000
AXPZ20 KNHC 151527
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC WED APR 15 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
15000 UTC.

...ITCZ...
THE INTERTROPICAL CONVERGENCE ZONE IS ALONG THE LINE 06N77W TO 
08N115W TO 06N140W. SCATTERED MODERATE CONVECTION IS WITHIN 45 
NM EITHER SIDE OF THE ITCZ FROM 115W TO 130W. SCATTERED MODERATE 
WITH ISOLATED STRONG CONVECTION IS WITHIN 60 NM OF THE POINT 
07.5N139.5W.

...DISCUSSION...
UPPER LEVELS...
STRONG SHORTWAVE IS OVER THE WESTERN UNITED STATES COAST AND 
EXTENDS SOUTH TO NEAR 23N. THE SHORTWAVE IS FORECAST TO MOVE 
EAST AND CHANGE LITTLE AND BY FRIDAY BE LOCATED OVER THE ROCKY 
MOUNTAINS OF THE UNTIED STATES AND THE NORTHERN SIERRA MADRE 
OCCIDENTAL OF MEXICO NORTH OF 25N. THE UPWARD VERTICAL MOTION 
ASSOCIATED WITH THE TROUGH IS LOCATED OVER MEXICO WITH SOME 
CONVECTION NOTED ALONG 105W NORTH OF 25N. OVER THE WESTERN PART 
OF MEXICO AND THE PACIFIC OCEAN SUBSIDING AIR IS PRESENT WITH 
DRY AND CLOUD FREE CONDITIONS IN THE MIDDLE AND UPPER LEVELS.
THE TROUGH IS EMBEDDED IN MODERATE WESTERLY FLOW NORTH OF 18N. 
THESE WESTERLIES ARE FORECAST TO CONTINUE THROUGH AT LEAST THE 
NEXT SEVERAL DAYS. ANOTHER WEAKER AND MAINLY UPPER SHORTWAVE IS 
FORECAST TO MOVE WEST ACROSS 140W THURSDAY.

SOUTH OF 18N A BROAD UPPER RIDGE IS ANALYZED AND THIS FEATURE IS 
FORECAST TO CHANGE LITTLE THROUGH THE NEXT COUPLE OF DAYS.

SURFACE...
WEAK COLD FRONT IS ALONG THE LINE THROUGH 32N113W TO 27N120W. 
THE FRONT IS FORECAST TO MOVE EAST OVER MEXICO AND WEAKEN. THERE 
IS LITTLE WEATHER ASSOCIATED WITH THE FRONT EXCEPT FOR 
INCREASING NORTHERLY WINDS IN THE 20 TO 25 KNOT RANGE NORTH OF 
THE FRONT. ELSEWHERE A MODERATE SURFACE RIDGE IS NORTH OF 17N 
WEST OF 115W.

EXCEPT FOR NORTH OF 25N EAST OF 125W...WHERE BROKEN SCATTERED 
STRATOCUMULUS ARE OBSERVED...THE AREA NORTH OF 20N IS COVERED BY 
OVERCAST STRATOCUMULUS CLOUDS.

LONG PERIOD NORTHERLY SWELL WITH HEIGHTS TO 16 FT IS OVER THE 
AREA MOSTLY NORTH OF 25N EAST OF 125W. THE SWELL IS FORECAST TO  
TO 10 FT OR LESS BY LATE THU. 

AN ASHFALL ADVISORY IS IN EFFECT FROM THE ONGOING ERUPTION OF LA 
CUMBRE ON ISLA FERNANDINA GALAPAGOS 00.4S91.5W. THE GOVERNMENT 
OF ECUADOR IS FLYING RECONNAISSANCE MISSIONS 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 THE POTENTIAL FOR REDUCED VISIBILITIES CAUSED BY VOLCANIC ASH 
DOWNWIND OF THE VOLCANO S OF 02N BETWEEN 92W AND 95W 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 103W. EXPOSURE TO SULFUR 
DIOXIDE GAS CAN BE DANGEROUS AND CAUSE SKIN AND EYE IRRITATION.

$$
LL