000
WTNT42 KNHC 101456
TCDAT2

POST-TROPICAL CYCLONE KATIA DISCUSSION NUMBER  50
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
1100 AM AST SAT SEP 10 2011

KATIA HAS LOST ITS TROPICAL CHARACTERISTICS...BUT IT STILL REMAINS
A POWERFUL POST-TROPICAL CYCLONE. THE CENTER OF KATIA PASSED JUST
NORTH OF CANADIAN BUOY 44140 AROUND 11Z...AND THE BUOY REPORTED A
PRESSURE OF 957 MB WITH 31 KT WINDS. BASED ON THAT INFORMATION...
THE CENTRAL PRESSURE OF KATIA IS ESTIMATED TO BE 954 MB. AT
12Z...THE SAME BUOY REPORTED A SUSTAINED WIND OF 62 KT IN THE
NORTHWESTERN QUADRANT. ALL OF THIS INFORMATION JUSTIFIES KEEPING
THE INTENSITY AT 70 KT.

THE INITIAL MOTION IS NOW A VERY BRISK 060/46 KT. KATIA IS EMBEDDED
IN DEEP-LAYER WEST-SOUTHWESTERLY FLOW AHEAD OF A STRONG SHORTWAVE
TROUGH DIGGING SOUTHEASTWARD ACROSS THE CANADIAN MARITIMES REGION.
POWERFUL POST-TROPICAL CYCLONE KATIA IS FORECAST TO CONTINUE TO
MOVE RAPIDLY TO THE EAST-NORTHEAST OR NORTHEAST THROUGH THE
REMAINDER OF THE FORECAST PERIOD...AND MOVE OVER OR NEAR THE
NORTHWESTERN BRITISH ISLES ON MONDAY. THE TIGHTLY PACKED NHC MODEL
GUIDANCE IS IN EXCELLENT AGREEMENT ON THIS SCENARIO...AND THE
OFFICIAL TRACK FORECAST IS A BLEND OF THE MULTI-MODEL CONSENSUS...
TVCN...AND GUIDANCE PROVIDED BY THE NOAA OCEAN PREDICTION CENTER.

KATIA HAS LOST MUCH OF ITS DEEP CONVECTION NEAR THE CENTER. ALTHOUGH
THE CENTRAL PRESSURE HAS DECREASED BY AT LEAST 10 MB OVER THE PAST
24 HOURS...THESE PRESSURE FALLS ARE ATTRIBUTED TO THE INCREASE IN
BAROCLINIC ENERGY ACROSS THE SYSTEM AND NOT DUE TO CONVECTIVE
FEEDBACK. SURFACE OBSERVATIONS INDICATE KATIA HAS MERGED WITH A
FRONTAL SYSTEM...AND THE CONTRAST BETWEEN THE VERY WARM AND MOIST
AIR TO THE SOUTH AND COLDER AIR TO THE NORTH OF THE FRONTAL
BOUNDARY SHOULD ACT TO KEEP KATIA AS A STRONG POST-TROPICAL CYCLONE
UNTIL IT REACHES THE BRITISH ISLES ON MONDAY. THE INTENSITY
FORECAST IS A BLEND OF NHC INTENSITY FORECAST GUIDANCE AND INPUT
FROM THE NOAA OCEAN PREDICTION CENTER. CURRENT WIND RADII WERE
ADJUSTED BASED ON RECENT BUOY REPORTS...AND FORECAST WIND RADII
WERE PROVIDED BY THE OCEAN PREDICTION CENTER.

NO 96-HOUR FORECAST POINT HAS BEEN PROVIDED DUE TO SOFTWARE ISSUES
WHEN SYSTEMS MOVE EAST OF ZERO DEGREES LONGITUDE.

ALTHOUGH THIS IS THE FINAL ADVISORY ISSUED ON KATIA BY THE NATIONAL
HURRICANE CENTER...INTERESTS IN AND AROUND THE BRITISH ISLES AND
NORTHERN EUROPE SHOULD CLOSELY MONITOR FUTURE PRODUCTS ISSUED BY
THE UK MET OFFICE AT WWW.METOFFICE.GOV.UK/WEATHER.

FORECAST POSITIONS AND MAX WINDS

INIT  10/1500Z 44.7N  47.7W   70 KT  80 MPH...POST-TROP/EXTRATROP
 12H  11/0000Z 47.5N  38.5W   70 KT  80 MPH...POST-TROP/EXTRATROP
 24H  11/1200Z 51.5N  27.5W   65 KT  75 MPH...POST-TROP/EXTRATROP
 36H  12/0000Z 54.5N  19.0W   65 KT  75 MPH...POST-TROP/EXTRATROP
 48H  12/1200Z 57.5N  11.5W   60 KT  70 MPH...POST-TROP/EXTRATROP
 72H  13/1200Z 61.0N   1.0W   50 KT  60 MPH...POST-TROP/EXTRATROP
 96H  14/1200Z...EAST OF ZERO DEGREES LONGITUDE

$$
FORECASTER STEWART