[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

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


This weather bulletin was brought to you by:
www.nashvilleweather.net