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Hurricane Franklin Discussion Number  39
NWS National Hurricane Center Miami FL       AL082023
500 AM AST Wed Aug 30 2023
 
Franklin has a large eye this morning since completing its eyewall
replacement cycle yesterday. The estimated diameter from satellite
data is about 50 n mi. With that said, there are some subtle signs
that vertical wind shear over the system has begun to increase.  The
hurricane's outflow has become restricted in the western side of the
storm, related to the outflow of Idalia spreading quickly towards
it. Intensity estimates have been gradually decreasing, and the
initial intensity was lowered to 95 kt this advisory. This intensity
lies roughly in between the higher TAFB and lower SAB subjective
estimates, and is very close to the most recent ADT and D-MINT
estimates provided by UW-CIMSS.
 
Franklin appears to be accelerating ever so slightly to the
northeast, with the motion of its large eye estimated at 040/11 kt.
This motion is expected to continue today with a turn to the
east-northeast in about 24-36 h. However, once again the guidance
this cycle has trended much slower compared to the previous
one. The ECMWF, which had been on the slow and south end of the
guidance envelope for days now, related to it missing the
mid-latitude trough capture, is no longer alone, with the latest GFS
forecast substantially slower and also missing an initial trough
capture. The track forecast has thus been slowed down again from the
prior cycle, but since most of this track adjustment was in the
along- and not across-track direction, it actually lies pretty much
on top of the prior NHC track, just slower. This current forecast
may need to be adjusted further in subsequent cycles, as suggested
by the TVCA and HCCA consensus aids. Even though the center of
Franklin is still forecast to pass to the northwest of Bermuda later
today, the large area of tropical-storm-force winds associated with
the hurricane to its southeast are expected to extend near or over
the island, where a tropical storm warning remains in place.
 
Intensity-wise, Franklin should gradually weaken early on, while
shear remains fairly low, but then more quickly as northwesterly
shear increases to between 20-30 kt from 24-48 h. Based on the
latest forecast track, it may take a bit longer for Franklin to
become an extratropical cyclone, and this is now delayed to day 4 in
the latest NHC intensity forecast. This intensity forecast is in
best agreement with the HCCA consensus aid.
 
 
KEY MESSAGES:
 
1. Tropical storm conditions are expected on Bermuda this morning,
when Franklin is forecast to make its closest approach to the
island.
 
2. Life-threatening surf and rip currents are occurring along the
east coast of the United States. These conditions are expected to
continue during the next several days.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  30/0900Z 33.0N  68.2W   95 KT 110 MPH
 12H  30/1800Z 34.0N  66.6W   95 KT 110 MPH
 24H  31/0600Z 35.0N  63.7W   90 KT 105 MPH
 36H  31/1800Z 35.8N  60.6W   80 KT  90 MPH
 48H  01/0600Z 37.0N  57.0W   70 KT  80 MPH
 60H  01/1800Z 38.0N  53.5W   65 KT  75 MPH
 72H  02/0600Z 40.0N  49.5W   60 KT  70 MPH
 96H  03/0600Z 44.1N  44.0W   55 KT  65 MPH...POST-TROP/EXTRATROP
120H  04/0600Z 49.0N  43.0W   50 KT  60 MPH...POST-TROP/EXTRATROP
 
$$
Forecaster Papin
 
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