000 AXPZ20 KNHC 100316 TWDEP TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 0405 UTC SAT JAN 10 2009 TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM THE EQUATOR TO 32N...EAST OF 140W. BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0300 UTC. ...ITCZ... ITCZ AXIS IS CENTERED ALONG 06N77W TO 05N82W TO 04N97W TO 08N122W TO 06N140W. NO SIGNIFICANT CONVECTION. ...DISCUSSION... A PAIR OF VIGOROUS SHORTWAVE TROUGHS...ONE DIGGING INTO THE SOUTH CENTRAL ROCKIES AND THE OTHER ONTO THE PLAINS...SHOULD LEAD TO THE FORMATION OF A BROAD...LARGE-SCALE TROUGH OVER THE EASTERN CONUS BY THE END OF THE WEEKEND. AS THE INITIAL SHORTWAVE IN THE ROCKIES DIVES SOUTHEAST LATE TONIGHT AND EARLY SAT...IT SHOULD INTRODUCE A RATHER STRONG COLD FRONT THROUGH THE DESERT SOUTHWEST AND EVENTUALLY THROUGH NORTHERN MEXICO AND THE NORTHERN GULF OF CALIFORNIA. AFTER THE FRONT SWEEPS THROUGH THE REMAINDER OF NORTHWEST MEXICO BY LATE SAT...THE GRADIENT BETWEEN A 1040+ MB SURFACE RIDGE BUILDING BEHIND THE FRONT OVER THE GREAT BASIN AND CENTRAL ROCKIES AND LOW PRESSURE TO THE SOUTH SHOULD HERALD THE ARRIVAL OF GALE CONDITIONS OVER THE GULF OF CALIFORNIA SAT INTO SUN. THE EVENT IS FORECAST TO LAST FOR ALMOST 48 HOURS...WITH THE STRONGEST WINDS OF UP TO 45 KT WITH HIGHER GUSTS SLATED FOR SAT. MARINERS CAN EXPECT SEAS TO BUILD UP TO 10 OR 11 FT OVER THE NORTH...WITH THE SWELL AND WIND-GENERATED WAVES SPREADING SOUTHWARD. AS A RESULT...WAVE HEIGHTS OF 8 TO 9 FT ARE POSSIBLE IN THE SOUTH HALF OF THE GULF OF CALIFORNIA IN STEEP NW WIND WAVES. ELSEWHERE...AFTER A TEMPORARY LULL IN WINDS NEAR AND DOWNSTREAM OF THE GULF OF PAPAGAYO THIS TIME THURSDAY...AN ASCAT PASS FROM 1506 UTC YESTERDAY CONFIRMED THAT GAP WINDS OF 20 TO 25 KT RETURNED. HOWEVER...AGAIN TONIGHT...A DIURNAL SIGNATURE IS NOTED IN THE INTENSITY AND AREAL COVERAGE OF GULF OF PAPAGAYO GAP WINDS...AS NE WINDS HAVE DIMINISHED TO 20 KT AND ARE CONFINED TO AN AREA VERY CLOSE TO THE COSTA RICAN/NICARAGUAN COASTS. OVER THE NEXT FEW DAYS...STRONG HIGH PRESSURE FORECAST TO BUILD IN THE WAKE OF THE LARGE-SCALE TROUGH FORMING OVER THE EASTERN CONUS...WITH THE RIDGE BUILDING SOUTHWARD INTO THE CARIBBEAN AND CENTRAL AMERICA. AS A RESULT...THE AREAL COVERAGE AND INTENSITY OF GAP WINDS DOWNWIND OF THE GULF OF PAPAGAYO SHOULD EXPAND AND INCREASE. IN FACT...WITHIN 24 HOURS...MODEL GUIDANCE SUGGESTS THAT NE TO E WINDS OF 20 TO 25 KT COULD LIE AS FAR W AS 91W AND WITHIN 60 NM EITHER SIDE OF 11N. THE INCREASE IN WIND SHOULD ACTIVATE THE OCEAN...AND WAVE HEIGHTS OF UP TO 10 FT ARE EXPECTED IN STEEP EASTERLY WIND WAVES. AS THE SURFACE RIDGE OVER THE EASTERN STATES WEAKENS A BIT AND SHIFTS E LATER SUN...IT APPEARS AS IF GAP WINDS NEAR THE GULF OF PAPAGAYO SHOULD BEGIN TO DECREASE AND CONTRACT EASTWARD. HOWEVER...NE WINDS TO 20 KT SHOULD CONTINUE VERY NEAR THE COAST PAST THE WEEKEND. OTHERWISE...THE COLD FRONT NOW ENTERING NORTHERN MEXICO SHOULD PLUNGE SOUTHEAST INTO THE GULF OF MEXICO SAT...LEADING TO GALE CONDITIONS IN THE SOUTHWEST GULF SUN AND MON. AS THE STRONG SURFACE HIGH BEHIND THE FRONT BUILDS SOUTHWARD INTO NORTHEAST MEXICO AND THE ISTHMUS OF TEHUANTEPEC...GAP WINDS IN THE GULF OF TEHUANTEPEC SHOULD BEGIN TO ABRUPTLY INCREASE LATE SUN AND GALE CONDITIONS ARE EXPECTED IN THE GULF OF TEHUANTEPEC EARLY NEXT WEEK. FINALLY...A 1040+MB SURFACE HIGH PRESSURE RESTING FROM THE INTERMOUNTAIN WEST WESTWARD INTO THE MID-LATITUDE NORTHEAST PACIFIC SHOULD MOVE LITTLE THOUGH THE WEEKEND. THE ENHANCED PRESSURE GRADIENT SOUTH OF THE RIDGE SHOULD ENSURE ABOVE NORMAL TRADES BLOWING OVER THE NW PART OF THE FORECAST AREA OVER THE NEXT FEW DAYS...A REINFORCEMENT TO THE PATTERN WHICH CURRENTLY EXISTS. CONSEQUENTLY...MARINERS CAN EXPECT 8 TO 10 FT SEAS IN A MIXTURE OF NW SWELL AND ROUGH NE WIND WAVES OVER MUCH OF THIS AREA...ESPECIALLY OVER THE AREA FROM 10N TO 20N W OF 130W. IN ADDITION...FRESH NORTHERLY SWELL SHOULD CONTINUE TO ENTER THE FAR NORTHERN WATERS BY TONIGHT N OF 27N ROUGHLY BETWEEN 120W AND 130W AND SPREAD SOUTHWARD. SEAS OF 8 TO 11 FT OVER THIS AREA SHOULD SUBSIDE A BIT BY LATE SAT AND SUN...AS LONGER PERIOD NW SWELL BECOMES DOMINANT OVER THE NORTHERN HALF OF THE AREA. $$ KIMBERLAIN