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August 2005 - Report and Summary

by Robert K. Peters, Ph.D. - National Weather Service Cooperating Observer

The month of August 2005 was warmer and drier than normal. Compared with August 2004, the month was 5.3 deg. warmer, and 2.73 inches drier. The month continued the drought, which began with the rainfall deficit starting last Fall. The effects of a wet July on vegetation had decreased by mid- month, and a string of eight consecutive days at or above 100 degrees began then. Catastrophic Hurricane Katrina's effects on the region were indirect at month's end. Year-to-date rainfall through August 31 was 13.93 inches less this year than last.

The Summer of 2005 saw an average temperature of 83.9 deg. This was 1.7 deg. warmer than normal. Rainfall for Summer 2005 was 6.47 inches. This was 76.8 percent of normal summertime rainfall. Climatological Summer differs from astronomical Summer: the former considers the months of June, July and August, while the latter runs from about June 21 to about September 21. The thirty-day outlook for August 2005 had called for near normal temperatures and near normal precipitation.

The week July 31-August 6 saw near normal temperatures, and rainfall about 20 percent of normal. The Sub-Tropical upper air high pressure ridge was the main weather feature for the week, and was responsible for the seasonably warm temperatures. A shear axis was along the Texas Coast for much of the week, which generated afternoon showers and thunderstorms each day. By late-week, this feature had weakened, but a dissipating cold front along Red River caused the activity on the 5th and 6th. The week's average temperature was 84.4 deg., and precipitation was 0.14 inch. The week was 0.8 deg. warmer than the previous week. Compared with the same week in 2004, the week was 1.1 deg. warmer, and 0.28 inch drier.

The week August 7-13 saw near normal temperatures and rainfall about 125 percent of normal. An upper air low pressure center was over the region during the first half of the week, replaced by upper air high pressure in the latter half. This resulted in widespread rainfall, some of which was locally heavy, between the 7th and 10th--continuing a pattern which had begun during the middle of the previous week. There were a few occurrences of severe weather on the 8th and 9th. The clouds and rain held down temperatures early in the week, with readings going back above normal by the end of the week. Tyler's average temperature was 83.2 deg., which was 1.3 deg. cooler than the previous week. Rainfall was 0.71 inch. Compared with the same week in 2004, the week was 6.4 deg. warmer, and 0.28 inch drier.

The week August 14-20 saw temperatures about 2 deg. above normal, and rainfall about 25 percent of normal. Early in the week, Active sea-breeze fronts brought shower activity through the 16th. On the 17th, upper air high pressure began building in from the southeast. This raised temperatures, and restricted afternoon showers to isolated--and mainly over the southern counties. The week's average temperature was 86.0 deg., and rainfall was 0.16 inch. The week was 2.8 deg. warmer than the previous week. Compared with the same week in 2004, the week was 8.7 deg. warmer, and 2.53 inches drier.

The week August 21-27 was the warmest of the season, with temperatures averaging about 6 deg. warmer than normal and rainfall about 110 percent of normal. A string of eight days with temperatures at or above 100 deg., which began on the 20th, ended on the 27th. Upper air high pressure controlled the region's weather throughout the week. Daytime heating caused widely scattered afternoon thunderstorms daily through the 26th, with a general thunderstorm outbreak on the 27th. There were a few occurrences of severe weather until a widespread severe outbreak on the week's last day. The thunderstorms of the 27th were the result of a cold front and upper air trough which were approaching. The week's average temperature was 89.2 deg., and rainfall was 0.74 inch. The week was 3.2 deg. warmer than the previous week. Compared with the same week in 2004, the week was 7.3 deg. warmer and 0.29 inch wetter.

Catastrophic Hurricane Katrina came ashore near Burruss, La. on the morning of the 29th. East Texas was on the outer fringe of this circulation. Winds went into the north on the 29th, and three feeder bands from the hurricane crossed the region. In Tyler, rain fell on the evening of the 29th from one of these bands. Then, dry air worked its way into the region as surface high pressure built down the Plains behind the departing storm. This brought warm afternoons and mild nighttime temperatures on the 30th and 31st, with a few showers on the afternoon of the 30th from the sea-breeze.

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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