000
AXPZ20 KNHC 111530
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC MON MAY 11 2009

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

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1500 UTC.

...ITCZ...
THE ITCZ EXTENDS ALONG 06N77W TO 10N97W TO 10N115W TO 03N130W TO 
05N140W. NUMEROUS MODERATE ISOLATED STRONG WITHIN 180 NM S OF 
AXIS E OF 80W. SCATTERED MODERATE FROM 04N TO 08N BETWEEN 100W 
AND 110W. SCATTERED MODERATE WITHIN 180 NM EITHER SIDE OF AXIS 
BETWEEN 110W AND 115W.

...DISCUSSION...

W OF 110W...BROAD UPPER TROUGH EXTENDS FROM 27N125W TO 11N119W. 
DIVERGENT FLOW ALOFT ON THE SOUTHEAST SIDE OF THE UPPER TROUGH 
IS FOSTERING A WELL DEFINED SURFACE TROUGH ALONG THE ITCZ FROM 
14N115W TO 06N119W...ALONG WITH SCATTERED MODERATE AND ISOLATED 
STRONG CONVECTION. OVERNIGHT SCATTEROMETER PASSES SHOW A SWATH 
OF N TO NE 20 KT WINDS MAINLY N OF 22N BETWEEN 125W AND 
135W...ON THE SE PERIPHERY OF A 1025 MB SURFACE HIGH PRES AREA 
CENTERED NORTH OF THE AREA NEAR 34N137W. LONG PERIOD SWELL UP TO 
11 FT OFF THE NORTHERN BAJA COAST IS ASSOCIATED WITH PERSISTENT 
NORTHERLY WINDS DOWN THE COAST OF SOUTHERN CALIFORNIA. ALTHOUGH 
THIS SWELL WILL DECAY THROUGH TUESDAY...THE SURFACE HIGH SLOWLY 
WILL MOVE EAST...INCREASING THE SQUEEZE PLAY ALONG THE 
CALIFORNIA COAST AND USHERING A NEW ROUND OF NORTHERLY SWELL 
ALONG THE BAJA COAST WED. 

E OF 110W...DEEP LAYER ANTICYCLONE IS NOTED NEAR 14N100W...WITH 
MID TO UPPER LEVEL TROUGH TO THE EAST ALONG 90W...FROM GUATEMALA 
TO NEAR THE EQUATOR. DIVERGENCE ASSOCIATED WITH THROUGH IS 
ENHANCING NOCTURNAL CONVECTION OFF THE COLOMBIAN COAST S OF THE 
ITCZ. ITCZ CONVECTION IS ALSO BEING FED BY 15 TO 20 KT CROSS 
EQUATORIAL SOUTHERLY FLOW...ALTHOUGH SUBSIDENT NORTHERLY FLOW 
ALOFT BETWEEN THE UPPER RIDGE AND THE MID/UPPER TROUGH IS 
LIMITING CONVECTION BETWEEN 85W AND 100W. A 12Z QUIKSCAT PASS 
SHOWS 20 KT FLOW THROUGH THE GULF OF PAPAGAYO. THIS IS A RESULT 
OF A COMBINATION OF STRONG CARIBBEAN TRADES FUNNELING THROUGH 
THE PASSES IN NORTHERN COSTA RICA...AND MORNING DRAINAGE FLOW 
OFF THE MOUNTAINS. THESE WINDS WILL DIMINISH THIS AFTERNOON AS 
DRAINAGE FLOW ABATES AND SEAS BREEZE INFLUENCES TAKE 
CONTROL...BUT SHOULD REAPPEAR OVERNIGHT THROUGH EARLY MORNING. 
THROUGH MID WEEK.

GULF OF CALIFORNIA...SOMEWHAT TIGHT GRADIENT BETWEEN THE 1025 MB 
HIGH PRES CENTERED NEAR 34N137W AND A SURFACE TROUGH EXTENDING 
FROM THE GREAT BASIN THROUGH SW ARIZONA. THIS IS ENHANCING 
GRADIENT FLOW OVER THE NORTHERN GULF OF CALIFORNIA THAT ALONG 
WITH MORNING DRAINAGE FLOW...MAY ALLOW 20 KT SW WINDS OFF THE 
NORTHERN BAJA MOUNTAINS INTO THE NORTHERN GULF OF CALIFORNIA. 
THE TROUGH WILL WEAKEN AND LIFT OUT HOWEVER...KEEPING WINDS 
BELOW 20 KT.

$$
CHRISTENSEN