000 WTNT42 KNHC 302035 TCDAT2 TROPICAL STORM LAURA DISCUSSION NUMBER 7 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL122008 500 PM EDT TUE SEP 30 2008 A 1653 UTC CIMSS AMSU INTENSITY ESTIMATE CONFIRMS THAT LAURA STILL HAS MAXIMUM WINDS OF 50 KT. IN ADDITION...THE SATELLITE PRESENTATION OF THE STORM'S CENTRAL FEATURES HAS NOT CHANGED APPRECIABLY SINCE THIS MORNING SO THERE IS LITTLE REASON TO CHANGE THE INITIAL INTENSITY. ALTHOUGH LAURA IS CURRENTLY A TROPICAL CYCLONE...VISIBLE IMAGERY SUGGESTS THAT SOME THERMAL ADVECTION IS BEGINNING TO OCCUR AS COLD AIR STRATUS CLOUDS WRAP AROUND THE WEST SIDE OF THE CIRCULATION. GLOBAL MODEL FIELDS INDICATE THAT THE EXTRATROPICAL TRANSITION PROCESS WILL CONTINUE THROUGH TONIGHT... AND LAURA COULD BE FULLY NON-TROPICAL IN 18-24 HOURS. THE SYSTEM IS NOW OVER SEA SURFACE TEMPERATURES NEAR 21C AND IS QUICKLY LOSING ITS TROPICAL ENERGY SOURCE...SO SOME WEAKENING IS SHOWN IN THE OFFICIAL FORECAST OVER THE NEXT 36 HOURS. THEREAFTER...BAROCLINIC FORCING WILL BECOME MORE PROMINENT AS THE EXTRATROPICAL LOW BECOMES EMBEDDED IN THE WESTERLIES...AND SOME RE-STRENGTHENING COULD OCCUR. LAURA IS NOW MOVING JUST EAST OF DUE NORTH AT 010/12. MOST OF THE TRACK GUIDANCE IS TIGHTLY CLUSTERED THROUGH 5 DAYS AND THE OFFICIAL FORECAST REMAINS VERY CLOSE TO THE MODEL CONSENSUS. THE NHC FORECAST TRACK SHOWS A SLIGHT WESTWARD BEND AT 36-48 HOURS DUE TO THE INFLUENCE OF A SHORTWAVE TROUGH OVER THE CANADIAN MARITIMES...BUT AFTER THAT LAURA IS ACCELERATED EASTWARD ACROSS THE NORTH ATLANTIC. A 120-HOUR POSITION IS NOT GIVEN IN THIS FORECAST SINCE IT WOULD BE LOCATED EAST OF THE PRIME MERIDIAN OVER THE NORTH SEA...AND THE LOW COULD BE ABSORBED BY A FRONTAL BOUNDARY BY THEN ANYWAY. FORECAST POSITIONS AND MAX WINDS INITIAL 30/2100Z 42.3N 48.6W 50 KT 12HR VT 01/0600Z 44.0N 48.0W 45 KT...BECOMING EXTRATROPICAL 24HR VT 01/1800Z 46.8N 46.8W 40 KT...EXTRATROPICAL 36HR VT 02/0600Z 50.0N 45.1W 40 KT...EXTRATROPICAL 48HR VT 02/1800Z 53.1N 42.4W 45 KT...EXTRATROPICAL 72HR VT 03/1800Z 56.5N 31.5W 45 KT...EXTRATROPICAL 96HR VT 04/1800Z 57.0N 17.0W 45 KT...EXTRATROPICAL 120HR VT 05/1800Z...ABSORBED $$ FORECASTER BERG/PASCH