####018003145####
WTNT45 KNHC 250841

TCDAT5

 

Hurricane Tammy Discussion Number  28

NWS National Hurricane Center Miami FL       AL202023

500 AM AST Wed Oct 25 2023

 

Satellite data indicate Tammy has strengthened this morning. 

Proxy-vis and infrared imagery depict a ragged eye has developed 

with deep convection wrapping around the center. There has been no 

microwave imagery this morning, but earlier SSMI/S and GMI 

images showed a tight inner core. The subjective Dvorak final-T 

intensity estimates have increased this cycle with a T5.0 and T4.5 

from SAB and TAFB, respectively. Given the improved satellite 

imagery and using a blend of these estimates, the initial intensity 

is raised to 85 kt for this advisory.



Although vertical wind shear is analyzed to have increased over 

the hurricane, the system is strengthening beneath upper-level 

divergence associated with a deep-layer trough over the western 

Atlantic. Models suggest some additional strengthening is possible 

over the next 12 hours or so, which is reflected in the NHC 

intensity forecast. Tammy is then expected to merge with a cold 

front, which is currently analyzed by TAFB and OPC just northwest of 

the system. Tammy is expected to undergo an extratropical 

transition, with this transition forecast to be complete within 24 

hours. As this transition occurs Tammy's wind field will expand as 

it becomes a hurricane-force extratropical cyclone. Global models 

are in fairly good agreement that the cyclone will then weaken 

throughout the remainder of the forecast period. There is some 

potential it could shed its frontal structure this weekend, but for 

now the model-simulated satellite imagery does not show much 

increase in convection during that time.

 

Tammy is moving northeastward at an estimated motion of 45 degrees 

at 9 knots, within the flow between a deep-layer trough over the 

western Atlantic and a subtropical ridge over the central Atlantic. 

Tammy is expected to turn northward later today, then move slowly 

northwestward in 2-3 days within weaker steering currents. The 

long-range forecast remains uncertain, with not much run-to-run 

model consistency and ensemble solutions that move in opposite 

directions. Given the uncertainty, there is little change from the 

previous forecast at this time range, with the NHC forecast track 

showing the cyclone slowing and meandering through the end of the 

the period.

 

 

FORECAST POSITIONS AND MAX WINDS

 

INIT  25/0900Z 25.6N  60.2W   85 KT 100 MPH

 12H  25/1800Z 27.0N  59.4W   90 KT 105 MPH

 24H  26/0600Z 28.9N  59.3W   75 KT  85 MPH...POST-TROP/EXTRATROP

 36H  26/1800Z 30.0N  60.4W   65 KT  75 MPH...POST-TROP/EXTRATROP

 48H  27/0600Z 30.6N  61.6W   60 KT  70 MPH...POST-TROP/EXTRATROP

 60H  27/1800Z 31.0N  62.3W   55 KT  65 MPH...POST-TROP/EXTRATROP

 72H  28/0600Z 31.3N  62.9W   50 KT  60 MPH...POST-TROP/EXTRATROP

 96H  29/0600Z 31.2N  63.5W   45 KT  50 MPH...POST-TROP/EXTRATROP

120H  30/0600Z 31.0N  63.9W   40 KT  45 MPH...POST-TROP/EXTRATROP

 

$$

Forecaster Kelly