000
AXPZ20 KNHC 110906
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC FRI SEP 11 2009

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN
FROM THE EQUATOR TO 32N...EAST OF 140W. 

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0845 UTC.

...SPECIAL FEATURE...

AT 11/0900 UTC...TROPICAL STORM LINDA IS LOCATED NEAR NEAR 20.0N 
130.8W...MOVING N-NW 0R 330 DEG AT 5 KT. THE MAXIMUM SUSTAINED 
WINDS ARE 45 KT WITH GUSTS TO 55 KT. THE ESTIMATED MINIMUM 
CENTRAL PRESSURE IS 1000 MB. CONVECTION IS DIMINISHING WITH 
SCATTERED MODERATE CONVECTION WITHIN ABOUT 200 NM OF CENTER IN 
THE NORTH QUADRANT. COOLER SURFACE WATERS AND STRONG UPPER LEVEL 
SHEAR HAVE TAKEN ITS TOLL ON LINDA...CAUSING THE BEGINNING OF 
THE FORECAST WEAKENING TREND. LINDA HAS BEEN FIGHTING SLY UPPER 
SHEAR OF 20-40 KT AND HAS RESULTED IN A WEAKENING OF THE SYSTEM 
AND STRETCHING OF THE LOW TO MID LEVEL CIRCULATION. LINDA WILL 
CONTINUE TO SLOWLY MOVE NNW OVER THE NEXT COUPLE OF DAYS 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. 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...

TROPICAL WAVE IS ANALYZED N OF 07N ALONG 99W MOVING WEST AT 15 
KT. ISOLATED MODERATE TO STRONG CONVECTION WAS NOTED NEAR THE 
WAVE AT ABOUT 12N. THE CONVECTION IS NOT ORGANIZED.

...THE ITCZ...

THE INTERTROPICAL CONVERGENCE ZONE IS ALONG THE LINE...08N78W TO 
08N90W TO 07N105W TO 07N140W. SCATTERED MODERATE TO STRONG 
CONVECTION IS WITHIN THE AREA FROM 06.5N TO 08.5N FROM 87W TO 
92W.

...DISCUSSION...

A DEEP LAYER CYCLONIC CIRCULATION IS CENTERED NEAR 34N128W WITH 
AN UPPER TROUGH W OF A LINE THROUGH 32N125W TO 20N140W. DRY AND 
STABLE MIDDLE AND 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 21N118W WITH A RIDGE EXTENDING W THE 
THE ABOVE TROUGH AND ALSO A RIDGE EXTENDS E-SE TO A SHARP CREST 
OVER CENTRAL MEXICO AT 20N97W. DEBRIS MOISTURE FROM FORMER ITCZ 
CONVECTION BETWEEN 125W AND 133W IS ADVECTED N MERGING WITH THE 
DEBRIS MOISTURE FROM TROPICAL STORM LINDA...WITH THE RESULTANT 
PLUME LIFTING N ACROSS NRN BAJA CALIFORNIA AND SOUTHERN 
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 S ACROSS THE W CARIBBEAN AND EASTERN 
MEXICO AND CENTRAL AMERICA TO THE ITCZ BETWEEN 82W AND 93W. 
CONVECTION ASSOCIATED WITH THE TROUGH HAS DIMINISHED EXCEPT FOR 
CONVECTION WITHIN THE ITCZ REGION MENTIONED ABOVE. 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. 

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. 

$$
LL