[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 131753
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT MON AUG 13 2012

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
1700 UTC.

...TROPICAL WAVES...

TROPICAL WAVE IS APPROACHING THE CAPE VERDE ISLANDS ALONG 22N20W
TO 11N21W MOVING W AT 10-15 KT. THE WAVE ALIGNS WITH A SURGE OF
DEEP LAYER MOISTURE PRESENT IN TOTAL PRECIPITABLE WATER IMAGERY.
THERE IS ALSO A CLEARING THE IN THE SAHARAN AIR LAYER AND
AFRICAN DUST PRESENT ACROSS MUCH OF THE EASTERN ATLC. THIS DRY
AIRMASS SURROUNDING THE WAVE IS LIMITING DEEP CONVECTION TO THE
MONSOON TROUGH REGION. ISOLATED MODERATE CONVECTION IS FROM
8N-14N BETWEEN 16W-21W. SCATTERED MODERATE/ISOLATED STRONG
CONVECTION IS FROM 7N-10N BETWEEN 21W-30W.

TROPICAL WAVE EXTENDS FROM 26N41W TO 18N45W THROUGH A 1016 MB
SURFACE LOW ALONG THE AXIS AT 22N44W MOVING W AT 20 KT. THE
SATELLITE REPRESENTATION OF THE WAVE IS WELL-DEFINED WITH CLEAR
LOW-LEVEL CYCLONIC FLOW AROUND THE LOW CENTER. THE SYSTEM ALSO
COINCIDES WITH A CUT-OFF AREA OF DEEP MOISTURE PRESENT IN TOTAL
PRECIPITABLE WATER IMAGERY. HOWEVER...DRY AIR AND DUST SURROUND
THE WAVE LIMITING MOST DEEP CONVECTION. ONLY SOME WEAK ISOLATED
CONVECTION IS FROM 22N-24N BETWEEN 43W-47W.

TROPICAL WAVE...REMNANTS OF T.D. SEVEN...IS MOVING W AT 20 KT
THROUGH THE CENTRAL CARIBBEAN FROM 19N72W TO 11N76W. SATELLITE
IMAGERY ALONG WITH SURFACE OBSERVATIONS AND A RECENT ASCAT
SCATTEROMETER PASS INDICATE SHARP CYCLONIC SURFACE FLOW IS
AROUND THE AXIS. THE WAVE ALSO LIES UNDERNEATH AN AREA OF
DIFFLUENCE ALOFT...WHICH IS HELPING PRODUCE
SHOWERS/THUNDERSTORMS NEAR THE WAVE. NUMEROUS MODERATE/SCATTERED
STRONG CONVECTION IS FROM 15N-19N BETWEEN 70W-77W INCLUDING MUCH
OF SOUTHERN HISPANIOLA.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS ACROSS W AFRICA TO THE COAST OF
SENEGAL AT 14N17W WHERE IT CONTINUES ACROSS ATLC WATERS ALONG
9N25W 9N37W. THE ITCZ BEGINS AT 9N37W AND CONTINUES ALONG 11N48W
TO 10N64W. BESIDES CONVECTION ASSOCIATED WITH TROPICAL
WAVES...SCATTERED MODERATE CONVECTION IS FROM 9N-12N BETWEEN
48W-54W.

...DISCUSSION...

