The month of June 1999 was slightly warmer and much wetter than normal. It stood in sharp contrast with June 1998. June 1999 was 5.0 deg. cooler, and 3.58 inches wetter. Year-to-date rainfall was 7.48 inches more through June 30, 1999 than it had been throught June 30, 1998. Rainfall during the preceeding twelve months was 138 percent of normal. The thirty-day outlook for June 1999 had called for near normal temperatures and near normal precipitation.
The first week in June saw temperatures running four degrees above normal and no rainfall. Upper atmospheric high pressure was over Central North America, and was responsible for both the high temperatures and lack of rainfall.
The second week in June saw temperatures two degrees above normal and rainfall about 125 percent of normal. A couple of upper air disturbances, strong enough to generate showers and thunderstorms, crossed during the week. The second pulled a cold front through, which lowered temperatures after the 13th. Otherwise, Tropical Maritime air covered the region from the Bermuda High Pressure Ridge. This resulted in seasonably warm and rather humid conditions.
The third week in June saw temperatures two degrees below normal, and rainfall about five percent of normal. The area was under a northwest flow aloft for much of the week. The surface air mass was quite humid, resulting in considerable cloudiness. The result was a pattern of below normal temperatures, arising from a couple of weak cold fronts. Though very heavy rainfall occurred over parts of West and South Texas late in the week, the triggering disturbances tracked well to the south of East Texas.
The final week in June saw temperatures two degrees above normal and rainfall 400 percent of normal. Most of the rain fell on the 24th-25th, when moisture aloft from Eastern Pacific Tropical Storm Adrian combined with a strong low-level moist flow and upper air disturbances to bring widespread rainfall. For most of the period, a deep layer of Tropical Maritime air held over East Texas. This kept nighttime temperatures high, but lowered daytime temperatures somewhat. On the 29th, a weakness in the upper air high, which built over the area after the 26th, permitted afternoon showers and thunderstorms to form.
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
June 1999, RECORDS AND SUMMARY: