Official Discussion issued by the National Hurricane Center

Tammy (AL202023) DATA RELEASED: 10/25/2023 9:00:00 PM UTC

Copy of official data

Hurricane Tammy Discussion Number  30
NWS National Hurricane Center Miami FL       AL202023
500 PM AST Wed Oct 25 2023

Tammy is beginning to interact with a front to its north. The eye 
has lost some of its definition as the northern eyewall slowly 
erodes. Outflow is now limited to the southern and eastern portions 
of the circulation. Subjective and objective satellite intensity 
estimates have fallen since the last advisory. Final T-numbers from 
SAB and TAFB are both T4.5 and ADT is down to T4.2. Given the recent 
degradation in satellite appearance, the initial intensity has been 
lowered to 85 kt.

It appears that Tammy has moved out of the region with favorable 
upper-level dynamics. Strong upper-level winds and surrounding dry 
air are expected to steadily weaken the system through the forecast 
period. Model guidance shows that the hurricane should become 
entangled with the frontal feature to its north and transition into 
an extratropical cyclone within the next 24 hours. By 48 hours, the 
global models depict Tammy occluding and shedding its front. 
Therefore, the most recent NHC forecast shows the system as a 
post-tropical cyclone instead of extratropical beginning at day 2. 
There is a possibility that Tammy could regain tropical or 
subtropical status as the vortex meanders over sufficiently warm 
ocean waters during days 2 and 3.

Tammy is still moving northeastward, but model guidance insists that 
the hurricane will make a turn to the north shortly. This is 
followed by a northwestward turn with a slower forward speed by 
Thursday. By Friday, Tammy is expected to meander over the 
northwestern Atlantic in the light steering currents between two 
building ridges over the eastern Atlantic and southeastern United 
States. The official NHC track forecast shows Tammy slowly turning 
back to the east by the weekend. However, more model guidance is 
showing a faster turn to the east resulting in a large spread in the 
track guidance envelope. The current forecast is on the western edge 
of the track solutions and is closest to the GFS. Further 
adjustments may be needed if these trends continue.


INIT  25/2100Z 28.0N  57.9W   85 KT 100 MPH
12H  26/0600Z 29.5N  58.4W   80 KT  90 MPH
24H  26/1800Z 30.5N  59.4W   70 KT  80 MPH...POST-TROP/EXTRATROP
36H  27/0600Z 31.1N  60.4W   60 KT  70 MPH...POST-TROP/EXTRATROP
48H  27/1800Z 31.5N  61.1W   55 KT  65 MPH...POST-TROPICAL
60H  28/0600Z 31.8N  61.5W   50 KT  60 MPH...POST-TROPICAL
72H  28/1800Z 32.1N  61.7W   50 KT  60 MPH...POST-TROPICAL
96H  29/1800Z 32.5N  61.5W   45 KT  50 MPH...POST-TROPICAL
120H  30/1800Z 32.8N  61.0W   40 KT  45 MPH...POST-TROPICAL

Forecaster Bucci/R. Zelinsky