000 WTNT42 KNHC 100256 TCDAT2 HURRICANE KATIA DISCUSSION NUMBER 48 NWS NATIONAL HURRICANE CENTER MIAMI FL AL122011 1100 PM AST FRI SEP 09 2011 KATIA HAS MOVED NORTH OF 40N AND OVER COOLER WATERS...YET IT STILL MAINTAINS A RING OF DEEP CONVECTION THAT HAS NOT CHANGED MUCH SINCE THE PREVIOUS ADVISORY. THE INITIAL INTENSITY IS HELD AT 75 KT...SUPPORTED BY A TAFB SATELLITE INTENSITY ESTIMATE OF T4.5 AND CONTINUITY OF THE CONVECTIVE PATTERN. THE CURRENT MOTION ESTIMATE IS 075/32...10 KT FASTER THAN THE PREVIOUS ADVISORY. AN SSMIS MICROWAVE PASS AT 2045 UTC SUGGESTS THAT THE CIRCULATION OF KATIA IS TILTED TO THE NORTHEAST... INDICATING THAT SOUTHWESTERLY SHEAR ASSOCIATED WITH A TROUGH TO THE NORTHWEST IS IMPACTING THE HURRICANE. AS KATIA CONTINUES TO INTERACT WITH THE TROUGH...IT SHOULD FURTHER ACCELERATE TO THE NORTHEAST AND BECOME AN EXTRATROPICAL CYCLONE DURING THE NEXT DAY OR SO. THE FORECAST TRACK IS NEAR THE CENTER OF THE TIGHTLY PACKED MODEL GUIDANCE...CLOSE TO THE GFS AND THE TRACK CONSENSUS TVCN. RELIABLE INTENSITY GUIDANCE SUGGESTS THAT KATIA WILL WEAKEN BELOW HURRICANE STRENGTH LATER SATURDAY. DESPITE THE EXTRATROPICAL TRANSITION OF KATIA...IT WILL REMAIN A POWERFUL CYCLONE AS IT TRAVERSES THE FAR NORTH ATLANTIC. THE STORM-FORCE WIND FIELD IS FORECAST TO REMAIN LARGE AS KATIA APPROACHES THE BRITISH ISLES BY 48 HOURS. INTERESTS IN AND AROUND THE BRITISH ISLES AND NORTHERN EUROPE SHOULD MONITOR PRODUCTS ISSUED BY THE UKMET OFFICE AT WWW.METOFFICE.GOV.UK/WEATHER/ . NO 96-HOUR FORECAST POINT HAS BEEN PROVIDED DUE TO SOFTWARE ISSUES WHEN SYSTEMS MOVE EAST OF ZERO DEGREES LONGITUDE. FORECAST POSITIONS AND MAX WINDS INIT 10/0300Z 41.3N 58.0W 75 KT 85 MPH 12H 10/1200Z 43.5N 50.3W 70 KT 80 MPH 24H 11/0000Z 47.3N 37.2W 65 KT 75 MPH...POST-TROP/EXTRATROP 36H 11/1200Z 51.1N 25.8W 60 KT 70 MPH...POST-TROP/EXTRATROP 48H 12/0000Z 55.6N 15.5W 55 KT 65 MPH...POST-TROP/EXTRATROP 72H 13/0000Z 61.6N 1.1W 50 KT 60 MPH...POST-TROP/EXTRATROP 96H 14/0000Z...EAST OF ZERO DEGREES LONGITUDE $$ FORECASTER HOGSETT/BLAKE