000
AXPZ20 KNHC 211604
TWDEP 

TROPICAL WEATHER DISCUSSION   
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC THU APR 21 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 
1430 UTC.

...ITCZ...

THE INTERTROPICAL CONVERGENCE ZONE AXIS WAS ANALYZED ALONG 
06N77W TO 04N80W TO LOW PRES 1010 MB NEAR 07N95W TO 04N106W TO 
07N120W TO 05N140W. SCATTERED MODERATE TO STRONG CONVECTION 
NOTED WITHIN 90 NM EITHER SIDE OF AXIS BETWEEN 97W AND 115W. 
SCATTERED TO LOCALLY NUMEROUS MODERATE TO STRONG CONVECTION 
NOTED WITHIN 150 NM N OF AXIS BETWEEN 117W AND 130W. 

...DISCUSSION...

ZONAL FLOW ALOFT CONTINUES TO DOMINATE THE EPAC N OF 20N...WHILE 
A MID LEVEL TROUGH EXTENDS FROM A DEEP LAYERED SHORTWAVE ACROSS 
SRN CALIFORNIA AND AZ...SW TO 28N123W THEN CONTINUES IN 
TUTT-LIKE FASHION TO 27N142W THEN SW TO BEYOND THE BIG ISLAND OF 
HAWAII. DRY AIR AND SUBSIDENCE WAS NOTED IN A 280 NM WIDE BAND 
STRADDLING THIS MID LEVEL FEATURE. S OF 20N...UPPER LEVEL 
RIDGING CONTINUES TO BE MAINTAINED BY ACTIVE CONVECTION ALONG 
THE ITCZ BETWEEN 95W AND 137W. AN UPPER HIGH-LOW COUPLET WAS 
NOTED WITH CENTERS NEAR 13N115W AND 03N125W RESPECTIVELY. NE OF 
THE RIDGE...A BROAD MID TO UPPER LEVEL TROUGH AXIS EXTENDED SW 
ACROSS SRN MEXICO TO NEAR 15N108W. 

AT LOWER LEVELS...A MODEST HIGH PRESSURE RIDGE AND ANTICYCLONIC 
FLOW DOMINATES MOST OF THE AREA N OF THE ITCZ AND W OF 
100W...CENTERED ON A 1022 MB SURFACE HIGH POSITIONED NEAR 
40N140W WITH A RIDGE AXIS EXTENDING SE TO NEAR 14N103W. A TIGHT 
PRES GRADIENT PERSISTS NE OF THIS RIDGE WITH TROUGHING LOCATED 
INLAND OVER CENTRAL MEXICO. AS A RESULT OF THIS PRES 
PATTERN...NW 20 KT WINDS ARE OCCURRING WITHIN 150 NM W OF THE 
NRN BAJA CALIFORNIA COAST AND THESE WINDS MAY BRIEFLY STRENGTHEN 
TO 20-25 KT DURING THE NEXT 24 HOURS ALTHOUGH WILL CHANGE LITTLE 
OVERALL DURING THE NEXT 48 HOURS. A SMALL AREA OF 20 KT NE TRADE 
WINDS IS SW OF THE RIDGE FROM 08N TO 14N W OF 126W. THESE FRESH 
TRADES WILL SHIFT SLIGHTLY WWD DURING THE NEXT 24 HOURS THEN 
EXPAND N AND NE BY 48 HOURS AND HIGH PRES BUILDS ACROSS W AND NW 
PORTIONS.

A BROAD 1010 MB SURFACE LOW PRES WAS LOCATED NEAR 07N95W WITH A 
TROUGH REACHING FROM THE LOW TO 12N96W. THIS LOW HAS BEEN 
LINGERING IN THIS SAME GENERAL AREA FOR THE PAST WEEK OR 
SO...OCCASIONALLY OPENING UP INTO JUST A TROUGH. THIS LOW WILL 
REMAIN WEAK WHILE FINALLY MOVING MORE QUICKLY OFF TO THE W 
DURING THE NEXT FEW DAYS.

ANOTHER SURFACE TROUGH IS EMBEDDED IN THE ITCZ IN THE VICINITY 
OF 120W. NUMEROUS MODERATE AND SCATTERED STRONG CONVECTION WAS 
OCCURRING FROM 07N TO 10N BETWEEN 118W AND 124W ASSOCIATED WITH 
THIS TROUGH. THIS TROUGH IS FORECAST TO DISSIPATE BY 48 HOURS.

VERY LONG PERIOD 19-21 SECOND CROSS-EQUATORIAL SW SWELL 
CONTINUES TO PROPAGATE NE ACROSS THE WATERS WITH COMBINED SEAS 
OF 8 FT CONFINED S OF 04N IN THE CENTRAL PORTION. THIS HIGH 
ENERGY SWELL HAS BEGUN TO REACH THE COASTLINES OF SOUTHERN 
CALIFORNIA...MEXICO AND CENTRAL AMERICA THIS MORNING AND WILL 
BUILD IN HEIGHT TO 3 TO 6 FT DURING THE NEXT 36 TO 48 HOURS. 
THESE VERY LONG PERIOD SWELLS WILL CREATE VERY HAZARDOUS SURF 
CONDITIONS DUE TO STRONG FAST MOVING WAVES...WHICH WILL GREATLY 
ENHANCED THE RIP CURRENT THREAT THROUGH SAT.

$$
STRIPLING