000
AXPZ20 KNHC 171000
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC SUN MAY 17 2009

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

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0915 UTC.

...ITCZ...

THE ITCZ AXIS WAS ALONG 09N83W TO 10N88W TO 09N97W TO 14N109W TO 
08N121W TO 08N135W TO 07N140W. ISOLATED MODERATE CONVECTION WAS 
WITHIN 120 NM OF AXIS E OF 100W. SCATTERED MODERATE WITH 
ISOLATED STRONG CONVECTION WAS WITHIN 90 NM OF AXIS BETWEEN 110W 
AND 121W...AND WITHIN 90 NM N OF AXIS BETWEEN 123W AND 135W. 

...DISCUSSION...

ALOFT...AN UPPER LEVEL ANTICYCLONE IS ESTIMATED NEAR 06N139W 
WITH A FLAT RIDGE N TO 18N AND THEN BECOMING HIGH AMPLITUDE NE 
TO 35N130W...AND CRESTING OVER CANADA NEAR 60N120W. IMMEDIATELY 
TO THE SE OF THIS LARGE RIDGE IS AN UPPER TROUGH THAT DISSECTS N 
AMERICA FROM NE TO SW INTO THE DISCUSSION AREA FROM 32N114W 
THROUGH A BROAD MID TO UPPER LEVEL CYCLONE AT 23N127W WITH 
TROUGH CONTINUING SW TO BASE NEAR 12N127W. DRY SINKING AIR IS 
INDICATED OVER MOST OF THE W AND SW PORTIONS OF THIS 
CIRCULATION...ROUGHLY N OF 12N AND TO THE W OF 120W. 

A QUASI STATIONARY UPPER ANTICYCLONE IS CENTERED NEAR 13N104W 
WITH A RIDGE EXTENDING NE ACROSS OLD MEXICO AND CONTINUING 
ACROSS THE NW GULF OF MEXICO. UPPER DIFFLUENCE...S OF THIS BROAD 
RIDGE HAS BEEN ENHANCING CONVECTION ALONG AND N OF THE ITCZ 
BETWEEN 95W AND 120W...WITH SOME OF THE DEBRIS MOISTURE 
SPREADING NE ACROSS OLD MEXICO TO THE S OF 25N AND SPILLING E 
ACROSS THE RIDGE AXIS OVER THE SW GULF OF MEXICO AND OVER 
CENTRAL AMERICA.

A STATIONARY UPPER RIDGE EXTENDS W ACROSS NORTHERN VENEZUELA AND 
COLOMBIA TO A CREST OVER THE COLOMBIA AND PANAMA BORDER. AN 
UPPER LEVEL CUT OFF CYCLONE OVER THE NW CARIBBEAN S OF WRN CUBA 
HAS AN UPPER TROUGH EXTENDING S ALONG 79W CROSSING THE EQUATOR 
AT 81W INTO AN UPPER CYCLONE NEAR 03S80W. THIS MID TO UPPER 
TROUGH SEPARATES THE FLOW ASSOCIATED WITH THE S AMERICAN RIDGE 
FROM THE TROPICAL E PACIFIC RIDGE DESCRIBED ABOVE. ITCZ 
CONVECTION IS ENHANCED ALONG THE E PERIPHERY OF PACIFIC RIDGE E 
OF 88W...WITH THE DEBRIS MOISTURE ADVECTED NE ACROSS THE SE 
CARIBBEAN.
     
AT THE LOW LEVELS...A RIDGE EXTENDS SE FROM A 1024 MB HIGH NEAR 
32N135W TO 21N114W. THE GRADIENT NE OF THE RIDGE HAS BEGIN THE 
RELAXING TREND FORECAST BY THE MODELS...AND WILL CONTINUE TO  
EFFECTIVELY SHRINKING THE AREA OF NORTHERLY WINDS OF 20 KT AND  
8 FT SEAS N OF 25N DURING THE NEXT 48 HOURS. AS THE RIDGE 
WEAKENS AND RETRACTS W...A BROAD LOW LEVEL TROUGH WILL DRIFT W 
OVER THE AREA N OF 25N AND E OF 127W THROUGH MON. EXPECT 
NORTHERLY WINDS TO 20 KT TO SET UP ALONG THE W SIDE OF THE 
TROUGH AS ITS SHIFTS W ACROSS THE NORTHERN WATERS. A RELATIVELY 
SMALL AREA OF NE TRADES CURRENTLY AROUND 20 KT...WITH SEAS TO 8 
FT...ARE OBSERVED S OF THE RIDGE BUT ARE EXPECTED TO DIMINISH 
BELOW 20 KT BY 24 HOURS AS THE RIDGE WEAKENS.       

GAP WINDS...A BROAD INVERTED TROUGH IS EXPECTED TO DOMINATE THE 
EASTERN GULF OF MEXICO EARLY NEXT WEEK...WHILE A COLD FRONT 
SWEEPS SE ACROSS THE WESTERN GULF OF MEXICO...SETTING UP THE 
CONDITIONS FOR N WINDS AT 20 KT AND GREATER TO BRIDGE THE 
ISTHMUS OF TEHUANTEPEC AND FLOW INTO THE GULF OF TEHUANTEPEC 
LATE TONIGHT...THEN INCREASE TO 25 TO 30 KT LATE MON.

$$
STRIPLING