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033
AXNT20 KNHC 180541
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
141 AM EDT Sat Aug 18 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 0000 UTC surface analysis and satellite imagery through 0515 UTC.


...SPECIAL FEATURES...

Tropical Storm Ernesto centered near 50.4N 25.6W at 18/0300 UTC or 750 nm N of The Azores moving ENE at 30 kt. Estimated minimum central pressure is 999 mb. Maximum sustained wind speed is 40 kt with gusts to 50 kt. Ernesto is expected to become post-tropical overnight, and slight weakening is forecast to occur Saturday while Ernesto merges with a frontal zone by Saturday night. On this forecast track the post-tropical cyclone and its remnants will move across Ireland and the United Kingdom Saturday night and early Sunday. See latest NHC forecast/advisory under AWIPS/WMO headers MIATCPAT5/WTNT35 KNHC for more details.


...TROPICAL WAVES...

A tropical wave is in the E Atlc with axis extending from 04N-16N along 35W, moving W at 20 kt. The wave is in a deep layer wind shear environment. 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 E Caribbean with axis extending from 06N-18N along 60W, moving W at 20 kt. The wave is in a 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. Widely scattered moderate convection is from 10N-14N between 53W-61W.

A tropical wave is in the central Caribbean with axis extending from 09N-18N along 76W, moving W at 20 kt. The wave is in a moderate deep layer wind shear environment. GOES-16 water vapor imagery at the lower levels shows very dry air over the central Caribbean. This is limiting convection to isolated moderate convection over E Cuba and W Hispaniola from 19N-23N between 72W- 80W.




...MONSOON TROUGH/ITCZ...

The monsoon trough extends from the coast of W Africa near 13N17W to 10N30W to 07N40W. The ITCZ begins near 07N40W and continues to 08N50W to 10N60W. Besides the convection mentioned in the tropical wave section, scattered moderate to isolated strong convection is over W Africa from 08N-14N between 04W-18W. Scattered showers are within 120 nm of the remainder of the monsoon trough and ITCZ.


...DISCUSSION...

GULF OF MEXICO...

A 1024 mb high is centered over the W Atlantic near 30N69W. A ridge axis extends W from the high along 30N to E Texas. 10 kt SE surface winds covers the Gulf of Mexico N of 24N. A surface trough is over the Bay of Campeche from 22N90W to 16N93W. Scattwered moderate convection is from 16N-19N between 92W-95W. In the upper levels, an upper level high is centered over SE Louisiana near 30N90W. Upper level diffluence is over the Yucatan Channel producing scattered showers.

Expect, a surface trough to develop along the Yucatan Peninsula during the late afternoons, then drift westward across the southwest gulf waters during the overnight hours accompanied by a fresh east to southeast wind shift with the trough dissipating along 96W during the late mornings. Otherwise, expect an east to west ridge extends across the gulf waters along 30N accompanied by gentle to moderate anticyclonic flow that is forecast to increase to a fresh southerly breeze across the northwest gulf waters on Sun evening, and continue through sunrise on Mon. The ridge will then shift south and extend east to west across the central waters during the middle of next week.

CARIBBEAN SEA...

Two tropical waves are over the Caribbean Sea. See above. A surface trough extends over the Gulf of Honduras near 18N86W to the E Pacific near 10N86W. Scattered showers are within 120 nm of the trough. Surface ridging extends from the Atlantic to the northern half of the Caribbean. Fresh to strong winds are over the south-central Caribbean. In the upper levels, an upper level low is centered over central Cuba near 22N80W. Upper level diffluence is over Jamaica and E Cuba enhancing convection.

Expect, strong nocturnal easterly trades along the northwest coast of Colombia through the middle of next week. A tropical wave along 76W will continue to move westward across the western Caribbean during the weekend. A second tropical wave along 60W will continue through the east Caribbean this weekend. A third tropical wave in the central Atlantic will reach along 55W on Mon night and reach the east Caribbean during the middle of next week

ATLANTIC OCEAN...

A tropical wave is over the Atlantic. See above. A 1024 mb high is centered over the W Atlantic near 30N69W. A surface trough is over the central Atlantic from 32N54W to 26N62W. Scattered showers are within 90 nm of the trough. A 1028 mb high is centered over the Azores near 38N29W.

Expect over the W Atlantic for fresh trades to be south of 23N, except becoming locally strong along the north coast of Hispaniola during the late afternoon into early evening hours. The surface ridge axis will shift south to central Florida early next week.

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

$$ Formosa



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