000
AXPZ20 KNHC 212202
TWDEP 

TROPICAL WEATHER DISCUSSION   
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC THU APR 21 2011

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

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2145 UTC.

...ITCZ...

AXIS IS ALONG 6N77W 7N89W TO LOW NEAR 7N95W 1010 TO 7N120W TO 
5N132W TO 5N140W. SCATTERED MODERATE CONVECTION WITHIN 120 NM
N OF AXIS BETWEEN 83W-85W...WITHIN 60 NM S OF THE AXIS BETWEEN
110W-114W AND 60 NM N OF THE AXIS BETWEEN 126W-134W.

...DISCUSSION...

ZONAL FLOW ALOFT CONTINUES TO DOMINATE THE AREA N OF 20N...WHILE 
A DEEP LAYER TROUGH EXTENDS FROM THE WESTERN U.S. SW TO NEAR 
28N123W. SATELLITE WATER VAPOR IMAGERY SHOWS MODERATE SUBSIDENCE
WITH ASSOCIATED DRY STABLE CONDITIONS FROM 26N TO 31N TO AS FAR
E AS NW MEXICO. SCATTERED TO BROKEN STRATOCUMULUS TYPE CLOUDS ARE
WITHIN THIS AREA. 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 
14N115W AND 03N124W 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...WITH THE ASSOCIATED PARENT HIGH OF 1022 MB CENTERED
WELL N OF THE DISCUSSION AREA NEAR 40N139W. A RIDGE EXTENDS FROM
THIS HIGH SOUTHEASTWARD TO 30N128W TO NEAR 17N108W. A TIGHT PRES
GRADIENT PERSISTS NE OF THIS RIDGE WITH TROUGHING LOCATED INLAND 
OVER CENTRAL MEXICO. AS A RESULT OF THIS PRES PATTERN...NW WINDS
OF 20-25 KT WINDS ARE PRESENT N OF 25N E OF 119W TO THE COAST OF
BAJA CALIFORNIA. LITTLE CHANGE IS EXPECTED WITH THESE WINDS 
DURING THE NEXT 24 HOURS...AND ARE EXPECTED TO SHRINK IN 
COVERAGE IN 48 HOURS.

A SMALL AREA OF 20 KT NE TRADE WINDS IS SW OF THE RIDGE FROM 7N
TO 15N BETWEEN 121W-128W. THESE FRESH TRADES WILL SHIFT SLIGHTLY 
WWD DURING THE NEXT 24 HOURS THEN EXPAND N AND NE BY 48 HOURS AS 
HIGH PRES BUILDS ACROSS W AND NW PORTIONS.

IN THE TROPICS...A BROAD 1010 MB SURFACE LOW IS LOCATED NEAR
7N95W. 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 TRACKING WESTWARD OVER 
THE NEXT FEW DAYS.

A WEAK SURFACE TROUGH MOVING W ABOUT 10 KT IS ALONG 121W FROM 4N 
TO 12N. DEEP C0CONVECTION EARLIER NOTED WITH THIS TROUGH HAS 
SINCE WEAKENED. GLOBAL MODELS TEND TO GRADUALLY DAMPEN OUT THE 
TROUGH OVER THE NEXT 24 TO 48 HOURS AS IT TRACKS W.

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 TODAY AND SHOULD
ALLOW FOR SEAS HEIGHTS OF 3 TO 6 FT DURING THE NEXT 36 TO 48 
HOURS. THESE VERY LONG PERIOD SWELLS ARE EXPECTED TO POSSIBLY 
PRODUCE VERY HAZARDOUS SURF CONDITIONS ALONG THOSE COASTS.

$$
AGUIRRE