000 AXPZ20 KNHC 230943 TWDEP TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 1005 UTC SAT AUG 23 2008 TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM THE EQUATOR TO 32N...EAST OF 140W. BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0915 UTC. ...TROPICAL WAVES... A TROPICAL WAVE LOCATED N OF 06N ALONG 88W HAS BEEN MOVING W AT 10 TO 15 KT...AS IT TRACKS ACROSS CENTRAL AMERICA. ACCORDING TO UPPER-AIR TIME SERIES DATA FROM THE CARIBBEAN...THE AMPLITUDE OF THE WAVE HAS BEEN CONFINED TO S OF ABOUT 15N THE PAST FEW DAYS...AND OBSERVATIONS INDICATE THAT THIS CONTINUES TO BE THE CASE. SATELLITE IMAGERY INDICATES THAT THE WAVE IS INTERACTING WITH A MID- TO UPPER-LEVEL CYCLONIC CIRCULATION DIRECTLY OFFSHORE THE HONDURAN/NICARAGUAN COAST...WHICH IS ENHANCING CONVECTION NOT ONLY OVER THE SW CARIBBEAN AND PORTIONS OF CENTRAL AMERICA BUT ALSO OVER E PACIFIC WATERS FROM 07N TO 13N E OF 90W. AN ACTIVE TROPICAL WAVE LOCATED FROM 06N TO 20N ALONG 107W IS MOVING W AT 10 TO 15 KT. SATELLITE IMAGERY AND AN 0350 ASCAT PASS SUGGEST A BROAD CYCLONIC CENTER ASSOCIATED WITH THE WAVE NEAR 17.6N106.5W...MOVING NW AT 15 KT. A SMALL CLUSTER OF DEEP CONVECTION IS APPARENT W OF THE CIRCULATION CENTER BUT HAS RECENTLY CONSOLIDATED WITH A NASCENT BANDING FEATURE FORMING OVER THE NORTHERN SEMICIRCLE. SCATTERED CONVECTION ALSO RISES OUT OF THE ITCZ TOWARD THE LOW CENTERED ALONG A CONFLUENT AXIS...WHERE LOW-LEVEL SW TO W FLOW INTERSECTS SOUTHERLIES. ...ITCZ... INTERTROPICAL CONVERGENCE ZONE AXIS 08N78W TO 08N94W TO 17N106W TO 12N113W TO 15N121W TO 07N140W. SCATTERED MODERATE CONVECTION LIES FROM 05N TO 12N BETWEEN 80W AND 90W. SCATTERED MODERATE CONVECTION WITHIN 120 NM EITHER SIDE OF AXIS BETWEEN 106W AND 120W. LOW PRES 13.6N125.6W...SCATTERED MODERATE ISOLATED STRONG WITHIN 360 NM SW QUADRANT AND WITHIN 150 NM NE QUADRANT. LOW PRES 17N106W...SCATTERED MODERATE TO STRONG WITHIN 240 NM N SEMICIRCLE. ...DISCUSSION... A NUMBER OF GLOBAL MODELS KEEP SURFACE LOW PRESSURE ALONG THE NORTHERN END OF THE ACTIVE TROPICAL WAVE CURRENTLY ALONG 107W AND MOVE IT NW AT 15 KT DURING THE NEXT 24 HOURS. HOWEVER... NEARLY OF ALL OF GLOBAL MODEL SOLUTIONS KEEP THIS FEATURE WEAK AND ULTIMATELY DISSIPATE IT JUST AROUND OR JUST BEYOND 24 HOURS. THIS SYSTEMS LESS-THAN-AUDACIOUS FUTURE IS LIKELY RELATED TO THE STRONG SHEARING ENVIRONMENT IN WHICH IT IS EMBEDDED. ALTHOUGH LATEST CIMSS ANALYSES SHOW 20 TO 25 KT OF