000
AXPZ20 KNHC 052123
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC MON OCT 05 2009

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

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2130 UTC.

...ITCZ...

THE ITCZ AXIS WAS ANALYZED ALONG 05N77W TO 07N95W TO 11N110W 
08N125W TO 13N138W. CLUSTER OF SCATTERED MODERATE ISOLATED 
STRONG IS FROM 04N TO 07N BETWEEN 81W AND 83W. SIMILAR 
CONVECTION IS NEAR 06N90W. SCATTERED MODERATE ISOLATED STRONG 
WITHIN 70 NM N OF ITCZ BETWEEN 112W AND 115W. 

...DISCUSSION...

AN UPPER LEVEL RIDGE EXTENDS FROM CENTRAL MEXICO THROUGH 13N135W 
IS SHIFTING EAST AND WEAKENING AHEAD OF A MID TO UPPER LEVEL 
TROUGH EXTENDING FROM NORTHERN CALIFORNIA TO 30N130W TO 17N135W. 
A QUIKSCAT PASS FROM 15Z ALONG WITH VISIBLE IMAGERY SHOWED 
EVIDENCE OF A WEAK SURFACE TROUGH ASSOCIATED WITH THE MID TO 
UPPER LEVEL TROUGH...EXTENDING FROM 30N127W TO 26N132W. THE 
QUIKSCAT PASS ALSO SHOWED NE WINDS TO 20 KT MAINLY W OF THE 
TROUGH. A 1031 MB SURFACE HIGH PRES AREA IS BUILDING OVER THE NE 
PACIFIC BEHIND THE TROUGH. VISIBLE SATELLITE IMAGERY HINTED A 
WEAK 1013 MB LOW PRES AREA ALONG THE ITCZ NEAR 15N139W. THE 15Z 
QUIKSCAT PASS INDICATED PERSISTENT 20 TO 25 KT TRADE WINDS 
BETWEEN THE LOW PRES AND THE RIDGE TO THE NORTH...MAINLY FROM 
14N TO 20N W OF 135W.

FURTHER SOUTH...SW CROSS-EQUATORIAL FLOW OF 15 TO 20 KT WAS 
NOTED ON A 13Z QUIKSCAT PASS AND A 17Z ASCAT PASS BETWEEN 100W 
AND 115W. THIS WAS THE IMPETUS FOR CONVECTION ALONG THE ITCZ 
BETWEEN 110W AND 115W...AND IS INTERACTING WITH THE NE TRADES N 
OF THE ITCZ TO SPAWN A WEAK SURFACE TROUGH NEAR 110W...REACHING 
AS FAR N AS 13N PER SCATTEROMETER. GLOBAL MODELS SHOW THIS 
TROUGH WILL PERSIST OVER THE NEXT COUPLE OF DAYS AS IT SLOWLY 
DRIFTS WNW. THIS IN TURN WILL INTERACT WITH THE SURFACE HIGH 
PRES TO THE NORTH AND INCREASE NE TRADE WIND FLOW TO NEAR 20 KT 
IN A BAND FROM 13N TO 22N. 

THE 17Z ASCAT PASS BACKED UP EVIDENCE FROM THE 13Z QUIKSCAT PASS 
SHOWING WINDS TO AT LEAST 20 KT OVER THE NORTHERN GULF OF 
CALIFORNIA. THIS WAS DUE TO A ANOTHER SURFACE TROUGH PASSING 
THROUGH ARIZONA...THE NORTHERN GULF...AND FAR NW MEXICO. A RIDGE 
IS EXPECTED TO BUILD OVER THE AREA TO THE NORTH BEHIND THE 
TROUGH...LIKELY ALLOWING THE FRESH NORTHERLY FLOW TO PERSIST 
INTO TUE BEFORE DIMINISHING.

A JASON ALTIMETER PASS FROM 0830Z CORROBORATED WAVEWATCH 
GUIDANCE SHOWING SEAS TO 9 FT...LIKELY IN PRIMARILY N SWELL...IN 
AN AREA N OF 18N BETWEEN 115W AND 125W. WAVEWATCH IS ALSO 
SHOWING AN AREA OF SEAS TO 8 FT IN THE AREA OF FRESH TO STRONG 
TRADES N OF THE ITCZ TO 20N MAINLY W OF 135W. WAVEWATCH AND 
FNMOC WAVE MODELS BOTH SHOW THESE AREAS OF SWELL DECAYING BELOW 
8 FT OVER THE NEXT COUPLE OF DAYS BEFORE THE TRADES INCREASE 
AGAIN IN THE WAKE OF THE TROUGH PASSAGE.

$$
CHRISTENSEN