000
AXPZ20 KNHC 120945
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC SUN AUG 12 2012

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 HECTOR IS CENTERED AT 18.6N 109.4W AT 0900 UTC 
MOVING WNW OR 285 DEG AT 10 KT WITH MAXIMUM SUSTAINED WINDS OF 
40 KT WITH GUSTS TO 50 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 
997 MB. HECTOR IS ENCOUNTERING STRONG EASTERLY SHEAR WITH 
NUMEROUS STRONG CONVECTION OBSERVED WITHIN 240 NM OVER THE SW 
SEMICIRCLE OF CENTER. A SINGLE CLUSTER OF STRONG CONVECTION IS 
OBSERVED WELL E OF HECTOR ALONG THE COAST OF MEXICO WITHIN 45 NM 
OF 21N106W. HECTOR IS EXPECTED TO GRADUALLY STRENGTHEN AND 
CONTINUE GENERALLY WESTWARD DUE TO A STEERING RIDGE OVER THE SW 
UNITED STATES. MODEL GUIDANCE VARIES ON THE STRENGTH OF RIDGE 
OVER THE NEXT FEW DAYS...AND HECTOR COULD MOVE SW...W...OR EVEN 
NW DEPENDING ON HOW THE RIDGE MATURES. SEE LATEST NHC 
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMEP3/WTPZ23 KNHC 
FOR MORE DETAILS.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...

A MONSOON TROUGH AXIS EXTENDS ALONG THE PACIFIC COAST OF CENTRAL 
AMERICA FROM NICARAGUA TO CENTRAL MEXICO NEAR 17N97W...THEN 
EXTENDS W OVER THE PACIFIC TO NEAR 16N105W WHERE IT LOSES 
IDENTITY IN THE INCREASING CYCLONIC CIRCULATION ASSOCIATED WITH 
TROPICAL CYCLONE HECTOR. THE MONSOON TROUGH AXIS BECOMES DEFINED 
AGAIN NEAR 16N123W AND CONTINUES SW TO BEYOND 09N140W. SCATTERED 
STRONG CONVECTION HAS MATURED NEAR 13.5N93W LIKELY ASSOCIATED 
WITH THE REMNANTS OF A TROPICAL WAVE RAPIDLY LOSING IDENTITY AS 
IT MOVES THROUGH THE MONSOON FLOW. ISOLATED MODERATE TO STRONG 
CONVECTION IS NOTED IN THIS MONSOONAL FLOW ELSEWHERE TO THE NE 
OF A LINE FROM 02N79W TO 09N110W...AND CONTINUES JUST INLAND 
CENTRAL AMERICA. SCATTERED MODERATE ISOLATED STRONG CONVECTION 
IS OBSERVED WITHIN 60 NM EITHER SIDE OF A LINE FROM 10N110W TO 
10N120W AND A SECOND LINE FROM 12N123W TO 09N134W. THE MONSOONAL 
SW LOW LEVEL FLOW IS EXPECTED TO WEAKEN OVER THE AREA W OF 130W 
TONIGHT AS CROSS EQUATORIAL SE FLOW SPREADS NW SETTING UP AND 
ITCZ FROM 12N130W TO 09N140W ON MON.

...DISCUSSION...

AN UPPER ANTICYLONE IS CENTERED NEAR 30N125W WITH A WELL DEFINED 
UPPER RIDGE EXTENDING SW TO BEYOND 22N140W. AN UPPER CYCLONE IS 
NOTED JUST NW OF THE AREA AT 35N141W WITH AN UPPER TROUGH 
EXTENDING SW ACROSS THE EASTERN HAWAIIAN ISLANDS. THIS UPPER 
TROUGH WILL SLOWLY SHIFT E OVER THE EXTREME NW PORTION IN ABOUT 
36 HOURS. A SECOND UPPER ANTICYLONE IS CENTERED OVER THE CENTRAL 
BAJA CALIFORNIA PENINSULA AT 28N113W WITH AN UPPER RIDGE 
EXTENDING SW TO A SHARP CREST OVER THE REMNANT LOW PRES OF 
FORMER TROPICAL STORM GILMA NOW DISSIPATING NEAR 21N121.5W. 
BETWEEN THESE TWO ANTICYCLONES IS A SMALL UPPER CYCLONE AT 
32N118W WITH A NARROW UPPER TROUGH EXTENDING SW ALONG 24N127W 
INTO ANOTHER UPPER CYCLONE OVER THE DEEP TROPICS AT 14N129W. 
THESE UPPER FEATURE ALL COMBINE TO DRY OUT THE UPPER LEVELS OF 
THE DISCUSSION AREA N OF 15N W OF 122W.  

ALTHOUGH AN UPPER CYCLONE IS DEEPENING OVER THE SW GULF OF 
MEXICO AND OVER EASTERN CENTRAL OLD MEXICO...BROAD ANTICYCLONIC 
FLOW STILL DOMINATES THE UPPER LEVELS S OF 20N BETWEEN 85W AND 
120W. THE DENSE DEBRIS MOISTURE FROM THE PREVIOUSLY DESCRIBED 
MONSOONAL CONVECTION IS ADVECTED SW CROSSING THE EQUATOR BETWEEN 
80W AND 115W. SOME DEBRIS MOISTURE FROM CYCLONE HECTOR IS NOW 
SPREADING N ACROSS THE SOUTHERN BAJA PENINSULA AND THE GULF OF 
CALIFORNIA. 

THE SOUTHERLY MONSOON FLOW IS EXPECTED TO INCREASE TO 20 TO 25 
KT ACROSS THE AREA FROM ABOUT 09N TO 17N BETWEEN 100W AND 117W 
MERGING THE SOUTHERLY FLOW EXPANDING OVER THE S SEMICIRCLE OF 
TROPICAL CYCLONE HECTOR.

NE WINDS AT 20 KT...WITH MERGING N AND NE SWELL RESULTING IN 
COMBINED SEAS TO 9 FT...IS FORECAST OVER THE AREA N OF 25N 
BETWEEN 125W AND 135W TODAY...WITH WINDS DIMINISHING TO 20 KT OR 
LESS AND SEAS SUBSIDING TO LESS THAN 8 FT ON MON.

GAP WINDS...NE WINDS AT 20 TO 25 KT ARE EXPECTED TO SURGE INTO 
AND JUST DOWNSTREAM OF THE GULF OF PAPAGAYO ON LATE TONIGHT AND 
CONTINUE THROUGH MON NIGHT BEFORE DIMINISHING.

$$
NELSON