000 AXPZ20 KNHC 200950 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 1005 UTC SAT SEP 20 2014 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 FEATURES... TROPICAL STORM POLO LOCATED NEAR 20.5N 108.6W OR ABOUT 185 MILES S-SE OF THE SOUTHERN TIP OF BAJA CALIFORNIA PENINSULA AT AT 0900 UTC SEP 20. THE MINIMUM CENTRAL PRESSURE IS ESTIMATED AT 997 MB. POLO IS MOVING NW OR 315 DEG AT 06 KT...AND IS EXPECTED TO TURN MORE W-NW IN RESPONSE TO A LOW LEVEL RIDGE. POLO WILL PASS S OF THE SOUTHERN TIP OF BAJA TONIGHT. MAXIMUM SUSTAINED WINDS ARE CURRENTLY ARE AT 45 KT WITH GUSTS TO 55 KT. STRONG NE WIND SHEAR IS EXPOSING THE CENTER TO THE E OF SCATTERED MODERATE ISOLATED STRONG CONVECTION THAT IS CURRENTLY OBSERVED WITHIN 180 NM OVER W SEMICIRCLE WITH SCATTERED MODERATE CONVECTION ALSO OBSERVED WITHIN 90 NM OF 17.5N110W. SCATTERED MODERATE ISOLATED STRONG CONVECTION IS ALSO OBSERVED OVER THE SOUTHERN GULF OF CALIFORNIA WITHIN 60 NM OF 25N108W. POLO IS EXPECTED TO PRODUCE RAINFALL AMOUNTS OF 1 TO 3 INCHES...WITH ISOLATED STORM TOTAL AMOUNTS OF 5 INCHES OVER EXTREME SOUTHERN BAJA CALIFORNIA OVER THE NEXT FEW DAYS. THESE RAINS COULD RESULT IN LIFE-THREATENING FLASH FLOODS AND MUD SLIDES. SWELLS GENERATED BY POLO WILL AFFECT PORTIONS OF THE PACIFIC COAST OF MEXICO FROM 17-24N...INCLUDING BOTH MAINLAND MEXICO AND THE SOUTHERN BAJA CALIFORNIA PENINSULA OVER THE NEXT FEW DAYS. THESE SWELLS CAN CONTRIBUTE TO THE GENERATION OF LIFE THREATENING SURF AND RIP CURRENT CONDITIONS. SEE THE LATEST PUBLIC ADVISORY UNDER AWIPS/WMO HEADERS MIATCPEP2/WTPZ32 KNHC AND FORECAST ADVISORY UNDER HEADERS MIATCMEP2/WTPZ22 KNHC FOR ADDITIONAL DETAILS. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS W ACROSS PANAMA AND COSTA RICA BETWEEN 08-10N TO THE PACIFIC COAST OF COSTA RICA AT 08N83W... THEN TURNS NW TO 11N92W...THEN TURNS W-SW TO 09N123W WHERE SCATTEROMETER WINDS INDICATE A TRANSITION TO AN ITCZ WHICH TURNS NW TO BEYOND 13N140W. SCATTERED MODERATE ISOLATED STRONG CONVECTION IS OBSERVED WITHIN 120 NM EITHER SIDE OF A LINE FROM 06N77W TO 09N86W TO 09N96W TO 09N113W. SCATTERED MODERATE ISOLATED STRONG CONVECTION IS ALSO OBSERVED OVER AND WITHIN 120 NM W OF THE COAST OF CENTRAL AMERICA AND MEXICO FROM 86-100W. ...DISCUSSION... A 1017 MB HIGH PRESSURE IS CENTERED NEAR 29N135W WITH A RIDGE EXTENDING SE TO NEAR 16N122W. THE RIDGE IS MAINTAINING NE-E 10- 15 KT TRADES ACROSS THE TROPICS N OF THE MONSOON TROUGH AND TO THE W OF 120W. THE SURFACE HIGH IS FORECAST TO SHIFT SE TO NEAR 28N133W ON TUE ALLOWING A COLD FRONT TO MOVE INTO THE FAR NW WATERS BEGINNING LATE SUN NIGHT. THE FRONT WILL BE INITIALLY BE ACCOMPANIED BY ONLY A SW-W-WNW 10 KT WIND SHIFT. THE WEAK FRONT WILL REACH FROM 32N134W TO TO 26N134W LATE TUE AND THEN IS EXPECTED TO DISSIPATE ALONG A LINE FROM 32N128W TO 26N135W LATE WED. BY THEN A SECONDARY NORTHWESTERLY 15 KT SURGE WILL PUSH NW SWELLS INTO THE AREA WHERE THEY WILL MIX WITH LONG PERIOD SE SWELL...RESULTING IN SEAS BUILDING 8-12 FT ACROSS THE WATERS NW OF THE DISSIPATING FRONT...WITH THE MAXIMUM SEAS ALONG 31N. THIS SECONDARY SURGE WILL REACH THE PACIFIC COAST OF THE BAJA PENINSULA LATE THU WITH NW FLOW INCREASING TO 20 KT AND SEAS BUILDING 7-9 FT IN MIXING NW AND SE SWELL. $$ NELSON