000
AXPZ20 KNHC 110244
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC SUN OCT 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 
0315 UTC.

...SPECIAL FEATURE... 

THE AREA OF LOW PRESSURE HAS BEEN RE-LOCATED FURTHER SOUTH NEAR 
15N108W BASED ON THE MOST RECENT VISIBLE SATELLITE IMAGERY AND 
CONTINUES TO ORGANIZE. SATELLITE IMAGERY INDICATED AN AREA OF 
SCATTERED TO NUMEROUS STRONG CONVECTION WITHIN 90-120 NM OF THE 
LOW LEVEL CENTER IN THE W QUADRANT. ADDITIONAL CONVECTION WAS
ORGANIZED IN SEVERAL BANDS LOCATED WELL AWAY FROM THE LOW LEVEL 
CENTER. UPPER LEVEL ANTICYCLONIC OUTFLOW FROM THE SYSTEM APPEARS 
TO BE EXPANDING IN ALL QUADRANTS SUGGESTING AN IMPROVING UPPER 
LEVEL ENVIRONMENT. A 1716 UTC ASCAT PASS INDICATED THAT THE 
CIRCULATION HAS BECOME MORE SYMMETRIC. THE LOW IS FORECAST TO 
MOVE SLOWLY NW TO N TO THE SOUTH OF CABO SAN LUCAS OVER THE NEXT 
SEVERAL DAYS AS A SHORT WAVE TROUGH CURRENTLY OFF THE CALIFORNIA 
COAST MOVES EASTWARD TO THE NORTH OF THE LOW. THERE IS NOW A 
HIGH CHANCE...GREATER THAN 50 PERCENT THAT THE LOW MAY FORM INTO 
A TROPICAL CYCLONE OVER THE NEXT 48 HOURS.

...TROPICAL WAVE...

A TROPICAL WAVE ALONG 90W/91W N OF 06N IS MOVING WEST AT 15 KT
AS AVERAGED OVER THE PAST 24 HOURS. THIS WAVE IS INTERACTING 
WITH AN UPPER LOW NEAR 14N93W. DIVERGENCE EAST OF THE UPPER LOW 
ALONG WITH 20 KT SWLY SURFACE FLOW TO THE SOUTH OF THE ITCZ IS 
ENHANCING SCATTERED MODERATE TO STRONG CONVECTION ALONG THE 
WAVE...AND ALSO ALONG THE COAST OF MEXICO JUST E OF THE GULF OF 
TEHUANTEPEC.

...ITCZ...

THE ITCZ AXIS WAS CENTERED ALONG 11N86W TO 10N98W TO 12N107W TO 
11N118W TO 13N130W TO 10N140W. SCATTERED MODERATE ISOLATED 
STRONG WITHIN 120 NM S OF THE AXIS BETWEEN 106W AND 117W. 
SCATTERED MODERATE WITHIN 120 NM N OF THE AXIS BETWEEN 91W AND 
94W.

...DISCUSSION...

FAIRLY PROGRESSIVE PATTERN IS IN PLACE N OF 20N WITH A SERIES OF 
TROUGHS AND RIDGES IN PLACE. A SHARP VIGOROUS AND BECOMING 
NEGATIVELY TILTED UPPER LEVEL TROUGH JUST NW OF THE AREA ALONG
143W TO 32N WAS SWEEPING EAST 20 KT. RATHER FLAT RIDGE ALONG 
133W N OF 20N IS MOVING E AT 15 KT. DOWNSTREAM SHORT WAVE TROUGH 
EXTENDS FROM THE CENTRAL CALIFORNIA COAST TO 23N122W IS MOVING 
EAST AT 20 KT AND IS BEGINNING TO RIDE NE OVER THE DOWNSTREAM 
FLAT RIDGE COVERING NORTHERN MEXICO. 

FURTHER SOUTH...AN ELONGATED MID TO UPPER LEVEL RIDGE AXIS 
EXTENDS FROM NE MEXICO AND IS ORIENTED EAST TO WEST ALONG 18N 
THROUGH 140W. SUBSIDENT WESTERLY FLOW ON THE NORTH SIDE OF THE 
UPPER RIDGE IS MAINTAINING FAIRLY DRY AIR NORTH AND WEST OF THE 
AREA OF LOW PRESSURE NOTED ABOVE BETWEEN 105W AND 120W. 

AT THE SURFACE...A WEAK SURFACE TROUGH IS ANALYZED FROM 09N TO 
15N ALONG 133W. A 1422 UTC HIGH RESOLUTION QUIKSCAT PASS SHOWED 
A SHRINKING AREA OF TRADES BETWEEN THE ITCZ AND 17N ON THE 
SOUTHERN PERIPHERY OF A BROAD SURFACE RIDGE N OF THE AREA. THESE 
WINDS WILL DIMINISH THROUGH TONIGHT AS THE RIDGE WEAKENS AHEAD 
OF A COLD FRONT APPROACHING THE AREA FROM THE CENTRAL PACIFIC. 
THE FRONT WILL MOVE INTO THE AREA BY LATE SUN AND EXTEND FROM 
30N131W TO 23N140W BY LATE MON. THE ACCOMPANYING STORM SYSTEM 
NORTH OF THE AREA IS FORECAST TO BECOME QUITE INTENSE AND COULD 
USHER IN STRONG WESTERLY WINDS APPROACHING GALE FORCE OVER THE 
FAR N PORTION OF THE AREA LATE TUE WITH SEAS POSSIBLY BUILDING 
TO 15 FT.  

LONG PERIOD NE SWELL IN THE AREA OF TRADES ROUGHLY FROM 10N TO 
20N W OF 120W WILL DECAY THROUGH TONIGHT...JUST AHEAD OF THE 
ARRIVAL OF NW SWELL TO 10 FT PUSHING INTO THE DISCUSSION AREA 
MONDAY BEHIND THE COLD FRONT NOTED ABOVE.

$$
COBB