000 AXPZ20 KNHC 242152 TWDEP TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 2205 UTC THU SEP 24 2009 TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM THE EQUATOR TO 32N...EAST OF 140W. BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2130 UTC. ...SPECIAL FEATURE... TROPICAL STORM NORA WAS CENTERED NEAR 17.5N 120.8W AT 24/2100 UTC MOVING WNW OR 285 DEG AT 7 KT. ESTIMATED MINIMUM CENTRAL PRESSURE WAS 1002 MB. MAXIMUM SUSTAINED WIND SPEED HAD DECREASED TO 40 KT WITH GUSTS TO 50 KT. SEE THE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMEP2/WTPZ22 KNHC FOR MORE DETAILS. WLY WIND SHEAR ACROSS NORA HAS PUSHED THE DEEP CONVECTION OFF TO THE E...LEAVING THE LOW LEVEL CENTER INCREASINGLY MORE EXPOSED AND OFF TO THE W. THIS SHEAR IS FORECAST TO PERSIST...AND THE STRUCTURE OF NORA COULD BECOME WORSE...OR MORE DETACHED AS THE LOW LEVEL CENTER OF NORA MOVES W TO WSW THE NEXT FEW DAYS. NORA IS FORECAST TO WEAKEN TO A TROPICAL DEPRESSION BY 36 HOURS AND THEN TO A REMNANT LOW BY 72 HOURS. ...THE ITCZ... THE INTERTROPICAL CONVERGENCE ZONE WAS ALONG 09N79W TO 10N95W TO 11N108W TO 15N119W...THEN RESUMES AT 15N124W TO 13N129W TO 10N140W. SCATTERED STRONG WITHIN 180 NM S OF THE AXIS BETWEEN 91W AND 97W. SCATTERED MODERATE ISOLATED STRONG WITHIN 60 NM OF THE AXIS BETWEEN 109W AND 111W AND BETWEEN 131W AND 136W. SCATTERED MODERATE WITHIN 240 NM S OF THE AXIS BETWEEN 97W AND 102W. ...DISCUSSION... W OF 120W... AN UPPER LEVEL RIDGE GENERALLY DOMINATED THE TROPICS BETWEEN 120W AND 155W...AND WAS PRODUCING DIFFLUENT AND ANTICYCLONIC FLOW ACROSS THE ITCZ...VENTING AND SUSTAINING CONVECTION NICELY...PARTICULARLY BETWEEN 128W AND 138W...ACROSS AN ELONGATED LOW LEVEL CYCLONIC CIRCULATION...WHICH EXTENDED FROM 13N127W TO 09N149W. EMBEDDED WITHIN THIS TROUGH WAS A 1007 MB LOW NEAR 11N136W...SHIFTING W NEAR 8 KT. A LATE MORNING QUIKSCAT PASS INDICATED THAT THE PRESSURE GRADIENT BETWEEN THIS ELONGATED TROUGH AND A 1022 MB HIGH NEAR 34N137W WAS PRODUCING A BROAD SWATH OF 20-25 KT OF NE TO E WINDS S OF 28N AND W OF NORA. SEAS ACROSS THE REGION WERE RUNNING 7-10 FT IN A CONFUSED AND BROAD SPECTRAL MIX OF SWELL AND WIND WAVE. S OF THE TROUGH...QUIKSCAT ALSO REVEALED 20-25 KT S TO SW WINDS FEEDING INTO THE TROUGH...BEYOND 120W. SEAS ON THIS SIDE OF THE TROUGH WERE ALSO CONFUSED AND WERE IN THE 7-8 FT RANGE PER RECENT WWII GUIDANCE. THIS WIND AND WAVE FIELD WILL SHIFT W AROUND 10 KT THROUGH THE WEEKEND...WITH THE UPPER LEVEL