by Robert K. Peters, Ph.D. - National Weather Service Cooperating Observer
The month of August 2001 saw near normal temperatures and above normal precipitation. It was four degrees cooler than August 2000, and nearly four inches wetter. As of August 31, the temperature in Tyler had not reached 100 degrees yet this season. This will be the first year since 1994 when that did not happen. Year-to-date rainfall through August 31, 2001 is 4.50 inches greater than it was through August 31, 2000. As further indication of the cooler summer this year than last, cooling degree-days thusfar this year stand at 1970 compared with 2227 one year ago. The 30-day outlook for August 2001 had called for above normal temperatures and near normal precipitation.
The week July 29-August 4 saw temperatures about one degree cooler than normal and no rainfall. A humid air mass was over the area between then 29th and 31st, with much drier air working its way in on the afternoon of the 31st. This permitted nighttime temperatures to fall into the lower 70s during the latter half of the week. Daytime readings were held down on the 2nd and 3rd because of cloudiness, in part associated with Tropical Storm Barry. There were isolated late-day thunderstorms on the 1st, though no rain fell in the city. Tyler and Longview airports received 0.01 inch and 0.02 inch respectively. There were reports of wind and lightning damage from the southern part of the county on the evening of the 1st.
The summertime upper air high began the week centered over North Louisiana. It migrated northward and then westward, and was centered over the Central Plains by the end of the week. Nonetheless, it continued to be the dominant feature on the weather map. The showers and thunderstorms of the 1st were caused by a disturbance travelling westward on the ridge's southern flank.
The week August 5-11 was one degree warmer than normal, and there was no rainfall. It was 0.6 deg. warmer than the previous week. High pressure aloft built northward from the Sub-Tropics during the week. This feature was responsible for the warm temperatures. The remnants of Tropical Storm Barry reached as far west as Northwest Mississippi on the 6th and 7th. This caused widely scattered thunderstorms each afternoon, which fell in parts of Smith County on the late-afternoon of the 6th. On the 8th, a sea-breeze front brought scattered thunderstorms as far north as Lufkin. Through the 11th, Tyler had not recorded rain in forty-one days.
The week August 12-18 saw temperatures one degree below normal, and rainfall about one-third normal. The string of rainless days ended on the 16th at forty-five. The week was 3.5 degrees cooler than the previous week, with an average temperature of 81.8 deg. A cold front moved through the area on the 13th. This lowered temperatures slightly, and brought scattered thunderstorms. On the 16th, upper air low pressure formed over the Central United States. Disturbances rotating about the base of this system combined with another cold front, which went stationary over Oklahoma, to produce rainfall. The presence of cloudiness and showers held down temperatures. On the 18th, a new record low maximum temperature was established, as widespread rain fell in the area most of the day. Rain was also widespread on the 17th. Amounts averaged between one and three inches during the three-day period. Rain which fell on the 18th set a new daily rainfall record, reported for the 19th.
The Week August 19-25 saw temperatures two degrees warmer than normal, and rainfall about twice normal--the rain actually fell on the 18th. Upper air high pressure established itself in place over the region during the entire week. This allowed the warmer temperatures. The weekly average was 83.1 deg., 1.3 deg. warmer than the previous week. Lengthening nights did result in comfortable nighttime readings, which dropped to the lower 70s nearly every morning.
The final week in the month (26th-31st) was wet. A persistent upper air low pressure trough was over West Texas, and a strong flow of very moist came inland off the Gulf of Mexico. The result was a textbook example of a warm-season rain event. Rain fell in Tyler daily from the 26th through the 31st, with rain continuing into early September. The presence of clouds and rain held temperatures well below normal. In fact, the week was 6.1 degrees cooler than the previous week. A record low maximum was established on the 30th.
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.
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AUGUST 2001, RECORDS AND SUMMARY: