Official Discussion issued by the National Hurricane Center

Tammy (AL202023) DATA RELEASED: 10/24/2023 9:00:00 AM UTC

Copy of official data

Hurricane Tammy Discussion Number  24
NWS National Hurricane Center Miami FL       AL202023
500 AM AST Tue Oct 24 2023

Tammy's satellite depiction has improved slightly compared to the 
sheared convective pattern from yesterday evening. The latest 
infrared satellite imagery depicts convective bursts are once again 
wrapping around the southern portion of the system. Earlier 
microwave imagery showed a well organized low-to mid-level 
circulation. The most recent TAFB Dvorak satellite estimate held 
steady at T4.0/65kt, which supports maintaining an initial intensity 
of 65 kt for this advisory.

The hurricane is currently moving northeastward, and should 
continue this motion for the next day or two. A mid-latitude trough 
approaching the system from the northwest will cause Tammy to begin 
to move more northward during the middle of the forecast period. It 
is after this point, the model guidance becomes increasingly 
divergent. Models are split on whether another mid-latitude trough 
will cause the system to accelerate east to northeastward, or have 
Tammy not being picked up by this trough and move the system 
westward to southwestward under a building mid-level ridge. The GFS 
has trended towards the west-southwest track scenario, closer to 
the ECMWF. Therefore, the NHC forecast track, which already favored 
the ECMWF solution, remains similar to the previous advisory and is 
close to a blend of GFS and ECMWF.

There is considerably better agreement among most of the 
intensity guidance, which indicates slight strengthening is possible 
during the next day or two, as Tammy interacts with an upper-level 
trough.  After 48 hours the system should begin to weaken and  
start to transition into a post-tropical cyclone. The latest model 
simulated satellite imagery depicts that this process is expected 
to be complete in about 60 h, though Tammy will likely continue to 
produce gale-to storm-force winds for several days even after this 
transition occurs.


INIT  24/0900Z 23.7N  62.8W   65 KT  75 MPH
12H  24/1800Z 24.5N  61.8W   70 KT  80 MPH
24H  25/0600Z 25.9N  60.3W   75 KT  85 MPH
36H  25/1800Z 27.9N  59.0W   75 KT  85 MPH
48H  26/0600Z 29.5N  58.9W   70 KT  80 MPH
60H  26/1800Z 31.0N  59.7W   60 KT  70 MPH...POST-TROP/EXTRATROP
72H  27/0600Z 31.7N  60.9W   55 KT  65 MPH...POST-TROP/EXTRATROP
96H  28/0600Z 32.4N  62.8W   50 KT  60 MPH...POST-TROP/EXTRATROP
120H  29/0600Z 32.8N  64.8W   45 KT  50 MPH...POST-TROP/EXTRATROP

Forecaster Kelly