000
AXPZ20 KNHC 230930
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC THU APR 23 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.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 06N78W TO 05N91W TO 04N100W TO 
05N110W TO 05N120W 04N130W TO 05N140W. SCATTERED MODERATE 
ISOLATED STRONG WITHIN 120 NM N OF AXIS BETWEEN 85W AND 90W. 
SCATTERED MODERATE WITHIN 90 NM N OF AXIS BETWEEN 130W AND 134W.

...DISCUSSION...

W OF 100W...
CURRENTLY A MID/UPPER RIDGE EXTENDS FROM NORTHERN 
CALIFORNIA TO ROUGHLY 10N130W...BLOCKING A CUT OFF DEEP LAYER 
LOW NE OF HAWAII NEAR 34N147W. AT THE SURFACE...THIS TRANSLATES 
TO A 1023 MB HIGH PRES CENTER BENEATH THE MID/UPPER RIDGE NEAR 
26N134W...MOVING SLOWLY EAST AHEAD OF A WEAK COLD FRONT 
ASSOCIATED WITH THE CUT OFF LOW. THE SURFACE HIGH PRES IS 
SUPPORTING A SMALL AREA OF 20 KT TRADE WINDS AS NOTED ON 
SCATTEROMETER IMAGERY FROM EARLIER MAINLY S OF 15N W OF 125W. 

THE ENTIRE PATTERN WILL START TO CHANGE LATER TODAY AS THE 
MID/UPPER RIDGE FLATTENS OUT AHEAD OF A LONG WAVE TROUGH DIGGING 
INTO THE PACIFIC NW STATES...PUSHING A COLD FRONT DOWN THE U.S. 
WEST COAST. THE CUT OFF LOW NE OF HAWAII IS ALREADY STARTING TO 
LIFT OUT TO THE NE AND WILL BECOME ABSORBED INTO THE UPPER 
TROUGH. THE SURFACE HIGH WILL WEAKEN AHEAD OF A COLD FRONT 
MOVING SOUTH ALONG THE CALIFORNIA COAST WITH THE UPPER TROUGH. 
THE MAIN FOCUS OF THE FRONT WILL PUSH INLAND HOWEVER OVER 
SOUTHERN CALIFORNIA...FOLLOWED BY STRONG HIGH PRES BUILDING OFF 
THE WEST COAST AND THE NORTH COAST OF BAJA BY SATURDAY. THIS 
WILL ALLOW AN INCREASE IN THE AREA OF TRADE WINDS AS WELL AS 
NORTHERLY WINDS TO 20 KT ALONG THE NORTHERN BAJA COAST. 

E OF 100W...
20 TO 25 KT FLOW PERSISTS THROUGH THE GULF OF PAPAGAYO THIS 
MORNING AS NOTED BY RECENT SHIP AND LAND BASED OBSERVATIONS AS 
SCATTEROMETER DATA. THESE WINDS WILL PERSIST THROUGH AT LEAST 
THE NEXT COUPLE OF DAYS AS CARIBBEAN TRADE WINDS REMAIN STRONG. 
A 00Z QUIKSCAT PASS SHOWED ON 10 TO 15 KT NORTHERLY WINDS 
THROUGH THE GULF OF TEHUANTEPEC. WINDS TO 20 KT MAY BE POSSIBLE 
GIVEN MORNING DRAINAGE FLOW EFFECTS. THIS SHOULD DIMINISH LATER 
IN THE DAY HOWEVER AS GRADIENT FLOW CONTINUES TO WEAKEN. 
SCATTEROMETER IS ALSO DEPICTING CYCLONIC TURNING INDICATING A 
SURFACE TROUGH ALONG THE ITCZ NEAR 92W...LIKELY AIDED BY THE 
PRESENCE OF NE TO E GAP WIND FLOW FROM TEHUANTEPEC AND PAPAGAYO 
ON THE N SIDE OF THE TROUGH. IN ADDITION...THIS IS IN AN AREA 
WHERE THERE HAD BEEN FAIRLY STRONG CONVECTION 
YESTERDAY...ALTHOUGH CURRENT CONVECTION IS SOMEWHAT LESS THIS 
MORNING.

$$
CHRISTENSEN