Original scientific paper
CAUSES OF SIMULTANEOUS LEE AND UPWIND RECORD SNOWFALL AND EXTRAORDINARY SNOWFALL VARIATION IN A ROCKY MOUNTAIN BLIZZARD
Gregory S. Poulos
; NCAR, Earth Observing Laboratory, Boulder, Colorado USA
Douglas A. Wesley
; UCAR, COMET, Boulder, Colorado, USA
John S. Snook
; ATMET, Gunbarrel, Colorado, USA
Abstract
We describe our investigation of an extreme snowfall event in the Colorado Rocky Mountains during Mar 2003. This event was characterized by extraordinary micro-scale snowfall variability and record snowfall both upwind and in the lee of the 3000 m north-south oriented barrier. We utilize observational analysis and numerical sensitivity tests with the MM5 mesoscale model to test our hypotheses. Stunning micro-scale snowfall variability observed in-situ and visualized by satellite is found to be a consequence of local terrain-induced warming and reduced microphysical efficiency and the
amplified influence of this effect due to the relatively warm temperatures accompanying this storm. Record snowfall (2 m)
downwind of the barrier simultaneous with record snowfall (2.2 m) upwind is very rare climatologically, and is found to be caused, in effect, by the exceptional synoptic dimensions of this storm. A rare combination of, 1) moist, deep inflow, 2) a reversal of the mid-latitude westerlies to the tropopause overlying a well-developed barrier jet for an extended period and, 3) static stability favoring cross-barrier microphysical production and hydrometeor transport rather than drying, are implicated.
Keywords
Precipitation; Mountain; Variability; Snowfall
Hrčak ID:
64917
URI
Publication date:
15.12.2005.
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