlantic.

A 1006 mb low pressure, the remnants of Tropical Depression
Mindy, is near 33N71W at 1500 UTC. A cold front extends from the
low to 31N75W to Daytona Beach Florida. Recent ASCAT data from
late Friday morning shows fresh W winds south of the low
pressure and north of 30N, between 69W-72W. Moderate N to NE
winds are seen north of the cold front and west of 76W.
Scattered showers and tstorms are noted near the front between
78.5W and the east coast of Florida. Scattered showers and
isolated tstorms are also seen within 60 nm of a line from
26N77W to 31N 68.5W. A surface ridge axis extends along 25N
across the western Atlantic, leading to light to gentle wind
speeds from 22N-28N between 61W-81W. Seas over the western
Atlantic are 6 to 8 ft north of 27N due to a combination of
swell from the remnants of T.D. Mindy and from Hurricane Larry.
Seas are 4 to 6 ft elsewhere over the open Atlantic east of the
Bahamas.

Farther east, the subtropical Atlantic is characterized by high
pressure ridging extending from a 1024 mb high pressure near
35N47W to 30N35W to a 1021 mb high pressure near 36N14W. ASCAT
data show fresh to locally strong NE winds from the Canary
Islands southward to 20N, between western Sahara and 24W, where
seas are likely 6 to 9 ft.

For the forecast over the western Atlantic, seas associated with
remnants of Mindy and swell generated from Hurricane Larry will
subside by tonight south of 31N. The cold front will become
stationary and will linger across the area through Sun which
will bring showers and thunderstorms  during the weekend.

$$
Hagen
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