000
AXPZ20 KNHC 230910
TWDEP 

TROPICAL WEATHER DISCUSSION   
NWS NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC MON MAY 23 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 
0745 UTC.
 
...ITCZ...
THE INTERTROPICAL CONVERGENCE ZONE WAS ANALYZED FROM 14N91W TO 
11N100W TO 06N116W TO 04N140W. SCATTERED MODERATE TO STRONG 
CONVECTION WAS WITHIN 360 NM S OF THE ITCZ AXIS BETWEEN 95W AND 
100W. SCATTERED MODERATE CONVECTION WAS WITHIN 150 NM N AND 
ISOLATED MODERATE CONVECTION WAS WITHIN 150 NM S OF THE ITCZ 
AXIS BETWEEN 129W AND 137W.

...DISCUSSION...
A TROUGH ALOFT EXTENDS FROM AN UPPER LOW NEAR 16N140W TO 
30N130W. THIS TROUGH IS BEGINNING TO SEPARATE FROM THE DEEP 
LAYER TROUGHING CURRENTLY OVER THE WESTERN UNITED STATES. 
MEANWHILE...A 1030 MB SURFACE HIGH PRES SYSTEM NEAR 33N140W 
EXTENDS A RIDGE INTO THE FORECAST AREA FROM 30N128W TO 14N111W. 
A MODERATE PRESSURE GRADIENT EXISTS BETWEEN THIS RIDGE AND THE 
TROUGHING OVER THE INTERIOR WESTERN UNITED STATES. FRESH NW TO N 
WINDS...AS INDICATED BY SHIP DHER AND THE 0440 UTC ASCAT 
PASS...LIE OVER NE WATERS AS A RESULT. THESE WINDS WILL SHRINK 
EASTWARD OVERNIGHT TUE NIGHT AS THE SUBTROPICAL HIGH WEAKENS 
AND THE TROUGHING OVER THE U.S. SHIFTS EASTWARD. STRONG NW WINDS 
CURRENTLY LIE OVER A BROAD AREA NEAR THE CALIFORNIA COAST N OF 
THE FORECAST AREA. THESE WINDS ARE EXPECTED TO REMAIN STRONG 
THROUGH MID DAY TUE AND NW SWELL WILL KEEP SEAS ABOVE 8 FT IN NE 
WATERS THROUGH THE END OF THE PERIOD EARLY WED MORNING. 

FRESH TRADE WINDS LIE SW OF THE RIDGE AXIS AS INDICATED BY THE 
0618 UTC ASCAT PASS. THE SUBTROPICAL HIGH TO THE N WILL BEGIN TO 
WEAKEN AS A COLD FRONT ENCROACHES UPON IT TONIGHT...AND THE 
FRESH TRADES WILL BEGIN TO SHRINK SOUTHWESTWARD. THIS FRONT WILL 
DISSIPATE WITH LITTLE FANFARE AS IT MOVES INTO NW WATERS WED.

A SURFACE TROUGH LIES FROM 11N111W TO 05N115W. SCATTERED 
MODERATE CONVECTION LIES WITHIN 150 NM SE OF THE TROUGH AXIS. 
THIS TROUGH IS EXPECTED TO MOVE LITTLE THROUGH WED MORNING AND 
WILL CONTINUE TO LIE UNDER A DIFFLUENT UPPER RIDGE AXIS THAT 
SHOULD HELP MAINTAIN CONVECTION NEAR THE TROUGH. THE UPPER RIDGE 
EXTENDS NORTHEAST TO AN ANTICYCLONE NEAR 15N105W. THE DEEPEST 
CONVECTION ALONG THE ITCZ LIES SE OF THIS ANTICYCLONE AND 
COINCIDES WITH AN AREA OF FRESH SOUTHWESTERLY FLOW S OF THE ITCZ 
AXIS BETWEEN 90W AND 100W. BUOY 43301 CONFIRMED THESE CONDITIONS 
AT 0700 UTC. AN UPPER TROUGH EXTENDS FROM THE EASTERN GULF OF 
MEXICO THROUGH HONDURAS AND E OF THE AFOREMENTIONED RIDGE AXIS 
ALOFT. THIS TROUGH WILL WEAKEN AND RETRACT NORTHEASTWARD OVER 
THE NEXT 24 HOURS...DECREASING THE DIFFLUENCE ALOFT AND MAKING 
THIS AREA LESS CONDUCIVE FOR CONVECTION. WINDS HERE ARE ALSO 
EXPECTED TO DIMINISH BELOW 20 KT BY TUE AFTERNOON.

$$
SCHAUER