000
AXPZ20 KNHC 231537
TWDEP 

TROPICAL WEATHER DISCUSSION   
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC MON MAY 23 2011

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 
1445 UTC.
 
...ITCZ...
THE INTERTROPICAL CONVERGENCE ZONE WAS ANALYZED FROM 10N86W TO 
09N90W TO 12N105W TO 04N120W TO 06N140W. SCATTERED MODERATE TO 
STRONG CONVECTION WITHIN 180 NM S OF THE ITCZ AXIS BETWEEN 93W 
AND 103W. SCATTERED MODERATE CONVECTION WAS WITHIN 45 NM EITHER 
SIDE OF THE ITCZ AXIS BETWEEN 125W AND 135W.

...DISCUSSION...
A WEAK UPPER TROUGH N OF 30N ALONG 125W WILL LIFT OUT TO THE NE 
LATER TODAY...FOLLOWED BY WEAK UPPER RIDGING THAT WILL SHIFT 
FROM 140W TO 130W. AN ASSOCIATED 1029 MB SURFACE HIGH PRES WILL 
WEAKEN THROUGH TUE AS A MID TO UPPER LEVEL SHORT WAVE TROUGH 
WILL DIG EASTWARD NORTH OF 30N THROUGH WED. 20 KT NW TO N WINDS 
PERSIST OFF THE BAJA COAST BETWEEN THE HIGH PRES AND LOW PRES 
OVER NW MEXICO. SEAS TO 10 FT IN NW SWELL ARE NOTED BY SHIP 
OBSERVATIONS OFF THE NORTHERN BAJA COAST. THE WINDS WILL BRIEFLY 
DIMINISH BY WED AFTER THE HIGH PRES WEAKENS...BUT INCREASE AGAIN 
LATER IN THE WEEK AS NEW HIGH PRES BUILDS TO THE WEST.

SCATTEROMETER DATA SHOW AN AREA OF FRESH TRADE WINDS FROM 10N TO 
20N W OF 130W S OF THE HIGH PRES. THESE WINDS WILL DIMINISH IN 
AREAL EXTENT THROUGH MID WEEK AS THE HIGH PRES TO THE NORTH 
WEAKENS. AN ALTIMETER PASS FROM 07Z SHOWED SEAS TO 8 FT IN THE 
AREA OF THE FRESH TRADE WINDS. LOOKING AHEAD TO LATE IN THE 
WEEK...HIGH PRES WILL BUILD BEHIND THE SHORT WAVE 
TROUGH...ALLOWING TRADES TO INCREASE AGAIN.

FURTHER SOUTH...AN UPPER TROUGH EXTENDS FROM A CUT OFF UPPER 
CYCLONE NEAR 17N140W TO 06N120W. DIVERGENCE ALOFT NEAR THE 
TROUGH AXIS IS ENHANCING MODEST CONVECTION OVER THE ITCZ BETWEEN 
125W AND 135W. 

RECENT SCATTEROMETER DATA ALSO SHOWED A SMALL CIRCULATION 
EMBEDDED WITHIN THE ITCZ NEAR 08N112W...WHERE LIGHT TO MODERATE 
NE TRADES MEET MODERATE SW FLOW TO THE SOUTH OF THE ITCZ. LITTLE 
TO NO CONVECTION IS NOTED WITH THIS FEATURE AND IT IS EXPECTED 
TO WEAKEN AS IT DRIFTS W THROUGH THE REMAINDER OF THE WEEK.

CLUSTERS OF MODERATE TO STRONG CONVECTION ARE PULSING MAINLY N 
OF THE ITCZ BETWEEN 93W AND 103W. THIS IS IN AN AREA OF 
DIVERGENCE ALOFT BETWEEN AN UPPER ANTICYCLONE NEAR 16N105W AND A 
SHARP UPPER TROUGH EXTENDING FROM THE NW CARIBBEAN THROUGH 
NORTHERN CENTRAL AMERICA TO NEAR 09N92W. MODERATE SW FLOW S OF 
THE ITCZ IS PROVIDING LOW LEVEL CONVERGENCE TO SUPPORT 
CONVECTIVE DEVELOPMENT. 

$$
CHRISTENSEN