Chaff

Chaff Detected by NWS Louisville Radar

It has been documented in the past, particularly in western states, that NWS NEXRAD radar can detect chaff. What is that you ask? Chaff is a radar countermeasure used by military aircraft consisting of very small pieces of metal such as aluminum. It can appear as narrow bands of reflectivity on the radar since they are dispersed by planes flying at high speeds along a path.

During the afternoon hours of 7 January 2006, the Louisville NEXRAD radar (KLVX) detected what appeared to be chaff. The day was mostly clear, with only a few high level cirrus clouds. Winds at the surface were out of the southwest, but higher up near the level the chaff was detected, winds were out of the west-northwest. The echoes presented here are somewhat weaker than normal, topping out around 16 dBz or so.

Below is a selection of still images. Click here for an animation of the radar data (754 KB filesize)

0.5 Degree Scan
KLVX 0.5 degree elevation scan at 3:41 PM EST on January 7th. The brightest chaff return between Louisville and Evansville (over Perry County Indiana) was at around 3,000 feet above ground level (AGL). You can see the banded streaks which are consistent with the nature of documented chaff returns. They were traveling toward the east-southeast.

1.5 Degree Scan
KLVX 1.5 degree elevation scan at the same time. Chaff returns over Perry County are between 4,800 and 5,800 feet AGL.

2.4 Degree Scan
KLVX 2.4 degree elevation scan, same time. The echos southwest of the radar are roughly 6,000 to 8,000 feet AGL.

Visible Satellite Image
Visible satellite picture around the same time with surface observations overlaid. The clouds there are cirrus, generally around 25,000 feet AGL.

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