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Tropical Storm Alex Forecast Discussion


000
WTNT41 KNHC 050857
TCDAT1

Tropical Storm Alex Discussion Number  11
NWS National Hurricane Center Miami FL       AL012022
500 AM EDT Sun Jun 05 2022

After the previous advisory, data from the Air Force Reserve 
Hurricane Hunters and GOES-16 Proxy-Vis satellite imagery indicated 
that a well-defined center had formed in association with what is 
now Tropical Storm Alex. With that said, the satellite structure of 
the storm is hardly classical, with the coldest convective cloud 
tops all shunted east of the low-level center which is still 
occasionally reforming northeastward where the strongest convection 
is located. Earlier, the reconnaissance aircraft found 850-mb 
flight-level winds up to 72 kt in the southeast quadrant of the 
circulation. A nearby released dropsonde, however, suggested that 
these flight-level winds were not mixing down to the surface at the 
standard reduction factor, and the highest SFMR winds were only 
between 35-40 kt. Thus, the initial intensity was set to only 45 kt 
at 0600 UTC and that remains the intensity this advisory. Another 
reconnaissance aircraft will sample the storm later today. 

Alex's general motion continues off to the northeast at 065/19 kt. 
This motion, with some further acceleration, is expected 
during the next day or two as the system remains well embedded in 
the mid-latitude westerly flow off the eastern US coastline. The 
current track continues to indicate that Alex will make its closest 
approach to Bermuda Monday afternoon or evening while the cyclone's 
track gradually bends eastward. Thereafter, both the GFS and ECMWF 
suggest Alex's surface circulation will decouple from the dwindling 
convection and slow down as it becomes a shallow and stretched-out 
vortex. The new NHC track maintains the slowdown trend made from 
the previous advisory after 48 hours following this general shift 
in the consensus track aids.

Some additional short-term strengthening is possible over the next 
12 hours as long as Alex remains closely tied to the deep 
convection. This convection is being aided by strong upper-level 
difluent flow over the anomalously warm Gulf Stream. However, nearby 
dry air combined with more than 30 kt of vertical wind shear is 
forecast to disrupt this convective structure, and the global model 
guidance suggests the convection could separate from the low-level 
circulation after 24 hours. Thus, weakening is anticipated to start 
on Monday. Continuing the trend from the previous forecast cycle, 
the latest round of guidance suggests that Alex will complete 
extratropical transition sooner as its circulation loses fidelity in 
an increasingly baroclinic environment. The latest NHC forecast now 
indicates the cyclone becoming post-tropical by 48 hours with 
complete dissipation by 120 hours. However, the latest GFS and ECMWF 
suggest Alex's remnant circulation could open up into a trough even 
sooner than the current forecast.

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 on Monday.


FORECAST POSITIONS AND MAX WINDS

INIT  05/0900Z 29.1N  76.3W   45 KT  50 MPH
 12H  05/1800Z 30.5N  74.0W   50 KT  60 MPH
 24H  06/0600Z 32.0N  70.0W   50 KT  60 MPH
 36H  06/1800Z 33.2N  65.3W   45 KT  50 MPH
 48H  07/0600Z 34.0N  60.5W   40 KT  45 MPH...POST-TROP/EXTRATROP
 60H  07/1800Z 34.3N  56.4W   35 KT  40 MPH...POST-TROP/EXTRATROP
 72H  08/0600Z 34.2N  52.6W   30 KT  35 MPH...POST-TROP/EXTRATROP
 96H  09/0600Z 34.7N  49.0W   30 KT  35 MPH...POST-TROP/EXTRATROP
120H  10/0600Z...DISSIPATED

$$
Forecaster Papin/Blake



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