The month of July 1999 saw near normal temperatures and near normal precipitation. The customary Summer features of upper atmospheric high pressure and the Bermuda-Azores Surface High Pressure Ridge were not as strong this year as last Summer.
July 1998 was the warmest month on record. It was also 6.9 degrees warmer and 2.59 inches drier than July 1999. Year-to-date rainfall through July 31st is 12.07 inches more this year than last. Rainfall over the past twelve months is 64.80 inches. This is 142 percent of normal. The thirty-day outlook had called for near normal temperatures and near normal precipitation.
The first week in the month saw temperatures about a degree above normal and rainfall about five percent of normal. A Tropical Maritime air mass was over the region throughout the week. Upper air high pressure slide to the east on the 3rd. This allowed for a more active sea-breeze front, which brought widely scattered to scattered afternoon showers and thunderstorms daily through the end of the week. The most widespread rains were on the 7th, when Tyler received rain which was reported the following day.
The second week in July saw temperatures two degrees below normal, and rainfall twice normal. The region was to the east of an upper air high pressure ridge, which permitted disturbances to drop southeastward in the northwest flow aloft. This both kept relatively mild air over the region, and also permitted widespread shower and thunderstorm activity.
The third week in July saw temperatures one degree below normal, and rainfall about one-third normal. During much of this week, the upper air high had moved to the northeast, leaving East Texas on its southern fringe. Disturbances moving west in the Easterlies alllowed for rather active sea-breeze fronts, which in turn caused scattered afternoon thunderstorm activity. The humid air mass, cloudiness, and presence of showers held temperatures down. The final ten days of the month saw temperatures near normal and rainfall about 75 percent of normal. After the 22nd, upper air high pressure built back over the area. This caused temperatures to rise tonormal values. The period's only rain fell on the evening of the 21st, when the last of the month's active sea-breeze fronts spread late-day thunderstorm activity over the region.
East Texas was on the periphery of a heat-wave which caused at least seventy-nine deaths in the Central and Eastern United States.
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
July 1999, RECORDS AND SUMMARY: