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Atlantic Tropical Weather Discussion

AXNT20 KNHC 180008

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
808 PM EDT Fri Aug 17 2018

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 1800 UTC surface analysis and satellite imagery through 
2315 UTC.


Tropical Storm Ernesto centered near 49.1N 29.8W at 17/2100 UTC
or 680 nm N of The Azores moving NE at 27 kt. Estimated minimum
central pressure is 1003 mb. Maximum sustained wind speed is 40
kt with gusts to 50 kt. A rapid northeast or east-northeast 
motion is expected during the next day or so. On the forecast 
track, the post-tropical cyclone and its remnants will move 
across Ireland and the United Kingdom Saturday night and early 
Sunday. Ernesto is expected to become post-tropical this evening, 
and some gradual weakening is forecast to occur Saturday and 
Saturday night. The post-tropical cyclone is expected to merge 
with a frontal zone by early Sunday. See latest NHC forecast/ 
advisory under AWIPS/WMO headers MIATCPAT5/WTNT35 KNHC for more 


A tropical wave is in the E Atlc with axis extending from 06N-18N
along 30W, moving W at 10-15 kt. The wave is in a low deep layer 
wind shear environment, however both CIRA LPW and GOES-16 water 
vapor imagery at the lower levels show dry air affecting the wave.
These two factors are contributing to the lack of convection at 
this time.

A tropical wave is in the central Atlc with axis extending from
05N-16N along 58W, moving W at 15-20 kt. The wave is in a low 
deep layer wind shear environment, and CIRA LPW imagery shows 
abundant low level moisture associated with it. However, some dry 
air intrusion is noted in the NW wave environment as shown both 
in CIRA LPW, and water vapor imagery at the lower levels.  
Scattered moderate isolated strong convection is from 10N-14N 
between 54W-61W.

A tropical wave is in the central Caribbean with axis extending 
from 10N-20N along 74W, moving W at 10-15 kt. The wave is in a 
moderate deep layer wind shear environment. GOES-16 water vapor 
imagery at the lower levels show very dry air over the central 
Caribbean. This is limiting convection to scattered moderate
convection over W Hispaniola from 18N-21N between 72W-74W. 


The monsoon trough extends from the coast of W Africa near 
14N17W to 10N28W. The ITCZ begins near 10N35W and continues to 
09N46W to 11N56W. Besides the convection mentioned in the tropical
wave section, scattered moderate to strong convection is over W 
Africa and the coast from 08N-15N between 00W-18W. Isolated 
moderate convection is from 10N- 12N between 24W-27W, and from 
10N-12N between 36W-49W. 



The Bermuda high extends a ridge axis SW across Florida and large
portions of the Gulf into eastern Mexico. The ridge is providing
return flow in the range of 5-10 kt across the region except in
the north-central Gulf where scattered heavy showers and tstms
enhance the winds to fresh. Widely scattered moderate convection
is N of 25N between 85W-92W. This convection is being supported 
by the inflow of shallow moisture from the Caribbean with 
southeasterly winds, and middle level diffluent flow. Elsewhere,
scattered moderate to isolated strong convection is over the
Yucatan Peninsula and the E Bay of Campeche from 17N-22N between
88W-93W. Surface ridging will prevail across the basin through 
early next week. Showers over the NE basin are forecast to 
continue through Sat night.


CIRA LPW imagery shows abundant shallow moisture across most of 
the Caribbean. In the western basin, an upper level anticyclone
provides divergent flow aloft, which supports a broad area of 
isolated moderate convection from 15N-23N between 83W-88W. A 
tropical wave is moving across the central basin. SAn area of 
scattered moderate convection is S of Puerto Rico from 15N-17N
between 65W-68W. Otherwise, surface ridging extending from the 
Atlantic to the northern half of the basin, continues to support 
fresh to strong winds in the south-central Caribbean. The next 
tropical is forecast to move across the Lesser Antilles Sat 
morning. Showers will prevail in the E Caribbean through the 


Two tropical waves are over the Atlantic. See above. The Bermuda 
high and the Azores high covers most of the Atlc ocean mainly 
supporting fair weather. A weakness in the ridge is analyzed as a 
surface trough that extends from 31N55W SW to 26N61W to 24N72W. 
Scattered showers and tstms are within 105 nm either side of the 
trough. Isolated showers are across the Bahamas. A large area of 
disorganized showers and thunderstorms is SE of the Windward 
Islands associated with a tropical wave. 

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