000
AXPZ20 KNHC 161000
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC SAT MAY 16 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 
0900 UTC.

...ITCZ...

AXIS WAS ALONG 09N84W TO 10N96W TO 13N107W TO 09N121W TO 09N129W 
TO 05N140W. SCATTERED MODERATE AND ISOLATED STRONG CONVECTION 
WAS NOTED WITHIN 210 NM EITHER SIDE OF AXIS. CONVECTION IS 
EXPECTED TO REMAIN ACTIVE NEAR AXIS NEXT 24 HOURS.

...DISCUSSION...

ALOFT...AN UPPER LEVEL ANTICYCLONE IS ESTIMATED JUST W OF THE 
REGION AT 08N146W WITH A RIDGE EXTENDING N AND NE ALONG 35N137W 
AND BEYOND INTO CANADA NEAR 60N127W. SOME UPPER MOISTURE THAT 
ORIGINATED IN THE W PACIFIC IS SPILLING ACROSS THE RIDGE OVER 
THE UPPER LEVELS OF THE DISCUSSION AREA TO THE N OF 25N BETWEEN 
125W AND 137W. AN UPPER TROUGH DISSECTING THE CENTRAL 
UNITED STATES EXTENDS SW ACROSS THE N PORTION OF THE DISCUSSION 
AREA FROM 32N110W THROUGH AN UPPER CYCLONE AT 27N117W WITH 
TROUGH CONTINUING SW TO BASE NEAR 15N130W. VERY DRY UPPER AIR 
AND SINKING MOTION IS GENERALLY DOMINATING ELSEWHERE NW OF A 
LINE FROM 07N140W TO CENTRAL OLD MEXICO AT 26N103W. 

AN UPPER ANTICYCLONE IS CENTERED AT 14N103W WITH A SHORTWAVE 
RIDGE EXTENDING N ACROSS OLD MEXICO ALONG 23N100W TO A CREST AT 
28N98W. UPPER DIFFLUENCE UNDER AND E OF THIS BROAD RIDGE IS 
ENHANCING CONVECTION INVOF THE ITCZ BETWEEN 90W AND 125W...AND 
ALSO LINGERING DIURNAL CONVECTION ACROSS CENTRAL AMERICA S OF 
20N. THIS DIURNAL CONVECTION HAS SHIFTED S OVER WATER DURING THE 
PAST FEW HOURS. 

A STATIONARY UPPER RIDGE EXTENDS W ACROSS NORTHERN VENEZUELA AND 
COLOMBIA TO A CREST OVER EASTERN PANAMA. AN UPPER CYCLONE OVER 
THE FLORIDA STRAITS HAS CUT OFF FROM ITS PARENT UPPER TROUGH 
OVER THE CENTRAL N ATLANTIC. A TROUGH EXTENDS SW FROM THIS 
CYCLONE ACROSS THE W CARIBBEAN ACROSS COSTA RICA INTO AN UPPER 
CYCLONE NEAR 02S82W...AND SEPARATES THE FLOW ASSOCIATED WITH 
THE S AMERICAN RIDGE FROM THE TROPICAL E PACIFIC RIDGE DESCRIBED 
ABOVE.  
     
AT THE LOW LEVELS...A RIDGE EXTENDS SE FROM A 1026 MB HIGH NEAR 
34N134W TO 16N106W. THE GRADIENT NE OF THE RIDGE IS SUPPORTING 
NORTHERLY WINDS AT 20 KT OVER THE PACIFIC WATERS N OF 24N 
BETWEEN 130W AND 118W WITH THE MAXIMUM SEAS HEIGHTS CURRENTLY AT 
11 FT NEAR 30N125W IN THE N SWELL. THIS GRADIENT SHOULD RELAX 
SOME LATER TODAY AS THE RIDGE WEAKENS AND RETRACTS W AND ALLOWS 
A BROAD LOW LEVEL TROUGH TO DRIFT W OVER THE AREA N OF 25N AND E 
OF 125W THROUGH SUN. A SMALL AREA OF NE TRADES CURRENTLY TO 
AROUND 20 KT ARE OBSERVED S AND SE OF THE RIDGE AND ARE EXPECTED 
TO GRADUALLY DIMINISH BELOW 20 KT THROUGH SUN AS THE RIDGE 
WEAKENS.       

OVERNIGHT SATELLITE IMAGERY AND QUIKSCAT PASSES CONTINUE TO 
SEVERAL WEAK CYCLONIC CIRCULATION EMBEDDED ALONG THE ITCZ...AND 
BEING SUSTAINED BY 20 KT SW TO W WIND FLOW ON THE S SIDE OF THE 
AXIS. THIS ACTIVE WEATHER IS EXECUTED TO PERSIST THROUGH THE 
WEEKEND...WITH POTENTIAL FOR ONE OF THESE WEAK CIRCULATIONS TO 
GRADUALLY GAIN SOME SOME ORGANIZATION.  

GAP WINDS...A BROAD TROUGH IS EXPECTED TO DOMINATE THE EASTERN 
GULF OF MEXICO EARLY NEXT WEEK SETTING UP THE CONDITIONS FOR N
WINDS AT 20 KT TO BRIDGE THE ISTHMUS OF TEHUANTEPEC INTO THE 
GULF OF TEHUANTEPEC SUN NIGHT INCREASING TO 25 TO 30 KT LATE MON.

$$
STRIPLING