[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 132339
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2300 UTC.

...TROPICAL WAVES...

TROPICAL WAVE EXTENDS FROM 12N21W TO 21N21W MOVING W AT 15 KT.
THE WAVE IS EMBEDDED WITHIN A LOW-LEVEL CYCLONIC GYRE OF THE
MONSOON TROUGH WHICH IS CENTERED NEAR THE SOUTHERN EXTENT OF THE
WAVE AXIS NEAR 12N. THE WAVE ALSO COINCIDES WITH A 700 MB LOW
NEAR 10N22W THAT EXTENDS A TROUGH AXIS NORTHWARD FROM THE LOW TO
21N WITH TOTAL PRECIPITABLE WATER IMAGERY INDICATING MAXIMUM
DEEP LAYERED MOISTURE FROM 08N-15N BETWEEN 16W-22W. ISOLATED
MODERATE CONVECTION IS FROM 11N-14N BETWEEN 16W-23W.

TROPICAL WAVE EXTENDS FROM 20N45W TO 28N43W MOVING WNW AT 15-20
KT. A WEAK 1016 MB LOW IS CENTERED ALONG THE WAVE AXIS NEAR
24N44W AND COINCIDES WITH AN AREA OF MAXIMUM DEEP LAYERED
MOISTURE NOTED IN TOTAL PRECIPITABLE WATER IMAGERY FROM 20N-25N
BETWEEN 42W-49W. HOWEVER...DRY AIR AND DUST SURROUND THE WAVE
LIMITING DEEP CONVECTION AT THIS TIME. ISOLATED SHOWERS ARE
POSSIBLE FROM 22N-26N BETWEEN 42W-51W.

TROPICAL WAVE EXTENDS FROM 11N78W TO 19N75W MOVING W AT 20 KT.
SATELLITE PRESENTATION AND ASSOCIATED SURFACE OBSERVATIONS
INDICATE CYCLONIC FLOW IN THE VICINITY OF THE AXIS. THIS
WAS CONFIRMED EARLIER BY A 13/1418 UTC ASCAT PASS IN THE WATERS
SOUTH OF THE WINDWARD PASSAGE ALONG 75W. SCATTERED MODERATE
CONVECTION IS FROM 17N-20N BETWEEN 66W-70W...INCLUDING PUERTO
RICO AND THE MONA PASSAGE...AND FROM 14N-20N BETWEEN
70W-79W...INCLUDING HISPANIOLA AND PORTIONS OF THE WINDWARD
PASSAGE.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS FROM NEAR 11N23W TO 08N36W. THE
INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 08N36W TO
11N50W TO 08N60W. SCATTERED MODERATE CONVECTION IS FROM 06N-10N
BETWEEN 20W-32W. ISOLATED MODERATE CONVECTION IS FROM 07N-13N
BETWEEN 47W-56W.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER LEVEL TROUGH IS PROGRESSING EASTWARD OVER THE
MISSISSIPPI RIVER VALLEY THIS EVENING WITH THE TROUGH AXIS
EXTENDING SOUTHWARD INTO THE NORTH-CENTRAL GULF N OF 25N BETWEEN
84W-93W. THIS MIDDLE TO UPPER LEVEL TROUGHING IS PROVIDING A
GENERAL SYNOPTIC-SCALE WEAKNESS IN THE UPPER LEVEL RIDGE THAT
EXTENDS FROM THE SW NORTH ATLC NEAR 26N77W TO 19N95W TO 32N103W.
THE COLD FRONT ASSOCIATED WITH THIS TROUGH IS WELL INLAND ACROSS
ARKANSAS AND TEXAS THIS EVENING...AND IS FORECAST TO WEAKEN
BEFORE APPROACHING THE NW AND NORTHERN GULF WATERS. HOWEVER...
MIDDLE TO UPPER LEVEL MOISTURE CONTINUES TO ADVECT NORTH-
NORTHEASTWARD ACROSS MUCH OF THE GULF AND ALONG WITH DAYTIME
HEATING AND MAXIMUM INSTABILITY CONTINUES TO GENERATE ISOLATED
SHOWERS AND TSTMS ACROSS THE FLORIDA PENINSULA AND PORTIONS OF
THE FLORIDA STRAITS FROM 22N-25N BETWEEN 81W-84W...AND OVER THE
CENTRAL GULF FROM 24N-31N BETWEEN 85W-93W. WITH THE UPPER LEVEL
ANTICYCLONIC CIRCULATION CENTERED OVER SOUTHERN MEXICO NEAR
19N95W...DIFFLUENCE IS MAXIMIZED AND IS GENERATING SCATTERED
SHOWERS AND TSTMS S OF 25N W OF 91W. WITH MUCH OF THIS WEATHER
ASSOCIATED WITH THE MIDDLE TO UPPER LEVELS OF THE ATMOSPHERE...
AT THE SURFACE...A RIDGE AXIS EXTENDS FROM THE SW NORTH ATLC
ALONG 27N TO A 1020 MB HIGH CENTERED NEAR 27N86W THEN SW TO A
1018 MB HIGH ALONG THE COAST OF MEXICO CENTERED NEAR 21N97W.

