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Atlantic Tropical Weather Discussion

AXNT20 KNHC 241805

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
205 PM EDT SAT SEP 24 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
1745 UTC.


Tropical Storm Karl is centered near 32.8N 62.7W at 24/1500 UTC
or about 109 nm east-northeast of Bermuda moving northeast at 16
kt. Estimated minimum central pressure is 994 mb. Maximum
sustained wind speed is 55 kt with gusts to 65 kt. Heavy showers
and thunderstorms are from 31N to 36N between 61W and 64W. Scattered
moderate convection is elsewhere from 29N to 40N between 57W and
66W. Please see the latest NHC Public Intermediate Advisory under
AWIPS/WMO headers MIATCPAT2/WTNT32 KNHC AND NHC Forecast/Advisory
under AWIPS/WMO headers MIATCMAT2/WTNT22 KNHC for more details.

Lisa restrengthens to a Tropical Storm at 24/1500 UTC. Its center
is near 24.7N 38.8W or about 982 nm northwest of the Cabo Verde
Islands moving northwest at 9 kt. Estimated minimum central
pressure is 1008 mb. Maximum sustained wind speed is 35 kt with
gusts to 45 kt. There are scattered showers associated to Lisa NE
of its center from 24N to 30N between 31W and 36W. Please see the
latest NHC Forecast/Advisory under AWIPS/WMO headers
MIATCMAT3/WTNT23 KNHC for more details.


A tropical wave is in the eastern Atlantic extending from 04N to
15N with axis near 25W, moving west near 20 kt over the past 24
hours. CIRA LPW imagery show shallow moisture in the wave
environment with patches of dry air. The wave is also in a region
of favorable deep layer wind shear, however no convection is
observed at the time. A 1013 mb low is embedded in the monsoon
trough ahead of the wave near 07N28W with scattered showers from
06N to 12N between 27W and 35W. The wave is going to merge with
this broad area of low pressure late today. Then, this
disturbance is expected to move rapidly westward across the
tropical Atlantic Ocean for the next several days. Environmental
conditions are expected to become conducive for gradual
development, and a tropical depression could form while the system
approaches the Lesser Antilles and moves into the Caribbean Sea by
the middle of next week.

A tropical wave is in the central Tropical Atlantic within 390 nm
east of the Lesser Antilles. The wave extends from 07N to 20N
with axis near 54W, moving west at 10 kt over the past 24 hours. 
The wave is in a region of favorable deep layer wind shear and shallow
moderate moisture with some pockets of dry air. In the upper
levels, water vapor imagery show strong dry air subsidence, which
is limiting the convection to scattered showers from 18N to 21N
and from 08N to 11N between 51W and 55W.

A tropical wave is in the Bay of Campeche. The wave extends from
07N to 20N with axis near 95W, moving at 5 kt over the past 24
hours. Low level moisture convergence and diffluence aloft support
scattered showers and isolated tstms across the SW Gulf of Mexico
S of 23N.


The Monsoon Trough extends across Africa into the east Tropical
Atlantic near 11N15W to a 1013 mb low near 07N28W to 06N38W. The
ITCZ begins near 06N38W and continues to 09N52W to the coast of
Guyana near 08N60W. For convection information see the tropical
waves section. Otherwise, scattered showers are from 05N to 13N E
of 21W.



Broad surface high pressure covering the E CONUS extends a ridge S
to the N-NE Gulf of Mexico, thus supporting gentle variable winds
in this portion of the basin. Gentle SE flow dominates over the
remainder waters of the Gulf and draws moisture from the Caribbean
Sea to support scattered showers and tstms N of 26N W of 89W.
Similar convection is in the SW basin associated with a tropical
wave. Please see the tropical waves section for further details.
The wave will fully move to E Pacific waters tonight, leaving a
weak low pressure center over the west Bay of Campeche that is
forecast to dissipate Monday.


A surface trough is off the Yucatan Peninsula extending from
21N86W to 15N88W generating isolated showers over the NW Caribbean
Sea W of 82W, including the Yucatan Channel. The other area of
convective activity is the SW basin where the E Pacific monsoon
trough and a 1011 mb low near 09N76W support heavy showers and
tstms S of 12N. Unfavorable or strong deep layer wind shear covers
the majority of the remainder basin, thus providing stable
conditions and fair weather. A tropical wave will enter the E
Caribbean waters Sunday possibly enhancing showers across the
Lesser Antilles.


Except for isolated showers across the NW Island, fair weather
prevails elsewhere. An upper-level low will coupled with the
easterly trade winds and enhance afternoon/evening showers and
thunderstorms through the weekend.


The main features in the basin are TS Karl N of the forecast
waters and TS Lisa, both discussed in the special features
section. A tropical wave near the Cape Verde Islands has medium
chance of becoming a tropical cyclone beyond the next two days.
See tropical waves section for further details. Over the SW N
Atlantic basin, a surface trough meanders from 30N78W to 25N80W to
the the Straits of Florida near 24N82W supporting showers over S
Florida and adjacent waters as well as the northern Bahamas.
Surface ridging and fair weather prevails elsewhere.

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