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Hurricane Danielle Discussion Number  19
NWS National Hurricane Center Miami FL       AL052022
900 PM GMT Mon Sep 05 2022
 
After a large degradation in Danielle's appearance earlier this 
afternoon, the hurricane appears to be holding more steady now with 
colder cloud tops wrapping further around its center than were noted 
6 hours ago. Dvorak-based intensity estimates still support an 
intensity near 75 kt. The hurricane has moved a little 
faster north-northeastward than anticipated during the last few 
hours, with an initial motion estimate of 030/kt.

A significant adjustment was made to the track forecast at days 4 
and 5, at which time Danielle is forecast to be an extratropical 
cyclone. For the first 3 days of the forecast period, Danielle is 
still forecast to move generally northeastward in the mid-latitude 
flow. After that, it looks like Danielle could occlude and "cut-off" 
from that steering flow, which may cause it to turn abruptly 
northward and then southeastward at days 4-5. This scenario has been 
consistently forecast for a few model cycles of the GFS and other 
global models, so large changes were made to the NHC track forecast 
to bring it closer to the model consensus. Other than a slight 
adjustment northward and faster, no important changes were made to 
the NHC track forecast for the first 72 h. Given the uncertainty at 
the extended portion of the forecast, it should be noted that 
confidence in the track forecast is substantially higher for the 
first 72 h than the later hours. It is worth noting that Danielle 
is forecast to be post-tropical by 96 h, so users should not focus 
on the exact track of the cyclone since the largest impacts could 
be felt far from its center.

Danielle should slowly weaken during the next few days as it moves 
over marginally cool water, but most dynamical guidance suggests it 
will still maintain its tropical characteristics for at least a 
couple more days. Around day 3, SHIPS diagnostics indicate the 
waters below the cyclone will be less than 20 deg C, and it will 
likely complete its extratropical transition around that time. 
The NHC forecast follows accordingly, but it should be noted this 
suggests a slightly later completion to the transition than 
previously forecast. The NHC intensity forecast is near the middle 
of the relatively low-spread intensity guidance envelope.

 
FORECAST POSITIONS AND MAX WINDS
 
INIT  05/2100Z 41.1N  43.2W   75 KT  85 MPH
 12H  06/0600Z 41.9N  42.2W   70 KT  80 MPH
 24H  06/1800Z 42.6N  40.4W   70 KT  80 MPH
 36H  07/0600Z 43.4N  38.1W   65 KT  75 MPH
 48H  07/1800Z 44.6N  35.3W   65 KT  75 MPH
 60H  08/0600Z 46.2N  32.4W   60 KT  70 MPH
 72H  08/1800Z 48.2N  29.7W   55 KT  65 MPH...POST-TROP/EXTRATROP
 96H  09/1800Z 50.0N  29.0W   50 KT  60 MPH...POST-TROP/EXTRATROP
120H  10/1800Z 47.5N  25.5W   45 KT  50 MPH...POST-TROP/EXTRATROP
 
$$
Forecaster D. Zelinsky
 
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