000
AXPZ20 KNHC 090918
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC FRI OCT 09 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.

...TROPICAL WAVE... 

A TROPICAL WAVE WAS ANALYZED ALONG 108W FROM 13N TO 18N...AND 
ESTIMATED TO BE MOVING W 10 TO 15 KT. THE WAVE IS UNDER THE 
DIVERGENT REGION OF AN UPPER TROUGH EXTENDING FROM THE NORTHERN 
PLAINS TO SOUTHERN BAJA. SW FLOW ALOFT ON THE EAST SIDE OF THE 
WAVE IS MAINTAINING STRONG CONVECTION...SHEARED TO THE E AND NE 
OF A POSSIBLE LOW LEVEL CENTER NEAR 19N106W OFF CABO CORRIENTES. 
THE WAVE ITSELF IS BECOMING DIFFICULT TO TRACK AS A DISTINCT 
FEATURE AS IT MOVES TO THE WEST OF THE MID TO UPPER LEVEL TROUGH 
AXIS...WHERE DRY SUBSIDENT NW FLOW ALOFT IS HOLDING THE DEEP 
MOISTURE ASSOCIATED WITH THE WAVE TO THE EAST OF 108W. GLOBAL 
MODELS SHOW THE LOW LEVEL CENTER STALLING THROUGH TODAY AS THE 
UPPER TROUGH LIFTS OUT...THEN SHIFTING TO THE N AND NE LATE SAT 
AND SUN AS ANOTHER MID TO UPPER TROUGH DIGS INTO THE AREA. THE 
TROPICAL WAVE PRESUMABLY WILL DECOUPLE FROM THE LOW LEVEL CENTER 
AND DRIFT WEST INTO THE DRIER AIR OVER THE NEXT COUPLE OF 
DAYS...ALTHOUGH LITTLE SENSIBLE WEATHER IMPACT IS EXPECTED.

...ITCZ...

THE ITCZ AXIS WAS CENTERED ALONG 8N82W TO 13N180W TO 11N123W TO 
11N130W TO 6N140W. SCATTERED MODERATE TO ISOLATED CONVECTION IS 
WITHIN 120 NM S OF THE AXIS BETWEEN 95W AND 105W...AND WITHIN 
120 NM N OF AXIS BETWEEN 110W AND 130W.

...DISCUSSION...

A MID TO UPPER LEVEL TROUGH EXTENDS FROM THE NORTHERN PLAINS TO 
SOUTHERN BAJA. THIS FEATURE DIGS INTO A RIDGE THAT EXTENDS FROM 
FLORIDA TO CENTRAL MEXICO...THEN WEST ACROSS THE EASTERN PACIFIC 
ALONG ROUGHLY 16N. 

E OF 110W...SOUTH OF THE RIDGE AXIS...AN UPPER LOW IS NOTED NEAR 
11N90W...DRIFTING WEST. THIS WILL ENHANCE CONVECTION ALONG THE 
CENTRAL AMERICAN PACIFIC COAST OVER THE NEXT COUPLE OF DAYS AS 
THE DIVERGENT AREA ON THE EAST OF THE UPPER LOW TRANSITS OVER 
THE REGION. AT THE SURFACE...A 00Z QUIKSCAT PASS SHOWED 20 KT 
FLOW ALREADY STARTING THROUGH THE GULF OF PAPAGAYO. THIS WILL 
INCREASE SLIGHTLY BY SUNRISE WITH ADDED DRAINAGE FLOW. 

W OF 110W...A MINOR MID TO UPPER LEVEL SHORT WAVE TROUGH SHIFT 
EASTWARD N OF THE RIDGE AXIS WILL DO LITTLE TODAY TO DIMINISH A 
SURFACE RIDGE DOMINATING THE AREA N OF 20N W OF 110W. 
SCATTEROMETER DATA SHOW AN AREA OF FRESH TO STRONG TRADE WINDS 
BETWEEN THIS SURFACE RIDGE AND A TROUGH ALONG 130W S OF 15N 
MOVING WESTWARD. A JASON ALTIMETER PASS FROM 21Z SHOWED AN AREA 
OF 8 FT SEAS ASSOCIATED WITH THESE WINDS...LENDING CREDENCE TO 
THE WAVEWATCH INITIALIZATION. WAVEWATCH SHOWS THESE SEAS 
SUBSIDING TO 6 FT OR LESS THROUGH TONIGHT. FRESH NORTHERLY FLOW 
IS NOTED ALONG THE NORTHERN BAJA COAST...ON THE EASTERN EDGE OF 
THE SURFACE RIDGE. THESE WINDS AS WELL AS TRADES WILL DIMINISH 
THROUGH AS THE SURFACE RIDGE SHIFTS SE AHEAD OF A DEEP LAYER 
TROUGH DIGGING INTO THE AREA FROM THE N CENTRAL PACIFIC...AND 
SHIFTS EASTWARD N OF 25N FROM LATE SAT THROUGH MON. 
MEANWHILE...SW CROSS-EQUATORIAL FLOW WILL INCREASE 
SLIGHTLY...INCREASING CONVECTION SLIGHTLY ALONG THE ITCZ.

WAVEWATCH MODEL IS SHOWING SW LONG PERIOD SWELL REACHING THE 
CENTRAL AMERICAN AND MEXICAN COAST BY LATE SUNDAY...WITH 
COMBINED SEAS TO 5 FT.

$$
CHRISTENSEN