[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 231742
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
142 PM EDT FRI SEP 23 2016

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.

...SPECIAL FEATURES...
Tropical Storm Karl is centered near 29.1N 65.3W at 23/1800 UTC
or about 200 nm S of Bermuda moving NNW or 335 degrees at 10 kt.
Estimated minimum central pressure is 990 mb. Maximum sustained
wind speed is 50 kt with gusts to 60 kt. Some strengthening is
forecast during the next 48 hours, and Karl is expected to become
a hurricane on Saturday. Numerous moderate and isolated strong
convection is noted within about 150 nm NW semicircle. Similar
convection is in a 90 nm wide band to the NE and E of the center.
On the forecast track, the center of Karl should pass near or to
the east of Bermuda late tonight or early Saturday. See latest NHC
Intermediate Public Advisory under AWIPS/WMO headers MIATCPAT2/
WTNT32 KNHC and the full Forecast/Advisory under AWIPS/WMO headers
MIATCMAT2/WTNT22 KNHC for more details.

Tropical Storm Lisa is centered near 22.2N 36.3W at 23/1500 UTC
or about 790 nm WNW of the Cape Verde Islands and about 1065 nm
SSW of the Azores moving NW at 6 kt. This motion with a faster
forward speed is expected to continue through Saturday night. A
turn toward the north-northwest is forecast on Sunday. Estimated
minimum central pressure is 1008 mb. Maximum sustained wind speed
is 35 kt with gusts to 45 kt. Weakening is forecast during the
next 48 hours due to strong wind shear, and Lisa is expected to
weaken to a tropical depression tonight and become a remnant low
this weekend. Numerous moderate convection is within about 150 nm
NE quadrant. See latest NHC Forecast/Advisory under AWIPS/WMO
headers MIATCMAT3/WTNT23 KNHC for more details.

...TROPICAL WAVES...
A tropical wave is added to the 1200 UTC analysis/surface map
along 17W based on surface data and the TPW product that depicts a
low amplitude moisture surge in association with this feature. In
addition...the wave remains within broad 700 mb troughing located
E of 20W. This wave is forecast to move rapidly westward across
the tropical Atlantic Ocean at about 20 kt for the next several
days. Environmental conditions could be conducive for some gradual
development while the system approaches the Lesser Antilles next
week.

A 5-day TPW loop indicates that another tropical wave is along
50W extending from 11N-19N. This wave previously spawned tropical
cyclone Lisa. The wave shows up reasonably well in the TPW product
and 700 mb streamline analysis.

A tropical wave is currently moving across the Bay of Campeche
where is generating some shower and thunderstorm activity. The
wave axis is along 93W south of 20N moving W at 15 kt. The most
recent scatterometer pass showed the wind shift associated with
the wave.

...ITCZ/MONSOON TROUGH...
The Monsoon Trough extends from the African coast near 10N13 to
08N20W to 06N30W. Isolated moderate convection is from 05N-07N
between 20W-30W.

...DISCUSSION...

GULF OF MEXICO...
A 1018 mb high pressure located over north-central Gulf will
dominate the region over the weekend producing mainly gentle to
moderate E-SE winds. As previously mentioned, a tropical wave is
moving across the Bay of Campeche, likely enhancing the thermal
trough that usually develops each afternoon and evening over the
Yucatan Peninsula and moves westward over the Bay of Campeche
during the overnight hours. A narrow band of showers with embedded
thunderstorms is noted along the Florida Keys and the SE Gulf
likely associated with a surface trough analyzed just E of Florida
and an upper level trough that extends from southern Georgia to
the central Gulf near 24N90W. This trough supports a 1012 mb low
centered along coastal South Carolina. Early next week...SE winds
will increase slightly across the western Gulf ahead of a cold
front forecast to emerge off the Texas and Louisiana coasts
sometime between Monday night and Tuesday.

CARIBBEAN SEA...
Weak pressure gradient is noted across the Caribbean Sea due to
the presence of Tropical Storm Karl located NE of the area. As a
result, mainly gentle to moderate trades are blowing across the
basin. A ridge extending from the central Atlantic reaches The
Lesser Antilles. Scattered showers and thunderstorms are over the
NW Caribbean, with a cluster of moderate to strong convection
just off the coast of Nicaragua. A diffluent pattern aloft is
helping to induce this convective activity. As Karls continues to
move away from the forecast area, the subtropical ridge will build
back increasing slightly the trade wind flow across the area.
Computer model suggests fresh to locally strong trade winds over
the south-central Caribbean this upcoming weekend but mainly
during the overnight and early morning hours.

...HISPANIOLA...
Available moisture will combine with the local effects and an
upper-level low located over the island to provide an overall
favorable environment for scattered showers and thunderstorms
this weekend, particularly during the afternoon and early evening
hours.

ATLANTIC OCEAN...
A surface trough is just E of Florida and extends from 31N79W to
the Florida Keys. Scattered showers and thunderstorms are along
the trough axis that continues over the SE Gulf of Mexico. Aloft...
southwesterly winds are transporting abundant mid to upper level
moisture from the Gulf of Mexico across South Florida into the
western Atlantic, keeping the atmosphere very moist and unstable
over the area. Farther east...Tropical Storm Karl and Tropical
Storm Lisa continue to affect the forecast region. Please, see
the Special Features section for details. Otherwise...the
remainder of the central and eastern Atlantic is under the
influence of a surface ridge anchored by a 1026 mb high centered
near 32N45W and a 1027 mb high centered between the Azores and the
Canary Islands near 32N23W. The pressure gradient between the
ridge and a weak 1012 mb low pressure located near 17N17W is
resulting in area fresh to strong NE winds north of 19N to the
Canary Islands and E of 20W. an Ascat pass confirmed the presence
of these winds.

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

$$
GR
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