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gefilmt und fotografiert vom Großen Sonnleitstein (1639m), Mürzsteger Alpen mit Start in Hinternaßwald - aus diesem Ort stammt der berühmte Bergsteiger Conrad Kain, der auch die Biographie 'Where the clouds can go' geschrieben hat.24.11.12, fog flows from southwest to northeast over a narrow pass called Naßkamm (1210m) between the mountains Raxalpe and Schneealpe.
Weather situation: Warm air advection aloft, with weak NWlies in mid-levels and rather weak southerly low-level winds. Extended low stratus decks were situated east of the Alps but significantly lower cloud tops (ca. 700 m) north of the location where this phenonemon was filmed. The fog waterfall persisted during the day, with a short weakening period in the afternoon when sun had warmed the valley downstream of the pass.
To my knowledge, warming of the valley atmosphere and pressure fall ''draws'' the fog over the pass.
What happens with sunset?
i) Nighttime cooling above the fog layer enhances the cold pool within the fog valley and rising fog tops could maintain the fog water fall.
ii) Nighttime cooling on both sides of the pass induce downslope winds and sinking cloud tops/dissipating fog.
PS: As only the deck layer of the cool air is able to cross the barrier, and vertical wind shear is present at the narrowest part of the pass, Kelvin-Helmholtz waves should be visible at the top of the fog.
3 Stunden früher :
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