000
AXPZ20 KNHC 231605
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC SAT MAY 23 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 LEVEL TROUGH EXTENDS SW ALONG 30N110W TO 20N120W 
TO 08N136W. HOWEVER THE UPPER LEVELS TO THE N OF 22N ARE 
DOMINATED BY ZONAL FLOW. SOME UPPER MOISTURE IS NOTED N OF 18N W 
OF 125W RACING E IN THE STRONG WESTERLIES. OTHERWISE THE UPPER 
LEVELS AREA DRY N OF 15N W OF 120W AND N OF 18N E OF 120W. 

A TROPICAL MID TO UPPER LEVEL ANTICYCLONE IS AT 12N104W WITH A 
RIDGE SW TO 05N132W AND A RIDGE E TO 08N85W. THE UPPER 
DIFFLUENCE UNDER THE RIDGE ENHANCED CONVECTION ALONG THE ITCZ 
BETWEEN 133W AND 85W WITH THE DEBRIS MOISTURE ADVECTED N TO 
ALONG 21N E OF 120W WITH THE MOISTURE EVAPORATING ALONG 21N.

AN UPPER ANTICYCLONE IS OVER COLOMBIA NEAR 04N77W. A DEEP 
LAYERED CYCLONE OVER THE NE GULF OF MEXICO HAS AN UPPER TROUGH 
EXTENDING S HONDURAS. CONVECTION IS ENHANCED ALONG THE PACIFIC 
ITCZ...TO THE S OF 11N E OF 85W...WITH SOME OF THE DEBRIS 
MOISTURE ADVECTED NE OF THE UPPER TROUGH ACROSS THE WESTERN 
CARIBBEAN.

.AT THE LOW LEVELS...A RIDGE EXTENDS ALONG 32N130W TO 19N110W. A 
WEAK SURFACE LOW IS NEAR 12N122W HAS NORTHERLY WINDS OVER THE W 
SEMICIRCLE TO 20 KT WITHIN 420 NM OF CENTER. THIS LOW IS 
EXPECTED TO WEAKEN INTO AN OPEN TROUGH IN ABOUT 24 HOURS. A 
SECOND LOW PRESSURE IS NEAR 14N112W WITH THE TIGHTEST GRADIENT 
CURRENTLY E OF THE CENTER WITH WINDS TO 20 KT. THIS SECOND LOW 
IS EXPECTED TO MEANDER IN THE SAME AREA FOR A FEW MORE DAYS.

$$
NELSON