October 19, 2002: Two Moderate Stratiform Precipitation Systems, A Bright Band, and Biological Scatterers Author: Pam Heinselman, CIMMS/OU Last Updated: 3 April 2003

Forecast/Weather:

Two stratiform precipitation systems moved into Oklahoma. The first system moved across southern Oklahoma between 00:02 and 11:30 UTC, whereas the second system moved into northern Oklahoma, and became quasi-stationary over west-central and central Oklahoma (11:00 - 23:57 UTC). As this second system moved into Oklahoma, there is evidence of a bright band in the polarmetric data (14:56 - 16:25 UTC). Interestingly, a group of biological scatterers are also observed from 7:29 - 10:59 UTC.

Radar Operations:

Start time: 00:02 10/19/02 UTC (19:02 10/19/02 local time)
Stop time: 01:01 10/19/02 UTC (20:57 10/19/02 local time)

Start time: 02:00 10/19/02 UTC (21:00 10/19/02 local time)
Stop time: 23:57 10/19/02 UTC (18:57 10/19/02 local time)

Radar/Operational Status:

Hydrometeor Classification Algorithm: Warm season

Operational Delivery:

Not applicable.

Snapshots:

Figure 1: Radar reflectivity at 08:28 UTC on 10/19/02 shows stratiform precipitation in southern Oklahoma and a group of biological scatterers northwest of KOUN.	Figure 2: Radar reflectivity shows a second stratiform precipitation system moving into northern Oklahoma at 15:26 UTC. The north-most band of higher reflectivities may indicate a bright band or melting layer.	Figure 3: Radar reflectivity shows the stratiform system at 20:25 UTC.
Figure 4: Differential reflectivity at 08:28 UTC on 10/19/02 indicates that small-to-moderate size drops comprise the stratiform precipitation in southern Oklahoma. The relatively high ZDR values northwest of KOUN, colocated with low reflectivity and correlation coefficient (see Figs. 1,7) indicate a group of biological scatterers northwest of KOUN.	Figure 5: Differential reflectivity indicates that small-to-moderate size drops comprise most of the second stratiform precipitation system moving into northern Oklahoma at 15:26 UTC. The north-most band of larger hydrometeors, colocated with a band of higher reflectivity values and lower correlation coefficients (0.9-0.93;see Figs. 2,8) may indicate the presence of a melting layer.	Figure 6: Differential reflectivity indicates that small-to-moderate size drops comprise the stratiform system at 20:25 UTC.
Figure 7: Large correlation coefficient values in southern Oklahoma indicate rainfall, whereas the low values northwest of KOUN indicate biological scatterers.	Figure 8: The band of lower correlation coefficient values within the stratiform precipitation may indicate hail within a melting layer.