Day 54: Texas Snow Examined
Today, areas south of the Dallas-Fort Worth metropolitan area received a significant snowfall by their standards. As of this writing (9 PM CST), the National Weather Service Forecast Office in Fort Worth, TX has a graphic indicating that Waco, TX had received 3″ of snow (light snow was still occurring). I thought tonight’s blog post would focus on what was the source of the lift associated with this precipitation.
As my former students should remember, when precipitation develops north of the surface warm front, typically one of two (or a combination of these two) mechanisms are responsible for the sustained lift necessary for precipitation to develop. These two mechanisms are isentropic lift or frontogenetical forcing associated in the 850-700 hPa layer. It just so happens that the heaviest precipitation across central Texas today coincided with the 850-700 hPa frontal zone. This is illustrated in the sequence of images below.
In the images below, the Petterssen Frontogenetical equation values are contoured in purple (essentially, the larger the number the stronger the front in the layer) as analyzed by the Rapid Update Cycle (RUC) numerical model. The corresponding radar reflectivity is underlayed in blue, green, and yellow. Notice how the precipitation and the 850-700 hPa frontal zone are juxtaposed very nicely throughout the day.
1200 UTC 23 February 2010 (6 AM CST23 Feburary 2010)
1500 UTC 23 February 2010 (9 AM CST23 Feburary 2010)
1800 UTC 23 February 2010 (12 PM CST23 Feburary 2010)
21 UTC 23 February 2010 (3 PM CST23 Feburary 2010)
00 UTC 24 February 2010 (6 PM CST 23 Feburary 2010)
