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January 2010 - Report and Summary

by Robert K. Peters, Ph.D. - National Weather Service Cooperating Observer

The month of January 2010 was cooler than normal, and saw near normal precipitation.

During the first two weeks of the month, the area was in the grip of Polar Continental air. After mid-month, a more typical El Nino pattern set up, with frequent storm systems crossing in the southern branch of the Westerlies. A major severe weather event occurred on the evening of the 21st. Compared with January 2009, the month was 4.3 deg. Cooler, and 1.46 inches wetter. The thirty-day outlook had called for below normal temperatures and above normal precipitation.

The week December 27-January 2 saw temperatures about 6 degrees below normal, and rainfall about 75 percent of normal. A cold air mass was present for most of the week. A series of upper air disturbances, a surface low in the Gulf, and a cold front on the 31st brought periods of light rain from the night of the 28th through the evening of the 31st. Colder air introduced the new year. The week's average temperature was 40.9 deg., and precipitation was 0.63 inch. This was 5.8 deg. Colder than the previous week. Compared with the same week in 2008-2009, the week was 11.7 deg. Colder, and 0.03 inch wetter.

The week January 3-9 saw temperatures about 17 degrees below normal, and precipitation about 20 percent of normal. Cold air was present all week, with a particularly strong cold front on the morning of the 7th which brought a string of 54 consecutive sub-freezing hours, some light frozen precipitation in parts of the region, and low temperatures in the teens on the mornings of the 8th, 9th, and 10th. Strong winds on the 7th and 8th lowered wind chill equivalent values into the single digits on the morning of the 9th. The cold outbreak saw the coldest temperatures in the region since January 30-February 4, 1996. The week's average temperature was 30.5 deg., and pecipitation was 0.15 inch. This was 10.4 deg. Colder than the previous week. Compared with the same week in 2009, the week was 19.3 deg. Colder, and 1.19 inches drier.

The ensuing two weeks warmed dramatically: 10.6 deg. (Still 5 deg. Below normal) during the week of the 10th, and another 15.4 deg. During the week of the 17th (10 deg. Above normal). Arctic air began eroding on the 11th. The minimum temperature finally held above freezing on the morning of the 14th the first time all month that had occurred. A weak cold front on the 15th lowered temperatures only slightly. Tropical Maritime air became entrenched on the 19th, with weak cold fronts on the 20th and 22nd. The front of the 20th brought a major severe weather event, with as many as nine tornadoes reported in the region including one about 12 miles southwest of Tyler. The average temperature during the week of the 10th-16th was 42.1, and precipitation was 0.49 inch. The average temperature during the week of the 17th-23rd was 57.5 deg., and precipitation was 1.08 inch.

The week of the 10th was 0.6 deg. Warmer than the same week in 2009, and there was no rainfall in 2009.

The week of the 17th was 6.6 deg. Warmer than 2009, and that week was dry in 2009, as well.

The week January 24-30 reversed the warming trend of the previous two weeks, with temperatures running about 3 deg. Below normal, and rainfall about 150 percent of normal. Temperatures warmed at mid-week as an upper air storm system crossed. This brought rainfall of between one and three inches to the area. Arctic air followed the system on the 29th, taking temperatures well below normal through the end of the month. There was a 32-hour string of sub-freezing temperatures, from late-evening on the 29th through early-morning of the 31st. The 31st saw clearing skies with warming temperatures under full sun. The week's average temperature was 44.6 deg., which was 12.9 deg. Cooler than the previous week. Rainfall was 1.20 inches. Compared with the same week in 2009, the week was 2.6 deg. Cooler and 0.84 inch wetter.

The reporting period for temperatures and phenomenon on each day is for the twenty-four hours ending at midnight hours GMT--6 p.m. CST and 7 p.m. CDT. The reporting period for precipitation is for the twenty-four hours ending at noon GMT--6 a.m. CST and 7 a.m. CDT. All times are given using the twenty-four hour clock, and are expressed in Greenwich Mean Time.

Observations are from NWS Station 41/9207/4 in Tyler, Texas. The term "normal" refers to averages from the standard climatic period 1971-2000.

January 2010



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