Dalhart Weather Review
by Aaron Graves
Thursday evening, Oct. 9, held the promise of rain. Clouds were approaching from the west. The sun had set, its rays replaced by flashes of lightning. Another beneficial downpour was at hand. Suddenly, the National Weather Service issued a tornado warning for Dalhart, with a possible tornado 10 miles from town. It was 10:07 p.m.
The "October Tornado" had everyone talking, but what really happened? Officially, no funnel cloud or tornado, or tornado damage for that matter, was reported to the National Weather Service in Amarillo. The warning was issued because Doppler radar detected a thunderstorm capable of producing a tornado.
"This storm was not a classic tornadic supercell," says Todd Lindley, Science and Operations Officer at the NWS, "but the structure and rotation was enough to support a brief, weak tornado." Lindley knows this because Doppler radar can determine which direction rain drops are moving in a storm, and can thus see rotating winds.
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| Figure 1 - Courtesy NWS Amarillo |
"The rotation with this storm reached about 100 mph about 6,000 feet above the ground," Lindley added. This can be seen in Figure 1. The green and red colors depict winds moving in opposite directions. The circled area indicates the rotation that triggered the warning. Figure 2 is a traditional radar image. Notice the notch in the storm as rain is wrapping around the rotation.
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| Figure 2 - Courtesy National Weather Service |
Both images indicate that a tornado was possible Thursday. However, with the NWS radar some 90 miles away from Dalhart, it cannot see the winds close to the ground due to the curve of the earth's surface. There is really no way to know if a tornado touched down if it wasn't seen by someone close by.
Fortunately, the storm was moving due east and not headed towards Dalhart. Even though a tornado was not confirmed, the storm dumped hail up to 2.75" in diameter (baseball size) as it crossed U.S. Hwy. 87 between Dalhart and Hartley.
It is surprising to have to deal with a tornado warning in October, but bad weather cannot be ruled out this time of year. "In addition to the typical spring severe weather season, we do see a relative peak in severe weather in the fall," Lindley said. "There typically is a window of opportunity for severe weather roughly from September to early November. This is when we start to see strong weather systems containing cold fronts and stronger winds aloft move through the area before the warm-season moisture is totally vacated from the region."
Such was the case on Oct. 9. The Storm Prediction Center in Norman, OK had sent word there was a slight risk of tornadoes across the Texas Panhandle. In addition, a cold front had stalled over the nearby. Such a boundary can enhance rotation in a storm, Lindley added.
Officially, we received 0.81" of rain at the airport from Thursday's storm. Texaspivot.com shows rain totals up to 1.40" where the core of the storm moved south of Dalhart. Storms rolled through again Oct. 12, giving us another 0.11" of rain.
Therefore, we have 0.92" of rain for October. This is a very good thing! Our year-to-date total precipitation is 11.11", still about 5" short of normal. However, this time last year, we only had 6.66".
A CoCoRahs volunteer reported 0.55" of rain in Texline on Oct. 9. Another volunteer on S. Sedan Road reported a total of 0.79" for Oct. 9 and Oct. 12.
September 2012 ended with 1.55" of precipitation for Dalhart, an average high of 82.1 degrees, and an average low of 57.6 degrees. Since October 1, our daily high temperatures have generally been in the 70s and 80s, although it got a bit chilly with a high of only 58 degrees on Oct. 10.
High and low temps the past two weeks
Sep 30: 81, 52
Oct 1: 83, 51
Oct 2: 71, 50
Oct 3: 64, 43
Oct 4: 77, 37
Oct 5: 82, 45
Oct 6: 84, 45
Oct 7: 87, 47
Oct 8: 86, 53
Oct 9: 77, 57
Oct 10: 58, 47
Oct 11: 60, 47
Oct 12: 82, 44
Oct 13: 62, 43
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