000
AXPZ20 KNHC 131557
TWDEP 

TROPICAL WEATHER DISCUSSION    
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC FRI MAR 13 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 EXTENDS ALONG 08N81W TO 01N105W TO 04N131W TO 03N140W. 
ISOLATED MODERATE CONVECTION IS NOTED WITHIN 60 NM OF AXIS 
BETWEEN 84W AND 93W. 

...DISCUSSION...

AN UPPER ANTICYCLONE IS CENTERED NEAR 09N135W WITH A SHORTWAVE 
RIDGE EXTENDING N TO A CREST BECOMING FLAT FROM 30N119W TO 
30N108W. THIS UPPER RIDGE IS BEGINNING TO COLLAPSE SE AS AN 
UPPER SHORTWAVE TROUGH DIGS SE INTO THE DISCUSSION AREA. THE 
TROUGH ORIGINATES FROM AN UPPER CYCLONE OVER THE NEW MEXICO AND 
ARIZONA BORDER AT 34N. A BAND OF UPPER DRY AIR IS WRAPPING 
CYCLONICALLY AROUND THE S SEMICIRCLE OF THIS CYCLONE WITHIN 120 
NM EITHER SIDE OF LINE 32N106W TO 31N115W TO BEYOND 34N123W. A 
SECOND UPPER CYCLONE LOCATED N OF HAWAII AT 28N155W CONTINUES TO 
MOVE W AND MOST OF THE ASSOCIATED UPPER FLOW IS W OF 140W ATTM. 
HOWEVER...UPPER DRY AIR IS INDICATED WITHIN 120 NM EITHER SIDE 
OF LINE 30N127W TO 26N139W. 

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 CURRENTLY OBSERVED WITHIN 30 NM 
OF 21N123W AND ALSO WITHIN 30 NM EITHER SIDE OF LINE FROM 
18N125W TO 16N127W TO 17N132W. THIS CONVECTION IS ASSOCIATED 
WITH A LOW LEVEL TROUGH EXTENDING FROM 15N139W TO 23N128W. THE 
RESULT IS A TROPICAL MOISTURE PLUME ROUGHLY WITHIN 
240 NM EITHER SIDE OF LINE FROM 16N140W TO 24N120W TO BEYOND 
32N125W EVENTUALLY FANNING OVER THE SE CONUS.

AN UPPER TROUGH EXTENDS W SW ACROSS THE N CARIBBEAN INTO AN 
UPPER CYCLONE AT 16N87W CONTINUING SW TO ANOTHER UPPER CYCLONE 
AT 05N105W. UPPER ANTICYCLONES ARE OBSERVED EITHER SIDE OF THIS 
TROUGH AT 02N116W AND 05N75W. ISOLATED 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 FEATURES COMBINE TO DRY OUT THE UPPER 
LEVELS SE OF LINE 24N93W 14N120W.

ELSEWHERE AT LOW LEVELS...A RIDGE EXTENDS ALONG 32N131W TO 
13N105W. N OF 22N TO THE E OF RIDGE THE NORTHERLY FLOW IS AT 15 
TO 20 KT AS FAR S AS THE SOUTHERN TIP OF BAJA. THE GRADIENT IS 
EXPECTED TO RELAX SOME BY SUN WITH THESE CONDITIONS RETRACTING 
NORTHWARD TO THE WATERS N OF 28N AND E OF THE NEARLY STATIONARY 
RIDGE. THE GRADIENT ASSOCIATED WITH THE LARGE CYCLONE N OF 
HAWAII EXTENDS OVER THE FORECAST WATERS N OF 23N W OF 133W WHERE 
E TO SE WINDS TO 30 KT ARE REPORTED...HOWEVER SEAS ARE ONLY 8 TO 
12 FT AS THE NW SWELL COMPONENT HAS DIMINISHED WITH THE 
INCREASING E WIND WAVE. ELSEWHERE SW OF THE RIDGE...THE EASTERLY 
TRADES ARE AT 20 TO 25 KT WITH THE ASSOCIATED E SWELLS MERGING 
WITH THE NW SWELLS THAT ARE PROPAGATING SE THROUGH THE WATERS 
GENERALLY W OF 105W. ADDITIONALLY...S PACIFIC LONG PERIOD 
SOUTHERLY SWELLS ARE MOVING N ACROSS THE EQUATOR BECOMING THE 
DOMINATE SWELL GROUP ARRIVING AT THE CENTRAL AMERICAN COAST TO 
THE E OF THE BAJA PENINSULA.

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 ALSO EXPECTED 
TO DIMINISH BELOW 20 KT BY SAT. REINTRODUCED A N 20 KT PULSE 
OVER THE GULF OF TEHUANTEPEC FOR INITIAL 06 HOURS THIS MORNINGS 
TEXT PACKAGE.   

$$
NELSON