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. . . Ticker for February 6, 2001 . . .
MESONET TICKER ... MESONET TICKER ... MESONET TICKER ... MESONET TICKER ... February 6, 2001 February 6, 2001 February 6, 2001 February 6, 2001 Great Mesonet In-Situ Cooling Case Sometimes, the best meteorological events occur during the most placid weather. And we had an exciting in-situ cooling event in eastern Oklahoma this morning. Take a look at the Mesonet weather map from 1:15 this morning: http://ticker.mesonet.org/archive/20010206/weather.gif Light southerly or southeasterly winds across most of the state, a ho-hum cold front pushing into northwestern Oklahoma ... not much to write home about, right? But take a look at conditions at Stigler, Wister and Broken Bow in eastern Oklahoma. While the rest of the region observed temps in the mid-40s or even mid-50s, the temps at these sites were 39, 30 and 31 F, respectively. Wister's temperature of 30 was twenty-five degrees colder than nearby Talihina. Twenty-five degrees! How can two stations that share a county report such different temps in the absence of a front or some dramatic event? The answer lies in the wind field. The three stations listed all have calm winds. When locations are protected and/or decouple from the ambient wind flow, they can cool rapidly via radiative processes. This "in-situ cooling" is exactly what happened here. In-situ cooling is different from "cold air drainage" processes, which take hours to set up and mature. In-situ cooling can occur rapidly after the location is protected from mixing, which is evident in the Mesonet meteograms below. Comparing Wister to Talihina: http://ticker.mesonet.org/archive/20010206/WIST.met.gif http://ticker.mesonet.org/archive/20010206/TALI.met.gif Wister's winds dropped quickly to near zero shortly after sunset, and the air temperature dropped rapidly to near the dew point. At Talihina, winds stayed above 5 mph all night, which was enough to keep mixing processes up and temperatures around 50 F. Stigler demonstrated in-situ cooling processes intermittently throughout the evening: http://ticker.mesonet.org/archive/20010206/STIG.met.gif Overnight winds at Stigler vacillated between near calm and strong enough to support mixing. The temperature trace vacillates with the winds. Another fun and exciting capture by Mesonet data! ================================================== The OCS/Mesonet Ticker https://ticker.mesonet.org/ To subscribe or unsubscribe from the Ticker or for questions about the Ticker or its content Phone or Email the Ticker Manager at OCS Phone: 405-325-2253 Email: ticker@mesonet.org --------------------------------------------------- -C- Copyright 2024 Oklahoma Climatological Survey ===================================================