000 WTPZ42 KNHC 040834 TCDEP2 TROPICAL DEPRESSION ROSA DISCUSSION NUMBER 21 NWS NATIONAL HURRICANE CENTER MIAMI FL EP172012 200 AM PDT SUN NOV 04 2012 ROSA STILL HAS A WELL-DEFINED LOW- TO MID-LEVEL CIRCULATION BASED ON CONVENTIONAL AND PASSIVE MICROWAVE SATELLITE IMAGERY. A 04/0452 UTC ASCAT OVERPASS INDICATED SURFACE WINDS OF ABOUT 25 KT IN THE EASTERN SEMICIRCLE...AND THAT THE RADIUS OF MAXIMUM WINDS HAVE EXPANDED OUTWARD TO ABOUT 60 NMI. HOWEVER...SINCE THE ASCAT PASS... A CURVED BAND OF MODERATE CONVECTION HAS DEVELOPED IN THE EASTERN SEMICIRCLE...AND A SMALL BURST OF DEEP CONVECTION HAS ALSO DEVELOPED OVER AND JUST SOUTH OF THE LOW-LEVEL CENTER. GIVEN THE RECENT INCREASE IN CONVECTION AND THE FACT THAT ROSA IS HEADING INTO THE NOCTURNAL CONVECTIVE MAXIMUM PERIOD...THE SYSTEM IS BEING MAINTAINED AS A 25-KT TROPICAL CYCLONE FOR THIS ADVISORY. THE INITIAL MOTION ESTIMATE IS SLOWLY WESTWARD...OR 270/03 KT. ROSA MADE A SLIGHT SOUTHWESTWARD JOG SINCE THE PREVIOUS ADVISORY...BUT THIS MOTION IS EXPECTED TO BE TEMPORARY. A WESTWARD OR EVEN A WEST-NORTHWESTWARD MOTION IS EXPECTED TO RESUME AND CONTINUE FOR THE NEXT 48 HOURS OR SO AS THE CYCLONE AND ITS REMNANTS ARE STEERED BY WEAK LOW-LEVEL EASTERLY TRADEWIND FLOW. THE NHC FORECAST TRACK IS A LITTLE SOUTH OF THE PREVIOUS ADVISORY TRACK TRACK...AND CLOSELY FOLLOWS THE ECMWF MODEL AND THE DYNAMICAL CONSENSUS MODELS. WATER VAPOR IMAGERY INDICATES ROSA IS MOVING WESTWARD INTO STRONG UPPER-LEVEL WEST-SOUTHWESTERLY WINDS AND VERTICAL SHEAR VALUES IN EXCESS OF 40 KT...AND ALSO INTO AN INCREASINGLY DRIER AIR MASS. OTHER THAN BRIEF BURSTS OF MODERATE CONVECTION...THESE UNFAVORABLE ENVIRONMENTAL CONDITIONS SHOULD RESULT IN ROSA DEGENERATING INTO A REMNANT LOW PRESSURE SYSTEM DURING THE NEXT 12 HOURS OR SO. THE OFFICIAL INTENSITY FORECAST FOLLOWS THE TREND OF THE PREVIOUS ADVISORY AND THE LATEST INTENSITY GUIDANCE...AND SHOWS A GRADUAL WEAKENING TREND OVER THE NEXT COUPLE OF DAYS WITH DISSIPATION EXPECTED BY 72 HOURS...IF NOT SOONER. FORECAST POSITIONS AND MAX WINDS INIT 04/0900Z 12.5N 121.5W 25 KT 30 MPH 12H 04/1800Z 12.6N 121.8W 25 KT 30 MPH...POST-TROP/REMNT LOW 24H 05/0600Z 12.8N 122.1W 25 KT 30 MPH...POST-TROP/REMNT LOW 36H 05/1800Z 13.0N 122.4W 20 KT 25 MPH...POST-TROP/REMNT LOW 48H 06/0600Z 13.0N 123.0W 20 KT 25 MPH...POST-TROP/REMNT LOW 72H 07/0600Z...DISSIPATED $$ FORECASTER STEWART