000
AXPZ20 KNHC 121553
TWDEP 

TROPICAL WEATHER DISCUSSION    
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC THU MAR 12 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 
1545 UTC.

...ITCZ...

ITCZ AXIS 08N82W TO 01N105W TO 03N130W TO 02N140W. SCATTERED 
MODERATE NOTED WITHIN 30 NM OF THE AXIS BETWEEN 84W AND 98W. 

...DISCUSSION...

AN UPPER ANTICYCLONE OVER THE EQUATOR AT 141W HAS A SHORTWAVE 
RIDGE EXTENDING N NE TO A CREST AMPLIFYING N ALONG 32N130W. THIS 
UPPER RIDGE IS SEPARATING TWO UPPER CYCLONES...ONE W OF THE AREA 
AND N OF HAWAII AT 32N153W...AND THE OTHER CYCLONE IS OVER SW 
CALIFORNIA AT 35N120W. UPPER DRY AIR IS ROTATING CYCLONICALLY N 
OVER THE DISCUSSION AREA TO THE N OF 28N W OF 135W. A BAND OF 
UPPER DRY AIR IS WRAPPING CYCLONICALLY AROUND THE SW SEMICIRCLE 
OF THE CALIFORNIA CYCLONE OVER THE AREA N OF 29N BETWEEN 123W 
AND 106W. UPPER DEBRIS MOISTURE ORIGINATING OVER THE CENTRAL 
TROPICAL PACIFIC STREAMS NE OVER THE DISCUSSION AREA...AND IS 
REINFORCED BY ADDITIONAL DEBRIS MOISTURE FROM SCATTERED MODERATE 
AND ISOLATED STRONG CONVECTION NOTED WITHIN 120 NM EITHER SIDE 
OF LINE FROM 14N138W TO 22N135W. THE COMBINED MOISTURE PLUME 
CONTINUES NE UNDER THE UPPER RIDGE COVERING MOST OF THE ARE N OF 
OF 13N BETWEEN 122W AND 138W.

A SHORTWAVE TROUGH EXTENDS SW ACROSS CENTRAL OLD MEXICO OVER THE 
E PACIFIC FROM 28N110W TO 12N122W. THIS TROUGH SEPARATES THE 
UPPER ANTICYCLONIC FLOW OVER THE W PORTION MENTIONED ABOVE FROM 
ANTICYCLONIC FLOW OVER THE SE PORTION MENTIONED NEXT. UPPER 
ANTICYCLONES ARE OBSERVED AT 03N107W AND OVER THE EQUATOR AT 
90W. AN ASSOCIATED UPPER RIDGE DOMINATES THE TROPICS CRESTING 
ALONG POINTS FROM 08N113W TO 16N100W TO 15N90W. CONVECTION ALONG 
THE ITCZ IS ENHANCED UNDER THE UPPER RIDGE...DESCRIBED ABOVE... 
BUT THE RESULTANT DEBRIS MOISTURE EVAPORATES IMMEDIATELY OVER 
THE CLUSTERS AS THE UPPER LEVELS ARE VERY DRY S OF 20N E OF 98W. 

ELSEWHERE AT LOW LEVELS...A RIDGE EXTENDS ALONG 32N130W TO 
12N102W. N OF 25N TO THE E OF RIDGE THE NORTHERLY FLOW IS AT 15 
TO 20 KT EXTENDING TO THE W COAST OF THE BAJA PENINSULA AND 
THESE CONDITIONS ARE EXPECTED TO SPREAD FURTHER S TO THE 
SOUTHERN TIP OF BAJA ON SAT. E TRADES SW OF THE RIDGE ARE AT 20 
TO 25 KT WITH THE ASSOCIATED E SWELLS MERGING WITH NW SWELLS 
THAT ARE PROPAGATING SE THROUGH THE WATERS GENERALLY W OF 110W. 
ADDITIONALLY...LONG PERIOD SW SWELLS ARE MOVING N OVER THE 
SOUTHERN WATERS AND BECOMING THE DOMINATE SWELL ARRIVING AT THE 
CENTRAL AMERICAN COAST.

GAP WINDS...NE WINDS CONTINUE TO BRIDGE ACROSS AND DOWNSTREAM OF 
THE GULF OF PAPAGAYO AT 15 TO 20 KT BUT ARE FORECAST TO DIMINISH 
SOME THIS WEEKEND. PULSES OF NORTHERLY WINDS TO 20 KT ARE NOTED 
OVER AND DOWNSTREAM OF THE THE GULF OF PANAMA AND EXPECTED TO 
DIMINISH BELOW 20 KT SAT. EXPECTING A 20 KT PULSE OVER THE GULF 
OF TEHUANTEPEC AT AND JUST AFTER SUNRISE FRI MORNING.  

$$
NELSON