000
AXPZ20 KNHC 050958
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC TUE MAY 05 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...

ITCZ AXIS EXTENDS ALONG 08N78W TO 09N91W TO 07N110W TO 04N120W 
TO 04N140W. ISOLATED MODERATE AND STRONG CONVECTION IS FLARING 
INTERMITTENTLY OVER THE PACIFIC FROM 03N TO 10N E OF 100W. 
SCATTERED MODERATE ISOLATED STRONG CONVECTION IS CONCENTRATED 
WITHIN 60 NM EITHER SIDE OF LINE FROM 08.5N109W TO 05N132W TO 
04.5N140W. A SMALL CLUSTER OF CONVECTION IS NOTED NEAR 
03N121W.

...DISCUSSION...

ALOFT...AN UPPER CYCLONE HAS CUT OFF NEAR 17N135W AND IS MOVING 
W WITH TIME. A QUASI STATIONARY UPPER ANTICYCLONE IS CENTERED AT 
09N126W WITH A RIDGE EXTENDING N TO NEAR 20N122W. THE RIDGE IS 
ENHANCING CONVECTION ALONG THE ITCZ BETWEEN 120W AND 145W WITH 
THE RESULTANT DEBRIS MOISTURE SPREADING N UNDER THE RIDGE AND 
WRAPPING AROUND THE NORTHERN SEMICIRCLE OF THE CUTOFF CYCLONE.
A SECOND UPPER CYCLONE IS NOTED NEAR 20N116W. TO THE N OF THESE 
CYCLONES IS A FLAT SHORTWAVE RIDGE WITH A CENTER ESTIMATED NEAR 
28N123W...WITH THE RIDGE EXTENDING NE TO CENTRAL ARIZONA WHERE 
SOME DENSE UPPER MOISTURE IS NOW OBSERVED. OTHERWISE THE UPPER 
LEVELS ARE DRY N OF 20N...AND OVER THE SW SEMICIRCLE OF THE 
WESTERNMOST CYCLONE.

A BROAD UPPER TROUGH DOMINATES THE CENTRAL CONUS AND EXTENDS SW 
ACROSS OLD MEXICO AND THEN S OVER THE E PACIFIC ALONG 109W TO 
THE EQUATOR. DRY UPPER AIR IS NOTED FROM 07N TO 20N BETWEEN 107W 
AND 115W AND SUPPRESSING CONVECTION. UPPER DIFFLUENCE ALONG THE 
UPPER TROUGH AXIS IS ENHANCING CONVECTION ALONG THE ITCZ AT 
08N110W. 

A STATIONARY UPPER RIDGE EXTENDS NW OFF COLOMBIA ALONG THE 
PACIFIC COAST OF CENTRAL AMERICA TO A CREST NEAR 16N103W. 
ASSOCIATED UPPER DIFFLUENCE HAS BEEN ENHANCING CONVECTION ALONG 
THE PACIFIC ITCZ TO THE E OF 100W...AND ALSO ENHANCED QUITE OF 
BIT OF CONVECTION OVER CENTRAL AMERICA BETWEEN 85W AND 93W. 
THE RESULTANT UPPER DEBRIS MOISTURE IS CONCENTRATED TO N OF 05N 
E OF 103W AND EXTENDS NE ACROSS ALL OF CENTRAL AMERICA AND THE W 
CARIBBEAN EVENTUALLY EVAPORATING OVER THE N CENTRAL CARIBBEAN 
ALONG 19N.

AT THE SURFACE...A 1024 MB HIGH PRES IS QUASI STATIONARY NEAR 
27N133W WITH A RIDGE EXTENDING SW TO BEYOND 25N140W...AND A 
RIDGE EXTENDING SE TO NEAR 11N108W. THE RIDGE IS BLOCKING THE 
SOUTHEAST PROGRESSION OF A SERIES OF COLD FRONTS TO N OF 
30N...HOWEVER NW SWELLS TO 12 FT WILL SPREAD SE INTO THE EXTREME 
NW PORTION TONIGHT. TO THE E OF THIS SURFACE RIDGE...NORTHERLY 
WINDS AT 20 KT ARE OBSERVED ALONG THE PACIFIC COAST OF THE BAJA 
PENINSULA AND EXPECTED TO CHANGE LITTLE TODAY...BUT INCREASE TO 
20 TO 25 KT WED WITH SEAS BUILDING TO 13 FT IN NW SWELL NEAR 
29N119W WED NIGHT INTO THU. EASTERLY TRADES S OF THE RIDGE AND N 
OF THE ITCZ ARE MOSTLY IN THE 15 TO 20 KT RANGE...AND NOT 
EXPECTED TO CHANGE MUCH FOR A COUPLE OF DAYS.

$$
NELSON