000
AXPZ20 KNHC 041603
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC MON MAY 04 2009

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

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1415 UTC.

...ITCZ...

ITCZ AXIS WAS ALONG 07N78W TO 06N82W TO 08N100W TO 07N110W TO 
04N122W TO 04N140W. SCATTERED MODERATE ISOLATED STRONG 
CONVECTION WAS WITHIN 120 NM N AND 240 NM S OF AXIS BETWEEN 80W 
AND 100W...AND ALSO A SEPARATE CLUSTERS WITHIN 180 NM OF 
05N119W. SCATTERED TO NUMEROUS MODERATE TO STRONG CONVECTION WAS 
90 NM EITHER SIDE OF LINE 09N126W TO 07N140W.

...DISCUSSION...

ALOFT...A MID TO UPPER LEVEL CYCLONE...MOVING SLOWLY WSW...HAS 
NEARLY CUT OFF FROM ITS PARENT TROUGH NEAR 16N134W...BUT THERE 
IS STILL EVIDENCE OF A CYCLONIC SHEAR AXIS EXTENDING N FROM THE 
CYCLONE ALONG 23N130W TO 26N117W...AND A BAND OF DRY UPPER AIR 
WITHIN 90 NM OF THE SHEAR AXIS. DRY UPPER AIR HAS BEEN NOTED 
OVER THE W SEMICIRCLE OF THE CYCLONE AND HAS ROTATED AROUND THE 
SE QUADRANT AND IS BECOMING ENTRAINED INTO THE CENTER. AN UPPER 
ANTICYCLONE NEAR HAWAII HAS A RIDGE EXTENDING E INTO THE 
DISCUSSION AREA TO A SHARP CREST NEAR 27N140W. A QUASI 
STATIONARY UPPER ANTICYCLONE WAS CENTERED AT 12N122W WITH ITS 
ENVELOPE OF ANTICYCLONIC FLOW DOMINATING THE UPPER LEVELS FROM 
05N TO 25N BETWEEN 112W AND 128W. HOWEVER THIS HIGH APPEARS TO 
HAVE BEGUN TO DRIFT W IN TANDEM WITH THE CUT OFF LOW. THE 
CYCLONIC SHEAR AXIS IS SLOWLY ERODING THE TOP OF THE RIDGE 
BETWEEN 130W AND 118W. UPPER DIFFLUENCE S OF THE RIDGE AND 
BETWEEN THE RIDGE AND THE CUTOFF CYCLONE HAS BEEN ENHANCING 
CONVECTION ALONG AND TO THE N OF THE ITCZ BETWEEN 125W AND 
145W...WITH THE DEBRIS MOISTURE ADVECTED NE.

A SERIES OF UPPER TROUGHS ARE OVER THE THE EASTERN CONUS AND THE 
WESTERN ATLANTIC WITH TWO UPPER TROUGHS MERGING OVER THE 
SOUTHERN GULF OF MEXICO...THEN CONTINUING SW ACROSS CENTRAL 
AMERICA ALONG 20N97W INTO AN ELONGATING MID TO UPPER CYCLONE 
OVER THE PACIFIC NEAR 09N106W...WITH THE UPPER TROUGH CONTINUING 
S ACROSS THE EQUATOR AT 105W. A STATIONARY UPPER RIDGE EXTENDS 
NW OFF COLOMBIA ACROSS CENTRAL AMERICA CRESTING ALONG THE E 
COAST OF THE YUCATAN PENINSULA. UPPER DIFFLUENCE E OF THE UPPER 
CYCLONE AT 09N106W IS ENHANCING CONVECTION OVER ITS E 
SEMICIRCLE. UPPER DIFFLUENCE UNDER THE RIDGE CONTINUES TO 
ENHANCED CONVECTION ALONG THE PACIFIC ITCZ TO THE E OF 100W. 

AT THE SURFACE...A 1023 MB HIGH PRES IS QUASI STATIONARY NEAR 
27N133W WITH A RIDGE EXTENDING SW TO BEYOND 26N140W...AND A 
RIDGE EXTENDING SE TO NEAR 16N116W. THE RIDGE IS BLOCKING THE 
SOUTHEAST PROGRESSION OF A SERIES OF COLD FRONTS TO N OF 
30N...HOWEVER LARGE NW SWELLS WILL PROPAGATE SE INTO THE EXTREME 
NW PORTION IN 24 HOURS...BUILDING SEAS TO 12 FT. TO THE E OF THE 
SURFACE RIDGE... NORTH NORTHWESTERLY WINDS OF 20-25 KT ARE 
OBSERVED ALONG THE PACIFIC COAST OF THE BAJA PENINSULA AND 
EXPECTED TO CHANGE LITTLE TODAY...DIMINISH SLIGHTLY ON TUE...AND 
INCREASE AGAIN TO 20 TO 25 KT WED...WITH PEAK SEAS ACROSS THE 
AREA BUILDING TO 13 FT IN NW SWELL OFF THE BAJA NEAR 30N118W WED 
NIGHT. NORTHEAST TO EASTERLY TRADES S OF THE RIDGE AND N OF THE 
ITCZ ARE MOSTLY IN THE 15 TO 20 KT RANGE...WITH ZONES OF 20 
KT...AND ARE EXPECTED TO SHRINK IN AREAL COVERAGE OVER THE NEXT 
COUPLE OF DAYS.

$$
STRIPLING