CARIBBEAN SEA...
AN UPPER LEVEL LOW IS CENTERED NEAR 11N80W AND CONTINUES TO AID
IN ADVECTION OF MOISTURE INTO THE TROPICAL WAVE ALONG 77W.
SCATTERED SHOWERS AND TSTMS ARE OCCURRING MOSTLY EAST OF THE
WAVE AXIS...HOWEVER THIS ACTIVITY STRETCHES W OVER JAMAICA.
OVERALL THE ACTIVITY IS FOUND FROM 14N-20N BETWEEN 66W-80W.
FARTHER SOUTH...THE TROPICAL WAVE IN TANDEM WITH THE MONSOON
TROUGH AXIS ALONG 09N IS GENERATING SCATTERED SHOWERS AND TSTMS
ACROSS THE SW CARIBBEAN S OF 13N BETWEEN 73W-82W...INCLUDING
NORTHERN COLOMBIA AND MUCH OF PANAMA. OTHERWISE THE NW CARIBBEAN
IS UNDER FAIRLY DRY AND STABLE CONDITIONS THIS EVENING DUE TO
VERY DRY AIR ALOFT W OF 80W AS NOTED ON WATER VAPOR IMAGERY.
WITH THE APPROACH OF THE TROPICAL WAVE IN THE NEXT FEW DAYS...
THE CHANCE FOR PRECIPITATION ACROSS CENTRAL AMERICA IS FORECAST
TO INCREASE. EAST OF 65W...MOST OF THE FAR EASTERN CARIBBEAN AND
LESSER ANTILLES ARE UNDER FAIR SKIES THIS EVENING AS AN AREA OF
DRY AIR ALOFT MOVES WESTWARD FROM THE TROPICAL ATLC.

ATLANTIC OCEAN...
AN UPPER LEVEL SHORTWAVE TROUGH IS LOCATED NORTH OF THE REGION
IN THE VICINITY OF 34N69W AND SUPPORTS A SURFACE TROUGH ANALYZED
FROM 32N71W TO 29N75W. WITH AN UPPER LEVEL ANTICYCLONIC
CIRCULATION CENTERED SOUTHWEST OF THIS SHORTWAVE TROUGHING...
UPPER LEVEL DIFFLUENCE IS MAXIMIZED NEAR THE SURFACE TROUGH
GENERATING SCATTERED SHOWERS AND TSTMS FROM 27N-32N BETWEEN
68W-74W. UPPER LEVEL DIFFLUENCE IS ALSO LARGELY INFLUENCING
SCATTERED SHOWERS AND TSTMS OCCURRING OVER THE FLORIDA PENINSULA
AND ADJACENT COASTAL ATLC WATERS THIS EVENING N OF 25N W OF 77W.
ELSEWHERE THE REMAINDER OF THE CENTRAL AND EASTERN ATLC ARE
UNDER THE INFLUENCE OF A BROAD SURFACE RIDGE ANCHORED BY A
STATIONARY 1025 MB HIGH CENTERED NEAR 33N46W. PRIMARILY STABLE
CONDITIONS AND FAIR WEATHER ARE OCCURRING OVER MUCH OF THIS AREA
WITH THE ONLY WEAKNESS FOUND WORKING TO ERODE THE RIDGING IS THE
TROPICAL WAVE ALONG 44N MENTIONED ABOVE.

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

$$
HUFFMAN




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