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WTNT45 KNHC 240231

TCDAT5

 

Hurricane Tammy Discussion Number  23

NWS National Hurricane Center Miami FL       AL202023

1100 PM AST Mon Oct 23 2023

 

Microwave data from multiple polar-orbiting satellites received

during the last few hours indicate that Tammy still has a

well-organized low- to mid-level circulation, even as its deep

convection is getting sheared northward. The most recent TAFB Dvorak

classification was a 4.0/65 kt, which supports maintaining Tammy as

a hurricane.

 

While Tammy's future path remains unusually unclear, especially at

the 4-5 day range, very little change was made to the official track

forecast. The hurricane is currently moving north-northeastward, and

it should get steered northward starting in about 2 days as the

hurricane interacts with a mid-latitude trough approaching from the

northwest. The uncertainty in the forecast increases considerably

after that point as Tammy will likely reach a col point in the

steering flow over the western Atlantic. Many models and ensemble

members indicate another mid-latitude trough will cause the cyclone

to begin to accelerate eastward or northeastward. However, it

appears equally likely that Tammy will then turn westward or

southwestward under the influence of a mid-level ridge that

should build behind the second trough. With no clear reason to

support one solution or another, the NHC track forecast is unchanged

for now. It remains near the consensus of the GFS and ECMWF through

about 72 h, and then favors the ECMWF and ECENS mean after that.

 

Conversely, the intensity forecast appears to be more 

straightforward. Most of the intensity guidance indicates that 

slight strengthening is possible during the next day or so, as Tammy 

gets a convective boost while interacting with an upper-level 

trough. However, after about 48 h, it should begin to weaken and 

transition to a post-tropical cyclone. Based on simulated satellite 

imagery, this process is expected to complete in about 72 h, though 

Tammy will likely continue to produce gale- to storm-force winds for 

several days thereafter.

 

 

FORECAST POSITIONS AND MAX WINDS

 

INIT  24/0300Z 22.9N  63.1W   65 KT  75 MPH

 12H  24/1200Z 23.6N  62.2W   70 KT  80 MPH

 24H  25/0000Z 24.7N  60.8W   75 KT  85 MPH

 36H  25/1200Z 26.5N  59.2W   75 KT  85 MPH

 48H  26/0000Z 28.5N  58.3W   75 KT  85 MPH

 60H  26/1200Z 30.0N  58.6W   65 KT  75 MPH

 72H  27/0000Z 31.1N  59.7W   55 KT  65 MPH...POST-TROP/EXTRATROP

 96H  28/0000Z 32.0N  62.0W   50 KT  60 MPH...POST-TROP/EXTRATROP

120H  29/0000Z 32.5N  64.0W   45 KT  50 MPH...POST-TROP/EXTRATROP

 

$$

Forecaster D. Zelinsky