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A preliminary investigation of an atmospheric bore and a waves atop a cold front that moved across northern Alabama on 4 December 2008. Patrick Gatlin ATS 651 Class Project Spring 2009. NEXRAD Mosaic 03,06,07 UTC. Mesoscale Analysis. Dashed line represents cold front position.
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A preliminary investigation of an atmospheric bore and a waves atop a cold front that moved across northern Alabama on 4 December 2008 Patrick Gatlin ATS 651 Class Project Spring 2009
Mesoscale Analysis Dashed line represents cold front position
NSSTC Observations • Outflow boundary from cold front convection triggers an atmospheric bore • Bore passes through NSSTC at 0800 UTC 2.5 mb pressure rise in 10-min BL deepens Hydraulic jump
ARMOR image of bore • Large variations in wind field behind bore • Bore already past radar at 0800 UTC
Surface Observations Hydraulic jump Hydraulic jump cold fropa cold fropa Bore speed ~ SE @ 14 m s-1
ARMOR images of cold front • RSA sounding shows very shallow duct (D ~ 500 m) conducive to wave propagation • Well delineated fine line in radar data (convergence ~ 0.06 s-1) • Radial velocity was all outbound at 2deg elevation very shallow airmass behind cold front Redstone 1200 UTC Duct 2.0 deg 0.7 deg
ARMOR reflectivity RHI scans perpendicular to cold front • 2 distinct airmasses are shown by the reflectivity field • Denser airmass is ~ 1.5 km deep • Flow up and over the denser airmass can be seen in the radial velocity field Watch as waves propagate along the interface of the airmasses λ ~ 1.2 km