000
AXPZ20 KNHC 110951
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC SUN OCT 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 
0915 UTC.

...SPECIAL FEATURE... 

CONVECTION IS BECOMING BETTER ORGANIZED AROUND LOW PRES CENTERED 
NEAR 15N109W...OR ABOUT 300 NM SW OF MANZANILLO MEXICO. PRESSURE 
IS ESTIMATED TO 1006 MB...AND THE LOW PRES MAY DEVELOP FURTHER 
INTO A TROPICAL DEPRESSION LATER THIS MORNING IF CURRENT TRENDS 
PERSIST. STRONG CONVECTION IS NOTED ON RECENT SATELLITE 
IMAGES...GENERALLY DISPLACED WITHIN 120 NM TO THE WEST OF THE 
LOW LEVEL CENTER. A BAND OF CONVECTION IS STARTING TO FORM TO 
THE NE OF THE CENTER AS WELL. THIS CONVECTION REMAINS FAIRLY 
WEEK AT THIS TIME....BUT IS LIKELY TIED TO DRAINAGE FLOW OFF THE 
COAST AND MAY INCREASE THROUGH SUNRISE. A 01Z QUIKSCAT PASS 
SHOWED A BAND OF AT LEAST 20 KT WESTERLY WINDS TO THE SOUTH OF 
THE LOW OUTSIDE OF THE CONVECTION. THE QUIKSCAT PASS ALSO SHOWED 
15 TO 20 KT SE WINDS ALONG THE MEXICAN COAST FROM PETATLAN TO 
CABO CORRIENTES. THE LOW IS EXPECTED TO MAKE A SLOW NORTHWARD 
TRACK OVER THE NEXT 24 TO 48 HOURS IN RESPONSE TO A PAIR OF MID 
TO UPPER LEVEL TROUGHS MOVING EASTWARD THROUGH THE SW U.S. TO 
THE NORTH OF THE LOW.

...TROPICAL WAVE...

A TROPICAL WAVE WAS ALONG 92W N OF 10N MOVING W AT 10 TO 15 KT. 
THE WAVE IS MOVING W IN TANDEM WITH AN UPPER LEVEL LOW LOCATED 
TO ITS W NEAR 12N97W. UPPER DIVERGENCE ON THE EAST SIDE OF THE 
UPPER LOW...ALONG WITH FRESH TO MODERATE SW FLOW S OF THE ITCZ 
ARE TOGETHER MAINTAINING CLUSTERS OF MOSTLY MODERATE CONVECTION 
WITHIN 90 NM EITHER SIDE OF THE TROPICAL WAVE. ISOLATED STRONG 
CONVECTION IS NOTED WITHIN 90 NM OF THE COAST AS WELL WHERE 
MORNING DRAINAGE FLOW IS ACTIVE.

...ITCZ...

THE ITCZ AXIS WAS CENTERED ALONG 10N85W TO 12N93W TO 10N98W TO 
12N106W TO 10N115W TO 14N133W TO 11N140W. SCATTERED MODERATE TO 
ISOLATED STRONG CONVECTION WAS WITHIN 120 NM S OF THE AXIS 
BETWEEN 100W TO 105W. SCATTERED MODERATE WITHIN 90 NM S OF AXIS 
BETWEEN 115W AND 120W. SCATTERED MODERATE TO ISOLATED STRONG 
WITHIN 90 NM N OF AXIS BETWEEN 130W AND 135W. 

...DISCUSSION...

A MID TO UPPER LEVEL TROUGH EXTENDS FROM SOUTHERN CALIFORNIA TO 
ROUGHLY 25N120W...MOVING EAST. THIS TROUGH DIVIDES A MID TO 
UPPER LEVEL RIDGE EXTENDING ALONG 17N. CONVECTION NEAR THE 
SURFACE LOW 1006 MB NEAR 15N109W IS INCREASING AS A RESULT OF 
BETTER UPPER SUPPORT SUPPLIED BY THE APPROACHING UPPER TROUGH. 
THIS TROUGH WILL LIFT OUT TOWARD THE SW U.S. THROUGH 
TODAY...FOLLOWED IN QUICK SUCCESSION BY A SECOND MORE 
SUBSTANTIAL DEEP LAYER TROUGH CURRENTLY SHIFTING EAST ACROSS 
138W N OF 20N. 

NOT ONLY WILL THESE TROUGHS ALLOW THE LOW NEAR 15N109W 
TO MOVE NORTHWARD THROUGH TONIGHT...BUT THEY WILL ALSO WEAKEN 
THE SURFACE HIGH PRES N OF 20N W OF NORTHERN BAJA. ASCAT PASSES 
FROM 04Z A SMALL AREA OF PERSISTENT 20 KT NORTHERLY FLOW OFF 
NORTHERN BAJA COAST ON THE EASTERN EDGE OF THE WEAKENING SURFACE 
RIDGE. A 0230Z QUIKSCAT PASS AND A 06Z ASCAT PASS INDICATE THAT 
FRESH TRADES SOUTH OF THE RIDGE ALONG THE ITCZ W OF 130W HAVE 
DIMINISHED TO BELOW 20 KT.
 
FURTHER TO THE NW...A SURFACE COLD FRONT ASSOCIATED WITH THE 
SECOND UPPER TROUGH IS MOVING EAST OF 140W...AND WILL SHIFT 
EASTWARD REACHING A POSITION FROM 32N135W TO 24N140W IN 24 
HOURS...AND 32N125W TO 22N140W BY 48 HOUR...BEFORE DIMINISHING 
BY EARLY TUE. THIS FRONT WILL FOLLOWED BY REINFORCING FRONT 
REACHING FROM 32N130W TO 28N140W BY LATE TUE. WINDS AHEAD OF AND 
BEHIND THE FRONT WILL REACH 20 KT THROUGH MONDAY. THE SECOND 
FRONT WILL BE A LITTLE STRONGER...WITH WINDS TO 25 KT POSSIBLE. 
LONG PERIOD NW SWELL WILL ACCOMPANY THE FIRST FRONT WITH HEIGHTS 
TO 9 FT.

$$
CHRISTENSEN