000
AXPZ20 KNHC 150323
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC WED APR 15 2009

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM 
THE EQUATOR TO 32N...EAST OF 140W. 

BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0130 UTC.

...ITCZ...

ITCZ AXIS CAN BE FOUND ALONG A LINE FROM 06N77W TO 05N83W TO 
06N100W TO 06N130W TO 08N140W. SCATTERED MODERATE CONVECTION 
LIES WITHIN 75 NM N AND 45 NM S OF THE ITCZ AXIS BETWEEN 110W 
AND 118W.

...DISCUSSION...

N OF 20N...
AN AMPLIFIED BUT PROGRESSIVE UPPER PATTERN IS IN PLACE ACROSS N 
WATERS...WITH A STRONG MID TO UPPER LEVEL TROUGH MOVING INTO THE 
WESTERN U.S. AND MAKING ITS WAY TOWARD BAJA CALIFORNIA. AT THE 
SURFACE...THE PRESSURE GRADIENT BETWEEN LOW PRES OVER THE GREAT 
BASIN AND THE HIGH PRES CENTER NEAR 38N134W HAS INCREASED WINDS 
OVER N WATERS. THE ASCAT PASSES FROM 1718 UTC AND 1858 UTC 
CONFIRM WINDS TO 25 KT WHILE A LONE SHIP OBSERVATION...3FPR9 
...REPORTED WINDS EARLIER TODAY TO 33 KT NEAR 29N129W AT 1500 
UTC. EXPECT THE AREA OF STRONG WINDS TO SLIDE SE AND DIMINISH 
OVER THE NEXT TWO DAYS AS THE LOW PRESSURE SYSTEM MOVES E INTO 
THE PLAINS AND THE RIDGE AXIS SETTLES SOUTHEASTWARD. N TO NW 
SWELL WILL CAUSE WAVES HEIGHTS TO BUILD TO THE 12 TO 18 FT RANGE 
ON WED OFF THE NORTHERN BAJA CALIFORNIA COAST AS FAR W AS 125W 
BEFORE SUBSIDING TO 8 TO 12 FT LATE THU.

THE STRONG PRESSURE GRADIENT OVER WESTERN NORTH AMERICA WILL 
ALSO KEEP SW WINDS TO 20 KT IN THE NORTHERN GULF OF CALIFORNIA 
THROUGH WED. ON THU...EXPECT THE SURFACE TROUGH ASSOCIATED WITH 
THE MID TO UPPER LEVEL SYSTEM PASSING FROM THE GREAT BASIN INTO 
THE PLAINS TO SWING THROUGH THE NORTHERN GULF OF CALIFORNIA AND 
FORCE WINDS TO BECOME NORTHERLY BEHIND IT. THE AREA OF 20 KT 
WINDS SHOULD SHIFT FARTHER S IN THE GULF OF CALIFORNIA 
THU...BETWEEN 25N AND 30N.

S OF 20N...
AN ASHFALL ADVISORY IS IN EFFECT FROM THE ONGOING ERUPTION OF 
THE FERNANDINA VOLCANO NEAR 0.4S91.5W. THE GOVERNMENT OF ECUADOR 
IS CURRENTLY FLYING A RECONNAISSANCE MISSION TO INVESTIGATE THE 
ERUPTION. ON THE RECOMMENDATION OF THE NESDIS SATELLITE ANALYSIS 
BRANCH...THE ASHFALL ADVISORY WAS EXTENDED THROUGH 48 HOURS DUE 
TO THE UNCERTAINTY IN THE TIMING OF THE END OF THE VOLCANIC 
ACTIVITY. WINDS ARE EXPECTED TO REMAIN EAST TO SE NEAR 10 KT IN 
THIS AREA DURING THAT TIME. MARINERS SHOULD EXERCISE CAUTION DUE 
TO REDUCED VISIBILITIES CAUSED BY VOLCANIC ASH DOWNWIND OF THE 
VOLCANO FROM 01S TO 02N BETWEEN 91W AND 96W FOR AT LEAST THE 
NEXT FEW DAYS. IN ADDITION...NASA OMI IMAGERY FROM 2306 UTC 
SHOWS A LARGE PLUME OF ELEVATED LEVELS OF SULFUR DIOXIDE FROM 
02S TO 05N BETWEEN 91W AND 105W. EXPOSURE TO SULFUR DIOXIDE GAS 
CAN BE DANGEROUS.

ELSEWHERE...SCATTERED MODERATE CONVECTION LIES WITHIN 75 NM N 
AND 45 NM S OF THE ITCZ AXIS BETWEEN 110W AND 118W IN A REGION 
OF UPPER LEVEL DIFFLUENCE BETWEEN THE SE SIDE OF AN UPPER LEVEL 
ANTICYCLONE CENTERED NEAR 08N124W AND AN UPPER LEVEL TROUGH 
WHOSE AXIS LIES FROM 12N108W TO 00N115W. 

TRADE WINDS...WITH NE TO E FLOW CURRENTLY IN THE 20 TO 25 KT 
RANGE PRIMARILY W OF 130W ACCORDING TO THE 1902 UTC ASCAT 
PASS...SHOULD SPREAD EASTWARD OVER THE NEXT FEW DAYS AS THE 
RIDGE AXIS MOVES EASTWARD.

$$
SCHAUER CLARK