000
AXPZ20 KNHC 060329
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC SAT SEP 06 2008

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 
0300 UTC.

...ITCZ...

ITCZ AXIS IS CENTERED FROM 08N81W TO 14N105W TO 10N115W TO 
12N129W TO 08N140W. NUMEROUS MODERATE ISOLATED STRONG CONVECTION 
FROM 10 TO 18N BETWEEN 92W AND 111W. ISOLATED WEAK CONVECTION 
WITHIN 120 NM N OF AXIS BETWEEN 111W AND 117W.

...DISCUSSION...

A STRONG MONSOON TROUGH...DISPLACED N OF ITS CLIMATOLOGICAL 
POSITION...LIES OFFSHORE THE MEXICAN AND CENTRAL AMERICAN COASTS 
FROM COSTA RICA TO SW OF PUERTO VALLARTA. EARLIER QUIKSCAT DATA 
INDICATED WIDESPREAD...ENHANCED SW TO W FLOW WITHIN ABOUT 10 
DEGREES S OF THE TROUGH AXIS BETWEEN 80W AND 110W. THE 
COMBINATION OF LOW-LEVEL SPEED CONVERGENCE AND CYCLONIC SHEAR 
ALONG THE TROUGH AXIS...NOT TO MENTION A PATTERN OF DIFFLUENCE 
ALOFT...IS FAVORING A BROAD AREA OF CLOUDS AND SCATTERED TO 
NUMEROUS CONVECTION FROM ABOUT 08N-18N BETWEEN 87W AND 111W. 

SATELLITE IMAGERY SUGGEST THE FORMATION OF A BROAD AND POORLY 
-DEFINED CYCLONIC GYRE ALONG THE WESTERN END OF THE TROUGH... 
WITH A MEAN CENTER CLOSE TO 14.5N105W. QUIKSCAT DATA FROM 
YESTERDAY MORNING SHOWED NOTHING BUT UNIFORM WESTERLY FLOW 
THROUGH THE REGION...BUT SEVERAL SHIP REPORTS THIS EVENING 
INDICATE THE PRESENCE OF LOW-LEVEL EASTERLY FLOW WITHIN A FEW 
HUNDRED MILES OF THE SW MEXICAN COAST. SEVERAL GLOBAL MODELS 
INSIST UPON TROPICAL CYCLOGENESIS EITHER WITHIN THIS AREA OR IN 
A REFORMATION OF LOW PRESSURE SLIGHTLY FARTHER WNW IN THE NEXT 
DAY OR TWO. A CONCENTRATED AREA OF CONVECTION REMAINS ACTIVE 
WITHIN ABOUT 360 NM OF THE W QUADRANT...NEAR AND WEST OF THE 
BEST LOW-LEVEL CYCLONIC TURNING. THIS PATTERN OF CONVECTION 
SEEMS IN LINE WITH THE LATEST CIMSS ANALYSES INDICATING AT LEAST 
20 KT OF NE SHEAR.

ELSEWHERE...THE REMAINS OF WHAT WAS TROPICAL DEPRESSION KARINA 
ARE DRIFTING SE IN THE LOW-LEVEL NW FLOW...DRAWING THE 
CIRCULATION INTO THE BROAD SURFACE LOW NOW FORMING WITHIN THE 
MONSOON TROUGH.  OTHERWISE...A NEW GROUP OF SW SWELL IS NOW 
ARRIVING OVER MUCH OF THE SOUTHERN HALF OF THE TROPICAL EAST 
PACIFIC...WITH WAVE HEIGHTS OF 8 TO 11 FT PREVAILING S OF 13N W 
OF 90W. THE HIGHEST WAVE HEIGHTS COINCIDE WITH THE STRONG WINDS 
WITHIN THE MONSOON TROUGH AND WITHIN 330 NM OF THE SE SEMICIRCLE 
OF THE ASSOCIATED...BROAD SURFACE LOW NEAR 14.5N105W.

FINALLY...LONG PERIOD N TO NE SWELL PROPAGATING AWAY FROM 
PERSISTENT GALE CONDITIONS OFF THE U.S. WEST COAST CONTINUE TO 
ARRIVE OVER THE NW WATERS. FOR THE MOST PART...WAVE HEIGHTS HAVE 
BEEN GRADUALLY SUBSIDING OVER THE AREA...BUT A NEW BATCH OF NE 
SWELL SHOULD BEGIN ARRIVING SAT AND SUN.  THE NEW-ARRIVING 
SWELLS SHOULD ALLOW WAVE HEIGHTS TO REBUILD TO 9 TO 10 FT OVER 
THE FAR NW WATERS.

$$
KIMBERLAIN