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Tropical Storm Danielle Forecast Discussion


000
WTNT45 KNHC 030852
TCDAT5

Tropical Storm Danielle Discussion Number   9
NWS National Hurricane Center Miami FL       AL052022
900 AM GMT Sat Sep 03 2022

Convection associated with Danielle has continued to decrease this 
morning, with a corresponding decrease in satellite intensity 
estimates.  Based on this decrease, it is estimated that Danielle 
has weakened to a tropical storm with an initial intensity of 60 kt. 
While it is not known why the storm has weakened, one possibility 
is that the slow motion has allowed the cyclone to upwell cold 
water underneath it. 

Danielle is essentially stationary with a 12-h motion of 270/1 kt.  
The cyclone is still caught south of a blocking high over the North 
Atlantic.  This pattern is expected to hold firm for a couple of 
days, with the system forecast to drift westward and then drift 
northward.  After 48-60 h, the block will weaken and allow the 
southern edge of the mid-latitude westerlies to steer Danielle 
generally northeastward at a faster forward speed.  There are no 
significant changes to the forecast track for the first 48-60 h.  
After that, the forecast has been nudged eastward due to a shift 
in the guidance envelope.

The intensity guidance is still calling for Danielle to strengthen 
for 72 h or so.  Given the possibility of upwelling and the 
forecast continued slow motion, the guidance might be a bit 
optimistic on that.  The new intensity forecast calls for little 
change in strength for 12 h or so, followed by slow strengthening 
on the premise that the storm will move over somewhat warmer water. 
After 72 h, the storm is likely to interact with an upper-level 
trough, which could help maintain the intensity even as Danielle 
moves toward much colder water in the North Atlantic.  This trough 
will also start extratropical transition, although this will 
likely not be complete by 120 h.


FORECAST POSITIONS AND MAX WINDS

INIT  03/0900Z 38.0N  43.8W   60 KT  70 MPH
 12H  03/1800Z 38.0N  44.1W   60 KT  70 MPH
 24H  04/0600Z 38.1N  44.7W   65 KT  75 MPH
 36H  04/1800Z 38.5N  44.7W   70 KT  80 MPH
 48H  05/0600Z 39.1N  44.3W   75 KT  85 MPH
 60H  05/1800Z 39.9N  43.6W   75 KT  85 MPH
 72H  06/0600Z 40.7N  42.6W   75 KT  85 MPH
 96H  07/0600Z 43.0N  39.5W   70 KT  80 MPH
120H  08/0600Z 46.5N  35.5W   65 KT  75 MPH

$$
Forecaster Beven



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