000
AXPZ20 KNHC 052152
TWDEP 

TROPICAL WEATHER DISCUSSION    
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC THU MAR 05 2009

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

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2145 UTC.

...ITCZ...

AXIS ALONG 04N77W TO 02N104W TO 03N140W. SCATTERED MODERATE 
CONVECTION IS NOTED WITHIN 60 NM EITHER SIDE OF LINE FROM 06N86W 
TO 04N92W.

...DISCUSSION...

A POSITIVE TILT LONGWAVE TROUGH DOMINATES WESTERN N AMERICA 
EXTENDING SE OFF THE CENTRAL COAST OF CALIFORNIA OVER THE E 
PACIFIC INTO THE DISCUSSION AREA FROM 30N127W TO 28N140W. A 
NARROW BAND OF DRY UPPER AIR IS OBSERVED FROM A SMALL EMBEDDED 
UPPER CYCLONE NEAR 36N122W TO 31N140W TO BEYOND 32N150W...AND IS 
MOVING S WITH TIME. JUST S OF THIS DRY AIR A BAND OF UPPER 
MOISTURE THAT SWEEPS CYCLONICALLY E THROUGH THE LONGWAVE TROUGH 
EVENTUALLY REACHING THE UPPER LEVELS OVER SOUTHERN CENTRAL 
CALIFORNIA AND ARIZONA. 

AN UPPER ANTICYCLONE IS CENTERED NEAR 19N92W WITH A RIDGE 
EXTENDING N TO WELL BEYOND 32N94W BECOMING UNSTABLE OVER THE 
UPPER MISSISSIPPI VALLEY AND COLLAPSING SE OVER THE TENNESSEE 
VALLEY. UPPER DEBRIS MOISTURE...ORIGINATING FROM CONVECTION IN 
THE TROPICAL CENTRAL PACIFIC...CONCENTRATES INTO A PLUME 
SPREADING NE AROUND THE W PERIPHERY OF THIS UPPER RIDGE... 
ROUGHLY WITHIN 210 NM EITHER SIDE OF POINTS 15N140W TO 15N130W 
TO 26N117W TO BEYOND 32N109W THEN SPILLING EASTWARD ACROSS THE 
RIDGE OVER THE LOWER MISSISSIPPI VALLEY...WITH SOME OF THE 
MOISTURE REACHING N FLORIDA BEFORE EVAPORATING.

FURTHER S...AN UPPER RIDGE EXTENDS N ACROSS THE EQUATOR CRESTING 
ALONG 14N140W TO 00N130W. THE ASSOCIATED ANTICYCLONIC FLOW IS 
ADVECTING UPPER MOISTURE OVER THE DISCUSSION AREA S OF 13N W OF 
130W.   

A LONGWAVE TROUGH OVER THE WESTERN N ATLC HAS AN UPPER TROUGH 
EXTENDING SW ACROSS CENTRAL AMERICA ALONG 13N85W TO 08N100W.
CONVECTION ALONG THE PACIFIC ITCZ IS ENHANCED BETWEEN 83W AND 
94W...WITH THE DEBRIS MOISTURE ADVECTED NE OVER COSTA RICA AND 
THE SW CARIBBEAN AS TRANSVERSE CIRRUS BANDING. OTHERWISE THE 
UPPER LEVELS APPEAR VERY DRY E OF 110W.

AT THE LOW LEVELS...A RIDGE IS BUILDING E ACROSS THE AREA ALONG 
29N140W TO 17N110W. NW SWELLS ARE PROPAGATING SE ACROSS THE 
WATERS W OF 110W MERGING WITH NE SWELLS S OF THE RIDGE. 

GAP WINDS...N WINDS IN AND DOWNSTREAM OF THE GULF OF TEHUANTEPEC 
HAVE DIMINISHED TO 20 TO 25 KT AND EXPECTED TO FURTHER DIMINISH 
BELOW 20 KT LATE FRI. NE WINDS IN THE GULF OF FONSECA AND THE 
GULF OF PAPAGAYO CONTINUE AT 20 TO 30 KT...AND EXPECTED TO 
DIMINISH TO 20 TO 25 KT LATE TONIGHT. THESE GAP WINDS ARE 
GENERATING A SWATH OF NE SWELL THAT PROPAGATES W TO AROUND 110W 
MIXING WITH THE TRAIN OF NW SWELLS MENTIONED ABOVE. CARIBBEAN 
TRADES ARE SURGING THROUGH THE ISTHMUS OF PANAMA MAINTAINING A 
20 KT NORTHERLY FLOW THROUGH THE GULF OF PANAMA...EXPECTED TO 
DIMINISH SOME ON SAT.   

$$
NELSON