000 AXPZ20 KNHC 110957 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 1005 UTC MON MAR 11 2013 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. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... AN ILL-DEFINED MONSOON TROUGH EXTENDS S FROM 10N85W TO 03N91W. SCATTEROMETER WINDS DEFINE THE ITCZ FROM 03N91W TO 04N115W TO 03N140W. SCATTERED MODERATE ISOLATED STRONG CONVECTION IS OBSERVED WITHIN 45 NM EITHER SIDE OF A LINE FROM 03N100W TO 07N112W...AND WITHIN 90 NM EITHER SIDE OF A LINE FROM 07N112W TO 03N125W. ...DISCUSSION... GULF OF TEHUANTEPEC...A COLD FRONT IS CURRENTLY ADVANCING SE ACROSS THE GULF OF MEXICO AND WILL MOVE INTO THE BAY OF CAMPECHE TODAY. NORTHERLY WINDS AT 10 TO 15 KT WILL SURGE INTO THE GULF OF TEHUANTEPEC THIS AFTERNOON...RAPIDLY INCREASING TO 20 TO 30 KT THIS EVENING...AND FURTHER INCREASING TO A MINIMAL GALE BY MIDNIGHT. MINIMAL GALE CONDITIONS ARE EXPECTED TO PERSIST THROUGH LATE WED. THE NORTHERLY FLOW WILL INCREASE TO 40 TO 45 KT WED EVENING...AND LIKELY INCREASE TO MINIMAL STORM FORCE BEFORE SUNRISE ON THU. THE GRADIENT SHOULD BEGIN TO RELAX ON THU...WITH GALE CONDITIONS ENDING BY MIDDAY SAT. GULF OF CALIFORNIA...THE GRADIENT BETWEEN A PACIFIC RIDGE AND A TROUGH OVER INTERIOR OLD MEXICO IS SUPPORTING NW WINDS AT 20 TO 25 KT ACROSS THE GULF OF CALIFORNIA TO THE S OF 29N...WITH SEAS TO 8 FT IN LONG FETCH S-CENTRAL WATERS. THE GRADIENT WILL RELAX TONIGHT INTO TUE WITH WINDS DIMINISHING TO 15 TO 20 KT TONIGHT...AND 10 TO 15 KT BY TUE AFTERNOON. GULF OF PAPAGAYO...NE WINDS WILL PULSE AT 15 TO 20 KT INCREASING TO 20 TO 25 KT DURING THE LATE NIGHT HOURS BEGINNING LATE TUE NIGHT. A SHORTWAVE TROUGH IS MOVING INTO A LONGWAVE TROUGH PATTERN OVER THE CENTRAL CONUS WITH THE SHORTWAVE AXIS EXTENDING SW INTO THE DISCUSSION AREA ACROSS NORTHERN OLD MEXICO TO A BASE OVER THE SOUTHERN BAJA PENINSULA. DRY UPPER AIR IS NOTED W OF THE SHORTWAVE ACROSS THE AREA TO THE N OF 25N BETWEEN 107W AND 120W. AN UPPER CYCLONE THAT CUT OFF A FEW DAYS AGO IS NOW FILLING NEAR 24N131W...BUT NOW TRAILS AN UPPER TROUGH S TO 10N134W. DRY UPPER AIR IS ALSO NOTED TO THE W OF THIS TROUGH. AN UPPER ANTICYCLONE IS CENTERED NEAR 11N103W...WITH AN UPPER RIDGE EXTENDING NW THROUGH 25N124W TO BEYOND 34N130W...WITH THE PREVIOUSLY MENTIONED CUT-OFF CYCLONE MOVING N AND ERODING THE RIDGE NEAR 28N127W. OF INTEREST TO AVIATORS IS AN AREA OF OF TRANVERSE CIRRUS BANDING THAT HAS RE-FORMED WITHIN 120 NM EITHER SIDE OF A LINE FROM 24N115W TO 29N125W. WEAK UPPER DIFFLUENCE SW OF THE UPPER RIDGE HAS ENHANCED THE NARROW LINE OF CONVECTION ALONG THE ITCZ AS PREVIOUSLY DESCRIBED. THE RESULTANT UPPER DEBRIS MOISTURE IS ADVECTED N MERGING WITH ADDITIONAL MOISTURE WITHIN THE UPPER RIDGE ENVELOPE. SOME OF THE MOISTURE CONTINUES TO CONCENTRATE INTO A 220 NM WIDE PLUME THAT GRADUALLY EVAPORATES AS IT MOVES E ACROSS CENTRAL OLD MEXICO AND THE WESTERN GULF OF MEXICO... TURNING NE IN RESPONSE TO THE RE-ENFORCING SHORTWAVE...AND EVENTUALLY FEEDS INTO THE LINE OF CONVECTION ADVANCING E ACROSS THE SOUTHERN MISSISSIPPI VALLEY. A SURFACE RIDGE EXTENDS FROM 32N135W TO 13N106W. THE NW LOW LEVEL WINDS TO THE NE OF THE RIDGE HAVE DIMINISHED TO 15 TO 20 KT...BUT MIXED N SWELL IS MAINTAINING COMBINED SEA HEIGHTS TO 8 FT ACROSS THE PACIFIC WATERS N OF 28N BETWEEN 120W AND 128W THIS MORNING...BUT THIS N SWELL IS EXPECTED TO DIMINISH TODAY WITH SEAS SUBSIDING TO 6 TO 7 FT BY TONIGHT. THE GRADIENT SW OF THE RIDGE IS SUPPORTING NE TRADES AT 20 KT ACROSS THE TROPICS FROM 03N TO 20N BETWEEN 113W AND 140W. THIS AREA IS EXPECTED TO SHRINK WESTWARD OVER THE NEXT COUPLE OF DAYS. $$ NELSON