[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 080007
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST WED MAR 07 2012

CORRECTED FOR PRECIPITATION INFORMATION IN NORTHWESTERN
COLOMBIA NEAR THE PANAMA BORDER...AND FOR THE
ATLANTIC OCEAN SECTION

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 2315 UTC.

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

THE MONSOON TROUGH EXTENDS SW FROM THE AFRICAN COAST AT 07N11W
TO 01N14W WHERE LOW LEVEL WINDS INDICATE A TRANSITION TO AN ITCZ
WHICH CONTINUES W ALONG THE EQUATOR TO 40W THEN TURNS SW TO THE
COAST OF S AMERICA AT 02S44W. ISOLATED MODERATE AND STRONG
CONVECTION IS NOTED N OF THE EQUATOR E OF 01W AND WITHIN 60 NM
OF THE ITCZ BETWEEN 24N AND 44W. LOCALLY BROKEN LOW AND MID
LEVEL CLOUDS WITH EMBEDDED SHOWERS ARE OBSERVED FROM 02N TO 07N
BETWEEN 07W AND 17W.

...DISCUSSION...

THE GULF OF MEXICO...
AN UPPER ANTICYCLONE IS OVER THE E PACIFIC AT 15N97W...WITH AN
UPPER RIDGE EXTENDING N ACROSS CENTRAL AMERICA AND THE GULF OF
MEXICO...AND CONTINUING NE ALONG THE EASTERN SEABOARD OF THE
CONUS. SOME UPPER MOISTURE WAS ADVECTED E ACROSS THE RIDGE
AXIS...AND IS NOW SPILLING SE OVER THE FLORIDA BIG BEND AREA IN
THE FORM OF THIN BROKEN MID AND UPPER LEVEL CLOUDS. SOME THIN
SCATTERED CIRRIFORM CLOUDS ARE RACING NE OVER THE BAY OF
CAMPECHE. OTHERWISE...THE UPPER LEVELS APPEAR VERY DRY ACROSS
THE GULF OF MEXICO. AT THE LOW LEVELS A RIDGE DISSECTS THE GULF
FROM NW FLORIDA TO THE BAY OF CAMPECHE. LOCALLY BROKEN LOW LEVEL
CLOUDS...ORIGINALLY ASSOCIATED WITH A DISSIPATING FRONT...ARE
NOW MOVING N OVER THE E CENTRAL GULF WATERS. AN AREA OF LOCALLY
OVERCAST LOW LEVEL CLOUDS...AND PATCHY FOG REDUCING VISIBILITIES
TO 3 SM...IS MOVING N IN THE LOW LEVEL SOUTHERLY FLOW OVER THE
NW GULF...AND EXTEND INLAND OVER THE NE TEXAS AND SW LOUISIANA
COASTAL PLAINS. THE SURFACE RIDGE IS EXPECTED TO WEAKEN AND
SHIFT EASTWARD OVER THE NEXT COUPLE OF DAYS...WITH THE SOUTHERLY
WINDS DIMINISHING SOMEWHAT. THE NEXT COLD FRONT WILL MOVE INTO
THE NEW WATERS ON FRI ACCOMPANIED BY NORTHERLY WINDS TO 30 KT.

THE CARIBBEAN SEA...
AN UPPER TROUGH HAS AMPLIFIED S OVER THE ENTIRE W CARIBBEAN AND
IS ACCOMPANIED BY VERY DRY AIR ALOFT. AN UPPER RIDGE EXTENDS N
FROM S AMERICA OVER THE E CARIBBEAN RESULTING ZONAL FLOW
ALOFT...WHICH ALSO APPEARS QUITE DRY. THE POST FRONTAL SHEAR
LINES OVER THE N CENTRAL AND NW CARIBBEAN HAVE FURTHER WEAKENED
TO BANDS OF LOCALLY BROKEN LOW LEVEL CLOUDS RACING WESTWARD OVER
THE CARIBBEAN TO THE N OF 15N. THE DRY AIR ALOFT IS SUPPRESSING
ASSOCIATED CONVECTION TO OROGRAPHICALLY INDUCED LIGHT SHOWERS
OVER THE E PORTIONS OF THE LARGER ISLANDS. THE EASTERLY TRADES
ARE ENHANCED ALONG THE NW COAST OF COLOMBIA WITH A 30 TO 35 KT
GALE WARNING IN EFFECT FROM 11N TO 15N BETWEEN 73W AND 79W THIS
AFTERNOON...BUT THE EFFECTED AREA IS FORECAST TO SHRINK FROM 11N
TO 13N BETWEEN 73W AND 77W ON FRI...WITH THE ASSOCIATED SEAS TO
18 FT TONIGHT SUBSIDING TO ABOUT A 16 FT MAXIMUM ON FRI.