GULF OF MEXICO...
WEAK SURFACE RIDGING COVERS THE MAJORITY OF THE GULF OF MEXICO
TODAY EXTENDING FROM THE CENTRAL ATLC. SURFACE WINDS ARE LIGHT
AND ANTI-CYCLONIC AROUND THE RIDGE. THE SURFACE RIDGE IS ALSO
SUPPORTING MOSTLY FAIR WEATHER. IT IS SUPPORTED BY AN UPPER
LEVEL RIDGE CENTERED OVER THE NW BAHAMAS. HOWEVER...AN UPPER
LEVEL TROUGH OVER CENTRAL MEXICO IS HELPING SUPPORT A LARGE
CLUSTER OF STRONG SHOWERS/THUNDERSTORMS IN THE SW GULF FROM
20N-24N BETWEEN 93W-97W. A BROAD UPPER TROUGH MOVING INTO THE
EASTERN CONUS IS ALSO SUPPORTING A WEAK STATIONARY FRONT ALONG
THE FLORIDA PANHANDLE. A FEW SHOWERS HAVE POPPED UP S OF THE
AXIS AS WELL AS DOWN THE FLORIDA PENINSULA. EXPECT LITTLE CHANGE
OVER THE NEXT 24 HOURS.

CARIBBEAN SEA...
DRY AIR ALOFT COVERS THE WESTERN CARIBBEAN AROUND AN THE WEST
SIDE OF AN INVERTED UPPER LEVEL TROUGH ALONG 79W. THE DRY AIR IS
SUPPORTING MOSTLY CLEAR SKIES W OF 77W. STRONG
SHOWERS/THUNDERSTORMS ARE IN THE EXTREME SW CARIBBEAN ALONG THE
MONSOON TROUGH THAT EXTENDS FROM NORTHERN PANAMA AT 10N82W TO
NORTHERN COLOMBIA AT 10N76W. THE CENTRAL CARIBBEAN IS IMPACTED
BY AN ACTIVE TROPICAL WAVE THAT EXTENDS FROM HISPANIOLA TO
NORTHERN COLOMBIA. IS IT SUPPORTING A LARGE AREA OF
SHOWERS/THUNDERSTORMS FROM 14N-19N BETWEEN 70W-77W. SEE TROPICAL
WAVE SECTION ABOVE FOR MORE DETAILS. THE WAVE LIES ON THE
DIFFLUENT SIDE OF THE UPPER LEVEL TROUGH ALONG 79W...WHICH MAY
BE HELPING ENHANCE SOME OF THE ACTIVITY NEAR THE WAVE. THE
EASTERN CARIBBEAN IS NOW MOSTLY CLEAR DUE TO DRY AIR MOVING INTO
THE AREA FROM THE TROPICAL ATLC AROUND AN UPPER LEVEL RIDGE OVER
THE CENTRAL ATLC. EXPECT THE WAVE TO MOVE WESTWARD DRAWING
MOISTURE WITH IT.

ATLANTIC OCEAN...
AN UPPER LEVEL RIDGE COVERS THE W ATLC SUPPORTING A WEAK SURFACE
RIDGE. HOWEVER...AN UPPER LEVEL SHORTWAVE TROUGH TO THE N ALONG
70W IS SUPPORTING SHOWERS/THUNDERSTORMS FROM 28N-31N BETWEEN
67W-73W. A WEAK SURFACE TROUGH IS ALSO ALONG 31N75W TO 29N79W
SUPPORTING A FEW ISOLATED SHOWERS NEAR THE AXIS. TO THE
EAST...AN UPPER LEVEL LOW IS CENTERED NEAR 30N61W SUPPORTING A
FEW ISOLATED SHOWERS N OF 29N BETWEEN 55W-61W. AN UPPER LEVEL
RIDGE IS TO THE E CENTERED NEAR 30N48W SUPPORTING A 1025 MB HIGH
NEAR 33N43W...WHICH IS PROVIDING SURFACE RIDGING AND FAIR
WEATHER ACROSS THE REMAINDER OF THE ATLC...BESIDES NEAR TROPICAL
WAVES. VISIBLE SATELLITE IMAGERY INDICATES THAT AN AREA OF DUST
EXTENDS FROM THE COAST OF AFRICA AROUND BOTH TROPICAL WAVES IN
THE TROPICAL ATLC. THE DRY AIR MASS IS LIMITING CONVECTION NEAR
THE TROPICAL WAVES.

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

$$
WALTON





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