000 AXPZ20 KNHC 270315 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 0405 UTC FRI OCT 26 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0245 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... MONSOON TROUGH EXTENDS FROM NORTHERN COSTA RICA TO LOW PRES NEAR 10N96W 1007 MB TO LOW PRES NEAR 10N106W 1007 MB TO 11N120W TO 09N130W TO 08N138W WHERE LOW LEVEL WINDS SUGGEST IT TRANSITIONS TO THE ITCZ TO BEYOND THE AREA AT 08N140W. SCATTERED MODERATE TO STRONG CONVECTION IS WITHIN 120 NM S OF THE TROUGH BETWEEN 133W-138W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 120 NM S OF THE TROUGH BETWEEN 125W-130W. ...DISCUSSION... ALOFT...A TROUGH/RIDGE PATTERN DOMINATES THE MAJORITY OF THE FORECAST AREA. AN UPPER LEVEL TROUGH STRETCHES FROM 32N123W SW TO 25N131W TO 19N137W AND S TO 10N138W. SE OF THE TROUGH...AN ANTICYCLONE IS CENTERED AT 17N112W. THE ASSOCIATED ANTICYCLONIC COVERS THE AREA TO SE OF THE TROUGH.UPPER DIFFLUENCE ON THE SOUTHERN PERIPHERY OF THE RIDGE IS HELPING TO INDUCE SOME CONVECTIVE ACTIVITY ALONG THE MONSOON TROUGH/ITCZ AS PREVIOUSLY DESCRIBED. THE UPPER TROUGH WILL PUSH EASTWARD TO THE N CENTRAL PORTION OF THE AREA BY SAT SUPPRESSING THE BROAD ANTICYCLONIC FLOW TO THE S. THE TROUGH WILL MOVE INLAND THE WESTERN AND CENTRAL CONUS SUN AS A BROAD UPPER RIDGE BRIDGE BEHIND IT SHIFTS EASTWARD TO OVER THE NE AND CENTRAL PORTIONS OF THE BASIN ALSO BY SUN. AT THE SURFACE...A 1027 MB HIGH CENTER IS ANALYZED N OF THE DISCUSSION AREA NEAR 35N135W WITH A RIDGE EXTENDING SE TO NEAR 20N119W. HIGH PRES GENERALLY COVERS THE WATERS N OF 15N W OF 115W. PRES GRADIENT BETWEEN THIS HIGH PRES AND A TROUGH OVER NW MEXICO IS SUPPORTING NW-N WINDS OF 20-25 KT N OF 23N BETWEEN 115W-125W WITH SEAS IN THE 8-10 FT RANGE. THE HIGH IS FORECAST TO MOVE SE AND OVER THE NEXT 24 HRS WHILE WEAKENING. AS A RESULT...THE NW-N 20-25 KT WINDS WILL SHIFT WESTWARD AND DIMINISH. N SWELLS PRODUCING SEAS OF 8 FT ARE EXPECTED TO SHIFT TO THE CENTRAL AND NW WATERS BY SUN NIGHT. THE PRES DIFFERENCE BETWEEN THE HIGH PRES OVER THE WESTERN CONUS AND LOW PRES TROUGHING OVER THE FAR WESTERN PORTION OF NW MEXICO WILL CONTINUE TO BRING FRESH TO STRONG NW WINDS ACROSS THE NORTHERN AND CENTRAL SECTIONS OF THE GULF OF CALIFORNIA THROUGH SAT AFTERNOON BEFORE DIMINISHING TO 20 KT OR LESS IN LATER DURING SAT EVENING. THE PRES DIFFERENCE BETWEEN THE SOUTHERN PERIPHERY OF THE RIDGE AND LOWER PRES ALONG THE TROPICAL REGION WILL CONTINUE TO SUPPORT NE WINDS OF 20-25 KT OVER THE AREA FROM 10N-20N W OF 120W THROUGH 24 HRS WITH SEAS TO 9 FT. THE ASCAT PASS FROM BETWEEN 1710 TO 1850 UTC THIS AFTERNOON DEPICTED THESE WINDS. THIS AREA OF TRADES THEN SHRINKS FROM ABOUT 12N-20N W OF 135W IN 48 HRS AS THE HIGH WEAKENS AS MENTIONED ABOVE. SATELLITE IMAGERY AND GLOBAL MODEL GUIDANCE CONTINUE TO SHOW A TRIO OF WEAK CIRCULATIONS ALONG THE MONSOON TROUGH AXIS...A WEAK FORMATION NEAR 11N120W...ANOTHER WEAK CIRCULATION NEAR 11N107W...AND A SOMEWHAT MORE DEVELOPED LOW PRES NEAR 10N96W WITH AN ESTIMATED SLP OF 1007 MB. THE SURFACE LOW FORMED AT THE BASE OF A SHARP UPPER TROUGH THAT CURRENTLY EXTENDS FROM THE NW CARIBBEAN SSW TO HONDURAS TO NEAR 13N90W WHERE IT INTERACTED WITH MODERATE SW FLOW. PULSES OF NORTHERLY FLOW ORIGINATING FROM THE GULF OF TEHUANTEPEC TO THE NORTH HAVE BEEN PROVIDING ADDED VORTICITY BUT ALSO INJECT SOMEWHAT DRIER AIR...AND LIMITING CONVECTION NEAR THE LOW. OPERATIONAL AND ENSEMBLE MODELS ARE IN GOOD AGREEMENT SHOWING THE EASTERN MOST LOW PRES AREA WEAKENING SLIGHTLY AS IT DRIFTS W...BUT DEEPEN THE OTHER TWO SYSTEMS A BIT THROUGH 48 HOURS. A COLD FRONT WILL MOVE THROUGH THE GULF OF MEXICO THROUGH SAT ACCOMPANIED BY A COOLER AND DRIER AIRMASS TAKING OVER THE WESTERN GULF. THIS DENSER AIR WILL SPILL THROUGH THE TEHUANTEPEC GAP STARTING TONIGHT...REACHING NEAR GALE FORCE BY EARLY SAT. THIS EVENT MAY PERSIST THROUGH EARLY NEXT WEEK GIVEN THE CHARACTER OF THE HIGH PRES BUILDING OVER THE GULF OF MEXICO. STRONGEST GAP WINDS WILL LIKELY BE IN THE EARLY MORNING WHEN DIURNAL EFFECTS ARE AT A MAXIMUM. WAVEWATCH GUIDANCE BUILDS SEAS 8-10 FT IN THE GULF. HIGH PRES BUILDING ACROSS THE WESTERN PART OF THE GULF OF MEXICO WILL BRING A NEW GAP WIND EVENT ACROSS THE GULF OF TEHUANTEPEC TONIGHT. WINDS WILL INCREASE TO 20-30 KT BY LATE FRI NIGHT... AND LAST INTO SAT EVENING WITH SEAS BUILDING TO 8-11 FT WHILE SPREADING DOWNSTREAM FROM THE GULF. $$ AGUIRRE