[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 151746
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT MON AUG 15 2011

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 1715 UTC.

...SPECIAL FEATURE...

THE CENTER OF TROPICAL STORM GERT AT 15/1500 UTC IS NEAR 32.0N
63.2W...ABOUT 80 NM ESE OF BERMUDA. GERT IS MOVING
NORTHWARD 10 KT. THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 1000
MB. THE MAXIMUM SUSTAINED WIND SPEEDS ARE 50 KT WITH GUSTS TO 60
KT. PUBLIC ADVISORIES ON TROPICAL STORM GERT ARE ISSUED UNDER
WMO HEADER WTNT32 KNHC AND UNDER AWIPS HEADER MIATCPAT2.
FORECAST/ADVISORIES ON TROPICAL STORM GERT ARE ISSUED UNDER WMO
HEADER WTNT22 KNHC AND UNDER AWIPS HEADER MIATCMAT2. THE STORM
CENTER IS EXPECTED TO PASS E OF BERMUDA OVER THE NEXT SEVERAL
HOURS. NUMEROUS MODERATE/SCATTERED STRONG CONVECTION IS LOCATED
WITHIN 75 NM OF THE STORM CENTER...STILL E OF BERMUDA. ISOLATED
MODERATE CONVECTION IS ALSO SE OF THE SYSTEM FROM 27N-31N
BETWEEN 58W-61W.

...TROPICAL WAVES...

TROPICAL WAVE HAS PUSHED OFF THE AFRICAN COAST EXTENDING FROM
19N20W TO 12N19W MOVING W 10-15 KT. SATELLITE IMAGERY SHOWS
CLEAR CUT CYCLONIC LOW-LEVEL FLOW AROUND THE WAVE AXIS CONFIRMED
BY AN ASCAT SCATTEROMETER PASS FROM THIS MORNING. TOTAL
PRECIPITABLE WATER IMAGERY INDICATES THAT A SURGE OF DEEP LAYER
MOISTURE IS ALSO MOVING OFF THE AFRICAN COAST IN ASSOCIATION
WITH THE WAVE. SCATTERED MODERATE/STRONG CONVECTION IS MAINLY S
OF THE AXIS FROM 7N-13N BETWEEN 15W-22W.

TROPICAL WAVE IS APPROACHING THE LESSER ANTILLES ALONG 16N58W TO
10N56W MOVING W NEAR 20 KT. SATELLITE IMAGERY AND SURFACE
OBSERVATIONS INDICATE CYCLONIC FLOW AROUND THE WAVE AXIS
ACCOMPANIED BY ENHANCED DEEP LAYER MOISTURE FROM 12N-17N. LARGE
CLUSTERS OF STRONG CONVECTION ARE FROM 14N-16N BETWEEN
57W-60W...AND FROM 15N-17N BETWEEN 61W-62W. SCATTERED
MODERATE/ISOLATED STRONG CONVECTION COVERS THE AREA ELSEWHERE
FROM 12N-18N BETWEEN 54W-63W. THESE AREAS OF ACTIVITY ARE
ALREADY IMPACTING MUCH OF THE LESSER ANTILLES.

TROPICAL WAVE IN THE BAY OF CAMPECHE IS APPROACHING THE MEXICAN
COAST ALONG 22N95W TO 17N95W MOVING W AT 10-12 KT. MODERATELY
HIGHER MOISTURE VALUES EVIDENT IN TOTAL PRECIPITABLE WATER
IMAGERY SURROUND THE WAVE. ISOLATED SHOWERS ARE WITHIN 50 NM OF
THE AXIS.

...THE ITCZ/THE MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS W OF A TROPICAL WAVE NEAR THE AFRICAN
COAST ALONG 11N21W 10N32W 12N42W. SCATTERED MODERATE/ISOLATED
STRONG CONVECTION IS FROM 5N-9N BETWEEN 23W-44W.

...DISCUSSION...

