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.

...SPECIAL FEATURES... 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: WWW.METEOFRANCE.COM/PREVISIONS-METEO-MARINE/BULLETIN/ 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 58W.



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 Sunday.


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 details.

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

$$ Ramos