000
AXPZ20 KNHC 152145
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC WED APR 15 2009

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

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2030 UTC.

...ITCZ...

THE INTERTROPICAL CONVERGENCE ZONE IS ALONG A LINE FROM 06N77W 
TO 07N88W TO 07N118W TO 06N130W TO 07N140W. SCATTERED MODERATE 
CONVECTION CAN BE FOUND WITHIN 60 NM OF THE ITCZ AXIS FROM 125W 
TO 136W.

...DISCUSSION...

N OF 20N...
A DEEP LAYERED LOW PRES SYSTEM CURRENTLY OVER THE GREAT BASIN 
WILL SLOWLY MOVE EASTWARD THROUGH THE ROCKY MOUNTAINS OVER THE 
NEXT TWO DAYS. AT THE SURFACE...THE PRES GRADIENT BETWEEN LOW 
PRES OVER THE GREAT BASIN AND THE HIGH PRES CENTER NEAR 36N131W 
HAS BROUGHT WINDY CONDITIONS OVER NE WATERS. THE QUIKSCAT PASS 
FROM 1308 UTC SHOWS A WIDESPREAD REGION W OF NORTHERN BAJA 
CALIFORNIA TO APPROXIMATELY 122W WHERE WINDS ARE TO 25 KT. A 
SHIP OBSERVATION...PHFV...REPORTED WINDS TO 24 KT NEAR 28N115W 
AT 1700 UTC...CONFIRMING THE EARLIER QUIKSCAT PASS. EXPECT THE 
AREA OF STRONG WINDS TO DIMINISH OVER THE NEXT TWO DAYS AS THE 
LOW PRESSURE SYSTEM MOVES E INTO THE PLAINS. N TO NW SWELL HAS 
GENERATED SEAS IN THE 12 TO 18 FT RANGE OFF THE NORTHERN BAJA 
CALIFORNIA COAST AS FAR W AS 125W. AS THE WINDS DIMINISH...THE 
SEAS WILL ALSO COME DOWN TO APPROXIMATELY 12 FT OFF BAJA 
CALIFORNIA OVER THE NEXT FEW DAYS AS THIS SWELL REACHES THE 
SOUTHERN HALF OF THE PENINSULA.

THE STRONG PRESSURE GRADIENT OVER WESTERN NORTH AMERICA HAS ALSO 
INCREASED WINDS IN THE NORTHERN GULF OF CALIFORNIA. THE QUIKSCAT 
PASS FROM 1308 UTC SHOWED SW WINDS AHEAD OF THE COLD FRONT 
ASSOCIATED WITH THE DEEP LAYERED LOW PRESSURE SYSTEM OVER THE 
WESTERN UNITED STATES INCREASING TO THE 20 TO 30 KT RANGE.  AT 
1800 UTC...THE COLD FRONT WAS ANALYZED OVER THE NORTHERN GULF OF 
CALIFORNIA BETWEEN 30N AND 31N. WINDS WILL BECOME NORTHERLY 
BEHIND THE COLD FRONT THIS EVENING. THE AREA OF 20 KT WINDS 
SHOULD SHIFT FARTHER S IN THE GULF OF CALIFORNIA THU...BETWEEN 
25N AND 30N. WINDS ARE EXPECTED TO DIMINISH BELOW 20 KT BY FRI 
AFTERNOON.

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. WINDS ARE 
EXPECTED TO REMAIN 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 02S TO 01N 
BETWEEN 91W AND 96W FOR AT LEAST THE NEXT FEW DAYS. IN 
ADDITION...NASA OMI IMAGERY FROM 1853 UTC SHOWS A LARGE PLUME OF 
ELEVATED LEVELS OF SULFUR DIOXIDE FROM 02S TO 04N BETWEEN 91W 
AND 105W. EXPOSURE TO SULFUR DIOXIDE GAS CAN BE DANGEROUS... 
CAUSING IRRITATION TO EYES AND SKIN.

ELSEWHERE...THE QUIKSCAT PASS FROM 1122 UTC REVEALED WINDS 
DOWNWIND OF THE GULF OF PAPAGAYO TO 25 KT THIS MORNING. THE 
SUBSEQUENT ASCAT PASS AT 1520 UTC MISSED THE CORE AREA OF 
WINDS...BUT DID MANAGE TO ENCOUNTER THE WESTERN EDGE OF THE WIND 
SWATH NEAR 10N90W WHERE WINDS WERE REPORTED TO 20 KT. THE 20 KM 
NAM FORECAST KEEPS WINDS ABOVE 20 KT HERE FOR THE NEXT FEW DAYS. 
SINCE IT HAS CAPTURED THE EVENT WHILE THE GFS IS CURRENTLY TOO 
WEAK...THE FORECAST RELIES ON THE STRONGER NAM.

SCATTERED MODERATE CONVECTION CAN BE FOUND WITHIN 60 
NM OF THE ITCZ AXIS FROM 125W TO 136W IN A REGION OF UPPER LEVEL 
DIFFLUENCE WHERE A PORTION OF THE 50 KT WESTERLY UPPER JET ALONG 
01N IS DIVERTED NORTHWARD UPSTREAM OF AN UPPER LEVEL ANTICYCLONE 
CENTERED NEAR 08N116W.

TRADE WINDS...NE TO E FLOW IS CURRENTLY IN THE 20 TO 25 KT RANGE 
PRIMARILY W OF 125W ACCORDING TO THE 1444 TO 1450 UTC QUIKSCAT 
PASSES.  TRADES SHOULD SPREAD EASTWARD OVER THE NEXT 24 HOURS AS 
THE RIDGE AXIS STRENGTHENS AS SHIFTS SLIGHTLY EASTWARD.

$$
SCHAUER CLARK