[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 151752
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT WED AUG 15 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.

...SPECIAL FEATURES...
A 1013 MB SURFACE LOW IS CENTERED IN THE CENTRAL ATLC NEAR
28N55W. A SURFACE TROUGH EXTENDS FROM THE LOW CENTER TO THE N TO
32N55W. THE SYSTEM HAS BECOME BETTER ORGANIZED FROM 24 HOURS
AGO. CURRENTLY SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS
FROM 27N-32N BETWEEN 53W-57W. THE LOW IS EXPECTED TO MOVE NNW
BEFORE TURNING SLIGHTLY EAST. IF THE SYSTEM BECOMES BETTER
ORGANIZED IT COULD FORM A TROPICAL DEPRESSION.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 19N24W TO 12N23W MOVING W AT 15-20 KT.
THE WAVE LIES IN THE MIDDLE OF A LARGE AREA OF ENHANCED DEEP
LAYER MOISTURE. A RECENT SCATTEROMETER PASS INDICATES THAT THERE
IS SOME LOW-LEVEL CYCLONIC FLOW AROUND THE NORTHERN EXTENT OF
THE WAVE...AND SATELLITE IMAGERY ALSO INDICATES MID-LEVEL
TURNING IS ALSO AROUND THE WAVE AXIS. DUE TO A LARGE DRY AIRMASS
ASSOCIATED WITH A SAHARAN AIR LAYER...NO DEEP CONVECTION IS
CURRENTLY ASSOCIATED WITH THE WAVE.

TROPICAL WAVE IS ALONG 18N41W TO 10N36W MOVING W AT 20-25 KT.
THE WAVE HAS BEEN MOVING QUICKLY AND THE WIND SURGE ASSOCIATED
WITH IT IS MAKING IT MORE AND MORE ELONGATED. THIS ELONGATION
CAN BE SEEN IN THE MOISTURE FIELD IN TOTAL PRECIPITABLE WATER.
THE MOIST AIR NEAR THE NORTHERN EXTENT OF THE WAVE IS OUTRUNNING
THE SOUTHERN PORTION AND DRIER AIR IS WRAPPING AROUND THE WEST
SIDE. THIS DRY AIR CAN ALSO BE SEEN IN ANALYSIS OF THE SAHARAN
AIR LAYER. DUE TO THE DRY AIR...NO DEEP CONVECTION IS ASSOCIATED
WITH THE WAVE BESIDES A SMALL AREA OF MODERATE CONVECTION S OF
THE AXIS FROM 7N-9N BETWEEN 35W-36W.

TROPICAL WAVE EXTENDS FROM 16N64W TO 11N64W MOVING W NEAR 20 KT.
THE WAVE HAS LOST MOST OF ITS ENERGY TO THE SURFACE TROUGH/LOW
TO THE N...WHICH BROKE OFF OF THE WAVE SEVERAL DAYS AGO. THE
WAVE STILL ALIGNS WITH A WEAK SURGE OF MODERATE DEEP LAYER
MOISTURE PRESENT IN TOTAL PRECIPITABLE WATER IMAGERY. NO DEEP
CONVECTION IS CURRENTLY ASSOCIATED WITH THE WAVE.

TROPICAL WAVE...REMNANTS OF T.D. SEVEN...IS MOVING W AT 15 KT
THROUGH THE WESTERN CARIBBEAN AND INTO THE YUCATAN PENINSULA
FROM 21N89W TO 15N86W. SATELLITE IMAGERY ALONG WITH SURFACE
OBSERVATIONS INDICATE CYCLONIC SURFACE FLOW IS STILL AROUND THE
AXIS. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS MAINLY E
OF THE AXIS FROM 12N-16N BETWEEN 78W-84W...AND FROM 16N-20N
BETWEEN 81W-87W.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS ACROSS W AFRICA TO THE COAST OF
SENEGAL AT 15N17W TO 10N34W. THE ITCZ BEGINS AT 9N40W TO 6N56W.
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM EQ-6N
BETWEEN 52W-55W.

...DISCUSSION...

