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WTNT45 KNHC 252051

TCDAT5

 

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.

 

 

FORECAST POSITIONS AND MAX WINDS

 

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