000
AXPZ20 KNHC 240909
TWDEP 

TROPICAL WEATHER DISCUSSION   
NWS NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC TUE MAY 24 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 
0730 UTC.
 
...ITCZ...
THE INTERTROPICAL CONVERGENCE ZONE WAS ANALYZED FROM 12N87W TO 
11N110W TO 06N117W TO 05N140W. SCATTERED MODERATE CONVECTION 
LIES WITHIN 45 NM N AND 75 NM S OF THE ITCZ AXIS BETWEEN 133W 
AND 138W. THERE ARE TWO EMBEDDED LOW PRES SYSTEMS WITHIN THE 
ITCZ. THE EASTERN LOW LIES NEAR 11N97W AND HAS ISOLATED MODERATE 
CONVECTION WITHIN 270 NM SE QUADRANT AND 150 NM W SEMICIRCLE. 
THE WESTERN LOW LIES NEAR 11N110W AND HAS NUMEROUS MODERATE TO 
STRONG CONVECTION WITHIN 180 NM N AND 120 NM S SEMICIRCLES.

...DISCUSSION...
A 1029 MB SURFACE HIGH NEAR 33N132W EXTENDS A RIDGE INTO THE 
FORECAST AREA FROM 32N124W TO 15N110W. THE PRESSURE GRADIENT 
BETWEEN THIS RIDGE AND TROUGHING OVER THE INTERIOR WESTERN 
UNITED STATES IS STRONG ENOUGH TO SUPPORT 20 KT WINDS OFF THE W 
COAST OF BAJA CALIFORNIA AS OBSERVED BY THE 0420 UTC AND 0600 
UTC ASCAT PASSES. THESE WINDS WILL SHRINK EASTWARD OVERNIGHT 
TONIGHT WHEN THE TROUGHING OVER THE U.S. SHIFTS EASTWARD AND THE 
SUBTROPICAL HIGH WEAKENS AS A COLD FRONT ENCROACHES ON IT FROM 
THE W. BY WED NIGHT...THE SUBTROPICAL HIGH WILL REORGANIZE W OF 
THE DISSIPATING COLD FRONT AS THE FRONT MOVES INTO THE WESTERN 
UNITED STATES. THE AREA OF FRESH NW WINDS THEN WILL EXPAND 
WESTWARD AS THE PRES GRADIENT REBUILDS. STRONG NW WINDS 
CURRENTLY LIE OVER A BROAD AREA NEAR THE CALIFORNIA COAST N OF 
THE FORECAST AREA AND ARE SENDING NW SWELL INTO NE FORECAST 
WATERS WHERE SEAS AREA AS HIGH AS 11 FT. THESE WINDS AND THE 
RESULTING SWELL ARE EXPECTED TO GRADUALLY DIMINISH THROUGH THE 
PERIOD.

FRESH TRADE WINDS LIE SW OF THE RIDGE AXIS OVER CENTRAL WATERS W 
OF 130W AS INDICATED BY THE 0558 UTC ASCAT PASS. LITTLE CHANGE 
IN THESE CONDITIONS IS EXPECTED THROUGH WED MORNING...BUT THE 
AREA OF FRESH TRADES WILL EXPAND NORTHEASTWARD WED NIGHT AS THE 
SUBTROPICAL HIGH REBUILDS W OF THE AFOREMENTIONED DISSIPATING 
COLD FRONT. THIS FRONT WILL BRING A BATCH OF NW SWELL WITH SEAS 
TO 9 FT INTO THE NW PORTION OF THE FORECAST AREA OVERNIGHT WED 
NIGHT...BUT WINDS WILL BE BELOW ADVISORY CRITERIA.

THE 0414 UTC ASCAT PASS HIT THE TWO LOW PRES SYSTEMS EMBEDDED IN 
THE ITCZ. CONVECTION NEAR THESE LOWS IS DESCRIBED IN THE ITCZ 
SECTION. THESE LOWS LIE UNDER THE DIFFLUENT UPPER RIDGE AXES 
THAT EXTEND FROM AN ANTICYCLONE NEAR 15N103W SOUTHEASTWARD TO 
09N92W AND SOUTHWESTWARD TO 11N117W. THE EASTERN LOW NEAR 11N97W 
HAS AN ELONGATED CENTER AND ONLY A SMALL AREA OF 20 KT WINDS IN 
ITS SE QUADRANT. CONVECTION NEAR THE LOW HAS DECREASED 
SIGNIFICANTLY SINCE YESTERDAY AND THE UPPER RIDGE AXIS IS 
EXPECTED TO MOVE NORTHEASTWARD AWAY FROM THE SURFACE 
LOW...DECREASING THE DIFFLUENCE ALOFT THAT HAD ENHANCED THE 
CONVECTION. THIS LOW IS FORECAST TO DISSIPATE BY WED MORNING. 
THE WESTERN LOW NEAR 11N110W IS ASSOCIATED WITH DEEPER 
CONVECTION AND STRONGER WINDS THAN THE EASTERN LOW. THE ASCAT 
PASS SHOWED 25 KT WINDS NEAR THE LOW FROM THE VECTORS THAT WERE 
NOT RAIN-FLAGGED. THIS LOW IS FORECAST TO DRIFT WESTWARD BEFORE 
DISSIPATING OVERNIGHT WED NIGHT AS THE RIDGE ALOFT BREAKS DOWN 
AND THE MID LEVEL SYSTEM BECOMES STEERED MORE TO THE W BY THE 
MID-LEVEL RIDGING BUILDING EASTWARD TO THE N OF THE SYSTEM.

CROSS-EQUATORIAL S SWELL HAS BROUGHT SEAS ABOVE 8 FT OVER S 
CENTRAL WATERS. THESE CONDITIONS WILL CONTINUE THROUGH THE 
PERIOD.

$$
SCHAUER