[Tropical] Tropical Cyclone Discussion

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WTNT43 KNHC 311456
TCDAT3

Hurricane Franklin Discussion Number  44
NWS National Hurricane Center Miami FL       AL082023
1100 AM AST Thu Aug 31 2023

Satellite imagery indicates that Franklin continues to battle
strong northerly shear associated with the outflow from Idalia.
Recent microwave data confirm its inner core has eroded, with deep
convection confined to the southeastern portion of the circulation.
There is a large spread in the recent intensity estimates, with
higher objective estimates than the consensus T4.5/5.0 Dvorak
classifications from SAB and TAFB. Given this uncertainty, the
initial intensity is held at 85 kt for this advisory.

Some gradual weakening is forecast during the next couple of days
while Franklin contends with the negative impacts of deep-layer
shear. However, the cyclone is expected to remain at or near
hurricane strength while increased baroclinic forcing and
interaction with the upper trough support its extratropical
transition. The GFS and ECMWF show fronts extending into Franklin's
circulation by 48 h, likely signaling completion of this process.
Therefore, the NHC forecast shows Franklin becoming a powerful
extratropical cyclone in 48 h. Thereafter, further weakening is
forecast while the cyclone moves deeper into the mid-latitudes, in
agreement with the latest global guidance.

Franklin is moving east-northeastward (70/12 kt) within the flow
between a deep-layer trough moving off the coast of the northeastern
U.S. and eastern Canada and a subtropical ridge to the east. The
latest track guidance remains in very good agreement that Franklin
will accelerate toward the east-northeast or northeast during the
next couple of days. The NHC track forecast in the near term is
essentially an update of the previous one and remains close to the
TVCN and HCCA aids. Track model solutions diverge beyond day 3
regarding the track and speed of motion for the extratropical
cyclone over the northern Atlantic, and in general the latest NHC
forecast lies between the consensus aids and ensemble means.


FORECAST POSITIONS AND MAX WINDS

INIT  31/1500Z 35.1N  61.6W   85 KT 100 MPH
 12H  01/0000Z 36.3N  59.3W   75 KT  85 MPH
 24H  01/1200Z 37.8N  55.8W   70 KT  80 MPH
 36H  02/0000Z 39.7N  51.7W   70 KT  80 MPH
 48H  02/1200Z 42.0N  47.2W   65 KT  75 MPH...POST-TROP/EXTRATROP
 60H  03/0000Z 44.2N  43.1W   55 KT  65 MPH...POST-TROP/EXTRATROP
 72H  03/1200Z 45.9N  39.1W   50 KT  60 MPH...POST-TROP/EXTRATROP
 96H  04/1200Z 48.0N  33.0W   45 KT  50 MPH...POST-TROP/EXTRATROP
120H  05/1200Z 50.5N  28.0W   40 KT  45 MPH...POST-TROP/EXTRATROP

$$
Forecaster Reinhart
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