000
AXNT20 KNHC 202352
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT FRI MAR 20 2009

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...METEOROLOGICAL ANALYSIS...WEATHER
OBSERVATIONS...AND RADAR.

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2315 UTC.

...ITCZ...
FROM 5N9W TO 2N20W...CROSSING THE EQUATOR ALONG 38W...INTO NE 
BRAZIL NEAR 2S45W. ISOLATED MODERATE CONVECTION IS WITHIN 90-120 
NM S OF THE ITCZ BETWEEN 20W AND 40W.
 
...DISCUSSION...

GULF OF MEXICO...
THE LOW PRESSURE TROUGH NOTED EARLIER EXTENDING N OUT OF THE 
YUCATAN PENINSULA HAS DISSIPATED. ISOLATED SHOWERS ARE 
ACCOMPANYING THE REMNANT OF THE TROUGH AS IT SLOWLY DRIFTS TO 
THE SW. A WEAKENING COLD FRONT IS CURRENTLY ACROSS THE FAR 
NORTHEASTERN GULF...EXTENDING OFF THE WESTERN FLORIDA COAST NEAR 
CEDAR KEY TO JUST SOUTH OF APALACHICOLA. THE FRONT IS FAIRLY 
WEAK...AND THERE ARE CLEAR SKIES IN THE VICINITY OF THE FRONT. A 
HIGH PRESSURE RIDGE AXIS EXTENDS ALONG THE S TEXAS AND MEXICO 
COAST. THERE ARE MOSTLY CLEAR SKIES OVER THE WESTERN 
GULF...EXCEPT FOR A FEW BROKEN CLOUDS AND ISOLATED SHOWERS NEAR 
24N ASSOCIATED WITH A SMALL REGION OF WEAK INSTABILITY. IN THE 
UPPER LEVELS...A WEAK UPPER LEVEL TROUGH OVER THE CENTRAL GULF 
WITH AN ATTENDANT VORTEX NEAR 26N89W IS DROPPING SE INTO THE E 
GULF...DOWNSTREAM OF AN AMPLIFYING UPPER RIDGE ALONG 102W.
MODERATE TO STRONG SUBSIDENCE/DRY AIR ALOFT COVERS THE GULF W OF 
90W...MAINLY BEHIND THE TROUGH AXIS. 
 
CARIBBEAN SEA...
1416 AND 1556 UTC ASCAT PASSES INDICATED PREDOMINATELY NE TO E 
WINDS OVER THE AREA...WITH WINDS OF 20 KT ALONG THE COLOMBIAN 
COAST... DECREASING TO 5-10 KT IN THE NW CARIBBEAN SEA. SKIES 
WERE MOSTLY CLEAR OVER THE AREA EXCEPT FOR A PATCH OF BROKEN 
CLOUDS AND ISOLATED SHOWERS S OF JAMAICA TO 15N AND WITHIN 
90-120 NM OF THE COAST OF BELIZE AND NE YUCATAN MAINLY DUE TO 
WEAK INSTABILITY. ALSO...AN AREA OF BROKEN CLOUDS CONTINUES 
ABOUT 90 NM N OF THE COLOMBIAN COAST...AS CYCLONIC TURNING 
AROUND THE LOW OVER COLOMBIA NEAR 10N74W HAS CREATED CONVERGENT 
FLOW IN THE AREA. AT THE UPPER LEVELS...WATER VAPOR IMAGERY 
INDICATES SUBSIDENCE ACROSS THE CARIBBEAN. SUBTROPICAL JET
STREAK WAS OVER THE YUCATAN PENINSULA TO CUBA WITH CORE SPEEDS 
OF 80-90 KT. THIS IN COMBINATION WITH LIFT AHEAD OF AN UPPER 
LEVEL TROUGH SWEEPING SE OVER THE GULF IS CAUSING BROKEN HIGH 
CLOUDS OVER THE NW CARIBBEAN AND THE STRAITS OF FLORIDA. THIS 
LIFT IS EXPECTED TO MARGINALLY DESTABILIZE THE ATMOSPHERE OVER 
CUBA AND THE BAHAMAS OVER THE NEXT 24 HOURS WITH AN INCREASE IN 
CLOUD COVER OVER THOSE AREAS.
 
ATLANTIC OCEAN...
STRONG QUASI-STATIONARY LOW PRESSURE IS CURRENTLY WELL N OF THE 
DISCUSSION AREA NEAR 37N42W. A 1228 UTC ASCAT PASS INDICATED NW 
TO N WINDS OF GALE FORCE TO THE NW OF THE LOW CENTER...WELL N OF 
THE AREA. A COLD FRONT EXTENDS INTO THE AREA FROM THE LOW TO 
32N37W THROUGH 28N40W TO 24N48W...THEN CONTINUES AS A 
STATIONARY FRONT TO 23N62W...AND AS A WARM FRONT TO A 1012 MB 
LOW NEAR 27N71W. A LOW PRES TROUGH EXTENDS SW FROM THE LOW TO NE 
CUBA NEAR 21N75W. SCATTERED MODERATE ISOLATED STRONG CONVECTION
WAS NOTED WITHIN 60 NM OF 27N66W TO 23N69W. THIS CONVECTION WAS 
PART OF A MUCH LARGER AREA OF MULTILAYERED CLOUDS WITH EMBEDDED 
SHOWERS WHICH COVERED THE AREA N OF 24N BETWEEN 60W AND 70W. 
WIDELY SCATTERED LOW TOPPED SHOWERS WERE OCCURRING WITHIN 60 NM 
EITHER SIDE OF THE COLD FRONT...AND WITHIN 90 NM N OF THE 
STATIONARY FRONT. THE LOW PRESSURE IS FORECAST TO MOVE NE TO 
NEAR 31N62W BY 24 HOURS. ELSEWHERE...A 1025 MB HIGH PRESSURE N 
OF THE AREA NEAR 37N55W IS CURRENTLY EXTENDING A RIDGE INTO THE 
REGION TO 25N49W...BEHIND THE COLD FRONT. OTHERWISE...MAINLY 
CLEAR SKIES WITH A FEW AREA OF BROKEN CLOUDS DOMINATE THE 
WEATHER OVER THE REMAINDER OF THE ATLC. AT THE UPPER LEVELS...A 
SHORTWAVE TROUGH FROM 31N69W TO THE SE BAHAMAS WAS SHEARING OUT 
TO THE NE OVER A BROAD FLAT RIDGE WITH AXIS ALONG 50W WHICH WAS 
IN PHASE WITH AN UPPER LEVEL ANTICYCLONE NEAR THE GUINEA COAST 
AT 2S44W. A BROAD AREA OF STRONG SUBSIDENCE WAS NOTED WITHIN THE 
RIDGE GENERALLY FROM 15N TO 23N BETWEEN 30W AND 65W. FURTHER 
E...ANOTHER UPPER LEVEL TROUGH WAS N OF 29N ALONG 42W AND WAS 
SKIRTING THE FAR N PORTIONS OF THE DISCUSSION AREA WITH STRONG 
SUBSIDENCE IN ITS WAKE. EXPECT THE OVERALL PATTERN TO AMPLIFY 
FURTHER OVER THE NEXT 24 HOURS ACROSS THE AREA.

$$
COBB