000 AXPZ20 KNHC 091600 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 1605 UTC SUN SEP 09 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1545 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS WESTWARD ACROSS THE EXTREME SW CARIBBEAN ALONG 10N...CROSSING CENTRAL COSTA RICA ALONG 10N THEN TURNING NW OVER THE EAST PACIFIC TO 12N92W...CONTINUING WSW THROUGH 11.5N106W TO 09.5N126W WHERE LOW LEVEL WINDS INDICATE A TRANSITION TO AN ITCZ...WHICH IN TURN CONTINUES W TO NEAR 09.5N136W WHERE IT IS INTERRUPTED BY A LOW LEVEL TROUGH THAT EXTENDS NE TO SW TO NEAR 04N142W. SCATTERED MODERATE ISOLATED STRONG CONVECTION IS OBSERVED WITHIN 240 NM EITHER SIDE OF A LINE FROM 06N83W TO 14N101W...AND ALSO WITHIN 150 NM EITHER SIDE OF A LINE FROM 12.5N108W TO 09N118W TO 12N123W TO 07N140W. ...DISCUSSION... AN UPPER CYCLONE IS OVER THE GULF OF CALIFORNIA AT 28N112W WITH AN UPPER TROUGH EXTENDING W ALONG 24N125W INTO SECOND UPPER CYCLONE AT 25N134W...WITH THE UPPER TROUGH CONTINUING SW TO BEYOND 21N140W. A 1008 MB SURFACE LOW IS NOW ANALYZED OVER THE BAJA PENINSULA AT 30N115W. A BLOCKING UPPER ANTICYCLONE IS CENTERED AT 21N124W WITH A RIDGE EXTENDING SW TO BEYOND 15N140W...AND A RIDGE ALSO EXTENDS NE ACROSS THE SOUTHERN TIP OF THE BAJA CALIFORNIA PENINSULA TO A CREST OVER THE MEXICAN COAST AT 24N106W. UPPER MOISTURE IS WRAPPING AROUND THE N SEMICIRCLE OF THE CYCLONE AT 28N112W. THIS MOISTURE EXTENDS FROM OVER THE EXTREME NORTHERN BAJA PENINSULA ACROSS SOUTHERN CALIFORNIA... ACROSS THE SOUTHERN TWO THIRDS OF ARIZONA AND THEN ACROSS THE SOUTHERN HALF OF NEW MEXICO. OTHERWISE THE UPPER LEVELS ARE VERY DRY TO THE N OF 20N AND W OF 110W. ANOTHER UPPER ANTICYCLONE IS CENTERED AT 21.5N106W WITH A RIDGE EXTENDING SE ACROSS CENTRAL AMERICA TO A CREST OVER THE NW COAST OF COLOMBIA. SCATTERED MODERATE ISOLATED STRONG CONVECTION CONTINUES TO MOVES SW OFF THE MEXICAN COAST NEAR 18N102W. SIMILAR CONVECTION IS NOTED OVER THE EASTERN GULF OF CALIFORNIA NEAR 26N109W AND ALSO WITHIN 90 NM OF 19N108W. THE DEBRIS MOISTURE FROM THESE AREAS IS FANNING OUT UNDER THE UPPER ANTICYCLONE COVERING THE AREA FROM 17N TO 15N BETWEEN 100W AND 110W. THE NE TO E UPPER FLOW ACROSS THE TROPICS S OF 17N IS DIFFLUENT AND ENHANCING THE CONVECTION ASSOCIATED WITH THE MONSOON TROUGH AS PREVIOUSLY DESCRIBED. THE RESULTANT UPPER DEBRIS MOISTURE IS ADVECTED SW BETWEEN 83W AND 103W EVAPORATING ALONG 02N. THE MOISTURE IS ADVECTED W IN A BAND FROM 07N TO 13N BETWEEN 103W AND 133W...THEN THE MOISTURE FANS OUT BOTH TO SW AND THE NW BETWEEN 133W AND 140W. A SURFACE RIDGE AXIS EXTENDS SE FROM NEAR 32N135W TO 15N107W. NORTHEAST TRADES S OF THIS RIDGE ARE ENHANCED TO 20 TO 25 KT...SEAS TO 9 FT...IN THE AREA FROM 09N TO 17N BETWEEN 132W AND 140W. THIS AREA OF ENHANCED WINDS IS EXPECTED TO SHRINK SLIGHTLY IN ABOUT 48 HOURS. .SOUTHERLY MONSOONAL WINDS ARE AT 20 TO 25 KT IN THE AREA FROM 05N TO 09N BETWEEN 95W AND 115W...WITH SEAS TO 8 FT. CYCLONIC SPINNING IS NOTED ALONG THE MONSOON TROUGH AXIS NEAR 11N92W THIS MORNING. GLOBAL MODEL GUIDANCE SUGGESTS A SURFACE LOW PRES WILL DEVELOP TONIGHT WITH A 1008 MB LOW REACHING NEAR 12N97W EARLY MON...ACCOMPANIED BY NE TO E WINDS INCREASING TO 20 TO 25 KT WITHIN 240 NM OVER ITS N SEMICIRCLE AND SEAS ABOUT 8 FT. THE SOUTHERLY FLOW WILL CONTINUE AT 15 TO 20 KT S OF THIS LOW IN THE AREA FROM 07N TO 10N BETWEEN 98W AND 110W...WITH SEAS TO 8 FT PRIMARILY IN CROSS EQUATORIAL SW SWELL. BY EARLY TUE THE FORECAST IS FOR A 1006 MB SURFACE LOW NEAR 13.5N1010W...WITH E TO SE WINDS 20 TO 25 KT WITHIN 180 NM N SEMICIRCLE AND S TO SW WINDS AT 20 TO 25 KT...SEAS TO 9 FT...WITHIN ABOUT 210 NM OVER THE S SEMICIRCLE. $$ NELSON