000
AXPZ20 KNHC 200956
TWDEP 

TROPICAL WEATHER DISCUSSION   
NWS NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC MON JUN 20 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 FEATURES...
TROPICAL STORM BEATRIZ IS CENTERED NEAR 15.7N 102.6W OR ABOUT 
155 NM S-SW OF ZIHUATANEJO MEXICO MOVING NW OR 315 DEG AT 08 KT. 
ESTIMATED MINIMUM CENTRAL PRESSURE IS 997 MB. MAXIMUM SUSTAINED 
WIND SPEED IS 50 KT WITH GUSTS TO 60 KT. NUMEROUS MODERATE AND 
SCATTERED STRONG CONVECTION HAS ORGANIZED IN FEEDER BANDS WITHIN 
240 NM OVER THE N SEMICIRCLE...AND WITHIN 300 NM OVER THE S 
SEMICIRCLE. MAXIMUM SEAS HEIGHTS ARE ESTIMATED AT 16 FT...BUT 
SEAS ARE EXPECTED TO BUILD TO NEAR 30 FT AS THE CYCLONE MOVES 
OVER WARM OCEAN WATERS AND STRENGTHENS OVER THE NEXT COUPLE OF 
DAYS. THE CYCLONE WILL LIKELY QUICKLY WEAKEN AFTER 48 HOURS AS 
IT MOVES OVER COOLER SEA SURFACE WATERS AND LESS FAVORABLE 
ENVIRONMENTAL CONDITIONS. SEE THE LATEST NHC FORECAST/ADVISORY 
UNDER AWIPS/WMO HEADERS MIATCMEP2/WTPZ22 KNHC FOR MORE DETAILS.
  
...ITCZ/MONSOON TROUGH...
THE MONSOON TROUGH EXTENDS NW OVER CENTRAL AMERICA FROM COSTA 
RICA TO GUATEMALA...THEN BECOMES DISTORTED OVER THE PACIFIC 
BETWEEN 92W AND 102W DUE TO STRENGTHENING TROPICAL STORM 
BEATRIZ. THE MONSOON TROUGH RESUMES TO THE SW OF TROPICAL STORM 
BEATRIZ NEAR 13N103W...AND EXTENDS SW TO 08N124W WHERE LOW LEVEL 
WINDS INDICATE THAT THE ITCZ BEGINS...AND EXTENDS SW TO BEYOND 
06N140W. BROKEN TO OVERCAST LOW AND MID LEVEL CLOUDS ARE 
OBSERVED OVER THE ENTIRE AREA N OF 05N TO THE E OF 107W...AND 
WITHIN 180 NM OF THE MONSOON TROUGH AXIS BETWEEN 107W AND 122W. 
SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS NOTED 
WITHIN 60 NM OF A CLUSTER AT 03N79W...AND WITHIN 30 NM EITHER 
SIDE OF A LINE FROM 10N88W TO 12N90W. SIMILAR CONVECTION IS 
NOTED WITHIN 150 NM EITHER SIDE OF THE MONSOON TROUGH AXIS 
BETWEEN 102W AND 118W.

...DISCUSSION...
A SERIES OF UPPER TROUGHS HAVE MOVED S OVER THE NE PORTION OF 
THE DISCUSSION AREA RESULTING IN WESTERLY UPPER FLOW...AND VERY 
DRY UPPER AIR...TO THE N OF 24N E OF 125W. AN UPPER CYCLONE HAS 
CUT OFF AT 26N142W AND SEEMS TO BE SHIFTING WESTWARD WITH 
TIME...WITH AN UPPER TROUGH EXTENDING SE TO A BASE AT 14N138W. A 
NARROW BAND OF UPPER MOISTURE IS ADVECTED N ALONG THE E 
PERIPHERY OF THE CYCLONE...ROUGHLY FROM 25N TO 32N ALONG 131W... 
THEN FANNING OUT FROM 32N TO 36N.    

A SMALL UPPER CYCLONE IS NOTED OVER THE DEEP TROPICS NEAR 
01N128W. AN UPPER RIDGE EXTENDS E OVER THE DEEP TROPICS S OF THE 
PREVIOUSLY DESCRIBED UPPER TROUGH...ALONG 08N TO THE W OF 135W 
AND ENHANCES SHOWERS ALONG THE ITCZ BETWEEN 134W AND 139W.     

AN UPPER ANTICYCLONE IS OVER W CENTRAL OLD MEXICO NEAR 18N100W 
WITH AN UPPER RIDGE EXTENDING SW TO A CREST NEAR 15N120W. UPPER 
DIFFLUENCE S OF THIS RIDGE IS ENHANCING THE CONVECTION 
ASSOCIATED WITH TROPICAL CYCLONE BEATRIZ...AND ALSO THE 
CONVECTION ALONG THE MONSOON TROUGH PREVIOUSLY MENTIONED. MOST 
OF THE RESULTANT DENSE DEBRIS MOISTURE IS ADVECTED SE...SOME 
CROSSING THE EQUATOR BETWEEN 110W AND 122W IN THE STRONG UPPER  
LEVEL NORTHEASTERLY FLOW. SOME MOISTURE ALSO SPREADS N ACROSS 
THE RIDGE AXIS TO OVER SW OLD MEXICO NEAR 18N99W. AN UPPER RIDGE 
ALSO EXTENDS SE FROM THE ANTICYCLONE TO A CREST OVER THE CENTRAL 
CARIBBEAN. THE ASSOCIATED UPPER NORTHEASTERLY FLOW IS ADVECTING 
CONVECTIVE DEBRIS MOISTURE SW OVER THE DEEP TROPICS TO THE E OF 
90W. 

ELSEWHERE AT THE LOW LEVELS...A BROAD RIDGE COVERS THE AREA N OF 
THE 10N TO THE W OF 118W. THE GRADIENT NE OF THE RIDGE IS 
MAINTAINING NORTHWESTERLY LOW LEVEL FLOW AT 15 TO 20 KT ALONG 
THE PACIFIC SIDE OF THE BAJA CALIFORNIA PENINSULA THIS MORNING...
BUT THE GRADIENT IS EXPECTED TO RELAX LATER TODAY WITH WINDS 
LESS THAN 20 KT. A DRY NORTHERLY SURGE WILL DIP S OVER THE 
MARINE AREA TO THE N OF 27N BETWEEN 120W AND 130W ON TUE...BUT 
WILL BE ACCOMPANIED BY ONLY A SLIGHT NORTHERLY WIND SHIFT. 
GUIDANCE NOW SUGGESTS A STRONGER NORTHERLY SURGE WILL MOVE INTO 
THE NW PORTION ON THU...ACCOMPANIED BY NORTHERLY 
SWELLS...DRIVING COMBINED SEAS TO 10 FT THU NIGHT NEAR 30N127W. 

LOW LEVEL SW WINDS CONTINUE AT 20 TO 25 KT S OF THE MONSOON 
TROUGH TO THE EQUATOR...WITH SOUTHERLY SWELLS REACHING THE COAST 
OF CENTRAL AMERICA BETWEEN 90W AND 102W. CROSS EQUATORIAL SW 
SWELLS ARE EXPECTED MOVE IN THE WATERS N OF THE EQUATOR BETWEEN 
82W AND 88W WITH SEAS TO 8 FT REACHING THE COAST OF CENTRAL 
AMERICA LATE TONIGHT.     

$$
NELSON