Tropical Storm Hermine Forecast Discussion Number 2

By | September 23, 2022

000
WTNT45 KNHC 232033
TCDAT5

Tropical Storm Hermine Discussion Number   2
NWS National Hurricane Center Miami FL       AL102022
800 PM CVT Fri Sep 23 2022

A large burst of convection has been occurring in the northeastern 
quadrant of the system today, with other shallow banding features 
to the southeast of the center.  Overall, the cyclone looks better 
than this morning and resembles a sheared tropical storm, which is 
confirmed by the Dvorak pattern-T of 2.5 (35 kt) from SAB.  Thus 
the wind speed is set to 35 kt, making this system the 8th tropical 
storm of the season.  

Hermine continues moving north-northwestward, now about 10 kt.  
Global model guidance is consistent on the cyclone moving northward 
through a large break in the eastern Atlantic subtropical ridge.  
The most significant change is that the storm could hold together a 
little longer in a marginal environment, which causes the forecast 
track to tug a little to the northeast before a weakening Hermine 
would move westward as a shallow system beneath the low-level ridge. 
The new forecast is shifted to the north and east, but is not as 
far northeast as the GFS or HWRF models.  

The storm has about a day over lukewarm water before all the models 
hit the system with strong upper-level southwesterly winds.  There 
is a minority solution in the models where the upper-trough cuts 
off, somewhat lessening the shear, but for now the NHC forecast 
stays closer to the faster dissipation scenario. Either way, Hermine 
should dissipate early next week due to very strong shear and dry 
air entrainment cutting off any deep convection. The official 
intensity forecast is a little higher than the last one, near the 
various consensus aids.

Note that 2 to 4 inches of rain, with isolated totals of 6 inches, 
are possible over the Canary Islands through this weekend due to a 
combination of a mid-latitude trough and moisture from Hermine.  
This rainfall could cause some flash flooding in areas of higher 
terrain.


FORECAST POSITIONS AND MAX WINDS

INIT  23/2100Z 18.6N  20.5W   35 KT  40 MPH
 12H  24/0600Z 19.8N  21.0W   40 KT  45 MPH
 24H  24/1800Z 21.6N  21.2W   35 KT  40 MPH
 36H  25/0600Z 23.1N  21.0W   30 KT  35 MPH
 48H  25/1800Z 24.1N  20.8W   30 KT  35 MPH
 60H  26/0600Z 24.5N  21.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
 72H  26/1800Z 24.8N  21.7W   25 KT  30 MPH...POST-TROP/REMNT LOW
 96H  27/1800Z 26.5N  25.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  28/1800Z...DISSIPATED

$$
Forecaster Blake

Leave a Reply