[Tropical] Tropical Cyclone Discussion

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WTNT45 KNHC 081438
TCDAT5

Post-Tropical Cyclone Danielle Discussion Number  30
NWS National Hurricane Center Miami FL       AL052022
300 PM GMT Thu Sep 08 2022

Satellite imagery this afternoon has shown Danielle develop a clear
comma-shaped cloud shield, a hallmark of an extratropical cyclone.
In addition, an ASCAT-B pass near 12Z showed a wind shift,
indicative of a front, that extended from the center of the cyclone
northeastward. Based on these data, Danielle has been classified as
post-tropical and this is the last NHC advisory. Peak winds in the
ASCAT pass were just above 50 kt, so the intensity of Danielle was
lowered slightly to 55 kt. It is worth noting that the peak winds
are generally not representative of the impacts associated with
extratropical cyclones and gale- to storm-force winds extend well
from the center of Danielle.

Danielle has begun its long-awaited counterclockwise loop, which
should take another 36 to 48 h to complete. After that, the
post-tropical cyclone is forecast to move initially southeastward,
then eastward as it is caught within the flow of a broader
mid-latitude trough moving eastward over the northeastern Atlantic.
The track forecast for the post-tropical cyclone is based heavily on
the multi-model consensus TVCN. All guidance indicates the cyclone
will gradually weaken, both in terms of maximum winds and size
through the end of the forecast period.

Danielle continues to produce a large area of very rough seas over
the central-north Atlantic. More information about the
post-tropical cyclone can be found in High Seas Forecasts issued by
the UKMET office under WMO header FQNT21 EGRR and on the web at
metoffice.gov.uk/weather/specialist-forecasts/coast-and-sea/high-
seas-forecast. Information can also be found in Meteo France's High
Seas Forecast at weather.gmdss.org/II.html.


FORECAST POSITIONS AND MAX WINDS

INIT  08/1500Z 47.9N  31.0W   55 KT  65 MPH...POST-TROP/EXTRATROP
 12H  09/0000Z 49.5N  31.2W   55 KT  65 MPH...POST-TROP/EXTRATROP
 24H  09/1200Z 49.9N  33.1W   50 KT  60 MPH...POST-TROP/EXTRATROP
 36H  10/0000Z 48.3N  33.5W   45 KT  50 MPH...POST-TROP/EXTRATROP
 48H  10/1200Z 45.2N  29.1W   40 KT  45 MPH...POST-TROP/EXTRATROP
 60H  11/0000Z 43.4N  23.8W   40 KT  45 MPH...POST-TROP/EXTRATROP
 72H  11/1200Z 41.5N  19.0W   35 KT  40 MPH...POST-TROP/EXTRATROP
 96H  12/1200Z 41.0N  13.0W   35 KT  40 MPH...POST-TROP/EXTRATROP
120H  13/1200Z 43.0N   9.4W   30 KT  35 MPH...POST-TROP/EXTRATROP

$$
Forecaster D. Zelinsky
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