One observer saw a violent gust, another a flutter. Their disparate accounts would be difficult to reconcile until the librarian noticed that each had watched from a different side of the building. (disparate: dissimilar, different, unlike) The wind was volatile, the corner unusually exposed and its effects inconsistent across the yard. (volatile: unstable, unpredictable, mercurial; inconsistent: contradictory, discrepant, incompatible) One observer had even noted a fluctuation while the others were still arguing. (fluctuation: variation, oscillation, wavering)
A yawp from a child at the windy corner helped the librarian place one more witness. (yawp: yell, raucous cry, clamor) She asked them to disseminate instructions for a simple test. (disseminate: circulate, propagate, distribute) Everyone would tie a thread to a matchbox and set it on a sill. The threads could evince a change of direction without any need for estimates. (evince: demonstrate, reveal, display) The low windows showed a flutter. An upstairs box flew into the basket of a passing cyclist.
His delivery slip fixed the time. The librarian filed the reports side by side. The day's best record of a weather event had turned up in a rather unexpected branch of the postal service.