THE ATLANTIC OCEAN...
AN UPPER RIDGE IS SHIFTING E OVER THE DISCUSSION AREA W OF 77W
AND IS IS ACCOMPANIED BY UPPER MOISTURE WHICH WILL MOVE S OVER
THE NW BAHAMAS TONIGHT IN THE FORM OF BROKEN MID AND UPPER
CLOUDS. IMMEDIATELY TO THE E...AN UPPER TROUGH HAS ITS MEAN AXIS
EXTENDING FROM BERMUDA TO E CUBA AND IS CONTINUING E WITH TIME
ACCOMPANIED BY DRY UPPER AIR WITHIN 300 NM W OF ITS AXIS. AN
UPPER ANTICYCLONE HAS DEVELOPED ALONG AN UPPER RIDGE NEAR
20N63W...WITH THE UPPER RIDGE CONTINUING ENE TO A UNSTABLE CREST
COLLAPSING SE NEAR 25N48W. A NARROW BAND OF UPPER MOISTURE IS
STREAMING NE ALONG THE NW PERIPHERY OF THIS RIDGE...ROUGHLY
WITHIN 120 NM EITHER SIDE OF A LINE FROM 27N67W TO 30N48W TO
BEYOND 33N43W. A MID TO UPPER LEVEL CYCLONE HAS CUT OFF OVER THE
CENTRAL ATLANTIC AT 30N35W...WITH A TROUGH EXTENDING SW TO AN
UPPER CYCLONE RAPIDLY FILLING AT 16N57W. THE ASSOCIATED SURFACE
LOW HAS WEAKENED TO AN OPEN TROUGH EXTENDING S TO N FROM 23N41W
TO 31N39W. LOW AND MID LEVEL CLOUDS AND CONVECTION IS OBSERVED
WITHIN 420 NM OVER THE E SEMICIRCLE OF THE PARENT UPPER CYCLONE
WITH THE RESULTANT DEBRIS MOISTURE SPREADING N WITH TIME. DRY
UPPER AIR IS INDICATED ALONG THE COLLAPSING RIDGE...AND ALSO
ALONG THE UPPER TROUGH...AND IS NOW ENTRAINING INTO THE W
SEMICIRCLE OF THE CUT OFF CYCLONE AT 30N35W.

AN UPPER TROUGH IS SHIFTING S OVER NW AFRICA WITH ITS BASE NEAR
22N05W AT THE MOMENT. A BROAD UPPER RIDGE DOMINATES THE SE
PORTION OF THE N ATLANTIC WITH A VERY DENSE MOISTURE PLUME...
ORIGINATING OVER S AMERICA...STREAMING NE ALONG THE NW PERIPHERY
OF RIDGE...ALL WITHIN 270 NM EITHER SIDE OF A LINE FROM 05N55W
TO 20N30W...THEN TURNING E ACROSS AFRICA TO THE S OF THE DIGGING
TROUGH JUST MENTIONED.

ELSEWHERE AT THE LOW LEVELS...A SHEAR AXIS EXTENDS FROM 31N48W
TO 25N65W TO 25N72W AND IS ACCOMPANIED BY LOCALLY OVERCAST LOW
AND MID LEVELS CLOUDS AND EMBEDDED SHOWERS WITHIN 90 NM EITHER
SIDE OF ITS AXIS. TO THE N OF THIS DENSE CLOUDINESS IS LOCALLY
BROKEN COLD AIR STRATOCUMULUS CLOUDS OBSERVED TO THE E COAST OF
THE CONUS.  THE SHEAR AXIS SHOULD GRADUALLY DISSIPATE OVER THE
NEXT DAY OR SO.

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

$$
NELSON






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