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Froude # Project at GSP. As a reminder: Fr = U/NH U is the wind speed orthogonal to the barrier N is the Brunt-Vaisala frequency H is the height of the barrier Fr is calculated each hour as a 850-950mb layer average
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Froude # Project at GSP • As a reminder: • Fr = U/NH • U is the wind speed orthogonal to the barrier • N is the Brunt-Vaisala frequency • H is the height of the barrier • Fr is calculated each hour as a 850-950mb layer average • We use 320 degrees as the wind direction that is orthogonal to the mountain barrier and assume a barrier height of 3500 feet • Calculated from the GFS, NAM, RUC, local WRF, and there is also a composite Fr group • So far this winter season, no high impact NWFS events until the recent storm
Froude # Project at GSP • First “warning” type of NWFS event this season • Previous (minor) events tended to have Fr values of 1.5 or less • NWFS seems to shut off completely close to 1 and below • Also have to consider the time lag of the airmass making through the upstream edit area to the upslope areas (~3 hrs?) • Would be nice to have at least one more “warning” type of event to compare to this one • Any thoughts or ideas are very welcome!