000
AXPZ20 KNHC 271553
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC WED MAY 27 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 
1515 UTC.

...TROPICAL WAVES...

A TROPICAL WAVE OVER COLOMBIA AND THE CARIBBEAN ALONG 75W HAS 
BEEN MOVING W AT ABOUT 17 KT. THIS MOTION WILL MOVE THE WAVE 
INTO THE TROPICAL PACIFIC LATER TODAY. SCATTERED MODERATE 
ISOLATED STRONG CONVECTION IS ALREADY FLARING ALONG THE 
COLOMBIAN COAST WITHIN 60 NM OF 05N77W.

...ITCZ...

THE ITCZ AXIS EXTENDS ALONG 08N77W TO 06N85W TO 09N105W TO 
02N131W TO 02N140W. AS MENTIONED ABOVE SCATTERED MODERATE 
ISOLATED STRONG CONVECTION IS NOTED WITHIN 60 NM OF 05N77W AND 
ELSEWHERE WITHIN 150 NM OF LINE 03N86W TO 09N103W TO 03N124W. 

.DISCUSSION...

ALOFT...THE SUBTROPICAL PORTION OF THE UPPER LEVELS IS DOMINATED 
BY A SERIES OF SHORTWAVE TROUGHS. AN UPPER CYCLONE IS NEAR 
32N132W AND RACING NE DRAGGING A TROUGH SW FROM 29N131W TO 
19N137W...ACCOMPANIED BY DRY UPPER AIR W OF THE TROUGH. A SECOND 
UPPER TROUGH LIES ALONG 32N114W TO TO 26N121W. A THIRD UPPER 
TROUGH IS STILL EVIDENT ALONG 30N105W TO 26N111W TO 22N122W AND 
HAS NEARLY CAUGHT UP WITH THE INITIAL SHORT WAVE WHICH IS ALONG 
26N105W TO 20N119W TO 17N130W. ALTHOUGH A SMALL SHORTWAVE RIDGE 
IS NOTED ALONG 130W FROM 28N TO 18N...THE SUBTROPICAL UPPER FLOW 
IS MOSTLY ZONAL TO THE W OF 105W.   

AN UPPER ANTICYCLONE IS AT 05N146W WITH A SHORTWAVE RIDGE 
EXTENDING NE CRESTING OVER THE DISCUSSION AREA ALONG 16N138W TO 
TO 11N124W. UPPER MOISTURE...FROM CENTRAL PACIFIC CONVECTION... 
IS TRAPPED UNDER THE RIDGE...ROUGHLY WITHIN 150 NM OF LINE 
09N140W TO 15N120W WITH SOME OF THE MOISTURE CONTINUING NE 
ACROSS CENTRAL OLD MEXICO. 

A TROPICAL MID TO UPPER LEVEL ANTICYCLONE IS ESTIMATED NEAR 
10N90W WITH A RIDGE W CRESTING ALONG POINTS 12N114W TO 23N110W. 
UPPER DIFFLUENCE HAS ENHANCED CONVECTION ALONG THE ITCZ UNDER 
THIS RIDGE WITH SOME OF THE MOISTURE SPREADING NE TO ALONG 22N 
BETWEEN 100W AND 80W WHERE MOST IT EVAPORATES. THE SOUTH 
AMERICAN UPPER RIDGE IS CRESTING WESTERN COLOMBIA TODAY. 
CONVECTION IS ENHANCED ALONG THE TROPICAL WAVE OVER W COLOMBIA 
WITH THE DEBRIS MOISTURE SPREADING NE OVER THE SW CARIBBEAN.
 
AT THE LOW LEVELS...A RIDGE EXTENDS SE ALONG 32N135W TO 12N108W. 
NE TRADES TO THE S OF THE RIDGE...FROM 10N TO 17N W OF 
135W...ARE IN THE 15 TO 20 KT RANGE WITH SEAS TO 8 FT...BUT 
EXPECTED TO DIMINISH BELOW 20 KT LATER TODAY. THE GRADIENT HAS 
TIGHTENED NE OF THE RIDGE ALONG THE BAJA PENINSULA BETWEEN 23N 
AND 27N SUPPORTING NW WINDS TO 20 KT. THIS GRADIENT SHOULD 
WEAKEN TONIGHT. 

GAP WINDS...A NE SURGE TO 20 KT WAS OBSERVED IN THE GULF OF 
PAPAGAYO THIS MORNING BUT IS NOT EXPECTED TO PERSIST FOR MORE 
THAN A FEW HOURS. 

$$
NELSON