[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 161748
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT TUE AUG 16 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 16/1500 UTC IS NEAR 38.1N
57.5W...ABOUT 500 NM NE OF BERMUDA. GERT IS MOVING NE AT 23 KT.
THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 1005 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 ACCELERATE NE BEFORE BECOMING
EXTRATROPICAL. ISOLATED MODERATE CONVECTION IS FROM 37N-39N
BETWEEN 56W-60W.

...TROPICAL WAVES...

WELL DEFINED TROPICAL WAVE IS MOVING W THROUGH THE CAPE VERDE
ISLANDS ALONG 17N24W TO 11N27W AT 15 KT. SATELLITE IMAGERY SHOWS
DISTINGUISHABLE LOW-LEVEL CYCLONIC FLOW AROUND THE WAVE AXIS
WHICH MAY BE FORMING A LOW CENTER ON THE WAVE AXIS. THIS
CYCLONIC FLOW IS ALSO EVIDENT IN SCATTEROMETER DATA. THE WAVE IS
EMBEDDED WITHIN A SURGE OF DEEP LAYER MOISTURE EXTENDING TO 21N.
WHILE NO DEEP CONVECTION IS IN CLOSE VICINITY OF THE WAVE...A
CLUSTER OF MODERATE/STRONG CONVECTION IS SW OF IT FROM 7N-10N
BETWEEN 28W-34W.

TROPICAL WAVE IS MOVING W ACROSS THE ERN CARIBBEAN ALONG 18N66W
TO 11N65W AT 20 KT. A RECENT ASCAT SCATTEROMETER PASS INDICATES
LOW-LEVEL CYCLONIC FLOW IS AROUND THE WAVE AXIS. VERY ENHANCED
MOISTURE VALUES SURROUND THE WAVE ACROSS THE ERN CARIBBEAN E OF
71W. NUMEROUS MODERATE/SCATTERED STRONG CONVECTION IS FROM
15N-18N BETWEEN 61W-71W. ACCORDING TO THE SAN JUAN PUERTO RICO
RADAR...MOST OF THE STRONGEST ACTIVITY IS S OF THE ISLANDS WITH
MORE SCATTERED ACTIVITY OVER THE ISLAND. AN AREA OF AFRICAN DUST
IS TO THE N OF THE ISLANDS WHICH MAY BE WHAT IS INHIBITING
CONVECTION TO THE N.

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

THE MONSOON TROUGH EXTENDS W OF A TROPICAL WAVE NEAR THE CAPE
VERDE ISLANDS ALONG 10N29W 10N43W. SCATTERED MODERATE/ISOLATED
STRONG CONVECTION IS JUST OFF THE AFRICAN COAST FROM 8N-12N
BETWEEN 18W-25W. SCATTERED MODERATE/STRONG CONVECTION IS FROM
5N-12N BETWEEN 40W-46W.

...DISCUSSION...

THE GULF OF MEXICO...
A LONGWAVE UPPER LEVEL TROUGH IS MOVING EWD WITH AXIS NOW OVER
THE ERN SEABOARD. THE UPPER TROUGH CONTINUES TO SUPPORT A
STATIONARY FRONT ACROSS THE NE GULF OF MEXICO FROM THE BIG BEND
OF FLORIDA NEAR 29N83W TO SE LOUISIANA NEAR 29N90W. ISOLATED
SHOWERS/THUNDERSTORMS ARE S OF THE FRONT WITHIN 300 NM BETWEEN
81W-86W OVER MUCH OF CENTRAL AND S FLORIDA. THE REMAINDER OF THE
BASIN IS UNDER WEAK SURFACE RIDGING AROUND A 1015 MB HIGH IN THE
NW GULF NEAR 27N92W. ALOFT...UPPER LEVEL RIDGING COVERS THE WRN
GULF AROUND AN UPPER LEVEL HIGH CENTERED OVER SRN NEW MEXICO
NEAR 32N107W. A FEW SHOWERS/POSSIBLE THUNDERSTORMS ARE IN THE
FAR SW BAY OF CAMPECHE S OF 21N W OF 95W WHICH MAY BE REMNANTS
OF A TROPICAL WAVE THAT DISSIPATED OVER MEXICO AT 16/0000 UTC.
EXPECT WEAK RIDGING TO REMAIN OVER THE WRN HALF OF THE BASIN
WITH THE STATIONARY FRONT CONTINUING TO SIT OVER THE NE GULF.