EASTERLY SHEAR...AN IMPROVEMENT OVER THE EASTERLY 30 KT SHEAR THIS TIME YESTERDAY... THE SHEAR IS LIKELY ENOUGH TO HAMPER MUCH IN THE WAY OF FURTHER DEVELOPMENT. THE MODEL CONSENSUS TRACKS THE SYSTEM TO NEAR THE SOUTHERN TIP OF THE BAJA PENINSULA BY EARLY SUN MORNING AND DISSIPATE IT SLIGHTLY NW OF THERE LATER IN THE DAY. EARLIER ASCAT DATA INDICATED A LARGE AREA OF 20 TO 25 KT WINDS WITHIN ABOUT 150 NM OF THE SE SEMICIRCLE. GIVEN THE TENDENCY FOR ASCAT TO UNDERESTIMATE ACTUAL WINDS...IT IS ESTIMATED THAT 20 TO 30 KT WINDS LIKELY EXTEND OUTWARD AT LEAST 180 OR 210 NM OVER THE SE SEMICIRCLE. NOAA WAVEWATCH GUIDANCE FAILS TO SHOW THESE WINDS AND IS ALSO LIKELY TO BE UNDERESTIMATING WAVE HEIGHTS IN THE VICINITY OF THE SURFACE LOW. WAVE HEIGHTS COULD BE AS HIGH AS 10 TO 11 FT WITHIN A FAIRLY BROAD AREA OF 8 FT OR GREATER SEAS OVER THE SE SEMICIRCLE. ELSEWHERE...THE ILL-DEFINED REMNANTS OF ISELLE HAVE ATTACHED THEMSELVES TO AN ELONGATED SURFACE TROUGH EXTENDING FROM THE ABOVE SURFACE LOW NEAR 17N107W TO NEAR 13N126W. BURSTS OF DEEP CONVECTION...SOME WITH CLOUD TOP TEMPERATURES TO -80C... CONTINUE TO RE-DEVELOP IN FITS AND STARTS...MAINLY TO THE SW AND W OF THE NOW DIFFUSE LOW-LEVEL CIRCULATION OF ISELLE. MORE RECENTLY...A SMALL AREA OF CONVECTION HAS EVEN BLOSSOMED NE OF THE CENTER...THOUGH THE CONVECTION IS BEING SHORN AS STRONG EASTERLY SHEAR AS HIGH AS 40 KT PER CIMSS ANALYSES CONTINUES UNABATED OVER ISELLE. DESPITE ISELLES SOMEWHAT REJUVENATED APPEARANCE AND THE FACT THAT GLOBAL MODELS PERSIST LOW PRESSURE OVER THIS AREA FOR SEVERAL MORE DAYS...THE UNFAVORABLE ATMOSPHERIC CONDITIONS WOULD SEEM TO PRECLUDE ANY SORT OF SUBSTANTIVE REGENERATION. FINALLY...NIGHTTIME QUIKSCAT DATA CONTINUES TO SHOW ENHANCED CROSS-EQUATORIAL FLOW S OF 10N BETWEEN 109W AND 140W...AND GLOBAL MODELS SHOW LITTLE CHANGE TO THIS PATTERN OVER THE NEXT DAY OR TWO. MEANWHILE...LONG PERIOD SE TO S SWELL PROPAGATING OUT OF THE SOUTHERN HEMISPHERE IS AFFECTING THE WATER OF THIS SAME AREA BUT WILL VERY GRADUALLY SUBSIDE THE NEXT FEW DAYS. OTHERWISE...LONG PERIOD NW SWELL COMING OUT OF THE N PACIFIC AND OFFSHORE THE CALIFORNIA COAST HAS RESULTED IN A SIGNIFICANT AREA OF 8 FT SEAS OVER THE FAR NORTHERN WATERS...GENERALLY N OF 25N BETWEEN 118W AND 131W. THESE MARINE CONDITIONS SHOULD BE SHORT- LIVED THOUGH...AS MODEL GUIDANCE SHOWS 8 FT SEAS SUBSIDING WITHIN 18 HOURS...ALMOST AS QUICKLY AS THEY BUILT. $$ KIMBERLAIN