000 AXPZ20 KNHC 111601 TWDEP TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 1605 UTC FRI SEP 11 2009 TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM THE EQUATOR TO 32N...EAST OF 140W. BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1545 UTC. ...SPECIAL FEATURE... TROPICAL STORM LINDA CENTERED NEAR 20.6N 130.9W AT 11/1500 UTC MOVING NNW OR 330 DEG AT 5 KT. MAXIMUM SUSTAINED WIND SPEED IS 40 KT WITH GUSTS TO 50 KT. THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 1000 MB. LATEST SATELLITE IMAGERY SHOWS THAT THE CYCLONE IS UNDERGOING EXTENSIVE SOUTHERLY SHEAR WHICH IS INHIBITING IT FROM ACQUIRING DEEP CONVECTION. THE CYCLONE IS OBSERVED AS A REMNANT LOW CONSISTING OF BROKEN TO OVERCAST LOW AND MID CLOUDS WITH WIDELY SCATTERED SHOWERS WITHIN 240 NM OF THE CENTER. DUE TO THE STRONG SHEAR...BROKEN HIGH CLOUDS ARE NOTED STREAMING NE FROM ITS NORTHERN SEMICIRCLE AND TOWARDS THE FAR NE PORTION OF THE REGION...AND INTO SRN CALIFORNIA. SINCE LINDA IS ALSO MOVING OVER COOLER SURFACE WATERS...IT WILL MOST LIKELY BE DOWNGRADED TO A TROPICAL DEPRESSION THIS AFTERNOON AS DEEP CONVECTION IS NOT EXPECTED TO REDEVELOP WITH IT. LATEST NHC FORECAST TRACK HAS LINDA CONTINUING IN ITS PRESENT MOTION THROUGH ABOUT THE NEXT COUPLE OF DAYS AS A REMNANT LOW. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMEP5/ WTPZ25 KNHC...AND PUBLIC ADVISORY UNDER TCPEP5/ WTPZ35 KNHC FOR MORE DETAILS. ...TROPICAL WAVE... A TROPICAL WAVE IS ALONG 99W FROM 6N-15N MOVING W AT ABOUT 17 KT. LATEST SATELLITE IMAGERY SHOWS A WEAK MID-LEVEL CYCLONIC CIRCULATION WHERE THE WAVE BISECTS THE ITCZ NEAR 8N100W. A CLUSTER OF SCATTERED STRONG CONVECTION WITH A DIAMETER OF 45 NM IS NOTED ON THE FAR NRN PORTION OF THE WAVE NEAR 15N99W. DEEP CONVECTION WITH THIS WAVE IS VERY LIMITED DUE TO STRONG UPPER LEVEL ELY SHEAR ACROSS THIS PORTION OF THE REGION. ONLY ISOLATED SHOWERS AND WEAK SMALL TSTM CELLS ARE SEEN ELSEWHERE WITHIN 120 NM EITHER SIDE OF THE WAVE. ...THE ITCZ... ITCZ AXIS IS ALONG 08N84W TO 08N90W TO 09N100W TO 06N107W TO 07N120W TO 07N130W TO 08N140W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 180 NM S OF THE AXIS BETWEEN 87W-90W... AND 120 NM S OF THE AXIS BETWEEN 80W-84W. SCATTERED MODERATE CONVECTION IS WITHIN 30 NM OF THE AXIS W OF 138W. ...DISCUSSION... AN UPPER LEVEL CYCLONE WELL N OF THE AREA NEAR 35N127W HAS AN ASSOCIATED TROUGH EXTENDING SW THROUGH 32N132W TO ANOTHER CYCLONE W OF THE AREA NEAR 22N142W...WITH A BROAD TROUGH CONTINUING S TO A BASE AT 13N146W. DRY AND STABLE MID TO UPPER LEVELS PREVAIL AROUND THE PERIPHERY OF THIS LATTER LOW S OF 20N...AND INTO THE SW FLANK OF LINDA. AN UPPER ANTICYCLONE IS NEAR 22N115W WITH A RIDGE EXTENDING SW ACROSS LINDA. ANOTHER RIDGE EXTENDS E-SE FROM THE ANTICYCLONE TO ALONG THE MEXICAN COAST TO NEAR 14N97W. A DEEP MOISTURE IS BEING ADVECTED WESTWARD OVER THE SRN PERIPHERY OF THE RIDGE TO NEAR 125W. LEFTOVER DEBRIS MOSITURE FROM LINDA IS BEING CHANNELED NORTHEASTWARD AND E AROUND THE NORTHERN CREST OF THE ANTICYCLONE TOWARDS NRN BAJA AND SRN CALIFORNIA. AN UPPER TROUGH EXTENDS SW ACROSS THE W CARIBBEAN AND CENTRAL AMERICA TO 08N83W. UPPER CONVERGENCE NOTED EARLIER ON THE W SIDE OF THIS TROUGH HAS DIMINISHED WITH DIURNAL CONVECTION PERSISTING ACROSS CENTRAL AMERICA. UPPER DIVERGENCE OVER THE ITCZ BETWEEN BETWEEN 84W AND 94W HAS BEEN ENHANCED IN RECENT HOURS. THIS TROUGH IS FORECAST TO SLIDE SLOWLY NW OVER THE NEXT 12 TO 24 HOURS AS AN EMBEDDED LOW ACROSS THE SW CARIB MOVES W INTO NICARAGUA. A TIGHT PRES GRADIENT CONTINUES IN EXISTENCE BETWEEN TROPICAL STORM LINDA AND RIDGING TO ITS N. THIS IS BRINGING NE WINDS OF 20 TO 33 KT ELSEWHERE WITHIN 300 NM N AND 180 NM S SEMICIRCLES OF LINDA WITH SEAS 8 TO 12 FT. HOWEVER...THESE CONDITIONS WILL SUBSIDE THROUGH THE NEXT 48 HOURS AS LINDA WEAKENS. BEYOND 48 HOURS..A COLD FRONT IS STILL FORECAST TO DROP INTO THE NW PORTION OF THE AREA DURING THE WEEKEND BRINGING LARGE LONG PERIOD NWLY SWELLS MAXING UP TO 10 OF 11 FT PER LATEST WAVE MODEL GUIDANCE. THESE SWELLS SHOULD OVERSPREAD ACROSS THE NW PART OF THE AREA THROUGH THE WEEKEND. CROSS EQUATORIAL SLY WINDS OF 20 KT AND SWELLS GENERATED BY A BROAD FIELD OF SE WINDS 20 TO 30 KT S OF THE EQUATOR WILL CONTINUE TO AFFECT THE FAR SOUTHERN PORTION S OF 7N BETWEEN 85W-114W AND TO S OF 8N BETWEEN 97W-118W WITHIN 48 HOURS. $$ AGUIRRE