The month of May 2004 was slightly warmer and slightly drier than normal. Most of the month's rain came on the 1st when a powerful storm crossed. For most of the month, upper air high pressure dominated, keeping the region warm and dry. Compared with May 2003, the month was 0.9 deg. cooler, and 0.47 inch wetter. Year-to-date rainfall through May 31 was 4.23 inches greater in 2004 than in 2003. May 2004 was unusual in the late occurrence of the first day with temperatures reaching 90 deg. This occurred on the 28th, which is 20 days later than the median first occurrence. The 30-day outlook for May 2004 had called for above normal temperatures and near normal precipitation.
The week April 25-May 1 saw temperatures 2 deg. cooler than normal, and rainfall about 400 percent of normal. There were two major storm systems which crossed during the week. The first was on the 24th/25th, and the second on the 30th- 2nd. Both brought general rains to the area, with amounts of two to four inches common in each. A cold front with the first storm on the 25th brought cooling, with warmer air returning by the 28th. The week's average temperature was 67.2 deg., and rainfall was 5.75 inches. This was 4.6 deg. cooler than the previous week. Compared with the same week in 2003, the week was 7.0 deg. cooler, and 5.62 inches wetter.
The week May 2-8 saw temperatures 3 deg. cooler than normal, and near normal rainfall. The rain came from the departing storm of the 30th-2nd, which brought significant cooling through the 4th. Warmer and more humid air returned on the 5th, and continued through the end of the week. The week's average temperature was 68.1 deg., and rainfall was 0.91 inch. The week was 0.9 deg. warmer than the previous week. Compared with the same week in 2003, the week was 10.9 deg. cooler and 0.80 inch wetter.
The week May 9-15 saw near normal temperatures, and rainfall about three-fourths of normal. Weak storms crossed on the 10th and 14th, with a cold front crossing on the 15th. The two storms were responsible for the week's rainfall. With the second, amounts ranged from a few hundredths of an inch along Red River to as much as six inches in the East Texas Lakes Country. Tropical Maritime air was in place until the 15th, when it was replaced by modified Polar Continental air. The week's average temperature was 71.5 deg., and rainfall was 0.76 inch. This was 3.4 deg. warmer than the previous week. Compared with the same week in 2003, the week was 3.2 deg. cooler. and 0.08 inch wetter.
The week May 16-22 saw temperatures about 3 deg. warmer than normal, and no rainfall. For the entire week, surface and upper air high pressure controlled the region's weather. These features brought a warm and increasingly humid air mass, with the upper air high suppressing rainfall. The week's average temperature was 77.3 deg., which was 5.8 deg. warmer than the previous week. Compared with the same week in 2003, the week was 2.6 deg. warmer, and 0.68 inch drier.
The week May 23-29 was 3 deg. warmer than normal, and rainfall was about one-third normal. For most of the week, upper air high pressure persisted. This kept a Tropical Maritime air mass in place, which resulted in warm and very humid weather. The week's only rain came on the 28th with a crossing upper air disturbance.The average temperature was 79.4 deg., which was 2.1 deg. warmer than the previous week. Precipitation was 0.35 inch. Compared with the same week in 2003, the week was 6.5 deg. warmer and 2.24 inches drier.
The final two days of the month continued warm and humid. Severe weather affected parts of the area on the nights of the 30th and 31st, though Tyler escaped these thunderstorms. A slow-moving upper air trough through the Northern Plains was responsible. Record high minimum temperatures were set on the morning of the 30th under the upper air ridge.
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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May 2004, RECORDS AND SUMMARY: