000
AXPZ20 KNHC 110257
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC FRI SEP 11 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 FEATURE...

AT 11/0300 UTC...LINDA WAS DOWNGRADED TO A TROPICAL STORM... 
LOCATED NEAR NEAR 19.9N 130.5W...MOVING N NW 0R 330 DEG AT 7 KT. 
THE MAXIMUM SUSTAINED WINDS WERE 55 KT WITH GUSTS TO 65 KT. THE 
ESTIMATED MINIMUM CENTRAL PRESSURE WAS 994 MB. SCATTERED 
MODERATE TO STRONG CONVECTION WAS NOTED WITHIN ABOUT 90 NM OF 
CENTER IN THE NORTHWEST QUADRANT...WITH SCATTERED MODERATE 
CONVECTION NOTED ELSEWHERE WITHIN 120 NM OF THE CENTER...MAINLY 
ACROSS THE N AND NE SEMICIRCLES. COOLER SURFACE WATERS AND 
STRONG UPPER LEVEL SHEAR HAVE TAKEN ITS TOLL ON LINDA...CAUSING 
THE BEGINNING OF THE FORECAST WEAKENING TREND. LINDA IS EXPECTED 
TO CONTINUE N-NW AND THEN NW OVER THE NEXT FEW DAYS...AND 
FURTHER WEAKEN TO A TROPICAL DEPRESSION THIS WEEKEND. SEE LATEST 
NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMEP5/WTPZ25 
KNHC AND THE PUBLIC ADVISORY UNDER TCPEP5/ WTPZ35 KNHC FOR MORE 
DETAILS.

...TROPICAL WAVE...

A TROPICAL WAVE WAS ANALYZED N OF 06N ALONG 97W. TPW ANIMATIONS 
OVER THE PAST FEW DAYS SUGGEST A PERTURBATION MOVING THROUGH THE 
TROPICAL EPAC AT ABOUT 22 KT AND NOW ALONG ABOUT 100W AND ABOUT 
TO ENCROACH UPON ANOTHER PERTURBATION ALONG 107W. ISOLATED 
MODERATE CONVECTION WAS NOTED WITHIN A FEW DEGREES OF THIS 
WAVE...WITH MORE SCATTERED CONVECTION 5 DEGREES EITHER SIDE OF 
THE WAVE AXIS. CYCLONIC TURNING WAS INDICATED IN CONVECTION 
ALONG THE ITCZ NEAR 08N98W. 

...THE ITCZ...

THE ITCZ AXIS WAS ANALYZED ALONG THE LINE 08N76W TO 06N82W TO 
09N95W TO 07N111W TO 11N124W TO 07N133W TO 09N140W. SCATTERED 
MODERATE TO STRONG CONVECTION WAS OCCURRING WITHIN 240 NM S OF 
AXIS E OF 94W AND WITHIN 150 NM EITHER SIDE OF AXIS BETWEEN 976W 
AND 108W.  

...DISCUSSION...

AN UPPER CYCLONE IS NEAR 32N128W WITH AN UPPER TROUGH EXTENDING 
SW ALONG 29N130W THROUGH ANOTHER CYCLONE AT 22N143W...WITH A 
BROAD TROUGH CONTINUING S TO A BASE AT 13N142W. DRY AND STABLE 
MID TO UPPER LEVELS PREVAIL AROUND THE PERIPHERY OF THIS LATTER 
LOW S OF 20N...AND INTO THE SW FLANK OF LINDA. 

AN UPPER ANTICYCLONE IS AT 22N114W WITH A RIDGE EXTENDING W 
ACROSS LINDA...AND A RIDGE ALSO EXTENDS E-SE TO A SHARP CREST 
OVER CENTRAL OLD MEXICO AT 22N100W. DEBRIS MOISTURE FROM FORMER 
ITCZ CONVECTION BETWEEN 120W AND 130W IS ADVECTED N MERGING WITH 
THE DEBRIS MOISTURE FROM HURRICANE LINDA...WITH THE RESULTANT 
PLUME LIFTING N ACROSS NRN BAJA CALIFORNIA AND INTO FAR SRN 
CALIFORNIA. S OF THE RIDGE AXIS...UPPER LEVEL ELYS PREVAIL S OF 
15N AND BETWEEN 100W AND 125W. DIFFLUENT FLOW S OF 10N AND 
ACROSS THE ITCZ IS ACTING TO VENTILATE CONVECTION MAINLY E OF 
110W.   

AN UPPER TROUGH EXTENDS SW ACROSS THE W CARIBBEAN AND CENTRAL 
AMERICA TO 08N83W. UPPER CONVERGENCE NOTED EARLIER ON THE W SIDE 
OF THIS TROUGH HAS DIMINISHED WITH DIURNAL CONVECTION PERSISTING 
ACROSS CENTRAL AMERICA. UPPER DIVERGENCE OVER THE ITCZ BETWEEN 
BETWEEN 84W AND 94W HAS BEEN ENHANCED IN RECENT HOURS. THIS 
TROUGH IS FORECAST TO SLIDE SLOWLY NW OVER THE NEXT 12 TO 24 
HOURS AS AN EMBEDDED LOW ACROSS THE SW CARIB MOVES W INTO 
NICARAGUA. 

LINDA HAS BEEN FIGHTING SLY UPPER SHEAR OF 20-240 KT THROUGHOUT 
THE AFTERNOON...AND HAS RESULTED IN A WEAKENING OF THE SYSTEM 
AND STRETCHING OF THE LOW TO MID LEVEL CIRCULATION. LINDA HAS 
BEEN DOWNGRADED TO A TROPICAL STORM IN THE PAST HOURS AND WILL 
CONTINUE TO MOVE TO MOVE WNW THEN NW OVER THE PAST FEW DAYS AND 
WHILE WEAKENING FURTHER. HOWEVER...THE PRESSURE GRADIENT BETWEEN 
LINDA AND THE RIDGE TO ITS NW CONTINUE TO PRODUCE AN AREA OF NE 
WINDS AROUND 20 KT AND SEAS TO 9 FT IN NE SWELL SOME 240 NM TO 
THE N AND NW OF LINDA. 

LOOKING AHEAD...A COLD FRONT WILL DROP INTO THE NW PORTION OF 
THE AREA DURING THE WEEKEND BRINGING LARGE LONG PERIOD NWLY 
SWELL. LARGE LONG PERIOD NW SWELLS OF ABOUT 16 SECONDS WILL 
PROPAGATE ACROSS THE NW PART OF THE AREA BUILDING SEAS TO 11 FT 
BY SAT MORNING. CROSS EQUATORIAL SLY WINDS OF 20 KT AND SWELLS 
GENERATED BY A BROAD FIELD OF SE WINDS 20 TO 30 KT S OF THE 
EQUATOR WILL CONTINUE TO AFFECT THE FAR SOUTHERN PORTION MAINLY 
S OF 05N AND E OF 100W. 

$$
STRIPLING