GULF OF MEXICO...
WEAK SURFACE RIDGING COVERS THE MAJORITY OF THE GULF OF MEXICO
CENTERED AROUND A 1017 MB HIGH NEAR 27N88W. THE RIDGE IN
COMBINATION WITH DRY AIR ALOFT AROUND THE EASTERN SIDE OF AN
UPPER LEVEL RIDGE CENTERED OVER CENTRAL MEXICO IS HELPING
PROVIDE FAIR CONDITIONS OVER MUCH OF THE AREA. HOWEVER...AN AREA
OF SHOWERS/THUNDERSTORMS IS OVER THE FLORIDA PANHANDLE AND S OF
THE NORTHERN GULF COAST DUE TO DIFFLUENCE ALOFT AROUND A
SHORTWAVE UPPER TROUGH MOVING THROUGH THE SE CONUS. A FEW
ISOLATED SHOWERS ARE ALSO EMBEDDED WITHIN THE LIGHT
ANTI-CYCLONIC FLOW AROUND THE SURFACE HIGH CENTER. EXPECT LITTLE
CHANGE OVER THE NEXT 24 HOURS. MOISTURE FROM A TROPICAL WAVE IN
THE WESTERN CARIBBEAN MAY BEGIN TO IMPACT THE SE GULF OR BAY OF
CAMPECHE.

CARIBBEAN SEA...
A TROPICAL WAVE MOVING INTO THE YUCATAN PENINSULA IS SUPPORTING
SCATTERED SHOWERS/THUNDERSTORMS OVER THE WESTERN CARIBBEAN FROM
12N-19N BETWEEN 78W-86W. AS THE WAVE MOVES OVER THE YUCATAN
PENINSULA...HEAVY SHOWERS AND FLOODING WILL BE POSSIBLE OVER
NORTHERN CENTRAL AMERICA AND THE YUCATAN. THE REMAINDER OF THE
BASIN IS EXPERIENCING MOSTLY FAIR WEATHER DUE TO DRY AIR ALOFT
AROUND AN UPPER LEVEL RIDGE IN THE W ATLC. A SECOND TROPICAL
WAVE IS IN THE EASTERN CARIBBEAN...BUT IT IS VERY WEAK DUE TO
LOSING MOST ITS ENERGY TO THE SURFACE TROUGH/LOW IN THE CENTRAL
ATLC. IT IS ONLY PRODUCING A FEW SHOWERS OVER THE LESSER
ANTILLES. TRADEWIND FLOW OF 15-20 KT IS PRESENT ACROSS THE
EASTERN AND CENTRAL CARIBBEAN. EXPECT BOTH WAVES TO CONTINUE
WESTWARD WITH LITTLE CHANGE ELSEWHERE.

ATLANTIC OCEAN...
AN UPPER LEVEL RIDGE COVERS THE W ATLC CENTERED NEAR THE NW
BAHAMAS SUPPORTING A WEAK SURFACE RIDGE. HOWEVER...AN UPPER
LEVEL TROUGH OVER THE EASTERN CONUS IS SUPPORTING SCATTERED
SHOWERS/THUNDERSTORMS N OF 28N BETWEEN 65W-73W...AND ISOLATED
SHOWERS/THUNDERSTORMS N OF 27N BETWEEN 75W-78W. AN UPPER LEVEL
RIDGE COVERS THE CENTRAL ATLC CENTERED NEAR 31N51W SUPPORTING A
1024 MB SURFACE HIGH NEAR 32N46W. A SURFACE LOW/TROUGH IS SW OF
THE HIGH CENTER CAUSING AN AREA OF SHOWERS/THUNDERSTORMS. THIS
SYSTEM MAY DEVELOP INTO A TROPICAL DEPRESSION. SEE SPECIAL
FEATURES ABOVE FOR MORE DETAILS. THE SURFACE RIDGE IS HELPING
PROVIDE FAIR CONDITIONS ACROSS THE REMAINDER OF THE EASTERN
ATLC. ALOFT...AN UPPER LEVEL RIDGE DOMINATES THE TROPICAL ATLC
WITH A BROAD UPPER TROUGH OVER THE NE ATLC EXTENDING OVER THE
AZORES ISLANDS TO NEAR THE CANARY ISLANDS. VISIBLE SATELLITE
IMAGERY CONTINUES TO SHOW AN AREA OF DUST EXTENDS FROM THE COAST
OF AFRICA AROUND BOTH TROPICAL WAVES IN THE ATLC. THE DRY AIR
MASS IS LIMITING CONVECTION NEAR THE WAVES.

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

$$
WALTON





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