000 AXPZ20 KNHC 112135 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 2205 UTC THU OCT 11 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2100 UTC. ...SPECIAL FEATURES... 1009 MB LOW PRES IS EMBEDDED ALONG THE MONSOON TROUGH NEAR 12N92W. A SECOND 1009 MB LOW IS EMBEDDED ALONG THE MONSOON TROUGH NEAR 11N104W. BOTH LOW PRES SYSTEMS CONTINUE TO SPORADICALLY SHOW SIGNS OF DEVELOPMENT DURING THE PAST 24 HOURS...AND ATMOSPHERIC CONDITIONS ARE CONDUCIVE FOR SOME GRADUAL DEVELOPMENT OF ONE OR BOTH OF THESE LOW PRES AREAS OVER THE NEXT 48 HOURS AS THEY MOVE W-NW. THE MOST RECENT MODEL GUIDANCE FAVORS DEVELOPMENT OF THE WESTERN LOW WITH DISSIPATION OF THE EASTERN LOW BY 48 HOURS. THE AREA FROM THE EASTERN LOW TO THE WESTERN LOW HAS A MEDIUM CHANCE OF DEVELOPING INTO A TROPICAL CYCLONE DURING THE NEXT 48 HOURS. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... THE MONSOON TROUGH IS ALONG 09N79W TO LOW PRES NEAR 12N92W 1009 MB TO LOW PRES NEAR 11N104W 1009 MB TO 12N113W TO 10N129W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 10N129W TO 08N140W. SCATTERED MODERATE CONVECTION IS FROM 03N TO 06N E OF 83W. SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS FROM 10N TO 15N BETWEEN 94W AND 100W...AND ALSO WITHIN 270 NM IN THE NW QUADRANT OF THE SECOND LOW. SIMILAR CONVECTION IS WITHIN 90-150 NM S OF THE MONSOON TROUGH AND THE ITCZ W OF 123W...AND FROM 10N TO 13N BETWEEN 133W AND 138W. ...DISCUSSION... W OF 110W...A CUTOFF UPPER LEVEL LOW NEAR POINT CONCEPTION IS MIGRATING NE-E ALONG THE COAST OF SOUTHERN CALIFORNIA...AND WILL PUSH ACROSS SOUTHERN CALIFORNIA AND THE NORTHERN PORTION OF BAJA CALIFORNIA THROUGH FRI. THIS UPPER FEATURE AND AN ATTENDANT UPPER TROUGH IS SUPPORTING A COLD FRONT EXTENDING FROM CENTRAL ARIZONA TO ACROSS THE NORTHERN GULF OF CALIFORNIA. IT IS ALSO SUPPORTING A SURFACE TROUGH TO THE W FROM NEAR SAN DIEGO THROUGH 29N118W TO 25N123W. MODEL GUIDANCE FORECASTS SW WINDS INCREASING TO 20 TO 25 KT AHEAD OF THE TROUGH IN THE NORTHERN GULF OF CALIFORNIA LATER THIS EVENING...WITH A SURGE OF NORTHERLY WINDS BEHIND THE TROUGH OVER FIRST THE SOUTHERN GULF OF CALIFORNIA FRI AFTERNOON...EXPANDING TO THE MAJORITY OF THE GULF BY SAT AFTERNOON AS STRONG HIGH PRES DEVELOPS OVER THE U.S. GREAT BASIN...AND LOW PRES TROUGHING SETS UP OVER NW MEXICO AND THE GULF OF CALIFORNIA REGION. MODERATE TO FRESH NORTHERLY WINDS WILL ALSO BE POSSIBLE ALONG THE W COAST OF THE BAJA CALIFORNIA PENINSULA FRI AFTERNOON INTO THE WEEKEND. AN UPPER LEVEL SHORT WAVE TROUGH IS DIGGING E AND SE INTO THE FAR NW PORTION OF THE DISCUSSION WATERS...REACHING FROM 38N137W THROUGH 32N138W TO 22N140W. THIS UPPER FEATURE IS SUPPORTING A LAGGING COLD FRONT MOVING JUST N AND W OF 32N. THE SOUTHERN EXTENT OF THIS FRONT APPEARS TO BE STALLING HOWEVER...AND WILL LIKELY NOT REACH THE DISCUSSION WATERS S OF 30N THROUGH FRI. THIS WILL LEAVE THE BROAD SURFACE RIDGE OVER THE AREA N OF 25N W OF THE SURFACE TROUGH LARGELY IN TACT THROUGH THE NEXT 48 HOURS WHICH WILL IN TURN MAINTAIN PRIMARILY MODERATE TO FRESH TRADE WIND FLOW ALONG AND S OF THE SOUTHERN EXTENT OF THE RIDGE. THE EXCEPTION WILL BE OVER THE W CENTRAL WATERS WHERE AN AREA OF FRESH TO STRONG NE TO E WINDS WERE CAPTURED BY RECENT ASCAT SCATTEROMETER PASSES. THESE WINDS ARE FORECAST TO PERSIST OVER ROUGHLY THE SAME AREA THROUGH THE NEXT 48 HOURS. ALSO...THE TRADE WIND FLOW IS ENHANCING CLUSTERS OF CONVECTION ALONG THE WESTERN EXTENT OF THE MONSOON TROUGH AND THE ITCZ AS IS DESCRIBED IN THE CONVECTION SECTION ABOVE. NW SWELL WITH PEAK WAVE PERIODS OF 15-17 SECONDS CONTINUES TO PROPAGATE FROM THE N CENTRAL PACIFIC INTO THE AREA...FROM 04N TO 23N W OF 125W...AND ALSO N OF 23N W OF 135W AS MEASURED BY EARLIER ALTIMETER PASSES. THIS SWELL WILL SINK SOUTHWARD REACHING THE EQUATOR BY 48 HOURS. E OF 110W...THE DOMINANT FEATURES ARE THE TWO LOW PRES AREAS ALONG THE MONSOON TROUGH LISTED IN THE SPECIAL FEATURES SECTION. THESE FEATURES HAVE PREVIOUSLY BENEFITED IN PART BY PASSING TROPICAL WAVE ACTIVITY IN THE LOWER TO MIDDLE PORTIONS OF THE ATMOSPHERE...AND TO SOME EXTENT BY PULSES OF FRESH TO STRONG GAP WIND FLOW THROUGH THE GULF OF TEHUANTEPEC. MODEL GUIDANCE DEVELOPS BOTH OF THESE SYSTEMS MORE OR LESS INDEPENDENTLY DURING THE NEXT 24 HOURS...WITH THE GFS AND ECMWF SHOWING A CONGLOMERATED AND BROAD MEAN LOW BY 48 HOURS. AT THIS STAGE... CLUSTERS OF CONVECTION ARE PULSING ALONG AND NEAR THE MONSOON TROUGH...IN MODEST EASTERLY SHEAR ALOFT ON THE SOUTHERN EDGE OF AN UPPER ANTICYCLONE CENTERED OVER W CENTRAL MEXICO. ASCAT AND ALTIMETER DATA SHOW THAT THE SW FLOW INTO THE MONSOON TROUGH REMAINS FAIRLY LIGHT...WHICH SO FAR HAS NOT BEEN VERY CONDUCIVE TO DEVELOPMENT. HOWEVER ADDED VORTICITY FROM THE GULF OF TEHUANTEPEC THROUGH THE NEXT 48 HOURS ALONG WITH PERSISTENT CONVECTION WILL OFFER SOME POTENTIAL FOR FURTHER DEVELOPMENT OF ONE OR BOTH SYSTEMS. $$ LEWITSKY