Hurricane Kirk Discussion Number  30
NWS National Hurricane Center Miami FL       AL122024
500 PM AST Sun Oct 06 2024

Satellite imagery suggests that Kirk has begun the process 
of extratropical transition.  Most of the convection is 
located on the north side of the low-level center due to strong 
south-southwesterly wind shear.  Subjective Dvorak estimates from 
SAB and TAFB range from 65-75 kt, while the latest objective 
intensity estimates from UW-CIMSS range from 65-80 kt.  The 
intensity has been lowered to 75 kt for this advisory.  ASCAT data 
from earlier this morning necessitated an increase in the initial 
wind radii, showing that Kirk is a very large hurricane.

There have been no significant changes to the track reasoning.  A 
narrow mid- to upper-level ridge east of Kirk will weaken over the 
next 24-36 h, allowing Kirk to turn east-northeastward or eastward 
within the zonal mid-latitude westerly flow.  The new NHC track 
forecast lies nearly on top of the previous NHC track, although the 
new track is a bit slower.  This track is relatively close to the 
TVCA and a bit slower than the HCCA corrected consensus guidance.  
The NHC forecast shows Kirk passing north of the Azores Monday night 
and Tuesday as an extratropical cyclone, and should reach western 
Europe late Wednesday, where it could bring gale force winds.

Kirk is forecast to continue to gradually weaken as it reaches 
cooler waters by tonight.  Additionally, the southwesterly vertical 
wind shear is forecast to increase significantly over the system by 
early Monday morning.  Global models show the development of frontal 
features on Monday, and extratropical transition has been moved up 
to 24 h in the latest official forecast.  Despite gradual weakening 
as Kirk becomes post-tropical, the cyclone is expected to remain a 
large and powerful cyclone until it reaches the coast of western 
Europe.  Therefore, the system will continue to spread very large 
swells across a large portion of the North Atlantic Ocean for a few 
more days.  The latest NHC intensity forecast is at the high end of 
the guidance during the extratropical portion of the forecast, in 
best agreement with the GFS and ECMWF global models.  By early 
Thursday, the cyclone will become elongated over western Europe, and 
the latest NHC forecast shows dissipation in 96 h.


FORECAST POSITIONS AND MAX WINDS

INIT  06/2100Z 37.0N  46.2W   75 KT  85 MPH
12H  07/0600Z 39.4N  42.9W   70 KT  80 MPH
24H  07/1800Z 42.1N  37.2W   65 KT  75 MPH...POST-TROP/EXTRATROP
36H  08/0600Z 43.3N  30.2W   60 KT  70 MPH...POST-TROP/EXTRATROP
48H  08/1800Z 43.6N  21.6W   55 KT  65 MPH...POST-TROP/EXTRATROP
60H  09/0600Z 44.7N  11.7W   50 KT  60 MPH...POST-TROP/EXTRATROP
72H  09/1800Z 47.1N   2.6W   45 KT  50 MPH...POST-TROP/EXTRATROP
96H  10/1800Z...DISSIPATED 

$$
Forecaster Hagen