000
AXPZ20 KNHC 090339
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC WED SEP 09 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 
0200 UTC.

...SPECIAL FEATURES...

AT 09/0300 UTC...TROPICAL STORM LINDA WAS LOCATED NEAR 15.6N 
128.4W MOVING NW OR 315 DEG AT 2 KT. MAXIMUM SUSTAINED WIND 
SPEED WAS 55 KT WITH GUSTS TO 65 KT. ESTIMATED MINIMUM CENTRAL 
PRESSURE WAS 994 MB. SEE LATEST NHC FORECAST/ADVISORY UNDER 
AWIPS/WMO HEADERS MIATCMEP5/WTPZ25 KNHC FOR MORE DETAILS. 
CONVECTION INCREASED THIS AFTERNOON WITH IMPROVED BANDING ACROSS 
THE N SEMICIRCLE...AS WIND SHEAR RELAXED. LINDA IS FORECAST TO 
BEGIN TO MOVE OFF TO THE NW AT AN INCREASED RATE OF SPEED DURING 
THE NEXT 12 TO 24 HOURS...AND WILL BEGIN TO ENCOUNTER COOLER 
WATERS...AND GRADUALLY MORE HOSTILE UPPER ATMOSPHERIC 
CONDITIONS. LINDA MAY INCREASE MILDLY OVERNIGHT IN 
INTENSITY...AND REACH AT OR JUST BELOW HURRICANE 
STRENGTH...BEFORE IT BEGINS TO ACCELERATE AND WEAKEN AFTER 36 
HOURS.

...THE ITCZ...

THE INTERTROPICAL CONVERGENCE ZONE WAS ANALYZED ALONG THE LINE 
09N84W TO 07N88W TO 10N97W TO 08.5N112W TO 13N123W...THEN 
CONTINUING FROM 12N132W TO 09N140W. 

...DISCUSSION...

A DEEP LAYER UPPER ANTICYCLONE LOCATED W OF 140W HAS A RIDGE 
AXIS EXTENDING EWD OVER THE WESTERN PORTION OF THE FORECAST 
REGION...AND TO WITHIN 5-6 DEGREES TO THE W OF LINDA. THE RIDGE 
AND THE ASSOCIATED UPPER CONVERGENCE OCCURRING ON THE E AND S 
PERIPHERY OF THE AXIS ARE MAINTAINING SINKING MOTION...AND DRY 
STABLE AIR IN THE MIDDLE LEVELS OF THE ATMOSPHERE...AND COVERS 
THE AREA N OF 10N AND W OF 132W.

AN OMEGA BLOCKING PATTERN N OF THE REGION HAS A RIDGE AXIS ALONG 
120W...WHILE AN UPPER LOW NEAR 34N127 WAS MOVING SLOWLY SE AND 
ATTEMPTING TO DROP IN UNDERNEATH THE ASSOCIATED UPPER HIGH OVER 
CENTRAL CALIFORNIA. A TROUGH AXIS EXTENDING FROM THE UPPER LOW 
TO THE SW NEAR 24N139W...AND WAS MOVING SE...WHILE THE TROUGH 
AXIS THEN TRAILED OFF TO THE W AS A TUTT TO N OF THE HAWAIIAN 
ISLANDS. ABOUT 6-8 DEGREES TO THE E OF THIS UPPER TROUGH WAS A 
WEAK AND SUBTLE MID TO UPPER LEVEL TROUGH THAT EXTENDED SW TO 
JUST NW OF LINDA...AND WAS INDUCING MID LEVEL DIVERGENCE N OF 
LINDA. TO THE E OF LINDA WAS ANOTHER UPPER LEVEL ANTICYCLONIC 
CIRCULATION CENTERED NEAR 16N116W AND WAS PART OF THE WRN END OF 
BROADER UPPER RIDGING ANCHORED OVER SOUTHERN MEXICO. THIS 
PATTERN HAS ACTED TO BLOCK TROPICAL STORM LINDA IN BETWEEN TWO 
RIDGES...TO THE E AND W...AND A BROAD UPPER TROUGH TO THE 
N...ALL LEAVING LINDA TRAPPED IN BETWEEN THESE SYSTEMS...AT 
LEAST FOR THE SHORT TERM. UPPER LEVEL ELYS ACROSS THE TROPICAL 
EPAC E OF 115W WERE ACTING TO VENTILATE AND MAINTAIN DEEP CVNTN 
WITH THE ITCZ. AN INVERTED UPPER LEVEL TROUGH WAS NOTED ALONG 
115W...WITH CYCLONIC TURNING SEEN IN MID AND UPPER CLOUDS INVOF 
10N115W. E OF THE HIGH OVER SRN MEXICO WAS A SHARP MID TO UPPER 
TROUGH SW TO NE ACROSS THE W CARIBBEAN...INDUCING UPPER LEVEL 
SWLY FLOW AND DIVERGENCE ACROSS THE EPAC E OF 88W. A FRESH AND 
MOIST LLVL FLOW ACROSS THIS FAR E PORTION OF THE EPAC WAS 
FORCING NUMEROUS MODERATE TO STRONG CONVECTION...THAT HAS 
PERSISTED THROUGHOUT THE DAY DUE TO THE UPPER DIVERGENCE. 
ABUNDANT LOW LEVEL MOISTURE GENERALLY DOMINATES THE AREA FROM 
THE PACIFIC COAST OF COLOMBIA W AND NW ALONG THE COAST OF 
CENTRAL AMERICA TO THE COAST OF MEXICO ALONG 105W. ACTIVE 
WEATHER WILL GENERALLY PREVAIL ACROSS THESE WATERS FOR THE NEXT 
24 HOURS DUE TO THE MOIST AND UNSTABLE CONDITIONS.

A SURFACE RIDGE CONTINUES TO DOMINATE THE NORTHERN PORTION OF 
DISCUSSION AREA MAINLY N OF 20N W OF 115W. THE PRESSURE GRADIENT 
BETWEEN LINDA AND THE RIDGE IS PRODUCING A LARGE AREA OF NE 
WINDS 20 KT AND SEAS TO 9 FT PARTICULARLY FROM 15N TO 25N AND W 
OF 130W. THESE CONDITIONS ARE EXPECTED TO PERSIST DURING THE 
NEXT 48 HOURS. STRATOCUMULUS CLOUDS ARE OBSERVED N OF 15N W OF 
120W.

SWELLS FROM THE NW ARE MOVING SE AND INTO THE NE PORTION OF THE 
AREA TONIGHT...OFFSHORE OF BAJA CALIFORNIA. FOR THE UPCOMING 
WEEKEND...LARGE LONG PERIOD W-NW SWELLS IN EXCESS OF 16 SECONDS  
WILL MOVE INTO THE NW PART OF THE AREA...BUILDING SEAS TO 11 FT 
BY SATURDAY MORNING. SELY SWELL CURRENTLY DOMINATES THE SE 
PORTIONS OF THE AREA...GENERATED BY A BROAD FIELD OF SE WINDS 
OFF THE COAST OF CHILE AND PERU...AND WILL SPREAD N AND NW AND 
RAISE SEA HEIGHTS TO 8 FT AND GREATER ACROSS THE EQUATOR BY 48 
HOURS.

$$

STRIPLING