000
AXPZ20 KNHC 160918
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC THU APR 16 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 
0900 UTC.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 05N77W TO 06N110W TO 07N140W. 
SCATTERED MODERATE CONVECTION IS WITHIN 180 NM N AND 120 NM S OF 
THE AXIS BETWEEN 87W AND 92W AND WITHIN 120 NM EITHER SIDE OF 
THE AXIS BETWEEN 129W AND 136W.

...DISCUSSION...

N OF 20N...
THE TIGHT PRESSURE GRADIENT BETWEEN A 1030 MB HIGH CENTERED NEAR 
33N131W AND BROAD LOW PRES OVER THE ROCKIES IS PRODUCING A 
NARROW SWATH OF STRONG NLY WINDS WITHIN 300 NM W OF THE BAJA 
COAST N OF 25N. A HI-RES QUIKSCAT PASS FROM 0130 UTC SHOWED PEAK 
WINDS NEAR 30 KT WITHIN 120 NM OF THE BAJA COAST...IN AGREEMENT 
WITH A SHIP REPORT. THIS AREA IS LIKELY BEING ENHANCED BY THE 
LOCAL TOPOGRAPHY. A BACK-DOOR TYPE COLD FRONT...ASSOCIATED WITH 
LOW OVER THE ROCKIES...EXTENDS NEAR THE FAR N GULF OF 
CALIFORNIA. SCATTEROMETER DATA HINTS THAT NW WINDS ARE UP TO 
20 KT BEHIND THE FRONT. GLOBAL MODELS ARE IN AGREEMENT IN 
SHOWING THIS BROAD LOW CRAWL E WITH HIGH PRES RIDGING 
GRADUALLY BUILDING OVER THE GREAT BASIN. THIS PATTERN SHOULD 
SUPPORT NLY WINDS OF 20 OR 25 KT OVER THE GULF OF CALIFORNIA 
OVER THE NEXT COUPLE OF DAYS. SEAS ARE ANALYZED UP TO 15 FT OFF 
THE N BAJA AND S CALIFORNIA COASTLINE WITH N SWELL. CONDITIONS 
SHOULD STEADILY SUBSIDE OVER THE NEXT FEW DAYS AS WINDS RELAX IN 
THIS REGION.

IN THE MID AND UPPER LEVELS...A WEAK SHORTWAVE TROUGH ALONG 135W 
IS GENERATING CLOUDINESS AND LIKELY EMBEDDED SHOWERS FROM 
20N-24N BETWEEN 125-134W. THIS FEATURE IS EXPECTED TO DAMPEN AS 
A RIDGE AMPLIFIES OVER THE REGION TONIGHT AND FRI. 

S OF 20N...
AN ASHFALL ADVISORY IS 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 91W AND 97W. 
IN ADDITION...NASA OMI IMAGERY FROM 15/2211 UTC SHOWS A LARGE 
PLUME OF ELEVATED LEVELS OF SULFUR DIOXIDE FROM 02S TO 03N 
BETWEEN 91W AND 112W. EXPOSURE TO SULFUR DIOXIDE GAS 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. 

AN EARLIER HI-RES QSCAT PASS SHOWED 20 KT NE WINDS FUNNELING 
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.

$$
CANGIALOSI