[Tropical] Tropical Cyclone Discussion

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WTNT45 KNHC 050841
TCDAT5

Hurricane Danielle Discussion Number  17
NWS National Hurricane Center Miami FL       AL052022
900 AM GMT Mon Sep 05 2022

There's been little change in Danielle's cloud pattern during the
past 6 hours, and a clear symmetric warm 13C banding eye feature
has persisted and has intermittently been closing off.  The
satellite intensity estimates haven't changed, and the initial
intensity is held at 80 kt for this advisory.

Little change in strength is forecast through today.  Afterward,
the cyclone should slowly weaken through the entire period as it
moves over cooler water while increasing southwesterly shear
disrupts the upper outflow pattern.  The CMC, UKMET, and the GFS
agree with Danielle to begin an extratropical transition around 36
hours and complete its change by 72 hours (Thursday).  This cyclone
transformation timeline is reflected in the NHC forecast, and the
predicted 5-day intensity closely follows the IVCN and HCCA aids.

The hurricane's initial motion is estimated to be 030 at 7 kt, a
little faster than previously noted.  Danielle should continue to
accelerate and move north-northeastward to northeastward through
early Tuesday in response to a mid-latitude baroclinic system
approaching from the northwest, out of the Canadian Maritimes.  By
Tuesday night, the cyclone should turn toward the east-northeast
within the mid-latitude westerly steering flow and continue in
this general motion for 60 hours.  A turn back toward the northeast
is forecast as an extratropical cyclone on Thursday.  It's
worth mentioning that earlier today, there was quite a bit of
uncertainty (global model cross-track spread) about Danielle's
trajectory beyond the mid-period.  The GFS and the UKMET predict
Danielle will turn back toward the northeast Wednesday in the
southwesterly peripheral flow of a larger baroclinic low
approaching the cyclone from the northwest Atlantic.  However, the
ECMWF 12 and 18z runs showed considerably less baroclinic low
influence while continuing toward the east-northeast, southwest of
the British Isles.  The latest 00z run, subsequently, has trended
more toward the GFS/UKMET solution, which has resulted in some
increase in track forecast confidence.  Accordingly, the NHC
forecast is again adjusted slightly north of the previous one to
align more with a consensus (TVCA) of the models mentioned above.


FORECAST POSITIONS AND MAX WINDS

INIT  05/0900Z 39.6N  44.4W   80 KT  90 MPH
 12H  05/1800Z 40.5N  43.6W   80 KT  90 MPH
 24H  06/0600Z 41.4N  42.4W   75 KT  85 MPH
 36H  06/1800Z 42.1N  40.6W   75 KT  85 MPH
 48H  07/0600Z 42.8N  38.3W   70 KT  80 MPH
 60H  07/1800Z 43.8N  35.6W   65 KT  75 MPH
 72H  08/0600Z 45.3N  32.5W   60 KT  70 MPH...POST-TROP/EXTRATROP
 96H  09/0600Z 48.2N  26.1W   55 KT  65 MPH...POST-TROP/EXTRATROP
120H  10/0600Z 50.8N  20.6W   50 KT  60 MPH...POST-TROP/EXTRATROP

$$
Forecaster Roberts
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