July 2007

Report and Summary

Tyler, Texas
July 2007
by Robert K. Peters, Ph.D.
National Weather Service Cooperating Observer

July 2007 was the wettest and the third coolest July on record in Tyler. The 13.75 inches of rain which fell in the city, and 12.73 which fell at the airport, beat out July 1979 when 9.85 inches of rain fell. The average temperature for July 2007 was 79.5 deg., which was about 4 degrees below normal. Cooler than July 2007 were July 1968 with an average temperature of 79.0 deg., and July 1972 with 79.3 deg. Continuous weather records have been kept in Tyler since January 1, 1896. Of the 1,339 months in that time, July 2007 is the fifth wettest on record. April 1957 with 17.10 inches is the wettest.

Two flooding events struck Tyler, and three eastern Cherokee County during the first of the month. Urban flooding occurred in Tyler on the morning of the 6th (after nearly five inches of rain,) and mid-day on the 8th (when nearly three inches fell in 90 minutes. Both of those events affected parts of Cherokee County, as did rain of nearly 6 inches on the morning of the 14th. Smith and Cherokee were both declared disaster areas by the President. Another flooding event occurred in Titus, Lamar and Franklin Counties on the morning of the 31st. From June 1 through July 31, 22.32 inches of rain fell. This is 384 percent of normal. Since January 1, 49.20 inches of rain fell. This is 197 percent of normal, 27.46 inches more than had fallen through July 31 2006, 10.80 inches more than fell during all of 2006, 24.86 inches more than fell in all of 2005, and 3.93 inches more than is normal for the entire year. There are 61 days between June 1 and July 31; measurable rain fell on 32 of those days.

Area lakes and streams were all either full or in flood for most of the month. Every major river system the Red, Sabine, Neches, and Trinity--was in flood throughout the entire month. The three smaller systems the Sulphur, Navasota, and Angelina were in flood much of the month. Lake Tyler, more than 8 feet down seven months ago, was flowing over its spillway during the entire month, rising 21 inches in 24 hours between the 5th and 6th and reaching nearly 3 feet over its spillway at one point.

One of the most dramatic comparisons is the precipitation percentage of normal during the twelve months ending July 31: in 2006 at the height of the drought, it was 64 percent; in 2007 with the drought ended, it is 146 percent. The area went out of drought status in May 2007. The excessive rain and cool temperatures are directly related. Frequent periods of rain and cloudiness along with very moist soils and green vegetation held down the thermometer. Compared with July 2006, the month was 4.6 deg. Cooler and 10.85 inches wetter. The thirty-day outlook for July 2007 had called for below normal temperatures and above normal rainfall.

The week July 1-7 saw temperatures running about 5 degrees below normal, and rainfall was 950 percent of normal. Major flooding occurred in Tyler on the morning of the 6th. Rain began falling about 7 p.m. on the 5th, with about 2 inches accumulating in 9 hours. During the next two hours, nearly 3 inches fell. The result was flooding, downed trees, and a 2-foot rise in Lake Tyler. Measurable rain fell daily except on the 7th. A pesky upper air low, which had affected the region since the 15th of June, held in or near the area through the night of the 6th, when it temporarily migrated northeastward. Clouds and rain, and very wet soils, held temperatures down. The week's average temperature was 77.7 deg., and rainfall was 7.53 inches. This was 1.3 deg. Cooler than the previous week. Compared with the same week in 2006, the week was 2.0 deg. Cooler, and 5.48 inches wetter.

The week July 8-14 saw temperatures about 2 degrees below normal, and rainfall about 800 percent of normal. Two more flooding rains occurred during the week: that on the 8th was in Tyler and Jacksonville; that on the morning of the 14th was over Eastern Cherokee County but spared Tyler. Rain on the 8th fell at a rate of nearly 2 inches per hour between 11:30 a.m. and 12:30 p.m. That on the morning of the 14th brought nearly 6 inches of rain to the area east of Jacksonville, with rain falling for about 6 hours between 2 a.m. and 10 a.m. Otherwise, there were scattered afternoon showers on most days, with temperatures returning to near seasonal levels at mid-week. The rains of the 8th were the result of the continued presence of the upper air low; those on the 14th formed along and ahead of a weak cold front. The week's average temperature was 80.9 deg., which was 3.2 deg. Warmer than the previous week. Rainfall was 4.17 inches. Compared with the same week in 2006, the week was 5.4 deg. Cooler, and there was no rain in 2006.

The week July 15-21 saw temperatures about 4 degrees below normal, and rainfall about 125 percent of normal. Though scattered showers were present daily except on the 15th, amounts were generally lighter. Weak upper air low pressure permitted active sea-breeze fronts, which was responsible for the mainly afternoon convective activity. This tended to concentrate near the Gulf Coast. Moist soils and afternoon showers held down temperatures. The effects of the weak cold front of the 14th were short-lived. The week's average temperature was 80.2 deg., which was 0.7 deg. Cooler than the previous week. Rainfall was 0.50 inch. Compared with the same week in 2006, the week was 7.6 deg. Cooler, and 0.20 inch drier.

The week July 22-28 saw temperatures nearly 6 degrees cooler than normal, and rainfall about 75 percent of normal. An unusual mid-Summer cold front entered the region on the 22nd, holding temperatures up to 9 degrees below normal until Tropical Maritime air returned late in the week. An upper air low slowly crossed the region from west to east late in the week, bringing afternoon showers beginning on the 26th. The week's average temperature was 78.4 deg., and rainfall was 0.39 inch. This was 1.8 deg. Cooler than the previous week. Compared with the same week in 2006, the week was 4.2 deg. Cooler, and 0.24 inch wetter.

The final three days of the month were mild and showery. Another weak front reached the area on the 30th. This, combined with the extremely moist air mass and remnant energy from the previous week's upper air low, produced showers daily in the area. Clouds and rain held down temperatures.

R FOLLOWING A TEMPERATURE OR PRECIPITATION VALUE = RECORD

The reporting period for temperatures, precipitation, 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. 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.

JULY 2007 DY MX MN OBS PCPN REMARKS

JULY 2007, RECORDS AND SUMMARY:

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