July 2013 Weather Highlights for West-Central Texas
Precipitation for July was much above normal across a large part of west-central Texas. This was largely due to an anomalous rainfall event which occurred in the middle of the month. The monthly rainfall amounts are shown below in Figure 1, and the percent of normal precipitation for the month is shown in Figure 2.
Figure 1: West-Central Texas Rainfall Amounts for July, 2013.
Figure 2: Percent of Normal Precipitation for July, 2013.
From Figure 1, the highest monthly rainfall amounts (over 10 inches) occurred in southeastern Callahan County. Monthly rainfall amounts of 6-10 inches occurred across the southeastern Big Country, parts of the Heartland and eastern Concho Valley. A few other locations in western and northern parts of west-central Texas received over 6 inches of rainfall in July. The lower rainfall amounts for the month (less than 2 inches) occurred across some of the southern third of west-central Texas, and into southern Tom Green County. A few other locations farther north received less than 2 inches for the month. From Figure 2, the only parts of west-central Texas with below normal rainfall in July were in south-central and southeastern sections of the region.
Temperatures averaged below normal for the month. This marked the first time in which temperatures averaged below normal for a summer month since 2010 in Abilene, and since 2008 in San Angelo.
At Abilene Regional Airport, the average temperature for July was 82.2 degrees. This was 0.9 degrees below the normal average temperature of 83.1 degrees. Total precipitation for Abilene in July was 4.44 inches. This was 2.57 inches above the normal of 1.87 inches.
At San Angelo Regional Airport, the average temperature for July was 82.7 degrees. This was 0.4 degrees below the normal average temperature of 83.1 degrees. Total precipitation for San Angelo was 3.17 inches. This was 1.97 inches above the normal of 1.20 inches.
The number of days in July with high temperatures of 100 degrees or more include:
6 at San Angelo, 4 at Abilene, and 5 at Junction.
Showers and a few thunderstorms move southeast across the southwestern part of west-central Texas on the 1st. The coverage of showers was lower across the rest of west-central Texas. Figure 3 (below) shows rainfall amounts across west-central Texas, for the 24-hour period ending at 7 AM, July 2.
Figure 3: West-Central Texas Rainfall for the 24-hour period ending at 7 AM, July 2.
Locally heavy rainfall amounts of 1.5 to 2 inches occurred along the border of northwestern Irion and eastern Reagan Counties. Rainfall amounts between one half inch and 1.5 inches occurred in parts of Irion and isolated parts of northern Crockett Counties. Elsewhere, the amounts varied under one half inch.
The significant pattern change across the U.S., which developed near the end of June and resulted in northerly flow aloft over Texas, continued during the first few days of July. With this setup, temperatures were cooler across west-central Texas, and drier air filtered south across the area. With considerable cloud cover cloud cover during much of the day on the 1st, temperatures were held in the 80s for highs. For a few locations in southern sections of west-central Texas, temperatures only reached the mid to upper 70s for highs. Clearing skies occurred during the late afternoon and evening hours. The combination of clear skies, a drier airmass, and light winds allowed temperatures to dip into the 50s for lows across much of west-central Texas, on the early morning of July 2nd and 3rd. New record low temperatures were set at San Angelo and Abilene, on the 2nd and 3rd.
A few showers and thunderstorms occurred in parts of the Big Country, and west of a line from Sterling City to Ozona, on the 4th.
A slow warming trend in temperatures occurred July 5-15, when an upper level high pressure system became the dominant weather influence. The center of this upper level high pressure system remained west and north of the area. As an upper level disturbance moved northwest across the Rio Grande Valley, scattered showers and thunderstorms occurred in central and southeastern parts of west-central Texas on the 8th. The hottest temperatures occurred on the 10th through 13th, when highs were in the 100-105 degree range across much of the area. A few showers and thunderstorms occurred in the Big Country on the 11th.
An anomalous weather event occurred in the middle of the month, with significant rainfall and much cooler temperatures for west-central Texas. This was brought about by a very unusual setup with the upper level flow pattern. With this setup, the upper level high pressure system weakened over the Plains and Texas, and strengthened from the mid-Atlantic west across the lower Great lakes region. The steering flow allowed an upper level low pressure system to move from the lower Great Lakes and Ohio Valley, southwest into southern Missouri and Oklahoma, by the 14th. With the approach of this system, a cold front moved to the west and southwest, into eastern sections of west-central Texas on the 14th. Behind this front, temperatures were cooler (highs in the 80s) with gusty east winds, across the eastern Big Country and Heartland areas. Temperatures were hot ahead of this front, and reached the upper 90s to 103 degrees for highs. A few showers and thunderstorms developed behind the front on the 14th.
