The month of May 2015 was warmer and very much wetter than normal. The thirty-day outlook had called for below normal temperatures and above normal precipitation. This was not changed with the April 30 issuance. May 2015 was very wet and stormy. The Texas State Climatologist reported May 2015 as the wettest month in Texas since weather records began in 1895. In Tyler, May 2015 was the sixth wettest May on record.
Surface and upper air high pressure brought seasonal temperatures and dry weather through the 4th. That changed starting on the 5th when a series of upper air low pressure areas in the southwesterly flow aloft and associated surface cold fronts began crossing. Heavy rains occurred in parts of the region in the two-part storm system crossing between the 5th and 9th. Heaviest rains fell in Harrison County on the morning of the 7th, and in Lamar and Red River Counties the following morning. These were both tropical warm core events.
Another system crossed on the 10th-11th with rains of two to ten inches. The heaviest rains were in Navarro County, with Van Zandt and Henderson Counties close behind. A tornado occurred in Van on the evening of the 10th with considerable damage, two fatalities, and about four dozen personal injuries. More than six inches of rain fell in parts of Harrison County with considerable flooding on the 10th.
The procession of upper air disturbances in the southwesterly flow aloft and their interaction with strong moisture plumes off the Gulf and Eastern Pacific up the vertical air column resulted in continuing shower activity. Rain fell in Tyler every day between the 11th and 27th seventeen consecutive days. Most amounts were light, with the heavier occurring late on the 13th, on the afternoon of the 21st, on the afternoon of the 24th.
There was one more major severe weather event on the night of the 25th. Considerable wind damage occurred in both Henderson and Jacksonville. There were, though, heavy rain bands on the morning of the 15th in the DFW area, on the morning of the 17th from DFW northeastward up the IH-30 Corridor, and from LaGrange to Lufkin and Shreveport on the morning of the 18th. Numerous thunderstorms developed from the 23rd through the 25th. Rainfall amounts of two to four inches were observed in this period. Additional thunderstorms occurred on the 29th and 30th when the three-week rainy period finally ended.
The presence of clouds and rain held up nighttime temperatures but held down daytime readings. Thus, temperatures were near to slightly above normal into late-May, falling below normal on the 31st as high pressure built in behind the final departing storm system. Tyler had not yet seen its first 90-degree high temperature through the end of the month. The median date for that occurrence is May 8.
May 2015 was 7.32 inches wetter than the previous may. Year-to-date rainfall through May 31 was 21.47 inches greater in 2015 than in 2014. May 2015 was 1.4 deg. Warmer than May 2014.
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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May 2015, RECORDS AND SUMMARY: