000
AXPZ20 KNHC 230951
TWDEP 

TROPICAL WEATHER DISCUSSION    
NWS NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC SAT JUL 23 2011

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM 
THE EQUATOR TO 32N...EAST OF 140W. THE FOLLOWING INFORMATION IS 
BASED ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND 
METEOROLOGICAL ANALYSIS.

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0945 UTC.

...SPECIAL FEATURE...
TROPICAL STORM DORA CENTERED NEAR 20.9N 111.2W AT 0900 UTC 
MOVING NW OR 310 DEGREES AT 08 KT. THE MAXIMUM SUSTAINED WINDS 
HAVE DIMINISHED TO 45 KT WITH GUSTS TO 55 KT MAINLY WITHIN ABOUT 
20 NM OF CENTER. THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 998 
MB. STRONG NORTHERLY SHEAR CONTINUES TO SUPPRESS CONVECTION TO 
WITHIN 150 NM OF THE CENTER...BUT ONLY OVER THE S SEMICIRCLE. 
THE CYCLONE IS MOVING WESTERLY UNDER A MID TO UPPER LEVEL RIDGE 
AND WILL WILL CONTINUE TO TRACK OVER INCREASINGLY COOLER OCEAN 
WATERS AND IS EXPECTED TO WEAKEN BELOW TROPICAL STORM FORCE IN 
24 HOURS. SEE LATEST NHC FORECAST/ ADVISORY UNDER AWIPS/WMO HEADERS 
MIATCMEP4/WTPZ24 KNHC FOR MORE DETAILS.

...ITCZ/MONSOON TROUGH...
THE MONSOON TROUGH EXTENDS FROM 08N78W TO 08N96W WHERE LOW LEVEL 
WINDS INDICATE THAT THE ITCZ AXIS BEGINS AND CONTINUES W TO  
08N107W...THEN TURNS SW TO 04N110W...THEN CONTINUES WNW TO 
BEYOND 07N140W. SCATTERED MODERATE ISOLATED STRONG CONVECTION IS 
OBSERVED ALONG THE COAST OF COLOMBIA TO THE N OF 03N AND E OF 
79W. SIMILAR CONVECTION IS ALSO NOTED WITHIN 90 NM EITHER SIDE 
OF LINES FROM 07N88W TO 08N100W AND FROM 12N116W TO 11N127W. 
SCATTERED MODERATE ISOLATED STRONG CONVECTION IS OBSERVED WITHIN 
180 NM OF COAST OF CENTRAL AMERICA FROM 88W TO 98W.

...DISCUSSION...
AN UPPER LEVEL TROUGH IS OVER THE NW PORTION OF THE DISCUSSION 
AREA WITH ITS AXIS EXTENDING SW FROM SOUTHERN CALIFORNIA TO 
31N130W...THEN CONTINUING W ALONG 31N INTO AN UPPER CYCLONE 
QUASI STATIONARY NEAR 31N149W. AN UPPER ANTICYCLONE HAS FORMED 
AT 20N138W. ANOTHER UPPER ANTICYCLONE IS OVER SE NEW MEXICO WITH 
AN UPPER RIDGE EXTENDING SW OVER THE PACIFIC TO A CREST AT 
22N132W. AN UPPER CYCLONE IS OVER THE DEEP TROPICAL PACIFIC AT 
03N132W...WITH AN INVERTED UPPER TROUGH EXTENDING N TO 
22N134W...EFFECTIVELY SEPARATING THE UPPER ANTICYCLONIC FLOW 
ASSOCIATED WITH THE TWO UPPER ANTICYCLONES JUST DESCRIBED. THESE 
UPPER FEATURES COMBINE TO DRY TO THE UPPER LEVELS TO THE N OF 
14N W OF 116W. THE INVERTED TROUGH WILL SHIFT W OF THE AREA LATE 
SUN WITH ANOTHER INVERTED TROUGH FORMING N OF 13N ALONG 117W.  

CONVECTION WAS ENHANCED EARLIER OVER NORTHERN OLD MEXICO UNDER 
THE UPPER ANTICYCLONE...AND ALSO OVER INTERIOR MEXICO. THE 
DEBRIS MOISTURE IS ADVECTED SW OVER THE PACIFIC MERGING WITH THE 
DEBRIS MOISTURE FROM TROPICAL CYCLONE DORA...RESULTING IN MOIST 
UPPER LEVELS TO THE N OF 12N BETWEEN 104W AND 115W. DEBRIS 
MOISTURE FROM THE PREVIOUSLY DESCRIBED ITCZ CONVECTION IS 
BEGINNING TO MOVE NW BUT EVAPORATES ALONG 13N.       
 
AN UPPER CYCLONE IS OVER THE DEEP TROPICS AT 05N99W OTHERWISE 
UPPER ANTICYCLONIC FLOW DOMINATES THE TROPICAL PACIFIC E OF 
102W...WITH UPPER EASTERLY FLOW ADVECTING DEBRIS MOISTURE FROM 
PREVIOUS CONVECTION W OVER THE PACIFIC WATERS TO THE N OF 04N E 
OF 90W.

AT THE LOW LEVELS A RIDGE EXTENDS FROM 32N140W TO 20N120W. NE 
TRADES TO THE S OF THE RIDGE CONTINUE TO PULSE AT 15 TO 20 KT 
NEAR 11N138W. CROSS EQUATORIAL SE SWELLS ARE PROPAGATING NW 
ACROSS THE WATERS SW OF A LINE FROM 14N140W TO THE EQUATOR AT 
110W...MIXING WITH NE TRADE SWELL ALONG 10N BETWEEN 130W AND 
140W. SOUTHERLY SWELL IS DOMINATE OVER THE PACIFIC WATERS E OF 
125W...AND IS MIXING WITH NW SWELL ALONG THE W COAST OF THE BAJA 
CALIFORNIA PENINSULA.

$$
NELSON