Showers and scattered with very heavy rainfall developed initially across the Big Country, and then overspread the Concho Valley and Heartland areas during the overnight hours of the 14th and 15th.
The upper level low pressure system moved from southwestern Oklahoma into the Texas Panhandle on the 15th, and into eastern New Mexico on the 16th. The airmass became very moist with the arrival of this system. This resulted in an unusually favorable setup for heavy rainfall, for this time of year. Showers and isolated thunderstorms with heavy rain affected all of west-central Texas on the 15th and 16th. The most concentrated heavy rainfall developed along an axis oriented south-southwest to north-northeast, across the eastern half of the area, from the late evening of the 15th, to the early morning of the 16th. This axis of heavy rain gradually shifted across the western half of the area on the 16th. A new daily rainfall record was set at Abilene on the 16th.
The overall coverage of precipitation began to decrease after the 16th, as the upper level low pressure system moved southwest across New Mexico. Scattered to numerous showers and a few thunderstorms with locally heavy rainfall occurred across west-central Texas, on the remainder of the 16th and 17th. Scattered showers and a few thunderstorms with locally heavy rainfall occurred on the 18th, mostly across the region south of Interstate 20.
Figure 4 (below) shows the total rainfall for this event.
Figure 4: Total Rainfall across West-Central Texas, for the event July 14-18.
The highest rainfall amounts of 10-12 inches occurred in east-central and southeastern Callahan County. Rainfall amounts of 7-10 inches occurred in parts of the southeastern Big Country, northern Heartland, and in Concho County just northeast of Eden. Amounts of 4-7 inches were common across much of the Big Country and Heartland, parts of the Concho Valley, and at a few locations in the Northern Edwards Plateau and Northwest Hill Country. The lowest rainfall amounts, under 1 inch, occurred in a small part of southeastern Kimble County.
Some minor flooding occurred during this event (most noteably in Coleman), but the widespread, heavy rainfall was beneficial for the region and brought short-term relief to ongoing drought conditions.
Runoff from the heavy rainfall flowed into area creeks, streams, and reservoirs. This resulted in some increase in area reservoir levels, including at Fort Phantom Hill, Lake Brownwood, Hubbard Creek, and Lake O.H. Ivie.
With the widespread rainfall coverage and extensive cloud cover, daytime temperatures were unseasonably cool on the 15th, when highs were only in the mid 60s to lower 70s. This marked the only occasion in July with a high temperature below 70 degrees at Abilene. For both Abilene and San Angelo, highs on the 15th set new records for not only the daily record low maximum temperatures, but also for the month of July. Daytime temperatures slowly moderated, but remained well-below normal with extensive cloud cover on the 16th and 17th.
A slow warming trend occurred in the following days (19th through 22nd), with humid conditions. With the moist airmass, isolated showers occurred in the northern Big Country on the 19th. Widely scattered showers and a few thunderstorms occurred across west-central Texas on the 20th, and across central and southern sections of the region on the 21st. A few locations between Junction and Mason received between one half and one inch of rainfall on the 21st. On the 22nd, a few showers and thunderstorms occurred over west-central Texas.
Temperatures were mostly above normal late in the month, as an upper level high pressure system became a more persistent feature over Texas. An exception was when a weak cold front (unusual for July) moved south across west-central Texas on the 26th. In the warm and fairly moist airmass well ahead of this front, scattered showers and thunderstorms with locally heavy rain occurred across northeastern sections of west-central Texas on the 25th. A few locations in the Big Country, especially in Throckmorton County, received 1-3 inches of rainfall. Scattered showers and thunderstorms, in the vicinity of the front, occurred across central and southern sections of west-central Texas on the 26th. The showers and storms were most numerous in Crockett County. Figure 5 (below) shows rainfall amounts for the 24-hour period, ending at 7 AM on the 27th.
Figure 5: West-Central Texas Rainfall for the 24-hour period ending at 7 AM, July 27.
A few locations across the northern half of Crockett County received 1.5 to 3 inches of rainfall.
Following the weak frontal passage, slightly cooler and drier conditions occurred on the 27th, with highs in the upper 80s to lower 90s. Temperatures dropped into the 60s for early morning lows on the 28th.
Showers and thunderstorms were isolated in coverage on the 28th. On the 29th, scattered showers and thunderstorms (associated with a weak upper level disturbance) occurred across the western Big Country, northern and western Concho Valley, and Crockett County on the 29th.
On the 31st, isolated showers and thunderstorms occurred along a rather weak cold front, which entered the Big Country before stalling.
By the end of the month, high temperatures reached or exceeded the century mark across an increasing part of west-central Texas.