000
AXPZ20 KNHC 221556
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC FRI MAY 22 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 
1545 UTC.

...ITCZ...

THE ITCZ AXIS EXTENDS ALONG 08N78W TO 10N88W TO 07N95W TO 
07N105W TO 09N115W TO 04N140W. SCATTERED MODERATE ISOLATED 
STRONG CONVECTION IS NOTED N OF 03N E OF 84W...WITHIN 90 NM OF 
06N90W...WITHIN 150 NM OF 10N96W...AND FROM 07N TO 14N BETWEEN 
110W AND 123W.

.DISCUSSION...

ALOFT...A MID TO UPPER CYCLONE IS IS OVER SOUTHERN ARIZONA AT 
32N111W WITH A MID LEVEL TROUGH EXTENDING S OVER THE BAJA 
PENINSULA TO 22N110W. A SECOND MID TO UPPER LEVEL TROUGH IS 
LOSING IDENTITY ALONG 23N124W TO 14N137W. AN UPPER RIDGE 
DOMINATES THE NW PORTION OF THE REGION WITH THE RIDGE AXIS ALONG 
24N140W TO 30N128W. SOME UPPER MOISTURE IS OBSERVED WITHIN THE 
RIDGE TO THE N OF 20N W OF 130W...OTHERWISE THE UPPER LEVELS ARE 
VERY DRY NW OF A LINE ALONG ANOTHER UPPER RIDGE...CRESTING ALONG 
POINTS 10N136W TO 22N120W TO 23N97W. THIS TROPICAL RIDGE IS 
ASSOCIATED WITH AN ANTICYCLONE CENTERED AT 10N104W. THE UPPER 
DIFFLUENCE UNDER THE RIDGE IS ENHANCING CONVECTION ALONG THE 
ITCZ BETWEEN 99W AND 137W WITH THE DEBRIS MOISTURE ADVECTED N TO 
ALONG THE RIDGE CREST DESCRIBED ABOVE.

AN UPPER ANTICYCLONE IS OVER COLOMBIA. A DEEP LAYERED CYCLONE 
OVER THE NE GULF OF MEXICO HAS AN UPPER TROUGH EXTENDING S TO 
NEAR 10N85W. CONVECTION IS ENHANCED ALONG THE PACIFIC ITCZ...TO 
THE S OF 11N E OF 98W...WITH SOME OF THE DEBRIS MOISTURE 
ADVECTED NE OF THE UPPER TROUGH ACROSS THE WESTERN CARIBBEAN.

.AT THE LOW LEVELS...A RIDGE EXTENDS ALONG 32N136W TO 12N113W. A 
WEAK SURFACE LOW IS NEAR 13N121.5W HAS NORTHERLY WINDS OVER THE 
W SEMICIRCLE TO 20 KT WITHIN 420 NM OF CENTER. THIS LOW IS 
EXPCTED TO W3EAKEN INTO AN OPEN TROUGH IN ABOUT 24 HOURS. A 
SECOND LOW PRESSURE IS NEAR 13N110.6W WIND THE TIGHTEST GRADIENT 
CURRENTLY E OF THE CENTER WITH WINDS TO 20 KT. THIS SECOND LOW 
IS EXPECTED TO PERSIST FOR A FEW MORE DAYS PULLING AWAY FROM THE 
ITCZ.

$$
NELSON