000
AXPZ20 KNHC 011546
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC THU MAY 01 2008

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 
1500 UTC.

...ITCZ...

ITCZ AXIS IS CENTERED RUNS FROM 08N82W TO 05N90W TO 06N110W TO 
04N120W TO 06N126W TO 03N140W. SCATTERED MODERATE CONVECTION 
FROM 04N TO 07N BETWEEN 78W AND 83W AND SCATTERED MODERATE 
ISOLATED STRONG CONVECTION FROM 08N AND 10N BETWEEN 84W AND 90W. 
SCATTERED MODERATE CONVECTION WITHIN 120 NM N OF AXIS BETWEEN 
119W AND 130W. SCATTERED MODERATE ISOLATED STRONG CONVECTION 
FROM 09N TO 12N BETWEEN 120W AND 122W.

...DISCUSSION...

ANOTHER IN A NEARLY CONSTANT PARADE OF STRONG...MID- TO 
UPPER-LEVEL TROUGHS IS CURRENTLY PUSHING THROUGH THE WESTERN 
U.S. AS A RESULT...DEEP LOW PRESSURE HAS FORMED OVER THE PLAINS 
AND THE RESULTING PRESSURE GRADIENT BETWEEN IT AND HIGH PRESSURE 
OVER THE NE PACIFIC HAS LED TO NORTHERLY WINDS TO NEAR GALE 
FORCE OFFSHORE THE CALIFORNIA COAST. RECENT QUIKSCAT IMAGERY AND 
SPOTTY SHIP REPORTS REVEAL THAT WEAKER NORTHERLY WINDS TO 20 KT 
EXTEND AS FAR SOUTH AS 28N BETWEEN 118W AND 126W.  LONG PERIOD 
...NW SWELL ORIGINATING IN THE GULF OF ALASKA SEVERAL DAYS AGO 
ALONG WITH NORTHERLY WIND WAVES GENERATED OFF OF CALIFORNIA HAVE 
LED TO SEAS OF 10 TO 14 FT OVER THIS SAME AREA.  FARTHER 
SOUTHWEST...A STRONG PRESSURE GRADIENT SOUTH OF THE 1027 MB 
SURFACE RIDGE NEAR 34N136W HAS TEMPORARILY ENHANCED THE TRADES 
IN A BAND FROM ABOUT 10N TO 24N W OF 128W...WITH SEAS OF 8 TO 11 
FT COMMON OVER THIS AREA IN MIXED LONG PERIOD NW SWELL COMING 
OUT OF THE GULF OF ALASKA AND EVEN LONGER PERIOD SW SWELL 
PROPAGATING OUT OF THE SOUTHERN HEMISPHERE. OUTSIDE OF THESE TWO 
REGIONS...SEAS OF GREATER THAN 8 FT AND A THICK SHIELD OF 
STRATOCUMULUS CLOUDS COVER MUCH OF THE NW HALF OF THE AREA 
...GENERALLY NW OF A LINE FROM 05N140W TO 18N130W TO 27N114W. 

BETWEEN NOW AND SATURDAY...THE WESTERN U.S. TROUGH SHOULD HEAD 
EAST AND CONSOLIDATE OVER THE MIDWEST...ALLOWING THE CURRENT 
...STRONG PRESSURE GRADIENT TO DIMINISH BY SAT. THIS SHOULD 
ALLOW WINDS TO LIKEWISE DIMINISH AND SEA TO SUBSIDE TO MUCH 
GREATER THAN 8 FT IN AN AREA SEVERAL HUNDRED MILES WIDE SW OF 
THE BAJA PENINSULA.  HOWEVER...BRISK NORTHERLY WINDS SHOULD 
AGAIN INCREASE OFF THE WEST COAST AS ANOTHER TRANSIENT TROUGH 
PUSHES INTO THE WESTERN U.S.  SEAS SHOULD ALSO BEGIN BUILDING 
AND SPREADING SOUTHWARD ALONG THE WEST COAST INTO THE FAR 
NORTHERN WATERS BY EARLY NEXT WEEK.  

ELSEWHERE...A WELL-DEFINED GROUP OF SW SWELL COMING OUT OF THE 
SOUTHERN HEMISPHERE CONTINUES TO PASS THE EQUATOR AND ARRIVE 
ALONG THE MEXICAN AND CENTRAL AMERICAN COASTS.  EARLIER JASON 
AND SHIP DATA SUGGEST THAT WAVE HEIGHTS RANGE FROM 6 TO 9 
FT...HIGHEST NEAR THE EQUATOR.  GOING INTO THE WEEKEND...THIS 
SWELL SHOULD GRADUALLY DIMINISH BUT STILL BE DOMINANT S OF 20N W 
OF 115W.

FINALLY...SATELLITE IMAGERY AND OUTGOING LONGWAVE RADIATION DATA 
CONTINUES TO INDICATE A WEAKENING PULSE OF TROPICAL CONVECTION 
TRAVELING ALONG THE EQUATOR IN THE WESTERN PACIFIC. THE RESPONSE 
FROM THIS ORGANIZED AREA OF CONVECTION IS BEING FELT IN THE 
TROPICAL EASTERN PACIFIC...AS ANOMALOUS UPPER-LEVEL WESTERLY 
FLOW OF 20 TO 60 KT IS INDICATED IN REAL-TIME NCEP RE-ANALYSIS 
WITHIN A FEW DEGREES OF THE EQUATOR BETWEEN THE DATELINE AND 
110W. ALTHOUGH WEAKER...THIS SIGNAL SHOULD REACH THE EASTERN 
PACIFIC AND LIKELY SPARK AN INCREASE IN CONVECTION S OF 10N BY 
NEXT WEEK...SPREADING FROM W TO E.


$$
KIMBERLAIN