000
AXPZ20 KNHC 120944
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC SUN APR 12 2009

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 
0930 UTC.

...ITCZ...

THE INTERTROPICAL CONVERGENCE ZONE LIES ALONG A LINE FROM 07N77W 
TO 06N96W TO 08N106W TO 07N119W TO 08N128W TO 03N140W. SCATTERED 
MODERATE CONVECTION IS WITHIN 30 NM OF 06.5N82W. SCATTERED 
MODERATE CONVECTION IS FROM 03N TO 05N BETWEEN 92W AND 94W. 
SCATTERED MODERATE CONVECTION IS WITHIN 30 NM OF 10N121.5W. 
SCATTERED MODERATE CONVECTION IS FROM 01N TO 06N W OF 132W.

...DISCUSSION...

A HIGH AMPLITUDE MID/UPPER-LEVEL LONGWAVE RIDGE COVERS MUCH OF 
THE NE PACIFIC. DEEP LAYER MOISTURE W OF THE RIDGE AXIS IS 
SUPPORTING SCATTERED SHOWERS N OF 19N W OF 132W. THIS 
MID/UPPER-LEVEL RIDGE IS ASSOCIATED WITH A SURFACE RIDGE OVER 
THE NW QUARTER OF THE DISCUSSION AREA...ANCHORED BY A 1032 MB 
SURFACE HIGH NEAR 32N132W. A BROAD AREA OF TRADE WINDS CONTINUES 
TO BE ENHANCED ON THE SOUTHERN PERIPHERY OF THIS SURFACE 
RIDGE...WHERE THE SURFACE PRESSURE GRADIENT IS RELATIVELY 
STEEPER. NE WINDS OF 20 TO 25 KT ARE PRESENT FROM 05N TO 21N W 
OF 115W BASED ON QUIKSCAT PASSES AROUND 12/0130 UTC AND 
12/0315 UTC. COMPUTER MODEL GUIDANCE INDICATES THESE WINDS 
CONTINUING DURING THE NEXT FEW DAYS WITH SURFACE RIDGES PRESENT 
N OF THE DISCUSSION AREA. ALSO...RECENT SATELLITE IMAGERY...AND 
RECENT QUIKSCAT AND ASCAT PASSES...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 13N120W TO 06N126W...WITH SCATTERED 
SHOWERS AND THUNDERSTORMS WITHIN 30 NM OF 10N121.5W. THE 
COVERAGE OF SHOWER AND THUNDERSTORM ACTIVITY WITH THE WESTERN 
SURFACE TROUGH IS GREATER...WHERE ENHANCED BOUNDARY LAYER 
MOISTURE CONVERGENCE IS SUPPORTING SCATTERED SHOWERS AND 
THUNDERSTORMS FROM 01N TO 06N W OF 132W. THE ACTIVITY WITH THE 
WESTERN SURFACE TROUGH IS ALSO BEING SUPPORTED BY ATMOSPHERIC 
INSTABILITY ASSOCIATED WITH A MID/UPPER-LEVEL TROUGH OVER SW 
PORTIONS OF THE DISCUSSION AREA.

THE AFOREMENTIONED MID/UPPER-LEVEL RIDGE CONTINUES TO DE-AMPLIFY 
AND TRANSLATE EASTWARD AS A FAST-MOVING MID/UPPER-LEVEL TROUGH 
FORCES THE RIDGE TO BREAK DOWN SOMEWHAT. A SURFACE COLD FRONT 
ASSOCIATED WITH THIS TROUGH IS CURRENTLY NW OF THE DISCUSSION 
AREA...AND IS FORECAST TO SLIDE SOUTHWARD DURING THE NEXT FEW 
DAYS. THIS FRONT IS EXPECTED TO ENTER THE NE DISCUSSION AREA BY 
EARLY TUESDAY...FOLLOWED BY NW TO N WINDS OF 20 TO 25 KT. SINCE 
THE TRACK OF THE MID/UPPER-LEVEL TROUGH IS MAINLY 
WEST-TO-EAST...THE SURFACE FRONT IS EXPECTED TO BE RATHER WEAK 
AS IT ENTERS THE DISCUSSION AREA...WITH THE STRONGEST WINDS N OF 
THE DISCUSSION AREA. DEEP-LAYER SUBSIDENCE ASSOCIATED WITH A 
MID/UPPER-LEVEL RIDGE FARTHER UPSTREAM WILL HELP A SURFACE HIGH 
BUILD N OF THE AREA EARLY NEXT WEEK IN THE WAKE OF THE FRONT. 
THIS WILL MAINTAIN THE TRADE WINDS THROUGH NEXT WEEK.

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. WAVEWATCH GUIDANCE INDICATES EVEN 
HIGHER WAVES IN NW SWELL ENTERING THE NE DISCUSSION AREA EARLY 
NEXT WEEK N OF THE AFOREMENTIONED FRONT...WHERE MAXIMUM SEAS ARE 
FORECAST TO REACH 16 FT.  

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 RECENT QUIKSCAT AND ASCAT PASSES.

$$
COHEN