Casebook 10 May 2005: Difference between revisions

Revision as of 06:32, 1 January 2008

CSU-CHILL Casebook: 10 May, 2005

Severe thunderstorm warnings due to large hail were initially issued for the greater Longmont area around 2300 UTC on the afternoon of 10 May 2005. This thunderstorm activity moved northeastward and reached the CSU-CHILL radar site around 0105 UTC on 11 May. (Approximately one inch diameter hail was observed at the radar.) Several polarimetric hail signatures were apparent as the storm approached the radar. At low elevation angles, a RHOhv minimum was present in the high reflectivity core at azimuth 241 degrees / range 30 km at 0027 UTC. (See VCHILL examples below.) Reductions in RHOhv to ~0.90 can occur when mixtures of large hailstones and raindrops exist in the radar pulse volume. This hail signature passed over the greater Johnstown area where hail diameters of up to 1.25 inches were reported.

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 ==CSU-CHILL Casebook: 10 May, 2005==
-Hail-producing severe thunderstorm developed over the foothills near Longmont around 2300 and tracked towards the Jamestown area.  Relatively narrow azimuth opening PPI sector scans were used.  Maximum elevation angle in these sectors was selected to get the beam height up to the approximately -25 to -30 degree C altitude in the storm.  (i.e., not necessarily all the way to echo top).  Periodic RHI volumes centered on the storm's right flank were also also done.  By 0056 UTC on the 11th, the storm was immediately southwest of the CHILL radar site.  At 0107:38 vertically pointed scans were started as pea sized hail began to fall at the radar.  By approximately 0120 the maximum hail diameters began to exceed 1 inch; additional vertically pointed scans were done through the hail shaft.  The storm faded out fairly rapidly as it moved east of Greeley.
-Note: Digitial pictures were taken of the storm as it approached the radar and of the hailstones that fell at the radar.
+Severe thunderstorm warnings due to large hail were initially issued for the greater Longmont area around 2300 UTC on the afternoon of 10 May 2005.  This thunderstorm activity moved northeastward and reached the CSU-CHILL radar site around 0105 UTC on 11 May.  (Approximately one inch diameter hail was observed at the radar.)  Several polarimetric hail signatures were apparent as the storm approached the radar.  At low elevation angles, a RHOhv minimum was present in the high reflectivity core at azimuth 241 degrees / range 30 km at 0027 UTC.  (See VCHILL examples below.)  Reductions in RHOhv to ~0.90 can occur when mixtures of large hailstones and raindrops exist in the radar pulse volume.  This hail signature passed over the greater Johnstown area where hail diameters of up to 1.25 inches were reported.
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 [[Category:Casebook|20050510]]
 [[Category:Hail]]