October 24, 2002: Moderate Stratiform Precipitation and Bright Band, Chaff, AP and Biological Scatterers Author: Pam Heinselman, CIMMS/OU Last Updated: 3 April 2003

Forecast/Weather:

Several types of targets appear in this data set. First, following the dissipation of the 23 October event, areas of AP appear around KOUN (00:01 - 6:14 UTC). Second, the apparent movement of an area characterized by low reflectivity, moderate ZDR, and low RhoHV just southwest of KOUN suggests the presence of biological scatterers (1:44 - 6:14 UTC). The magnitude of the differential backscattering within these areas would improve confidence in the classification of these signals. Third, a stratiform precipitation system moves into western Oklahoma around 7:39 UTC and slowly moves from western OK into central OK through the period. Finally, a chaff cloud is observed by KOUN between 7:57-10:02 UTC, just ahead of the oncoming precipitation.

Radar Operations:

Start time: 00:01 10/24/02 UTC (19:01 10/23/02 local time)
Stop time: 23:58 10/24/02 UTC (18:58 10/24/02 local time)

Radar/Operational Status:

Hydrometeor Classification Algorithm: Warm season

Operational Delivery:

Not applicable.

Snapshots:

Anomalous Propagation and Possible Biological Scatterers

Figure 1a: Radar reflectivity at a) 2:05 UTC, b) 4:09 UTC, and c) 6:14 UTC indicates AP around KOUN and possibly biological scatterers southwest of KOUN.	Figure 1b: Reflectivity at 04:09 UTC.	Figure 1c: Reflectivity at 06:14 UTC.
Figure 2a: Differential reflectivity at a) 2:05 UTC, b) 4:09 UTC, and c) 6:14 UTC indicates AP around KOUN and possibly biological scatterers southwest of KOUN.	Figure 2b: Differential reflectivity at 04:09 UTC.	Figure 2c: Differential reflectivity at 06:14 UTC.
Figure 3a: Small correlation coefficient values around KOUN at a) 2:05 UTC, b) 4:09 UTC, and 6:14 UTC indicate AP around KOUN and possibly biological scatterers southwest of KOUN.	Figure 3b: Correlation coefficient at 04:05 UTC.	Figure 3c: Correlation coefficient at 06:14 UTC.
Figure 4a: Radar reflectivity at 8:59 UTC shows precipitation moving into western Oklahoma and a solitary chaff cloud.	Figure 4b: Although reflectivity values comprising the solitary cloud are higher than those comprising the precipitation, the ZDR values are similar. This indicates that the solitary cloud is chaff (i.e., chaff needles are elongated and horizontally-oriented).	Figure 4c: Correlation coefficients associated with the chaff cloud are clearly lower than and those associated with precipitation.
Figure 5a: Radar reflectivity at 15:17 UTC shows widespread precipitation across central Oklahoma.	Figure 5b: The band of relatively low RhoHV (0.93) sandwiched between bands of relatively high RhoHV (.97) indicates hail within a melting layer.