THE GULF OF MEXICO...
A LONGWAVE UPPER LEVEL TROUGH COVERING THE ERN CONUS SINKS INTO
THE NRN GULF FROM N CENTRAL FLORIDA TO S OF LOUISIANA NEAR
28N92W. THE UPPER TROUGH SUPPORTS A FRONTAL BOUNDARY THAT BARELY
ENTERS THE NE GULF FROM THE FLORIDA PANHANDLE NEAR 31N84W TO SE
LOUISIANA NEAR 30N90W. A SURFACE TROUGH IS AHEAD OF THE FRONTAL
BOUNDARY ALONG 30N81W TO 27N88W. ISOLATED SHOWERS/THUNDERSTORMS
DOT THE FLORIDA PENINSULA S OF THE TROUGH AXIS AS WELL AS WITHIN
300 NM S OF THE AXIS OVER WATER. SIGNIFICANT DRY AIR IS N OF THE
FRONTAL BOUNDARY. A TROPICAL WAVE IS MOVING WWD ACROSS THE BAY
OF CAMPECHE SUPPORTING A FEW ISOLATED SHOWERS S OF 23N BETWEEN
93W-97W. THE REMAINDER OF THE BASIN IS UNDER WEAK SURFACE
RIDGING AROUND A 1014 MB HIGH IN THE NW GULF NEAR 27N93W.
ALOFT...BESIDES THE UPPER TROUGH COVERING THE NE GULF...UPPER
LEVEL RIDGING COVERS THE REMAINDER OF THE BASIN ANCHORED OVER
NRN MEXICO NEAR 31N107W. EXPECT THE FRONTAL BOUNDARY IN THE NE
GULF TO DIP DOWN A LITTLE FARTHER S BEFORE COMING STATIONARY.
WEAK RIDGING SHOULD COVER THE REMAINDER OF THE BASIN.

THE CARIBBEAN SEA...
A SURFACE TROUGH EXTENDS ACROSS THE MONA PASSAGE ALONG 23N70W TO
18N76W SUPPORTING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS
WITHIN 200 NM NW OF THE AXIS ACROSS ERN CUBA. A WEAK UPPER LEVEL
LOW IS TO THE SW OF THE TROUGH WHICH MAY BE HELPING TO ENHANCE
SOME OF THE ACTIVITY. STRONG SHOWERS/THUNDERSTORMS COVER THE SW
CARIBBEAN S OF 13N BETWEEN 75W-85W INFLUENCED BY THE MONSOON
TROUGH THAT EXTENDS FROM THE E PACIFIC ACROSS COSTA RICA TO NRN
COLOMBIA. THE CENTRAL AND ERN CARIBBEAN ARE UNDER EXTREMELY FAIR
CONDITIONS DUE TO AN AREA OF STRONG SUBSIDENCE AND DRY AIR IN
ELY FLOW ALOFT. HOWEVER...A TROPICAL WAVE E OF THE LESSER
ANTILLES IS BRINGING STRONG SHOWER ACTIVITY TO THE FAR ERN
CARIBBEAN S OF 18N E OF 63W. THE ISLANDS IN THIS AREA SHOULD
EXPECT SHOWER ACTIVITY TO CONTINUE OVER THE NEXT 24 HOURS AS THE
WAVE CROSSES.

THE ATLANTIC OCEAN...
SCATTERED SHOWERS/THUNDERSTORMS ARE ACROSS MUCH OF THE W ATLC N
OF 25N W OF 70W ASSOCIATED WITH A DEEP LAYER TROUGH COVERING THE
ERN CONUS. AN UPPER LEVEL RIDGE IS CENTERED TO THE E OF TROPICAL
STORM GERT. SEE SPECIAL FEATURES ABOVE. A SURFACE TROUGH IS
MOVING ACROSS THE SE BAHAMAS FROM 23N70W TO THE MONA PASSAGE AND
INTO THE CARIBBEAN. SCATTERED SHOWERS/POSSIBLE THUNDERSTORMS ARE
WITHIN 120 NM W OF THE AXIS. FARTHER E...WEAK AND BROAD SURFACE
RIDGING COVERS THE CENTRAL AND ERN ATLC ANCHORED BY A 1022 MB
HIGH NEAR 33N50W...AND A 1021 MB HIGH S OF THE AZORES ISLANDS
NEAR 33N25W. ALOFT...AN UPPER LEVEL LOW IS CENTERED NEAR 26N48W.
AN UPPER LEVEL RIDGE COVERS THE FAR ERN ATLC CENTERED OVER THE
CANARY ISLANDS NEAR 29N17W. VISIBLE SATELLITE IMAGERY INDICATES
THAT AN AREA OF DUST IS W OF THE TROPICAL WAVE NEAR THE AFRICAN
COAST AND EXTENDS TO NEAR 40W. A SECOND AREA OF DUST IS BETWEEN
45W-60W N OF THE TROPICAL WAVE E OF THE LESSER ANTILLES.

FOR ADDITIONAL INFORMATION PLEASE VISIT
HTTP://WWW.HURRICANES.GOV/MARINE

$$
WALTON






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