000 WTNT44 KNHC 052034 TCDAT4 TROPICAL STORM GRACE DISCUSSION NUMBER 4 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL092009 500 PM AST MON OCT 05 2009 GRACE CONTINUES TO HAVE THE SATELLITE APPEARANCE OF A TROPICAL CYCLONE AND A MODERATE TO DEEP WARM CORE AS INDICATED BY RECENT AMSU PASSES. HOWEVER...CLOUD TOP TEMPERATURES HAVE CONTINUED TO WARM OVER THE PAST FEW HOURS AS THE CYCLONE IS NOW OVER SSTS OF 17-18C. THE INTENSITY IS DECREASED TO 50 KT BASED A SUBTROPICAL CLASSIFICATION OF 3.5 FROM TAFB AND A DVORAK CI-NUMBER OF 3.0 FROM SAB. A QUIKSCAT PASS SHOULD PROVIDE SOME INFORMATION ON THE INTENSITY AND STRUCTURE OF GRACE SOON. THE CENTRAL PRESSURE IS HELD AT 990 MB BASED ON AN 1800 UTC OBSERVATION OF 992 MB AND A WIND OF 20 KT FROM SHIP A8I02 ABOUT 30 NM NORTH OF THE CENTER OF GRACE. THE INITIAL MOTION ESTIMATE IS 025/26 KT...AS GRACE IS BEING STEERED BY DEEP-LAYER SOUTHWESTERLY FLOW AHEAD OF A MID- TO UPPER-LEVEL TROUGH ALONG 27W. BY TUESDAY MORNING...ALL OF THE GLOBAL MODELS SHOW GRACE BEING ABSORBED BY A FRONT ASSOCIATED WITH A DEEPENING EXTRATROPICAL CYCLONE TO THE NORTHWEST OF THE BRITISH ISLES. IT IS WORTH NOTING THAT OTHER ATLANTIC TROPICAL STORMS HAVE FORMED FARTHER NORTH THAN GRACE DID. IN 2008 TROPICAL STORM LAURA WAS FIRST CLASSIFIED AS A TROPICAL STORM AT 40.6N....SLIGHTLY FARTHER NORTH THAN THE LATITUDE OF 40.2N WHERE GRACE WAS FIRST CLASSIFIED AS A TROPICAL STORM AT 0000 UTC TODAY. ALSO...IT IS LIKELY THAT POST-STORM ANALYSIS WILL SHOW GRACE BECOMING A TROPICAL STORM EARLIER...AND FARTHER SOUTH...THAN INDICATED OPERATIONALLY. FORECAST POSITIONS AND MAX WINDS INITIAL 05/2100Z 47.7N 14.8W 50 KT 12HR VT 06/0600Z 50.6N 12.0W 50 KT 24HR VT 06/1800Z...DISSIPATED $$ FORECASTER BRENNAN