000
AXPZ20 KNHC 161523
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC THU APR 16 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...

ITCZ AXIS IS CENTERED ALONG 04N77W TO 06N110W TO 07N124W TO 
05N140W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 
02N TO 05N BETWEEN 87W AND 92W. SCATTERED MODERATE CONVECTION IS 
WITHIN 100 TO 120 NM N OF AXIS BETWEEN 115W AND 135W.

...DISCUSSION...

N OF 20N...
THE TIGHT PRESSURE GRADIENT BETWEEN A 1029 MB HIGH CENTERED NEAR 
33N130W AND BROAD LOW PRES OVER THE ROCKIES IS PRODUCING A 
NARROW SWATH OF FRESH TO STRONG NW WINDS WITHIN 300 NM W OF THE 
BAJA PENINSULA COAST N OF 24N. THESE WINDS ARE EXPECTED TO 
GRADUALLY DIMINISH AS HIGH PRES N OF AREA WEAKENS. NW WINDS UP 
TO 20 KT ARE NOTED OVER THE N PORTION OF THE GULF OF CALIFORNIA. 
MODEL GUIDANCE INDICATES THAT WINDS MAY REACH 25 KT FURTHER 
SOUTH IN ABOUT 24 TO 36 HOURS WITH HIGH PRES RIDGING GRADUALLY 
BUILDING OVER THE GREAT BASIN. SEAS ARE ANALYZED UP TO 12 FT OFF 
THE N BAJA PENINSULA COASTLINE WITH NW SWELL. CONDITIONS SHOULD 
STEADILY SUBSIDE OVER THE NEXT FEW DAYS AS WINDS RELAX IN THIS 
REGION.

S OF 20N...
AN ASHFALL ADVISORY REMAINS IN EFFECT FROM THE ONGOING ERUPTION 
OF LA CUMBRE VOLCANO ON ISLA FERNANDINA IN THE GALAPAGOS ISLANDS 
LOCATED AT 00.4S91.5W. ON THE RECOMMENDATION OF THE NESDIS 
SATELLITE ANALYSIS BRANCH...THE ASHFALL ADVISORY WILL REMAIN IN 
EFFECT FOR AT LEAST THE NEXT FEW DAYS DUE TO THE UNCERTAINTY IN 
THE TIMING OF THE END OF THE VOLCANIC ACTIVITY. MARINERS SHOULD 
EXERCISE CAUTION DUE TO REDUCED VISIBILITIES CAUSED BY VOLCANIC 
ASH DOWNWIND OF THE VOLCANO FROM 02S TO 01N BETWEEN 91.5W AND 
97W. GAS/STEAM WILL COVER A LARGE PART OF THE EQUATORIAL REGION 
OUT WEST T0 110W AND FURTHER THIS AFTERNOON. EXPOSURE TO THIS 
GAS/STEAM CAN BE DANGEROUS...CAUSING IRRITATION TO EYES AND SKIN.

TRADE WINDS REMAIN 20-25 KT ACROSS A LARGE PORTION OF THE AREA N 
OF THE ITCZ W OF ABOUT 110W. LITTLE CHANGE IS EXPECTED THROUGH 
FRI AS THE HIGH STAYS IN PLACE. HOWEVER...BY FRI NIGHT AND SAT 
THE HIGH IS EXPECTED TO SHIFT NE AS A FRONT APPROACHES THE NW 
CORNER. THIS SHOULD ALLOW TRADES TO DIMINISH. 

GAP WINDS...
NE WINDS OF 20 KT CONTINUE TO FUNNEL THROUGH THE GULF OF 
PAPAGAYO. THIS FLOW SHOULD CONTINUE TO PULSE OVER THE NEXT FEW 
DAYS...ESPECIALLY IN THE EARLY MORNING HOURS WHEN DRAINAGE FLOW 
IS AT A MAXIMUM.

IN THE MID AND UPPER LEVELS...A WEAK SHORTWAVE TROUGH ALONG 135W 
IS GENERATING CLOUDINESS AND LIKELY EMBEDDED SHOWERS FROM 
19N-23N BETWEEN 122-129W. THIS FEATURE IS EXPECTED TO DAMPEN AS 
A RIDGE AMPLIFIES OVER THE REGION TONIGHT AND FRI. 

$$
GR/JC