000 AXPZ20 KNHC 230324 TWDEP TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 0405 UTC TUE SEP 23 2008 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 0245 UTC. ...SPECIAL FEATURES... A BROAD 1008 MB SURFACE LOW PRESSURE IS LOCATED NEAR 16N106W OR ABOUT 200 NM SSW OF MANZANILLO MEXICO AND IS MOVING W TO WNW AT 5 TO 10 KT. SINCE THIS TIME YESTERDAY...SEVERAL CONVECTIVE BURSTS HAVE GIVEN RISE TO A WELL-DEFINED BUT BROAD LOW-LEVEL CIRCULATION. HOWEVER...THE CONVECTION HAS NOT PERSISTED LONG ENOUGH TO RESULT IN THE BEGINNING STAGES OF A TROPICAL CYCLONE. PERHAPS THE STRONG EASTERLY SHEAR ENVIRONMENT IN WHICH THE LOW PRESSURE REMAINS HAS CONTINUED TO LIMIT ITS DEVELOPMENT. INTERESTINGLY...GLOBAL MODELS ARE LESS BULLISH ON TROPICAL CYCLONE FORMATION FROM THIS AREA THAN THEY WERE OVER THE PAST FEW DAYS. NEW CONVECTION IS AGAIN REDEVELOPING THIS EVENING WITHIN 180 NM OF THE W SEMICIRCLE BUT IS NOT WELL-ORGANIZED. ...TROPICAL WAVES... A RELATIVELY INACTIVE TROPICAL WAVE ALONG 82W/83W S OF 17N IS MOVING W AT 10 TO 15 KT. SATELLITE PICTURES GIVE NO HINT OF THIS FEATURE...AND IT IS BEING EXTRAPOLATED FORWARD BASED UPON TIME SERIES DATA FROM THE CARIBBEAN BASIN. A MORE ACTIVE TROPICAL WAVE NOW ALONG 90W S OF 20N IS ALSO MOVING W AT 10 TO 15 KT. SATELLITE IMAGERY OVER THE PAST 24 HOURS INDICATES A FAIR AMOUNT OF CONVECTIVE ENHANCEMENT ASSOCIATED WITH THIS FEATURE...WITH CONVECTION DEVELOPING FROM THE YUCATAN THROUGH CENTRAL AMERICA AND THEN SOUTHWARD INTO THE TROPICAL EAST PACIFIC. MORE RECENTLY...EARLIER CONVECTION HAS APPARENTLY LED TO THE FORMATION OF A WELL-DEFINED MID-LEVEL CYCLONIC CIRCULATION IN THE VICINITY OF 11N89W...WHICH IS BEING STEERED WESTWARD BY THE STRONG MID-LEVEL EASTERLY FLOW. GLOBAL MODELS SUGGEST SOME WEAK SURFACE LOW PRESSURE ASSOCIATED WITH THIS SYSTEM SHOULD MOVE WESTWARD THE NEXT FEW DAYS IN A HOSTILE EASTERLY SHEAR ENVIRONMENT. AS SUCH...NO GUIDANCE IS KEEN ON TROPICAL CYCLONE DEVELOPMENT. NUMEROUS SCATTERED ISOLATED STRONG CONVECTION IS NOTED WITHIN 180 NM W OF A LINE FROM THE EASTERN BAY OF CAMPECHE TO 12N93W. ...ITCZ... ITCZ AXIS IS CENTERED ALONG 10N85W TO 15N93W TO 12N107W TO 10N122W TO 09N140W. SCATTERED MODERATE CONVECTION WITHIN 120 NM S OF AXIS FROM 118W TO 123W. ...DISCUSSION... AN EXTENDED AND STRONGER-THAN-AVERAGE PACIFIC JET DROPS SE FROM THE CENTRAL NORTH PACIFIC INTO WEST COAST...WITH STRONGER-THAN- AVERAGE MEAN WESTERLY FLOW COVERING THE AREA FROM NORTHERN BAJA INTO THE GULF OF MEXICO. TIME SERIES PLOTS INDICATE THAT THE ENHANCED WESTERLY FLOW NOW IN THE SUBTROPICAL AND MID-LATITUDE PACIFIC SEEMS RELATED TO ANOMALOUS WESTERLIES WHICH PROPAGATED FROM THE EQUATOR POLEWARD OVER THE PAST SEVERAL WEEKS AS A RESULT OF THE ACTIVE PHASE OF THE MJO. MEANWHILE...ANOMALOUS EASTERLY FLOW CURRENTLY ALONG THE EQUATOR IS BEGINNING TO PROPAGATE POLEWARD AS EVIDENCED BY STRENGTHENING ANTICYCLONIC FEATURES EXTENDING FROM THE CENTRAL PACIFIC TO AROUND 125W AND S OF 15N E OF 110W. OTHERWISE...NW TO N WINDS TO 20 KT CONTINUE N OF 29N BETWEEN 118W AND 124W IN THE WAKE OF A RECENT STORM SYSTEM WHICH IS NOW MOVING ACROSS THE WESTERN STATES. SHIP REPORTS AND NOAA WAVEWATCH GUIDANCE INDICATE SEAS TO 8 FT OVER THIS AREA. IN ADDITION...ENHANCED TRADES FROM ABOUT 13N TO 20N AND W OF 130W PERSIST WITH SEAS UP TO 8 FT IN NE WIND WAVES AND LONG PERIOD NW SWELL. FINALLY...QUIKSCAT DATA YESTERDAY SUGGESTED SE TO S WINDS TO 20 KT OVER THE FAR SW WATERS GENERALLY S OF 05N W OF 135W. SEAS ARE ESTIMATED TO BE UP TO 8 FT OVER THIS AREA IN A COMBINATION OF SE WIND WAVES AND SW SWELL. A NEW AND WELL-DEFINED BATCH OF LONG PERIOD SW SWELL IS ALREADY ARRIVING OVER THE SOUTHERN WATERS OF THE TROPICAL EAST PACIFIC AND WILL CONTINUE OVERSPREADING THE AREA DURING THE NEXT 24 TO 36 HOURS. AS A RESULT...EXPECT SEAS TO BUILD TO 8 TO 9 FT IN SW SWELL S OF 10N BETWEEN 95W AND 130W. $$ KIMBERLAIN