[Tropical] Tropical Cyclone Discussion

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WTNT41 KNHC 222058
TCDAT1

Tropical Storm Ophelia Discussion Number   6
NWS National Hurricane Center Miami FL       AL162023
500 PM EDT Fri Sep 22 2023

The structure of the cyclone has undergone some noteworthy changes
today. GOES-16 1-min visible imagery, along with data from the Air
Force Hurricane Hunters and earlier scatterometer data, indicate
that the center of the system has become better defined and is no
longer attached to fronts. The satellite presentation has evolved as
well, with the center becoming tucked under an area of deep
convection this afternoon. The radius of maximum wind has contracted
to around 50 to 60 n mi, further supporting its designation as
Tropical Storm Ophelia earlier this afternoon. Aircraft data reveal
that Ophelia has also strengthened, with the minimum pressure down
to 986 mb and reduced flight-level and SFMR winds that support an
initial intensity of 60 kt.

Ophelia is moving north-northwestward (345/11 kt) within the flow
between an upper-level trough over the southeastern U.S. and a ridge
over the western Atlantic. This general motion should continue
through Saturday while the center of Ophelia approaches North
Carolina and moves inland within the warning area. Thereafter, a
slight decrease in forward speed and a turn toward the north and
north-northeast is forecast through the weekend. There was a slight
westward shift in the near-term track guidance, and the updated NHC
forecast has been nudged in that direction toward the latest
multi-model consensus aids.

The intensity forecast is more challenging given the unexpected
strengthening trend observed today. Most of the intensity guidance
shows little change in strength before landfall, although the global
models show additional deepening of the low. However, some
additional strengthening cannot be ruled out as Ophelia traverses
the warm waters of the Gulf Stream on its approach to eastern North
Carolina. While this does not seem like the most likely outcome and
is not explicitly forecast, the increased risk warrants the issuance
of a Hurricane Watch for a portion of the North Carolina coast from
north of Surf City to Ocracoke Inlet. After landfall, the system is
expected to quickly weaken due to the combination of land
interaction, drier air, and strong upper-level winds. Ophelia is
likely to become extratropical again in 36-48 h, with dissipation by
72 h as it becomes absorbed by a frontal boundary over the
mid-Atlantic region.


Key Messages:

1. Tropical storm conditions are expected along portions of the
southeastern and mid-Atlantic U.S. coasts within the Tropical Storm
Warning area today into Saturday night. Hurricane conditions are
possible within the Hurricane Watch area early Saturday.

2. There is a danger of life-threatening storm surge inundation
over portions of eastern North Carolina and southeastern Virginia,
including Pamlico and Albemarle Sounds, the Neuse and Pamlico
Rivers, the lower James River, and the lower Chesapeake Bay, where
Storm Surge Warnings are in place.  Residents in these areas should
follow advice given by local officials.

3. Heavy rainfall from this system could produce locally
considerable flash, and urban flooding impacts across portions of
the Mid-Atlantic states from North Carolina to New Jersey through
Sunday.

4. Swells generated by this system will affect much of the U.S.
east coast through the weekend, likely causing life-threatening
surf and rip currents.


FORECAST POSITIONS AND MAX WINDS

INIT  22/2100Z 32.9N  76.3W   60 KT  70 MPH
 12H  23/0600Z 34.4N  76.8W   60 KT  70 MPH
 24H  23/1800Z 36.1N  77.2W   45 KT  50 MPH...INLAND
 36H  24/0600Z 37.6N  77.2W   30 KT  35 MPH...POST-TROP/EXTRATROP
 48H  24/1800Z 38.9N  76.6W   25 KT  30 MPH...POST-TROP/EXTRATROP
 60H  25/0600Z 39.9N  76.1W   25 KT  30 MPH...POST-TROP/EXTRATROP
 72H  25/1800Z...DISSIPATED

$$
Forecaster Reinhart
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