The month of July 2001 was slight warmer and much drier than normal. The typical summertime pattern of a persistent upper air high pressure was in place for most of the month. Temperatures were held down somewhat by the fact that this ridge was not very strong for most of the month, and the lush vegetation present for much of the month. The only showery periods came when the center of this upper air high would shift away from the area. Compared with July 2000, last month was 0.1 deg. warmer and 0.13 inch drier.
Year-to-date rainfall through July 31, 2001 was 4.88 inches greater than that through July 31, 2000. Rainfall over the past twelve months is 136.7 percent of normal. The thirty-day outlook had called for near normal temperatures and near normal precipitation.
The week July 1-7 saw temperatures near normal, and rainfall about one-half normal. Upper air high pressure began ridging over the region on the 2nd. This brought the most recent round of showers to an end, as a closed low aloft drifted over the region from northeast to southwest and weakened. The upper air high virtually shut down precipitation, with only a few isolated late-day showers on the 3rd and 5th. The week July 8-14 saw temperatures two degrees warmer than normal, and no rainfall in Tyler. Upper air high pressure was over the region for most of the week. This warmed the temperature and largely suppressed any shower development. By late in the week, the upper air high had drifted westward into New Mexico. This allowed a cold front to move through on the 14th, which lowered temperatures and caused scattered showers over the southern and eastern counties. The proximity of the front caused showers north of the IH-30 Corridor on the morning of the 13th.
The week July 15-21 saw temperatures one degree warmer than normal, and no rainfall. Upper air high pressure was in control of the area's weather. This was responsible for the warm weather. Temperatures were slightly warmer than during the previous week as topsoils and vegetation continued to dry. There were a few isolated showers over the southern counties on afternoons during the week. The center of the ridge was to the north of East Texas for much of the week. Disturbances rotating around the southern fringe of the ridge permitted this development. The week July 22-28 saw temperatures one degree warmer than normal and no rainfall. Upper air high pressure was drifting slowly westward after mid-week. As a consequence, temperatures fell gradually during the week.
An upper air disturbance moved slowly westward beginning Thursday from Northern Mississippi into Northeast Texas. This brought scattered shower and thunderstorm activity from the 25th into the 28th. Activity was most numerous and widespread Friday afternoon--the 27th. No rain fell in the city, though Tyler--Pounds Field Airport did pick up 0.06 inch of rain at that time, and Longview--Gregg County Airport 0.09.
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.
MX MN OBS PCPN REMARKS
July 2001, RECORDS AND SUMMARY: