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May 2007 - Report and Summary

May 2007 saw the end of the more than two years long drought in East Texas. Twelve-month precipitation exceeded 100 percent of normal at the end of May 2007, marking the last of the drought markers to fall. Measurable rain fell on 16 of the month's 31 days. The city's accumulation of 8.33 inches was far from the record of 14.08 inches which fell in May 1944, but it was 6.12 inches greater than that which fell in 2006. Rainfall through month's end was 9.36 inches greater in 2007 than in 2006.

Lake Tyler, which was more than 8 feet low in early-December 2006, had climbed to within 5 inches of full pool by May 31. The drought began in Spring 2005, with only 53 percent of normal rainfall falling that year. There was a brief improvement in January-February 2006, the late-Summer of 2006, and the beginning of the end in mid-December 2006. The categorical measurement of drought uses a four-level scale. Tyler was in Level 3 extreme drought during much of late-2005 and 2006. Otherwise, the month saw normal temperatures It was 1.8 deg. cooler than May 2006. The thirty-day outlook for May 2007 had called for above normal temperatures and near normal precipitation.

The week April 29-May 5 saw temperatures about 2 degrees warmer than normal, and rainfall about 400 percent of normal. The week began with a weak Polar Maritime air mass in control, which was replaced on the 30th by Tropical Maritime air. An upper air storm, crossing between the 1st and 3rd, brought heavy rainfall and scattered occurrences of severe weather. The week's average temperature was 71.5 deg., and precipitation was 3.80 inches. The week was 2.4 deg. Warmer than the previous week which was also very wet with 4.00 inches of rain having fallen. Compared with the same week in 2006, the week was 2.5 deg. Cooler, and 2.43 inches wetter.

The week May 6-12 saw temperatures 4 deg. Above normal, and rainfall about 250 percent of normal. Tropical Maritime air was over the region throughout the week. A very slow-moving upper air storm dominated the week's weather, moving from Northwest New Mexico at the beginning of the week into the Northwest Gulf of Mexico by week's end. East Texas was spared the severe weather and flooding event which affected the Central and Southern Plains. However, thunderstorms occurred in the region daily from the 67th through the 12th, with a few of these severe. In Tyler, rain fell daily from the 9th through the 12th. The week's average temperature was 76.0 deg., and rainfall was 2.40 inches. This was 4.5 deg. Warmer than the previous week. Rainfall from April 25 through May 12 was 10.40 inches about 300 percent of normal. Compared with the same week in 2006, the week was 4.1 deg. Warmer, and 2.26 inches wetter.

The week May 13-19 saw temperatures about 1 degree below normal, and rainfall about5 percent of normal. A cold front on the 16th brought the week's only rainfall, and lowered temperatures through the end of the week. Otherwise, upper air high pressure kept the region dry. The week's average temperature was 71.5 deg., and rainfall was 0.06 inch. The week was 5.0 deg. Cooler than the previous week. Compared with the same week in 2006, the week was 0.5 deg. Warmer, and 0.66 inch drier.

The week May 20-26 saw temperatures about 2 deg. Below normal, and rainfall about 200 percent of normal. Upper air low pressure was present over the Inter-Mountain West and Southern Plains most of the week. Disturbances coming off this low were responsible for the week's rains, and the clouds and rain were responsible for the lower temperatures. Flooding rains occurred over parts of North Texas late in the week. The week's average temperature was 72.5 deg., and rainfall was 2.24 inches. This was 1.0 deg. Warmer than the previous week. Compared with the same week in 2006, the week was 7.4 deg. Cooler, and there was no precipitation in 2006.

The final five days of the month were mild and wet. The upper air low, which had affected the region's weather since the 18th, slowly crossed between the 28th and 30th. There were showers on each day, with parts of the region again receiving very heavy rainfall. The 30th saw a thunderstorm system move in from the northwest, causing severe weather northwest of a Henderson-Clarksville line. With the low in the northern Gulf of the 31st, the day was mostly dry and seasonably warm.

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.

May 2007



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