RIDGE BUILDING W WITH IT. THUS ACTIVE WEATHER AND ROUGH AND CONFUSED SEAS SHOULD BE EXPECTED. THE PRESSURE GRADIENT BETWEEN THE 1022 MB HIGH...AND AN ASSOCIATED STRONG HIGH PRESSURE RIDGE TO THE N-NE...AND LOW PRESSURE FROM BAJA CALIFORNIA INTO SRN CALIFORNIA WAS ALSO PRODUCING A LONG FETCH OF NLY WINDS OF 20-25 KT OFF THE ENTIRE W COAST OF THE U.S. SWD TO 30N...WHERE THESE WINDS FANNED OUT LATERALLY BETWEEN 119W AND 130W. SEAS ALONG 30N WERE 6-8 FT THIS AFTERNOON AND WILL BUILD TO 8 TO 9 FT THROUGH SAT...AS THIS NLY WIND SWELL BEGINS TO MIX WITH LONG PERIOD NW AND SW SWELL. A LARGE UPPER LOW MOVING SLOWLY E INTO THE CENTRAL PLAINS HAD A NARROW TUTT LIKE TROUGH SNAKING WSW ACROSS EXTREME NW MEXICO THEN MORE W ACROSS N CENTRAL BAJA TO A BROAD MID TO UPPER LOW NEAR 26N130W...THEN CONTINUED SW THEN W TO ANOTHER LARGE SYNOPTIC LOW CENTERED ACROSS THE HAWAIIAN ISLANDS. MUCH OF THE AREA WITHIN AND N OF THIS TROUGH E OF 135W WAS UNDER DRY AND SUBSIDENT CONDITIONS...YIELDING FAIR WEATHER. SWLY FLOW ALOFT S OF 25N AND E OF 130W HAD BEGUN TO IMPACT NORA AND PRODUCE STRONG SHEAR ACROSS THE SYSTEM. E OF 120W... AN UPPER RIDGE EXTENDING FROM THE FLORIDA PANHANDLE SW TO JUST E OF NORA WAS PRODUCING A STRONG NELY MID LEVEL WIND SURGE ACROSS THE BAY OF CAMPECHE AND INTO S CENTRAL MEXICO. MID LEVEL ENERGY ASSOCIATED WITH OLD TUTT AXIS ACROSS THE SW ATLC AND WRN CARIB HAD COMBINED ON THE S SIDE OF THIS UPPER RIDGE...WITH A LOW TO MID LEVEL TROUGH MOVING ACROSS THE SW CARIB...LIKELY A TROPICAL WAVE...AND HAVE PRODUCE A SHARP LOW TO MID LEVEL TROUGH ALONG ABOUT 90W EXTENDING S INTO THE EPAC ITCZ. THIS HAS ENHANCED THE BROAD MONSOONAL CIRCULATION ACROSS THIS PORTION OF THE EPAC. THIS TROUGH WILL SHIFT W OVER THE NEXT FEW DAYS AND BRING ABUNDANT MOISTURE AND ACTIVE WEATHER FROM THE W CARIB ACROSS CENTRAL AMERICA AND INTO EXTREME SE MEXICO...AND THE ADJACENT EPAC. BROAD SWLY FLOW PREVAILS S OF THE ITCZ ACROSS THE AREA...WHILE N OF THE ITCZ...FLOW IS GENERALLY NE TO E WITH SEVERAL LOW LEVEL CYCLONIC SWIRLS INDICATED IN SATELLITE IMAGERY TODAY. AS THIS TROUGH SHIFT W...ITCZ CONVECTION WILL INCREASE E OF 110W OVER THE NEXT FEW DAYS...AND IT WOULD NOT BE SURPRISING TO SEE ANOTHER WELL ORGANIZED LOW DEVELOP WITHIN THE ITCZ DURING THIS TIME. MIXED PULSES OF SE AND SW SWELL WILL CONTINUE TO AFFECT THESE OFFSHORE WATERS E OF 120W THROUGH THE WEEKEND AND MAINTAIN SEAS 6 TO 8 FT...AND 5 TO 6 FT WITHIN 120 NM OF THE COASTLINES. $$ STRIPLING