THE CARIBBEAN SEA...
ISOLATED SHOWERS/THUNDERSTORMS DOT THE NW CARIBBEAN FROM BELIZE
TO CENTRAL CUBA ASSOCIATED WITH A SURFACE TROUGH ACROSS ERN CUBA
AS WELL AS AN UPPER LEVEL TROUGH EXTENDING FROM HONDURAS TO WRN
CUBA. WATER VAPOR IMAGERY INDICATES DRY AIR ALOFT COVERS THE
CENTRAL CARIBBEAN WHICH IS HELPING TO MAINTAIN FAIR CONDITIONS.
SCATTERED SHOWERS/THUNDERSTORMS ARE ACROSS THE SW CARIBBEAN FROM
12N-16N BETWEEN 78W-85W...AND ACROSS PORTIONS OF PANAMA AND
COSTA RICA INFLUENCED BY THE MONSOON TROUGH THAT EXTENDS FROM
THE E PACIFIC ACROSS CENTRAL COSTA RICA TO NRN COLOMBIA. A
TROPICAL WAVE IS IMPACTING THE ERN CARIBBEAN BRINGING STRONG
SHOWERS/THUNDERSTORMS TO THE AREA FROM 15N-18N BETWEEN 61W-71W.
A CLUSTER OF STORMS HAS ALSO JUST POPPED UP OVER ERN DOMINICAN
REPUBLIC. WHILE MUCH OF THE ACTIVITY IS S OF THE ISLANDS...THERE
IS STILL THE POTENTIAL FOR HEAVY ACTIVITY OVER THE N CENTRAL
CARIBBEAN OVER THE NEXT 24 HOURS. SEE TROPICAL WAVE SECTION
ABOVE FOR MORE DETAILS. ALOFT...MAINLY ELY FLOW ALOFT COVERS THE
ERN CARIBBEAN WITH WEAK UPPER RIDGING CENTERED NEAR 15N80W.

THE ATLANTIC OCEAN...
SCATTERED SHOWERS/THUNDERSTORMS ARE ACROSS MUCH OF THE W ATLC N
OF 26N W OF 71W ASSOCIATED WITH A DEEP LAYER TROUGH EXTENDING
DOWN THE ERN SEABOARD. A PAIR OF WEAK UPPER RIDGES COVER THE SW
N ATLC CENTERED N OF CUBA NEAR 23N76W...AND N OF PUERTO RICO
NEAR 19N66W. A SURFACE TROUGH EXTENDS FROM THE CENTRAL BAHAMAS
NEAR 24N74W TO ERN CUBA NEAR 20N78W SUPPORTING SCATTERED
SHOWERS/THUNDERSTORMS WITHIN 50 NM OF THE AXIS. THE REMAINDER OF
THE CENTRAL AND ERN ATLC IS DOMINATED BY BROAD SURFACE RIDGING.
ALOFT...AN UPPER LEVEL LOW IS CENTERED NEAR 24N53W. AN UPPER
LEVEL RIDGE IT TO THE N CENTERED NEAR 39N52W. ANOTHER UPPER
LEVEL RIDGE IS CENTERED OVER THE CANARY ISLANDS NEAR 29N18W.
VISIBLE SATELLITE IMAGERY INDICATES TWO AREAS OF DUST. THE FIRST
IS N OF A TROPICAL WAVE ACROSS THE CAPE VERDE ISLANDS N OF 20N E
OF 30W. THE SECOND IS N OF 18N BETWEEN 45W-65W.

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

$$
WALTON





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