[Tropical] Tropical Cyclone Discussion

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WTNT45 KNHC 051436
TCDAT5

Hurricane Danielle Discussion Number  18
NWS National Hurricane Center Miami FL       AL052022
300 PM GMT Mon Sep 05 2022

Danielle's satellite presentation has degraded since this morning.
Cloud tops have warmed and its eye-like feature is not very well
defined anymore. The hurricane has reached a relatively cool part
of the Gulf Stream, which could be a main factor in its apparent
weakening. Satellite intensity estimates from TAFB, SAB, and
UW-CIMSS (both ADT and SATCON) have decreased, so the initial
intensity has been lowered conservatively to 75 kt, which is at the
high end of the estimates.

The lower initial intensity has also contributed to a lower
intensity forecast, but the idea is generally the same. Danielle
should slowly weaken during the next few days as it continues
northeastward over marginally warm waters. The exact timing of the
cyclone's upcoming extratropical transition is still uncertain, but
most models indicate it should complete the process on or by
Thursday. Further weakening is expected by all global models after
that time, which continues to be reflected in the NHC forecast.

Negligible change was made to the portion of the track forecast when
Danielle is expected to be a tropical cyclone. The hurricane is
forecast to move generally northeastward today and
east-northeastward through the middle of the week, steered by a
mid-latitude system approaching from the northwest. At the end of
the forecast period, most global models now suggest Danielle could
make a sharp northward turn as an extratropical cyclone. This would
represent a significant change to the day 4-5 forecast, so I would
prefer to see if that stays consistent for another cycle of model
runs before making too big of a change. The official track forecast
is therefore very close to the multi-model consensus through 72 h,
but is notably to the south and east of the consensus at days 4 and
5, That said, it has still been adjusted to the northwest of the
previous forecast at those times.


FORECAST POSITIONS AND MAX WINDS

INIT  05/1500Z 40.2N  43.9W   75 KT  85 MPH
 12H  06/0000Z 41.1N  43.0W   70 KT  80 MPH
 24H  06/1200Z 41.9N  41.5W   70 KT  80 MPH
 36H  07/0000Z 42.5N  39.4W   65 KT  75 MPH
 48H  07/1200Z 43.4N  36.7W   65 KT  75 MPH
 60H  08/0000Z 44.7N  33.9W   60 KT  70 MPH
 72H  08/1200Z 46.3N  30.9W   55 KT  65 MPH...POST-TROP/EXTRATROP
 96H  09/1200Z 49.5N  25.0W   50 KT  60 MPH...POST-TROP/EXTRATROP
120H  10/1200Z 52.0N  21.5W   45 KT  50 MPH...POST-TROP/EXTRATROP

$$
Forecaster D. Zelinsky
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