000
AXPZ20 KNHC 111524
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC SAT APR 11 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 08N100W TO 08N93W TO 04N120W TO 04N140W. SCATTERED MODERATE 
WITHIN 200 NM S OF AXIS BETWEEN 89W AND 93W. SIMILAR CONVECTION 
IS NOTED NEAR 3N134W. 

...DISCUSSION...

AT THE SURFACE...
A SFC TROUGH EXTENDS FROM NW MEXICO NEAR 31N110W ACROSS THE BAJA 
CALIFORNIA PENINSULA INTO THE EPAC ALONG 22N116W 20N125W. A 
NARROW BAND OF LOW CLOUDS IS ASSOCIATED WITH THIS TROUGH. NW 
WINDS OF 20 TO 25 KT AND WAVE HEIGHTS OF 10 TO 12 FT ARE IN THE 
WAKE OF THIS TROUGH. A QSCAT PASS FROM AROUND 1300 UTC CONFIRMED 
THESE WINDS. OVER THE N GULF OF CALIFORNIA...WINDS BEHIND THE 
AFOREMENTIONED TROUGH...HAVE DIMINISHED BELOW GALE FORCE AS THE 
SFC LOW...WHICH WAS PREVIOUSLY AFFECTING THE AREA...MOVES INLAND 
OVER THE SW CONUS. A BROAD AREA OF TRADE WINDS IS BEING ENHANCED 
ON THE SOUTHERN PERIPHERY OF A SURFACE RIDGE EXTENDING FROM 
32N138W...WHERE A 1027 MB SFC HIGH IS ANALYZED...TO 20N110W. 
THESE MODERATE TO FRESH WINDS WILL PERSIST OVER THE NEXT COUPLE 
OF DAYS AS THE SFC HIGH LOCATED N OF THE DISCUSSION AREA DRIFTS 
MAINLY EWD. WIND WAVES RESULTING FROM THE PERSISTENT TRADE WINDS 
WILL REACH 8 TO 9 FT...WITH A LARGE AREA OF SEAS OF 8 TO 10 FT 
IN MERGING SW AND NW SWELL AFFECTING MUCH OF THE DISCUSSION AREA 
DURING THE NEXT FEW DAYS. ALSO...RELATIVELY LOWER SURFACE 
PRESSURE OVER MEXICO DURING THE NEXT FEW DAYS...COMBINED WITH 
LOCAL TOPOGRAPHICAL EFFECTS...WILL LOCALLY ENHANCE NORTHWESTERLY 
WINDS NEAR THE W COAST OF MEXICO FROM 17N TO 21N. ACCORDING TO 
THE NAM COMPUTER MODEL...THESE WINDS WILL LOCALLY REACH 25 KT IN 
THIS AREA SUN MORNING. A SURFACE TROUGH IS EMBEDDED WITHIN THE 
ITCZ AXIS. THIS SURFACE TROUGH EXTENDS ALONG 131W/132W S OF 7N. 
A 1010 MB LOW IS ALONG THE TROUGH AXIS NEAR 2.5N. SCATTERED 
SHOWERS ARE NEAR THE LOW CENTER...AND THE NORTHERN END OF THE 
TROUGH. BY EARLY MONDAY...A WEAKENING COLD FRONT WILL APPROACH 
THE NE DISCUSSION AREA...WITH INCREASED N WINDS AND BUILDING 
SEAS IN NW SWELL ENTERING THE FORECAST AREA.

GAP WIND...
TRADE WINDS OVER THE CARIBBEAN REGION ARE FORECAST TO EXTEND 
INTO THE GULF OF PAPAGAYO DURING THE NEXT FEW DAYS...WHEN 
SURFACE WINDS ARE EXPECTED TO OCCASIONALLY REACH 20 KT. 

ALOFT...
AN UPPER-LEVEL RIDGE WITH AXIS ALONG 140W DOMINATES THE WESTERN 
PORTION OF THE FORECAST AREA N OF 15N W OF 130W. E OF THIS 
RIDGE...THE EPAC REGION IS UNDER THE INFLUENCE OF A VIGOROUS 
SHORTWAVE TROUGH MOVING EWD. THE BASE OF THIS TROUGH REACHES 
16N. CONFLUENT FLOW INTO THE TROUGH IS RESULTING IN AN AREA OF 
MODERATE SUBSIDENCE AND RATHER STABLE CONDITIONS FROM 19N-29N 
BETWEEN 112W AND 128W. STRONG SWLY UPPER-LEVEL WINDS OF 90-110KT 
AHEAD OF THIS TROUGH...AND ASSOCIATED WITH A JET STREAM BRANCH 
ARE OBSERVED OVER NW MEXICO. TO THE E AND SE OF THE UPPER 
TROUGH...BROAD UPPER RIDGE ANCHORED BY AN UPPER-LEVEL HIGH NEAR 
6N102W IS MAINTAINING RATHER DRY AND STABLE CONDITIONS OVER THE 
SE PORTION OF THE AREA. 

$$
GR