000
AXPZ20 KNHC 182152
TWDEP 

TROPICAL WEATHER DISCUSSION   
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC WED MAY 18 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 
2030 UTC.
 
...ITCZ...
AXIS ALONG 11N87W TO 05N114W 
TO 06N125W TO 03N140W. SCATTERED MODERATE TO STRONG CONVECTION 
NOTED FROM 03N TO 11N BETWEEN 80W AND 110W. SCATTERED MODERATE 
ISOLATED STRONG CONVECTION NOTED WITHIN 90 NM S AND 150 NM N OF 
AXIS W OF 123W.

...DISCUSSION...
A REX BLOCK PATTERN HAS EVOLVED DURING THE PAST 24 HOURS ACROSS 
THE E CENTRAL PACIFIC...CENTERED ON AN ANTICYCLONE-CYCLONE 
COUPLET ALONG 139-141W. ASSOCIATED DOWNSTREAM CYCLONE WAS 
CENTERED OVER THE WRN U.S. AND EXTENDED S-SE TO THE 
CALIFORNIA-ARIZONA BORDER. THE UPPER CYCLONE CENTERED NEAR 
19N141W ANCHORED A NEARLY STATIONARY MID TO UPPER LEVEL TROUGH 
THAT EXTENDED NE THEN E ACROSS CENTRAL BAJA CALIFORNIA. SE OF 
THESE FEATURES REMAINED A BROAD UPPER RIDGE GENERALLY N OF 
05N...WITH ANTICYCLONIC FLOW ALOFT SPANNING FROM 74W TO 130W. 
PULSING DEEP CONVECTION NEAR THE ITCZ BETWEEN 90W AND 110W 
DURING THE PAST FEW DAYS COUPLED WITH SHORTWAVE ENERGY LIFTING 
OVER THIS UPPER RIDGE HAVE AIDED IN THE RIDGE BUILDING N AND NW 
THE PAST 24 HOURS. WATER VAPOR IMAGERY SHOWED A SMALL UPPER 
ANTICYCLONE NEAR 04N106W...LOCATED IN THE SW PORTION OF THIS 
BROAD ANTICYCLONIC FLOW. OTHERWISE...NO DISTINCT ANTICYCLONIC 
CENTERS WERE NOTED IN WATER VAPOR IMAGERY...WITH THE UPPER RIDGE 
BEING MAINTAINED BY INDUCED DIVERGENCE CREATED FROM INTERMITTENT 
LARGE CLUSTERS OF DEEP CONVECTION ACROSS THIS AREA THE PAST FEW 
DAYS. GLOBAL MODELS SHOW A SHARP LONGWAVE TROUGH APPROACHING THE 
REGION FROM THE W DURING THE NEXT FEW DAYS AND ACTING TO BREAK 
DOWN THE REX BLOCK OVER THE UPCOMING WEEKEND....ALLOWING A BROAD 
BLOCKING UPPER RIDGE TO REALIGN ALONG 108W.

A WEAKENING SURFACE RIDGE CONTINUES ACROSS N AND NW PORTIONS OF 
AREA THIS AFTERNOON...CENTERED ON 1023 MB HIGH NEAR 34N135W AND 
EXTENDS SE...BRIDGING ACROSS A DISSIPATING COLD FRONT ACROSS FAR 
NRN BAJA CALIFORNIA TO 26N130W...WITH RIDGING CONTINUING TO 
NEAR 19N111W. THE FRONT WILL MOVE SE AND INLAND TONIGHT ALLOWING 
THE RIDGE TO BUILD E AND SE AND BRING FRESH NW BREEZE ALONG W 
COAST OF BAJA CALIFORNIA. EPAC MONSOONAL FLOW PREVAILS E OF 
110W...WITH S TO SW WINDS DEPICTED BY RECENT SCATTEROMETER 
PASSES S OF THE DEFINED ITCZ FROM COLOMBIA TO 120W. ABUNDANT 
TROPICAL MOISTURE ACROSS THIS REGION FROM 03N TO 11N AND E OF 
110W IS EXPECTED TO CONTINUE TO PULSE IN CLUSTERS OF DEEP 
CONVECTION DURING THE NEXT 24 HOURS.

LARGE VERY LONG PERIOD CROSS EQUATORIAL SW SWELLS CONTINUE TO 
PROPAGATE THROUGH THE AREA WATERS AND BEYOND...HAVING BEGUN TO 
REACH 35N THIS AFTERNOON PER COASTAL BUOY DATA...AND WILL PEAK 
THIS EVENING AND TONIGHT ACROSS THE COASTAL WATERS OF CENTRAL 
AMERICA AND MEXICO TONIGHT TO PRODUCE VERY LARGE AND POWERFUL 
SURF WITH THE POTENTIAL FOR COASTAL FLOODING ALONG THE 
COASTLINES...WITH OFFSHORE WAVE HEIGHTS PEAKING AT 10 TO 11 
FT...BEFORE THE SW SWELL SUBSIDES STEADILY THU THROUGH FRI. 

$$
STRIPLING