Surprise Snow Storm December 28 th 2012
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Transcript of Surprise Snow Storm December 28 th 2012
Surprise Snow Storm December 28th 2012
Ben MillerMeteorologist National Weather Service – St. Louis, Missouri
Overview My Midnight Shift Forecast
Model Forecast Data from 00Z December 28th 2012 HPC Snow Forecast My Snowfall Forecast
What Happened? Radar Imagery Total Snowfall Map
Where Did The Forecast Go Wrong? Satellite Imagery Synoptic Analysis An Ageostrophic Response Banded Snowfall Potential
00Z FCST12/28/12
12Z FCST12/28/12
00Z FCST12/29/12
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500 mb Vorticity Maximum fromthe 00Z forecast on 12/28/12
ECMWFGFSNAMSREF
GEMWRF
00Z12/28 12Z
12/28
00Z12/29
12Z12/29
HPC Mid Shift Snowfall FCST for 12/28/12
4-6”
My Snowfall Forecast
So What Happened?
Surprise!
Observed Snowfall from 12/28
How Did That Happen?
00Z 28 December 2012
12Z 28 December 2012
00Z 29 December 2012
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00Z 12/28/12 24 HR FCST of 295KMixing Ratio and Ageostrophic Wind
00Z 12/29/12 00 HR FCST of 295KMixing Ratio and Ageostrophic Wind
12Z NAM FCST on 12/28/12KFAMRed: OmegaYellow: Elevated CAPE
Summary• Shortwave was a little stronger and took on a slightly
negative tilt
• Coupled jet developed
• Ageostrophic flow brought richer moisture farther north/northwest
• Limited instability allowed for banded precipitation
Questions and or Comments…
Except for Fred