Hurricane Franklin Forecast Discussion Number 40

By | August 30, 2023

WTNT43 KNHC 301446

Hurricane Franklin Discussion Number  40
NWS National Hurricane Center Miami FL       AL082023
1100 AM AST Wed Aug 30 2023

The large eye of Franklin has become a bit ragged in recent
satellite images. Upper-level outflow from Hurricane Idalia
continues to impinge on the western side of Franklin's circulation,
and recent SSMIS microwave data show a thinner ring of inner core
convection on the western side of the eye, though the eyewall
remains closed. The overall satellite presentation has degraded some
since yesterday, and this is reflected in the latest objective and
subjective satellite estimates. The initial intensity is lowered
slightly to 90 kt, based on consensus T5.0/90 kt Dvorak estimates
from SAB and TAFB and UW-CIMSS ADT and AiDT estimates around 85-90
kt. Radar data from Bermuda reveal an outer band of the hurricane is
passing near the island, and tropical storm conditions are expected
to spread over the area within the next few hours.

The flow between a deep-layer trough over the eastern United States
and Canada and a high pressure ridge over the central Atlantic is
steering Franklin northeastward (50/11 kt). The aforementioned
trough is forecast to move eastward during the next couple of days,
and the flow ahead of this feature should cause Franklin to move
slightly faster toward the east-northeast. Little change was made to
this portion of the forecast. It is still unclear whether or not
Franklin will become completely captured by the trough, which
introduces greater uncertainty in the days 3-5 track forecast. The
GFS favors a faster northeastward motion with greater trough
interaction, while the ECMWF and UKMET keep Franklin on a slower
eastward track before it is steered deeper into the mid-latitudes.
The updated NHC forecast follows the consensus trends and is again
slower than the previous prediction beyond 72 h. Franklin is
forecast to become extratropical by 96 h, although this timing
largely depends on the extent of trough interaction.

Increasing northwesterly shear is expected over Franklin during the
next couple of days. This should induce at least gradual weakening
in the near term, though the tropical-storm-force wind field is
likely to expand as the system accelerates and gains latitude. The
updated track forecast brings Franklin over sub-26C waters in
about 72 h, with extratropical transition forecast to occur by 96
h. Note that this timing largely depends on the extent of trough
interaction that occurs in the coming days, so future adjustments
could be necessary.


1. Tropical storm conditions are expected on Bermuda today while
Franklin makes 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 couple of days.


INIT  30/1500Z 33.6N  67.1W   90 KT 105 MPH
 12H  31/0000Z 34.4N  65.2W   85 KT 100 MPH
 24H  31/1200Z 35.2N  62.2W   80 KT  90 MPH
 36H  01/0000Z 36.1N  58.9W   75 KT  85 MPH
 48H  01/1200Z 37.2N  55.3W   70 KT  80 MPH
 60H  02/0000Z 38.4N  52.0W   65 KT  75 MPH
 72H  02/1200Z 40.1N  49.0W   60 KT  70 MPH
 96H  03/1200Z 44.5N  44.0W   50 KT  60 MPH...POST-TROP/EXTRATROP
120H  04/1200Z 49.1N  40.0W   45 KT  50 MPH...POST-TROP/EXTRATROP

Forecaster Reinhart

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