September 14, 2002: Multiple Convective Lines w/ Biological Scatters Author: Pam Heinselman, CIMMS/OU Last Updated: 14 September 2003

Forecast/Weather:

On September 14, several convective lines develop ahead of a shortwave trough in the westerlies, that moves across Oklahoma between 00 UTC 14 September and 12 UTC 15 September. The cells at the leading edge of these lines produce heavy precipitation, as evinced by a precipitation accumulation of 1.45" at OKC. Unfortunately, interference from another radar makes the data appear noisy during the first four hours (00-04 UTC). Several gust fronts are illuminated by biological scatters during this event.

Radar Operations:

Start time: 00:02 9/14/02 UTC (17:02 9/13/02 local time)
Stop time: 23:44 9/14/02 UTC (18:44 9/14/02 local time)

Radar/Operational Status:

Hydrometeor Classification Algorithm: Cold season

Operational Delivery:

Not applicable.

Snapshots:

A number of meteorological and non-meteorological features exist in the polarimetric data at 3:09 UTC 14 September 2002. The precipitation northeast of KOUN is the remnants of the 13 September precipitation (Figs 1-4). A melting layer within the precipitation is indicated by the area of high ZDR, low rhohv, and high reflectivity (Figs 1-3). A new convective line has developed just west of KOUN, with a gust front ahead of its leading edge. This gust front is evident in these data from 2:20-6:00 UTC, due, inpart, to the abundance of biological scatterers(Figs. 1-12). The bloom of low reflectivities around KOUN exemplies the presence of such scatterers (esp. north of KOUN from 1:29-6:00 UTC). The hydrometeor classification algorithm does a good job identifying these non-meteorological targets (Figs. 4,8,12). The "noisy" non-meteorological signal (especially northwest of the convective line) results from interference from another radar.

Following the passage of the convective line through central Oklahoma, flying creatures are observed west of KOUN from 14:56-17:38 (Figs. 13-16). By 21 UTC, another convective line has formed west of KOUN with a group of biological scatterers just ahead of it (Figs. 17-20). As this line evolves, its downdrafts produce a gust front, observed from 21:49-23:44 UTC (Figs. 21-28). Cell intensity and new cell growth ahead of the line is enhanced by interactions between the gust front and inflow air (Figs. 25-28).

Figure 1: Reflectivity at 3:09 UTC 14 September 2002.	Figure 2: Differential Reflectivity at 3:09 UTC 14 September 2002.
Figure 3: Correlation coefficient at 03:09 UTC 14 September 2002.	Figure 4: Hydrometeor Classification Algorithm output at 3:09 UTC 14 September 2002.

Figure 5: Reflectivity at 4:11 UTC 14 September 2002.	Figure 6: Differential Reflectivity at 4:11 UTC 14 September 2002.
Figure 7: Correlation coefficient at 04:11 UTC 14 September 2002.	Figure 8: Hydrometeor Classification Algorithm output at 4:11 UTC 14 September 2002.

Figure 9: Reflectivity at 5:20 UTC 14 September 2002.	Figure 10: Differential Reflectivity at 5:20 UTC 14 September 2002.
Figure 11: Correlation coefficient at 05:20 UTC 14 September 2002.	Figure 12: Hydrometeor Classification Algorithm output at 5:20 UTC 14 September 2002.

Figure 13: Reflectivity at 16:35 UTC 14 September 2002.	Figure 14: Differential Reflectivity at 16:35 UTC 14 September 2002.
Figure 15: Correlation coefficient at 16:35 UTC 14 September 2002.	Figure 16: Hydrometeor Classification Algorithm output at 16:35 UTC 14 September 2002.

Figure 17: Reflectivity at 20:59 UTC 14 September 2002.	Figure 18: Differential Reflectivity at 20:59 UTC 14 September 2002.
Figure 19: Correlation coefficient at 20:59 UTC 14 September 2002.	Figure 20: Specific differential phase at 20:59 UTC 14 September 2002.

Figure 21: Reflectivity at 22:01 UTC 14 September 2002.	Figure 22: Differential Reflectivity at 22:01 UTC 14 September 2002.
Figure 23: Correlation coefficient at 22:01 UTC 14 September 2002.	Figure 24: Specific differential phase at 22:01 UTC 14 September 2002.

Figure 25: Reflectivity at 22:51 UTC 14 September 2002.	Figure 26: Differential Reflectivity at 22:51 UTC 14 September 2002.
Figure 27: Correlation coefficient at 22:51 UTC 14 September 2002.	Figure 28: Specific differential phase at 22:51 UTC 14 September 2002.