[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT43 KNHC 281459
TCDAT3

Hurricane Franklin Discussion Number  32
NWS National Hurricane Center Miami FL       AL082023
1100 AM EDT Mon Aug 28 2023

Visible, infrared and microwave imagery depict a strengthening major
hurricane with a well-defined eye, a thick eyewall, and very cold
cloud tops. This was further supported by data from the Air Force
Reserve Hurricane Hunters, who have been investigating the storm
this morning. Minimum pressure has decreased from the previous
advisory based on a dropsonde measuring a pressure of 937 mb around
12 UTC. Flight-level, SFMR winds and dropsondes in the eyewall
indicate maximum sustained winds have increased to 125 kt.
Subjective and object satellite estimates also have drastically
increased with this advisory. Given these data, the initial
intensity is raised to 125 kt for this advisory, and Franklin has
rapidly intensified into a Category 4 major hurricane.

The hurricane continues to make a gradual turn northward, with the
latest motion estimate northward at 350/8 kt. A northward then
northeastward motion is forecast during the next 48 hours as
Franklin rounds the western edge of the subtropical ridge. After 48
hours, a deep trough is expected to move off the U.S. northeast
coast and Canada, and has Franklin becoming captured in the
southwesterly flow, with an increase in forward motion to the
northeast. There is better agreement in cross-track guidance
compared to the previous few advisories. However, there is still a
slight difference in the along track guidance with the GFS being
faster, and the ECMWF a little slower. The latest NHC track forecast
is similar to the previous forecast, with only a minor nudge to the
north.

Some additional intensification is possible today, as Franklin
remains in a low shear environment and is over warm sea-surface
temperatures. The latest intensity forecast peaks Franklin as a
strong Category 4 major hurricane. However, inner core changes, such
as eyewall replacement cycles, could occur at any time, making the
peak intensity and short-term forecast a little more challenging.
Some gradual weakening is forecast in about a day or so when models
forecast a slight increase in northwesterly shear. Toward the end of
the forecast period, further weakening is expected as Franklin
encounters increased vertical wind shear and moves over cooler SSTs.
The latest forecast shows the storm becoming a extratropical cyclone
in 120 h, though this could occur sooner.

KEY MESSAGES:

1.Tropical storm conditions are possible on Bermuda beginning
Wednesday morning, when Franklin is forecast to make its closest
approach to the island.

2. Life-threatening surf and rip currents are occurring along the
coast of the southeast United States. These conditions are
expected to spread northward along the remainder of the U.S.
east coast, Atlantic Canada, and Bermuda during the next couple of
days.


FORECAST POSITIONS AND MAX WINDS

INIT  28/1500Z 27.8N  71.0W  125 KT 145 MPH
 12H  29/0000Z 29.0N  71.2W  135 KT 155 MPH
 24H  29/1200Z 30.7N  70.8W  130 KT 150 MPH
 36H  30/0000Z 32.5N  69.6W  120 KT 140 MPH
 48H  30/1200Z 34.5N  67.4W  110 KT 125 MPH
 60H  31/0000Z 36.3N  64.1W  100 KT 115 MPH
 72H  31/1200Z 38.7N  59.9W   90 KT 105 MPH
 96H  01/1200Z 44.5N  49.7W   75 KT  85 MPH
120H  02/1200Z 51.8N  39.8W   65 KT  75 MPH...POST-TROP/EXTRATROP

$$
Forecaster Kelly/Brown
This weather bulletin was brought to you by:
www.nashvilleweather.net