000 WTNT43 KNHC 130259 TCDAT3 TROPICAL DEPRESSION EIGHT DISCUSSION NUMBER 3 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082007 1100 PM EDT WED SEP 12 2007 THE DEPRESSION HAS NOT APPRECIABLY CHANGED IN ITS CONVECTIVE ORGANIZATION OR ESTIMATED INTENSITY SINCE THIS AFTERNOON. WHILE DVORAK...ADT...AND AMSU ESTIMATES ARE AT MINIMAL TROPICAL STORM INTENSITY...SSMI AND SSMIS MICROWAVE IMAGERY SUGGESTS INSTEAD THAT THE CENTER OF THE SYSTEM IS OFFSET ON THE NORTHEAST SIDE OF THE CONVECTION. UPPER TROPOSPHERIC MOTION VECTORS SHOW THAT THERE REMAINS SOME MODERATE NORTHEASTERLY SHEAR THAT CONTINUES TO IMPACT THE SYSTEM. SINCE THE ESTIMATED CENTER IS NOT WELL EMBEDDED WITHIN THE CONVECTION...THIS INDICATES THAT THE SYSTEM REMAINS A TROPICAL DEPRESSION AT THIS TIME. TD EIGHT IS SOUTH OF A WEAK DEEP LAYERED RIDGE WHICH IS CURRENTLY PROVIDING A STEERING OF ABOUT 280/10...SLIGHTLY MORE WESTWARD THAN INDICATED IN THE PREVIOUS ADVISORY. ALL OF THE GLOBAL AND REGIONAL MODELS SHOW THE CYCLONE SLOWING BETWEEN 24 AND 48 HOURS IN RESPONSE TO THE INFLUENCE OF AN MID- TO UPPER-LEVEL TROUGH THAT IS CURRENTLY NORTH OF 25N AT THE SAME LONGITUDE OF THE DEPRESSION. THE TROUGH SHOULD CUTOFF AND RETROGRADE WEST-SOUTHWESTWARD. THIS HAS THE COMBINED EFFECT OF WEAKENING THE WEST-NORTHWESTWARD STEERING AS WELL AS INDUCING RATHER STRONG SOUTHWESTERLY SHEAR AT THE LONGER TIME PERIODS. THE FORECAST TRACK IS THE CONSENSUS OF THE GFS...UKMET...GFDL...AND HWRF MODELS AND IS SLIGHTLY SOUTH OF THE PREVIOUS OFFICIAL FORECAST. THE ECMWF AND NOGAPS MODELS ARE DISCOUNTED AS THEY UNREALISTICALLY TAKE THE DEPRESSION NORTHWARD ALMOST IMMEDIATELY. THOUGH THE DEPRESSION IS OVER WARM 28C WATERS...NONE OF THE INTENSITY GUIDANCE TAKES TD EIGHT TO A HURRICANE IN THE NEXT FIVE DAYS. THIS MAY BE DUE TO THE CLOSE PROXIMITY TO RATHER DRY AIR JUST TO THE NORTH AND WEST OF THE SYSTEM IN THE EARLY TIME PERIODS AND THE RATHER SHARP INCREASE IN SHEAR AT THE LATER TIME PERIODS. THE INTENSITY FORECAST IS CLOSE TO THE SHIPS AND LGE MODELS THROUGH THREE DAYS AND A BLEND OF THESE TWO WITH THE GFDL AND HWRF MODELS AT DAYS FOUR AND FIVE. FORECAST POSITIONS AND MAX WINDS INITIAL 13/0300Z 13.4N 46.4W 30 KT 12HR VT 13/1200Z 13.9N 47.6W 35 KT 24HR VT 14/0000Z 14.3N 48.6W 40 KT 36HR VT 14/1200Z 14.6N 49.5W 45 KT 48HR VT 15/0000Z 15.0N 50.6W 50 KT 72HR VT 16/0000Z 16.0N 53.5W 55 KT 96HR VT 17/0000Z 17.0N 56.5W 50 KT 120HR VT 18/0000Z 18.0N 59.0W 45 KT $$ FORECASTER LANDSEA/PASCH