000
AXPZ20 KNHC 110907
TWDEP 

TROPICAL WEATHER DISCUSSION   
NWS NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC WED MAY 11 2011

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

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0845 UTC.

...ITCZ...
AXIS EXTENDS FROM EMBEDDED 1008 MB LOW PRES NEAR 08N86W TO 
ANOTHER 1008 MB LOW PRES NEAR 09N103W TO 09N110W TO 05N125W TO 
07N135W TO 05N0140W. SCATTERED MODERATE TO ISOLATED STRONG 
CONVECTION S OF AXIS FROM 02N TO 07N BETWEEN 85W AND 95W. 
SCATTERED MODERATE CONVECTION WITH 120 NM S OF AXIS BETWEEN 95W 
AND 105W.

...DISCUSSION...
W OF 110W...AN UPPER RIDGE N OF HAWAII IS BREAKING DOWN AHEAD OF 
AN ADVANCING UPPER TROUGH PUSHING EASTWARD INTO THE NE PACIFIC. 
THIS IN TURN HAS WEAKENED A SURFACE HIGH PRES AREA NE OF HAWAII 
AS A COLD FRONT ASSOCIATED WITH THE UPPER TROUGH MOVES SE FROM 
THE N CENTRAL PACIFIC. AS A RESULT TRADE WIND FLOW BETWEEN THE 
ITCZ AND 20N W OF 120W CONTINUES TO DIMINISH. ASCAT PASSES FROM 
LATE YESTERDAY SHOWED BASICALLY 10 TO 15 KT TRADE WINDS. A PAIR 
OF ALTIMETER PASSES FROM YESTERDAY CONFIRMED WAVEWATCH 
INITIALIZATIONS SHOWING GENERALLY 5 TO 6 FT SEAS OVER THE 
DISCUSSION AREA W OF 110W. 20 KT NW FLOW ALONG THE COAST OF BAJA 
CALIFORNIA IS ALSO STARTING TO DIMINISH AS THE HIGH PRES TO THE 
WEST WEAKENS. LOOKING AHEAD...WHILE THE FRONT WILL STALL AND 
DISSIPATE N OF 30N...NEW HIGH PRES BUILDING EASTWARD BEHIND THE 
FRONT WILL A SMALL AREA OF 20 KT NE TRADES WILL FORM NEAR THE 
ITCZ W OF 130W BY LATE FRI...AHEAD OF A PAIR OF WEAK SURFACE 
TROUGHS MIGRATING WESTWARD ALONG THE ITCZ. SUBSIDENT DRY AIR IN 
THE MID AND UPPER LEVELS ALONG WITH LITTLE MAJOR TRADE WIND 
CONVERGENCE IN THE LOW LEVELS WILL LIMIT CONVECTION ALONG THE 
ITCZ.

E OF 110W...BANDS OF CONVECTION CONTINUE TO PULSE AROUND A 
STATIONARY 1008 MB LOW PRES AREA CENTERED ALONG THE ITCZ NEAR 
09N103W. CONVECTION IS AIDED BY UPPER LEVEL OUTFLOW FROM A 
DEVELOPING UPPER ANTICYCLONE DIRECTLY OVER THE LOW LEVEL 
CIRCULATION. FURTHER EAST...ANOTHER 1009 MB LOW PRES IS CENTERED 
NEAR 08N85W. CONVERGENCE OF MODERATE CROSS-EQUATORIAL SW FLOW 
INTO THESE LOW PRES AREAS IS RESULTING IN CLUSTERS OF CONVECTION 
FLARING TO THE S OF THE ITCZ BETWEEN 85W AND 95W. BOTH OF THESE 
SURFACE FEATURES WEAKEN THROUGH THE REMAINDER OF THE WEEK AS 
CONDITIONS ALOFT BECOME LESS FAVORABLE FOR CONVECTIVE GROWTH. 

$$
CHRISTENSEN