Dallas, Georgia and Dallas, Texas are both southern towns. The one near Atlanta is close to 34 degrees of latitude and 1,056 feet elevation. In Dallas, Texas, City Hall is 70 miles closer to the equator and 600 feet lower in elevation. There’s often a similarity in the daily weather of the two towns. But this February, the jet stream demonstrated its power to create vastly different situations.
February 2021 started with mild weather in both places. Dallas, Georgia reported highs in the 50s and lows around freezing. Dallas, Texas was warmer. Farther south and closer to sea level than its Georgia namesake, temperatures there were in the 60s during daytime and 40s at night.
The following week, an oddly steep curve in the jet stream pushed a cold front into Texas and neighboring states. The jet stream is the track controlling the movement of winter storms. Normally, its southward turns involve all of the South Central and Southeastern United States. For example, in 1985 a deep freeze spread all the way to the Georgia Coast. But this year was different. February 10 brought the first freezing low to Texas at 28 degrees. Meanwhile, the Atlanta area remained on the southern side of the jet stream, remaining in the warmer air mass. The mercury in Dallas, Georgia rose close to the 70 degree mark.
On February 14, conditions in Texas became worrisome as the nighttime low dropped to 11 degrees, and snow began to fall during the day. Dallas, Georgia noticed none of this as both the highs and the lows remained in the 40s for a couple of days.
The jet stream now showed a sharp embedded shortwave trough. That’s like a steep curve on a mountain road which suddenly, without warning, gets even tighter. Instead of continuing east towards Georgia, the winter storm was deflected northeastward into Tennessee and Kentucky. The worst day for the Texas city was February 16, when residents woke up to a bone-chilling 3 degrees, and the high for the day only reached 21. Dallas, Georgia remained on the warmer side of the jet stream and only dropped a little below the freezing mark that night. When the winter storm was gone, both Dallas towns reached the 70s during the last week of February. Once again, the curvature of the jet stream had controlled our weather.
Rudi Kiefer, Ph.D., is a professor at Brenau University, teaching physical and health sciences on Brenau’s Georgia campuses and in China. His column appears Sundays and at gainesvilletimes.com.