000 AXPZ20 KNHC 300934 TWDEP TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 1005 UTC TUE SEP 30 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. ...SPECIAL FEATURES... LOW PRES 1008 MB IS LOCATED AT 11N97W...ALONG THE INTERSECTION OF THE ITCZ AND A TROPICAL WAVE N OF 07N ALONG 97W. THE LOW APPEARS FAIRLY ELONGATED ON IR SATELLITE IMAGERY...WITH THE MAJOR AXIS EXTENDING FROM NW TO SE. THE WAVE/LOW COMPLEX IS MOVING W AT 7 KT. A QUIKSCAT PASS FROM EARLIER IN THE EVENING SHOWS HORIZONTAL VORTICITY AROUND THE LOW IS BEING ENHANCED BY STRONG NE WINDS THROUGH THE GULF OF TEHUANTEPEC THAT IS CONVERGING WITH A BROAD AREA OF MODERATE TO STRONG S TO SW WINDS TO THE SOUTH OF THE LOW AND ITCZ. THE LOW IS CENTERED ON THE EASTERN EDGE OF AN UPPER RIDGE...ALLOWING FOR SOME EASTERLY SHEAR OVER THE AREA. AS SUCH...CONVECTION REMAINS FAIRLY MODEST AND IS PRIMARILY DOWNSHEAR TO THE WEST OF THE LOW CENTER. THE SHEAR IS WEAK ENOUGH HOWEVER TO ALLOW FOR FURTHER DEVELOPMENT AND GLOBAL MODELS CONTINUE TO SUGGEST THAT THIS FEATURE WILL HOLD TOGETHER AS IT MOVES IN A GENERAL WESTWARD DIRECTION OVER THE NEXT FEW DAYS WITH A MEDIUM POTENTIAL OF IT UNDERGOING SOME SLOW DEVELOPMENT. ...TROPICAL WAVES... TROPICAL WAVE ALONG 89W N OF 06N IS MOVING W ABOUT 10 KT. WHILE SUBTLE CYCLONIC CURVATURE IS EVIDENT ON IR SATELLITE IMAGERY...QUIKSCAT DATA AND A SHIP OBSERVATION SHOW S TO SW FLOW ACROSS THE LENGTH OF THE WAVE. THIS HINTS THAT AT LEAST AT THE SURFACE THERE IS NO DISTINCT EASTERLY FLOW WITH CYCLONIC TURNING TYPICAL OF A TROPICAL WAVE...AND THE POSITION OF THIS FEATURE NEEDS TO BE RE-EVALUATED ONCE VISIBLE IMAGERY BECOMES AVAILABLE. TROPICAL WAVE EMBEDDED WITHIN A BROAD LOW PRES AREA FROM 10N TO 19N ALONG 115W. AN ASSOCIATED WEAK SURFACE LOW PRES AREA 1008 MB IS CENTERED NEAR 17N112W. THE WAVE/LOW COMPLEX IS MOVING W AT 10 KT. ...ITCZ... ITCZ AXIS IS CENTERED ALONG 11N86W TO 13N92W TO 11N104W TO 15N114W TO 09N126W TO 11N137W TO 10N140W. SCATTERED MODERATE CONVECTION WITHIN 90 NM E OF THE WAVE ALONG 89W N OF 09N. MODERATE TO STRONG CONVECTION FROM 12N TO 16N BETWEEN 112W AND 116W. SCATTERED MODERATE ISOLATED STRONG WITHIN 150 NM S OF AXIS W OF 138W. ...DISCUSSION... E OF 110W...AN ASCAT PASS FROM 04Z SHOWS CONTINUING 20 TO 30 KT WINDS ACROSS THE GULF OF TEHUANTEPEC. THE WINDS RESULT FROM NORTHERLY FLOW OVER THE WESTERN GULF OF MEXICO FUNNELING THROUGH THE BAY OF CAMPECHE AND ISTHMUS OF TEHUANTEPEC THEN CONVERGING INTO THE LOW NEAR 11N97W. IF THIS LOW DEVELOPS AS MOST GLOBAL MODELS INDICATE...THE ENHANCED WINDS THROUGH THE GULF OF TEHUANTEPEC WILL PERSIST FOR AT LEAST THE NEXT 2 TO 3 DAYS. LOW LEVEL CONVERGENCE ASSOCIATED WITH THE STRONG NORTHERLY WINDS IS IGNITING SCATTERED MODERATE TO ISOLATED STRONG CONVECTION FROM 12N TO 14N BETWEEN 93W AND 96W. ELSEWHERE S OF THE ITCZ MODERATE TO FRESH S TO SW CROSS EQUATORIAL FLOW PERSISTS. LOOKING AHEAD...MUCH WILL DEPEND ON DEVELOPMENT AND TRACK OF THE LOW NEAR 11N97W. WHILE FAIRLY DISORGANIZED CURRENTLY...WEAKENING EAST SHEAR MAY ENCOURAGE FURTHER DEVELOPMENT. W OF 110W...DIVERGENT SE FLOW ALOFT AROUND THE SOUTHERN EDGE OF AN UPPER ANTICYCLONE NEAR 20N110W IS ENHANCING CONVECTION ALONG THE TROPICAL WAVE ALONG 115W MENTIONED ABOVE. THE ASSOCIATED LOW IS NOT EXPECTED TO DEVELOP MUCH MORE...AS IT MOVES INTO AN AREA OF MORE STABLE AIR AND COOLER WATER. ELSEWHERE DEEP LAYER MOISTURE REMAINS MINIMAL OUTSIDE OF THE ITCZ. A WEAK 1012 MB SURFACE LOW IS CENTERED ALONG THE ITCZ NEAR 11N136W. THIS LOW WILL CONTINUE TO FILL AS IT SHIFTS W OF 140W THROUGH TONIGHT. FURTHER TO THE NORTH...A VIGOROUS UPPER TROUGH CONTINUES TO DIG INTO FORECAST AREA ALONG ROUGHLY 140W N OF 15N. AN ASSOCIATED COLD FRONT EXTENDS FROM 30N136W TO 27N140W. SCATTEROMETER AND SHIP OBSERVATION SHOW A BAND OF 20 TO 25 KT SW WINDS WITHIN 150 NM E OF THE FRONT. THESE WINDS ARE EXPECTED TO GRADUALLY DIMINISH THROUGH THE NEXT COUPLE OF DAYS AS THE SUPPORTING UPPER DYNAMICS LIFT OUT TO THE NW. SHIP OBSERVATIONS CONFIRM THE WAVEWATCH MODEL SHOWING LONG PERIOD NW SWELL TO 11 FT...EXPECTED TO CONTINUE TO PROPAGATE INTO THE AREA GENERALLY N OF 15N W OF 125W THROUGH THE REMAINDER OF THE WEEK. $$ CHRISTENSEN