The month of May 2000 was warmer and much wetter than normal. A series of powerful migratory storms crossed periodically during the month, bringing widespread rainfall. Between these, upper air high pressure was in control for most of the month.
May 2000 was 4.0 degrees warmer and 4.67 inches wetter than May 1999. Rainfall through May 31 was 2.37 inches more than through the same same period in 1999. Precipitation during the past twelve months is 97.4 percent of normal. The rainfall deficit of July 1999-February 2000 has been virtually made up. The 30-day outlook for May 2000 had called for above normal temperatures and below normal precipitation.
The week April 30-May 6 saw temperatures two degrees above normal, and rainfall about 300 percent of normal. A closed-off upper air low crept slowly across the Southern Plains between the 1st and 5th. It was responsible for the rainfall, which was heaviest on the morning of the 4th. There were instances of severe weather and localized flooding on the 4th, with amounts of from three to five inches widespread. These rains, combined with earlier rainfall in April, caused watercourses and lakes to rise, as water ran off. The storm finally went out of range on the 6th, but would later bring torrential rains from the Middle Arkansas River Valley into the Middle Mississippi River Valley on the morning of the 7th.
The week May 7-13 saw temperatures six degrees warmer than normal, and near normal rainfall. For most of the week, upper atmospheric high pressure was in control. A storm crossed overnight the 12th/13th, bringing heavy rainfall, severe weather, and some small hail to Tyler.
The week May 14-20 saw temperatures about a degree above normal, and rainfall about 400 percent of normal. The week began cool with a surfacehigh pressure ridge over the area. Temperatures warmed during the week as Tropical Maritme air returned and upper air high shifted northeastward. Late in the week, a slow-moving upper air storm began crossing. A cold frontal boundary became stationary in or near the area. The result was widespread thunderstorm adctivity on the 19th, which brought rainfall amounts of from four to six inches to the area. Tyler's storm total was 5.27 inches. Severe weather with flash flooding occurred on the early- morning of the 19th.
The week May 21-27 saw temperatures average six degrees above normal, and there was no rainfall in Tyler. Upper atmospheric high pressure brought a rapid warm-up beginning the 22nd. This quickly eroded a cool air mass which moved in behind the storm of the 29th-20th. Record high minima were tied or broken on the 25th, 26th, and 27th. Daytime temperatures were held down slightly by the breezy to windy conditions experienced during the daylight hours, and the high humidities. Surface high pressure was to the east with low pressure to the west during most of the week. A few disturbances crossed to the north during the week. This brought some shower activity to the west and north--above IH-30, but none of this reached Tyler. A storm feature crossed the night of the 27th, producing rainfall and reports of severe weather. This was followed by a brief cool-down, with upper atmospheric high pressure returning on the 29th.
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
March 2000, RECORDS AND SUMMARY: