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Atlantic Tropical Weather Discussion

AXNT20 KNHC 251749

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1805 UTC Mon Sep 25 2023

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.


Tropical Storm Philippe is centered near 17.3N 45.5W at 25/1500 
UTC or 1010 nm E of the Northern Leeward Islands, moving W at 11 
kt. Estimated minimum central pressure is 1000 mb. Peak seas are 
near 21 ft. A turn to the west-northwest is expected by tonight, 
and a northwestward motion is forecast to occur in a couple of 
days. Little change in strength is forecast during the next few 
days. Please, read the latest HIGH SEAS FORECAST, that is issued 
by the National Hurricane Center, at the website-, and the latest 
Tropical Storm Philippe NHC Forecast/Advisory and Public 
Advisory, at, for more details.

Eastern Tropical Atlantic (AL91): A tropical wave located 
several hundred miles west-southwest of the Cabo Verde Islands 
continues to produce disorganized showers and thunderstorms. 
Maximum winds are 20 kt and peak seas to 8 ft. Scattered 
moderate and isolated strong convection is noted from 07N-12N 
between 27W-33W.  Environmental conditions are forecast to be 
conducive for gradual development, and a tropical depression is 
likely to form within the next few days as the system moves west-
northwestward across the central tropical Atlantic. There is a 
medium chance of formation through 48 hours.


An east Atlantic tropical wave - Invest AL91 - has its axis 
along 31W between 03N-17N, moving westward at 10-15 kt. See 
SPECIAL FEATURES above for more information.

A central Caribbean tropical wave has its axis along 77W, south 
of 20N, moving westward at 10-15 kt. Numerous moderate and 
scattered strong convection is noted from 10N-19N between 76W-


The monsoon trough leaves the coast of Mauritania near 17N16W 
and continues to a 1012 mb low pressure (AL91) near 10N31W and 
then to 08N32W. The ITCZ extends from there to 07N40W, where 
there is a break. The monsoon trough begins again at 16N46W to 
10N53W, where the ITCZ then extends to the south of Venezuela 
near 09N61W. Scattered moderate and isolated strong convection 
is noted from 07N-12N between 27W-33W and from 09N-12N between 
48W-53W. Scattered moderate convection is noted from 10N-14N 
east of 20W.


A surface trough extends from the Yucatan peninsula near 21N89W 
north-northeastward to 28N85W. Isolated moderate convection is 
noted south of 28N and east of 87W, as the surface trough and 
convection are being forced by a deep-layered trough over the 
same location. A weak 1015 mb high is centered near the Texas 
and Louisiana coast at 29N93W. Winds away from any thunderstorms 
are light to gentle with seas 2-3 ft.

For the forecast, the surface trough over the southeast and 
south-central Gulf accompanied by scattered showers and 
thunderstorms will drift slowly into the western Gulf through 
mid week and dissipate. Meanwhile, weak high pressure will 
persist over the north-central and northeast Gulf. This pattern 
will support gentle to moderate NE to E winds and slight seas 
across the basin through the middle of the week.


The Bermuda-Azores High well north of the Caribbean interacting 
with the 1008 mb Colombian Low to produce generally fresh trades 
over the central Caribbean and gentle to moderate elsewhere. 
Seas are 5-9 ft over the central Caribbean and 2-4 ft elsewhere.
Numerous moderate and scattered strong convection is noted from 
10N-19N between 76W-83W in association with the tropical wave 
near 77W. Winds and seas are higher in association with the 
thunderstorm activity.

In the forecast, high pressure north of the area will continue 
to support moderate to fresh trade winds across most of the 
eastern and central Caribbean into mid week, with fresh to 
strong pulses off northwest Venezuela and northeast Colombia 
during mainly the overnight and early morning hours. Seas will 
build in mixed NE and E swell across the waters east of the 
Leeward Islands starting late Tue, ahead of Tropical Storm 
Philippe. Philippe is expected to turn NW before reaching 55W, 
and move into the central Atlantic. 


Refer to the SPECIAL FEATURES section for details on Tropical 
Storm Philippe and Invest AL91.

An expansive Bermuda-Azores High and associated ridge extends 
just north of our waters. Aside from higher winds near Philippe 
and Invest AL91, the trades are generally gentle to moderate 
(with seas 6-8 ft) in the central and eastern Atlantic and light 
to gentle (with seas 4-6 ft) in the western Atlantic. A surface 
trough extends from 25N65W to 28N63W with scattered moderate 
convection within 120 NM east of the trough axis, but no 
enhancement of winds or seas.

Philippe will move to 17.6N 47.2W this evening, 18.1N 49.2W Tue 
morning, 18.9N 51.2W Tue evening, 19.9N 52.9W Wed morning, 21.1N 
54.2W Wed evening, and 22.1N 55.4W Thu morning. Philippe will 
change little in intensity as it moves to near 23.7N 56.9W early 
Fri. Regardless of the exact position of the center later in the 
week, rough seas ahead of the storm can be expected east of 60W 
starting late Tue. Elsewhere, seas may build by Thu north of the 
Bahamas and east of Florida in NE swell.