000
AXPZ20 KNHC 121536
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC SUN APR 12 2009

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 
1530 UTC.

...ITCZ...

THE INTERTROPICAL CONVERGENCE ZONE LIES ALONG A LINE FROM 06N77W 
TO 08N110W TO 07N122W THEN FROM 06N132W TO 04N137W. SCATTERED 
MODERATE/ISOLATED STRONG CONVECTION FROM 02N TO 06N W OF 132W. 
SIMILAR CONVECTION IS WITHIN 30NM OF NEAR 07N130W...AND WITHIN 
160 NM N OF AXIS BETWEEN 82W AND 84W.

...DISCUSSION...

A HIGH AMPLITUDE MID/UPPER-LEVEL RIDGE COVERS THE WESTERN 
PORTION OF THE FORECAST REGION MAINLY N OF OF 20N W OF 120W. 
DEEP LAYERED MOISTURE W OF THE RIDGE AXIS...WHICH EXTENDS ALONG 
130W...IS SUPPORTING SCATTERED SHOWERS N OF 22N W OF 132W. THIS 
MID/UPPER-LEVEL RIDGE IS ASSOCIATED WITH A SURFACE RIDGE 
EXTENDING FROM 30N130W TO 16N110W. THE RIDGE IS ANCHORED BY A 
1029 MB HIGH LOCATED NEAR 32N132W...FORECAST TO DISSIPATE IN 
ABOUT 24 HOURS AS A COLD FRONT APPROACHES THE AREA FROM THE NW. 
A BROAD AREA OF TRADE WINDS CONTINUES TO BE ENHANCED ON THE 
SOUTHERN PERIPHERY OF THIS SURFACE RIDGE...DUE TO A RATHER THIGH 
SURFACE PRESSURE GRADIENT. NE WINDS OF 20 TO 25 KT ARE PRESENT 
FROM 08N TO 21N W OF 118W BASED ON AN EARLIER QUIKSCAT PASS AND 
COMPUTER MODEL GUIDANCE. THESE WINDS ARE EXPECTED TO PERSIST 
DURING THE NEXT COUPLE OF DAYS BUT THE AREA WILL SHRINK FROM 
118W TO 130W. SATELLITE IMAGERY AND THE SSMI-DERIVED TPW...TOTAL 
PRECIPITABLE WATER...PRODUCT INDICATE TWO INVERTED SURFACE 
TROUGHS EMBEDDED WITHIN THE ITCZ...AND EACH OF THESE SURFACE 
TROUGHS IS LOCALLY ENHANCING THE TRADE WINDS. THE EASTERN 
SURFACE TROUGH EXTENDS FROM 12N125W TO 03N132W...WITH A SMALL 
CLUSTER OF MODERATE CONVECTION WITHIN 30 NM OF 07N130W. THE 
COVERAGE OF SHOWER AND THUNDERSTORM ACTIVITY WITH THE WESTERN 
SURFACE TROUGH IS GREATER...FROM 02N TO 06N W OF 132W. A 
DIFFLUENT PATTERN ALOFT BETWEEN A RIDGE JUST W OF THE FORECAST 
REGION AND A MID/UPPER-LEVEL TROUGH OVER SW PORTION OF THE 
DISCUSSION AREA IS ENHANCING THIS CONVECTIVE ACTIVITY.  

A WEAK COLD FRONT IS EXPECTED TO CLIP THE NE DISCUSSION AREA BY 
EARLY TUESDAY...FOLLOWED BY N WINDS OF 20 TO 25 KT AND WAVE 
HEIGHTS OF UP TO 13 FT WITH NW SWELL. WAVEWATCH GUIDANCE 
INDICATES EVEN HIGHER WAVES IN NW SWELL ENTERING THE NE 
DISCUSSION AREA EARLY WED WITH MAXIMUM SEAS REACHING 16 FT.

SIGNIFICANT WAVE HEIGHTS RESULTING FROM THE PERSISTENT TRADE 
WINDS WILL REACH 8 TO 11 FT...WITH A LARGE AREA OF SEAS OF 8 TO 
10 FT IN MIXED SW AND NW SWELL ALSO AFFECTING MUCH OF THE 
DISCUSSION AREA DURING THE NEXT FEW DAYS. LONG PERIOD SWELLS OF 
AROUND 16 SECONDS FROM THE SW ARE REACHING THE W COAST OF MEXICO 
AND CENTRAL AMERICA FROM LOS CABOS IN SOUTHERN BAJA CALIFORNIA 
ALL THE WAY SOUTH TO THE COAST OF COLOMBIA.    

GAP WINDS...
TRADE WINDS OVER THE CARIBBEAN REGION HAVE WEAKENED SOMEWHAT. AS 
A RESULT...WINDS IN THE GULF OF PAPAGAYO HAVE FALLEN BELOW 20 KT 
BASED ON AN EARLIER QSCAT PASS AND SFC DATA. 

$$
GR