Please download the latest version of Java Virtual Machine from http://www.java.com if you're having trouble viewing this loop.

Loop shows 15-minute GOES-10 visible imagery and 15-minute CG lightning data from 16:30 to 23:00 on 28 June 2000.

An office is asked to describe what they see in the loop. The following points should be noted: 1) around 17:00UTC, cumulus development occurs on the Mogollon Rim near Humphreys Peak; 2) at 18:00 UTC, the first negative CGs are observed, presumably associated with first precipitation at the surface; 3) around 19:15 UTC, a line of negative CGs is observed and the southern cloud edge of the convective line becomes well-defined, evidence for organized outflows; 4) by 20:30 UTC, the line breaks up into negative CG clusters of various sizes as outflows move southwestward; 5) from 19:30 to 20:30 UTC, CG lightning is consistently observed behind the convective line near Humphreys Peak. This CG lightning is predominantly positive.

The office is then asked if precipitation is reaching the surface beneath the negative CG clusters. The office should recognize that precipitation is likely reaching the surface beneath the larger clusters of negative CGs based on the amount of graupel necessary to produce that much lightning. Precipitation is probably not reaching the surface beneath the smaller clusters, since the amount of graupel produced by these storms may not be sufficient to penetrate the dry layer. Surface observations and discussions with WFO Flagstaff confirm these guesses. The office is also asked whether they expect any precipitation behind the convective line. Based on the discussion of stratiform precipitation and lightning, the office should state that stratiform precipitation is likely occurring in association with the positive CGs around Humphreys Peak. Stratiform precipitation is probably not occurring beneath eastern portions of the trailing cloud shield.