Skip Navigation Links
NOAA NOAA United States Department of Commerce

Atlantic Tropical Weather Discussion

AXNT20 KNHC 221804

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
204 PM EDT Sat Jul 22 2017

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.

Please refer to the METEO-FRANCE High Seas Forecast, that is 
listed under the following links: MARINE...BULLETINS 
EXPERTISES...GRAND LARGE...METAREA II...or on the website:
GRANDLARGE/METAREA2. Gale-force winds are forecast for the area
that is called: AGADIR. 


A tropical wave came off coast of W Africa earlier this morning.
It axis extends from 15N17W to 05N17W. The wave is in a region of
favorable to neutral vertical shear, however is being engulfed by
Saharan dry air dust. The CIRA LPW imagery confirm the intrusion 
of the dry air mainly in the northern wave environment. Abundant
moisture in the African monsoon region along with upper level
diffluence support scattered showers and tstms from 06N to 11N E
of 24W. 

A tropical wave is in the central Atlc with axis extending from
20N31W to 11N33W, moving W at 5 kt within the last 24 hours. The 
wave is in a region of favorable to neutral vertical shear, 
however extensive intrusion of Saharan dry air dust to its
environment hinder deep convection at the time. Isolated showers
are confined to the SW wave environment due to the presence of the
monsoon trough. 

A tropical wave is in the central Atlc with axis extending from 
14N43W to 07N44W. The wave is in a region of favorable to neutral
vertical shear, however it is being severely affected by intrusion
of Saharan dry air dust to its environment. Middle to upper level
diffluence support isolated showers from 08N to 13N between 42W
and 47W.

A tropical wave is in the E Caribbean with axis extending from
21N61W to 10N62W, moving W at 10 kt within the last 24 hours. The
wave is in a region of favorable vertical wind shear and moderate
shallow moisture is in its vicinity. Even though the wave does
not show too much of a signal of Saharan dry air influencing its
environment, strong dry air subsidence from aloft seems to be
hindering the development of deep convection. Scattered to
isolated showers are expected across the NE Caribbean, including
Puerto Rico.

A tropical wave is in the central Caribbean with axis extending
from 20N72W to 10N74W, moving W at 20 kt within the last 24 hours.
The wave is in a region of neutral to unfavorable vertical shear
that along with dry air subsidence from aloft hinder deep
convection. Shallow moisture support scattered to isolated 
showers across Hispaniola and adjacent waters of E Cuba.


The monsoon trough axis extends from 10N14W and continues along
09N28W to 11N39W. The ITCZ begins near 09N47W and continues to
08N59W. Aside from the convection associated with the tropical 
waves, scattered heavy showers are from 05N to 11N between 52W and



Weak surface ridging continues to dominate across the Gulf with
gentle to light southerly winds advecting shallow moisture from
the Caribbean. This moisture along with a very unstable
environment aloft composed of middle level diffluent flow and an
upper level low support an elongated area of low pressure across
the northern Gulf analyzed as a surface trough from the Florida
big bend near 29N83W west-northwest to SE Texas near 29N94W.
Scattered heavy showers and tstms associated with this area of low
pressure are N of 26N E of 96W. Scatterometer data show fresh to
near gale winds in the vicinity of the trough associated with this
convection. Similar convection is off the SW Florida coast
extending about 75 nm into the SE Gulf waters. Not major changes
expected during the rest of the weekend. 


The main features in the Caribbean are two tropical waves. The
easternmost wave supporting scattered to isolated showers in the
NE basin and a second wave moving across central waters supporting
similar convection for Hispaniola, the Windward Passage and E
Cuba. For further details see the tropical waves section above. In
the SW portion of the basin, the monsoon trough support scattered
heavy showers within 60 nm off the coast of N Panama. The
remainder basin is under the influence of strong or unfavorable
vertical wind shear and dry air subsidence, which is supporting
fair weather. Otherwise, strong high pressure over the Atlc
extending a ridge along the northern basin increase the pressure
gradient enough to maintain the continuation of fresh to strong
winds in the south-central Caribbean. These winds are forecast to
prevail the next two days.


A tropical wave has been moving across the Island this morning,
which has been supporting scattered to isolated showers. The axis
of the wave is in the Winward Passage and will continue a westward
path, which will allow for fair weather to re-establish early
Sunday. However, a second tropical wave currently over E Caribbean
waters will allow for the re-development of showers the remaining


Aside from the tropical activity associated with the waves, the
remainder basin remains under the influence of a broad and strong
ridge that support fair weather. No major changes expected the two
to three days. See tropical waves section above for further

For additional information please visit