000
AXPZ20 KNHC 042200
TWDEP 

TROPICAL WEATHER DISCUSSION  
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC WED NOV 04 2009

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM 
THE EQUATOR TO 32N...EAST OF 140W. 

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2145 UTC.

...TROPICAL LOW...

.LOW PRES IS CENTERED NEAR 11N92W AND IS DRIFTING W TOWARDS AN 
UPPER LEVEL TROUGH WITH INCREASING SOUTHWESTERLY WIND SHEAR. 
CURRENTLY SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS 
NOTED WITHIN 30 NM 11N91W WITH THE CONVECTION TRYING TO BAND N 
OF THE CENTER. 

...ITCZ...

THE ITCZ AXIS EXTENDS ALONG 11N86W TO 08N100W TO 13N110W TO 
08N117W TO 11N127W TO 08N140W. SCATTERED MODERATE ISOLATED 
STRONG CONVECTION IS NOTED WITHIN 120 NM EITHER SIDE OF LINE 
FROM 11N89W TO 08N96W TO 10N101W TO 08N108W. 

...DISCUSSION...

AN UPPER LEVEL ANTICYCLONE IS CENTERED NEAR 13N121W WITH A SHORT 
WAVE RIDGE AMPLIFYING N TO A CREST NEAR 32N112W. THE SHORT WAVE 
RIDGE IS LOSING IDENTITY INTO A LONG WAVE RIDGE THAT HAS ITS 
MEAN AXIS N TO S ALONG 98W OVER ALL OF N AMERICA. A TROPICAL 
RIDGE EXTENDS SW FROM THE ANTICYCLONE TO A SHARP CREST OVER THE 
ITCZ AT 08N134W WITH ANOTHER RIDGE EXTENDING SE FROM THE 
ANTICYCLONIC CENTER TO 12N108W. DEBRIS MOISTURE FROM ITCZ 
CONVECTION BETWEEN 121W AND 131W...AND FROM FORMER ITCZ 
CONVECTION W OF THE AREA NEAR 06N148W...IS ADVECTED NE ALONG THE 
W PERIPHERY OF THE TROPICAL RIDGE...ROUGHLY WITHIN 60 NM EITHER 
SIDE OF LINE 06N150W TO 15N130W WHERE IT MERGES WITH A LARGER 
PLUME. THE COMBINED MOISTURE PLUME CONTINUES NE WITHIN 150 NM OF 
LINE 14N129W TO 25N114W WHERE THE PLUME SPLITS WITH ONE BRANCH 
TURNING SE ACROSS THE SHORTWAVE RIDGE BACK OVER THE TROPICS TO 
NEAR 17N108W. THE SECOND BRANCH OF MOISTURE CONTINUES N FANNING 
OUT OVER THE BAJA PENINSULA AND THE GULF OF CALIFORNIA AND 
CONTINUING NE OVER SOUTHERN PARTS OF ARIZONA AND CALIFORNIA.
UPPER DIFFLUENCE ENHANCED A CLUSTER OF CONVECTION EARLIER NEAR 
16N116W WITH THE DEBRIS MOISTURE ADVECTED SE TO NEAR 10N113W.
OTHERWISE...SUBSIDENCE IS INDICATED OVER THE S SEMICIRCLE OF THE 
ANTICYCLONE AND IS SUPPRESSING ITCZ CONVECTION BETWEEN 110W AND 
122W. 

TO THE NW OF THE ANTICYCLONE...A SHORTWAVE TROUGH HAS MOVED INTO 
THE AREA WITH ITS AXIS ALONG 140W TO THE N OF 20N. UPPER 
MOISTURE PRECEDES THIS SECOND TROUGH...AND IS ROUGHLY WITHIN 120 
NM EITHER SIDE OF LINE 32N130W TO 20N140W. OTHERWISE...THE UPPER 
LEVELS ARE DRY BETWEEN THE TROPICAL RIDGE AND THE UPPER 
TROUGH.

A LONG WAVE TROUGH IS MOVING ACROSS EASTERN N AMERICA WITH ITS 
AXIS EXTENDING S INTO THE AREA ALONG 32N96W INTO A SMALL UPPER 
CYCLONE AT 18N97W WITH THE TROUGH CONTINUING S TO A BASE OVER 
THE DEEP TROPICS AT 09N100W. THE DEEP LAYERED CYCLONE OVER THE 
SW CARIBBEAN HAS FURTHER DEEPENED AND HAS BECOME TROPICAL STORM 
IDA. CONVECTION IS ENHANCED ALONG THE ITCZ BETWEEN 90W AND 110W
AND IN ASSOCIATION WITH THE NEWLY FORMED TROPICAL STORM. SOME OF 
THE RESULTANT DEBRIS MOISTURE SPREADING N AND NE ACROSS THE 
WESTERN GULF OF MEXICO AND THE SW CARIBBEAN.    

AT THE LOW LEVELS...A SURFACE HIGH PRES IS NEAR 26N122W 1018 MB. 
A COLD FRONT IS LOSING ITS PUSH ALONG 32N133W TO 26N140W. NW 
WINDS ARE EXPECTED TO INCREASE BRIEFLY TO 20 KT OVER THE 
DISCUSSION AREA NW OF THE FRONT WITH NW SWELLS CONTINUING TILL A 
SECOND COLD SURGE ARRIVES FRI WITH EVEN LARGER SEAS...PERHAPS TO 
20 FT FRI NIGHT. 

GAP WINDS...
GALE FORCE WINDS EXPECTED TO CONTINUE THROUGH THE GULF OF 
TEHUANTEPEC AND INCREASE TO NEAR STORM FORCE THU NIGHT AND FRI 
THEN DIMINISH LATE FRI NIGHT.

$$
NELSON