000 WTPZ44 KNHC 120838 TCDEP4 TROPICAL STORM HERNAN DISCUSSION NUMBER 23 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP092008 200 AM PDT TUE AUG 12 2008 NEARLY ALL OF THE DEEP CONVECTION HAS DISSIPATED...AND HERNAN NOW CONSISTS OF A SWIRL OF LOW CLOUDS WITH SOME MID-LEVEL DEBRIS CLOUDINESS. IN ADDITION...MICROWAVE IMAGES SUGGEST THE LOW-LEVEL CIRCULATION HAS BECOME DETACHED FROM THE MID-LEVEL CIRCULATION. BOTTOM LINE...HERNAN HAS FINALLY SUCCUMBED TO COOL WATERS AND IS RAPIDLY WEAKENING. AN EARLIER QUIKSCAT PASS AT 0328 UTC SUGGESTED THAT THE INTENSITY WAS NEAR 50 KT AT THAT TIME. GIVEN THE LACK OF DEEP CONVECTION...THE INITIAL INTENSITY IS SET JUST BELOW THAT ESTIMATE AT 45 KT. CONTINUED WEAKENING IS FORECAST DURING THE NEXT SEVERAL DAYS AS THE CIRCULATION GRADUALLY SPINS DOWN...AND HERNAN IS EXPECTED TO WEAKEN TO A TROPICAL DEPRESSION DURING THE NEXT DAY OR SO. IN FACT...IF HERNAN CANNOT GENERATE NEW CONVECTION SOON...IT COULD WEAKEN FASTER THAN WHAT IS SHOWN IN THE OFFICIAL FORECAST. A SERIES OF MICROWAVE PASSES SUGGEST THAT HERNAN IS MOVING JUST SOUTH OF DUE WEST OR 265/08. A TURN TOWARD THE WEST-SOUTHWEST IS EXPECTED LATER TODAY AS THE INCREASINGLY SHALLOW CYCLONE IS STEERED BY THE LOW-LEVEL FLOW. TRACK GUIDANCE REMAINS IN GOOD AGREEMENT... AND THE NEW OFFICIAL TRACK FORECAST IS ESSENTIALLY AN UPDATE OF THE PREVIOUS ONE. THE WIND RADII HAVE BEEN ADJUSTED BASED ON A RECENT QUIKSCAT PASS...AND THE RADIUS OF 12 FT SEAS HAVE BEEN DECREASED BASED ON ESTIMATES PROVIDED BY THE TROPICAL ANALYSIS AND FORECAST BRANCH. FORECAST POSITIONS AND MAX WINDS INITIAL 12/0900Z 18.5N 132.7W 45 KT 12HR VT 12/1800Z 18.3N 134.0W 40 KT 24HR VT 13/0600Z 17.8N 135.4W 35 KT 36HR VT 13/1800Z 17.3N 137.0W 30 KT 48HR VT 14/0600Z 16.7N 138.6W 25 KT...REMNANT LOW 72HR VT 15/0600Z 15.5N 142.5W 25 KT...REMNANT LOW 96HR VT 16/0600Z 15.0N 146.5W 25 KT...REMNANT LOW 120HR VT 17/0600Z 15.0N 151.0W 20 KT...REMNANT LOW $$ FORECASTER RHOME