[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT43 KNHC 310842
TCDAT3

Hurricane Franklin Discussion Number  43
NWS National Hurricane Center Miami FL       AL082023
500 AM AST Thu Aug 31 2023

Franklin continues to slowly succumb to the increasingly
unfavorable conditions the large hurricane is embedded in. The large
eye that had been evident over the last day or so is no longer
observed on infrared satellite imagery, likely due to 25-30 kt of
northerly shear affecting the convective structure which now favors
the southern side of the storm. This observation is also consistent
with the radar reflectivity returns from the Bermuda radar. With
that said, both the subjective and objective intensity estimates
this morning still support an intensity in the 85-90 kt range. Thus
Franklin's intensity will remain 85 kt this advisory, though this
may be generous.

Franklin continues to move to the east-northeast this morning at an
estimated 070/12 kt. As previously discussed, the hurricane is being
steered by the flow between a subtropical ridge to its southeast and
a trough now ejecting eastward out of the northeastern U.S. After
days of large track spread, the guidance this cycle is in better
agreement this morning, showing a continued east-northeast or
northeastward motion with gradual acceleration. The latest NHC
track forecast is not that much changed from the prior one, though
with a bit more acceleration towards the end of the forecast
period, trending towards the TVCN and HCCA consensus aids.

With continued northerly shear expected to persist another 24 hours,
Franklin should continue to weaken in the short-term. There may be a
brief period between 24-48 h where the shear temporarily decreases
as the hurricane becomes positioned in the right entrance region of
a jet streak as it interacts with a mid-latitude trough. This is why
the intensity forecast shows the weakening trend briefly pausing in
36-48 h. However, this baroclinic forcing will also likely hasten
its transition into an extratropical cyclone, with the latest
forecast now showing this being completed by 60 h, consistent with
simulated-IR imagery from the GFS and ECMWF at that time.

Now that Franklin is moving further away from Bermuda, the
Meteorological Service of Bermuda has discontinued the Tropical
Storm Warning for the island.


KEY MESSAGES:

1. Life-threatening surf and rip currents are occurring along the
east coast of the United States and Bermuda. These conditions are
expected to continue during the next day or two.


FORECAST POSITIONS AND MAX WINDS

INIT  31/0900Z 34.9N  63.2W   85 KT 100 MPH
 12H  31/1800Z 35.8N  60.9W   75 KT  85 MPH
 24H  01/0600Z 37.2N  57.6W   70 KT  80 MPH
 36H  01/1800Z 38.7N  53.8W   65 KT  75 MPH
 48H  02/0600Z 40.8N  49.6W   65 KT  75 MPH
 60H  02/1800Z 43.3N  45.2W   60 KT  70 MPH...POST-TROP/EXTRATROP
 72H  03/0600Z 45.5N  40.0W   60 KT  70 MPH...POST-TROP/EXTRATROP
 96H  04/0600Z 47.5N  34.9W   50 KT  60 MPH...POST-TROP/EXTRATROP
120H  05/0600Z 50.1N  30.0W   50 KT  60 MPH...POST-TROP/EXTRATROP

$$
Forecaster Papin
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