Atlantic Basin Tropical Cyclones

Tropical Storm Alex Forecast Discussion


737 
WTNT41 KNHC 052039
TCDAT1

Tropical Storm Alex Discussion Number  13
NWS National Hurricane Center Miami FL       AL012022
500 PM EDT Sun Jun 05 2022

Earlier this afternoon, an Air Force Reserve Hurricane Hunter 
aircraft reported reliable-looking SFMR winds of 50-55 kt near the 
center of Alex, and 700-mb flight-level winds of up to 77 kt in the 
southeastern quadrant.  The central pressure was near 991 mb. Based 
on these data, the initial intensity is set to 55 kt.  While Alex 
continues to generate a cluster of convection close to the center in 
the northeastern quadrant, overall the cyclone looks a little less 
tropical than it did this morning.  This is likely due to 
entrainment of upper-level cool/dry air from a trough just west of 
the cyclone.

Alex has likely peaked in intensity, as the system is moving toward
cooler water and the divergent outflow caused by the aforementioned 
upper-level trough is decreasing.  Steady weakening is forecast 
after 12 h, and Alex is now forecast to become extratropical by 36 
hr as it merges with a frontal system.  After that, most of the 
numerical weather prediction models forecast the system to decay 
quickly and weaken to a trough between 72-96 h, and the official 
forecast follows this scenario.  However, an alternative scenario 
comes from the UKMET and the HMON, which show the cyclone becoming  
a strong extratropical low that continues quickly northeastward 
into the northeastern Atlantic.

The initial motion is now 060/24 kt.  A general east-northeastward
motion is expected during the next 24 h or so, with the center of
Alex passing north of Bermuda on Monday.  After that, the majority
of the dynamical models forecast Alex to turn eastward and slow its
forward speed as it finishes extratropical transition and becomes a
shallow and elongated vortex, and the forecast track follows that
scenario instead of the UKMET/HMON scenario.  The new forecast
track is slightly faster than the previous track through 24 h, then
is a little slower than the previous track thereafter.  The new
forecast is in best agreement with the GFS model, and after 36 h it
lies to the south of the various consensus models.


KEY MESSAGES:

1. Alex is forecast to pass near or just north of Bermuda on Monday,
and tropical storm conditions are expected on the island late
tonight and Monday.


FORECAST POSITIONS AND MAX WINDS

INIT  05/2100Z 31.5N  71.5W   55 KT  65 MPH
 12H  06/0600Z 32.6N  68.0W   55 KT  65 MPH
 24H  06/1800Z 33.9N  63.2W   50 KT  60 MPH
 36H  07/0600Z 34.8N  58.6W   45 KT  50 MPH...POST-TROP/EXTRATROP
 48H  07/1800Z 35.0N  54.6W   40 KT  45 MPH...POST-TROP/EXTRATROP
 60H  08/0600Z 35.1N  51.3W   35 KT  40 MPH...POST-TROP/EXTRATROP
 72H  08/1800Z 35.7N  48.5W   30 KT  35 MPH...POST-TROP/EXTRATROP
 96H  09/1800Z...DISSIPATED

$$
Forecaster Beven




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