South Texas Weather Modification Association History 1996 - 2011,
2016 - Present

The South Texas Weather Modification (STWMA) was formed. It consisted of representatives from seven counties in south-central Texas: Atascosa, Bee, Frio, Karnes, Live Oak, McMullen, and Wilson.


Our first year of seeding commenced in May, with the radar site located at Stinson Field, San Antonio. The radar, planes (two twin-engine planes), pilots, and meteorologist were all contracted from Atmospherics, Inc. out of Fresno, CA. The seeding period ran from May through the end of September. Top seeding was exclusively performed, using both hygroscopic materials and silver iodide (AgI) in flares and generators mounted on the planes.
This year saw a number of advances for the STWMA. Early in the year, the association was fortunate enough to purchase a WSR-74C radar, which at one time was commissioned at Corpus Christi. The radar was installed at the Pleasanton Municipal Airport in Atascosa County, and a small building was built beside the tower to house its components and the meteorologist's computers. In May, at the very start of the seeding season, Tommy Shearrer and Mike Mahoney traveled to Texas Tech University in Lubbock to interview three candidates for the position of meteorologist. Todd Flanagan became the newest addition to the project and moved to Pleasanton in July. He began work in August, interning under AI meteorologist Alan Horn. The season got off to a dry start in May, and it wasn't until August when the rains began. August was a particularly busy month, with 33 flights sent out. The rest of the season went well, ending September 30th. Before the seeding season's end, the TNRCC granted the STWMA a four year permit to seed, good through 2002. The next major events for the STWMA were the purchase of a single-engine Comanche for base seeding and the addition of its own pilot, Tim Pickens. The Comanche needed some work before it would be ready for the 1999 season.
Todd Flanagan became the project meteorologist in charge of the program, with help from Mark Berteau, who interned with him during the summer. The project began officially on May 1, with one plane stationed at Stinson Field in San Antonio and STWMA's own plane stationed in Pleasanton. Once again, all seven counties that had participated thus far were included in the program. This year also brought a new challenge -- coordination with other projects. Two new weather modification projects started up adjacent to STWMA. The Edwards Aquifer project to our north, based out of Hondo, began in April, covering counties immediately north of our project. The Southwest Texas Rain Enhancement Association, based out of Cotulla, covered an area from Webb County to Zavala County, to the west. Hurricane Bret moved ashore in Kenedy County as a strong Category 3 hurricane on August 22. A day earlier, Bret’s outer rain bands moved across the target area and were seeded. This is the first time in years (possibly since StormFury) that any part of a hurricane was seeded. Later in the season, the STWMA purchased an additional plane (affectionately known as "Lime Aid" due to its lime-green color), which would be worked on for the 2000 season. It was also decided that the STWMA project would be converted into a year-long operation from now on.
Although the project is now a year-long affair, our first seeding mission did not take place until mid-March. By this time, "Lime Aid" was ready to fly. A few more changes took place. Bee County left the program, reducing the size of the program to six counties. Two new pilots, Larry Dement and Craig Funke, both from Runge (near Kenedy), were recruited to fly for the project. They have flown on a number of missions with Tim and are now able to do their own missions. As such, 09P was moved to Kenedy. With our own pilots, planes, radar, and meteorologist, the project is thriving.
The project continues to progress! The first part of the year was not so great, as the Pleasanton Airport was closed for construction (runway lengthening, addition of taxiways, and repainting and repaving). This was finally completed by spring. One of the Kenedy pilots, Craig Funke, left the STWMA to become chief pilot for the WTWMA in San Angelo. This left Larry Dement as our only Kenedy Pilot. We brought back Jim Transue, a former STWMA pilot, as a backup, keeping the number of available pilots at three. An 80' x 80' hangar was constructed adjacent to the radar building during the spring months, with expansion of the radar building taking place during November and December. A third plane was purchased during the fall, which will be stationed at Pleasanton. Overall, this year was less active than years past, but we are hoping for a change in the weather pattern soon.
Several changes for the 2002 season were made before the end of 2001. Bee County returned to the program after a two-year absence. The association also decided to abandon the use of generators after tests revealed that the particle sizes in the AgI plume from generators were too small to activate. The flare racks were expanded to hold 38 flares per wing as opposed to the former 12 per wing. Also, our state permit was re-written to allow for seeding in counties affected by Severe Thunderstorm, Tornado and Flash Flood Warnings so long as the seeding did not affect the warned storm. We welcomed two pilots to the association in the spring. Ron Merks, who worked with the program back in 1997-98 when AI was running operations, joined us once again in 2002. In addition, Mickey Chadwell, a flight instructor at Stinson Field, trained with us this year to become STWMA’s fifth and newest pilot. With the additional pilots, there came another Comanche. N57AA, also referred to as “Strawberry Five” or “Lipstick Special” due to its iridescent pink paint, was purchased in the spring and became operational in June. With the departure of WMI from the EAA Precipitation Enhancement Program, seeding to our north was halted by the end of 2001. The EAA, however, was still interested in having a weather modification program in some of the counties. Working with the STWMA and the SWTREA programs, they developed a contract whereupon the STWMA would annex the counties of Bandera, Bexar and Medina into the target area for the May-September period, and the SWTREA would acquire Uvalde County. This was to be a three-year contract, with one of the planes (N57AA) being located at Stinson Field in south San Antonio. Our hopes of having a busy year of seeding went down the river, so to speak, when an upper level low parked itself over the area from the end of June into the first part of July. Tapping into abundant tropical moisture, torrential rainfall began on June 30th and continued into the first week of July. Some parts of the target area, mainly the northern half, received over two feet of rain in a 10-day period. This caused extensive flooding across the area, with rivers unable to handle the deluge of water. As such, seeding was suspended from July 1st until the second week of August, when the soils were finally dry enough and rivers were down below bankfull levels. Another system in early September brought another one to two feet of rain to parts of the target area, so seeding was suspended once again. As a result of these two flooding events, the 2002 season saw the fewest number of seeding missions in its history. This outcome was bittersweet we missed several convective events, but the long-term drought was broken with the extended period of heavy rainfall.
The EAA portion of the seeding project continued, with pilots as well. The EAA contract was extended one month to the end of October. Hurricane Claudette moved across the central and southern target area on July 15 bringing high winds and heavy rains, but not as much rain as one would expect with a hurricane.
2004 marked the first year of working with Weather Decision Technologies, Inc. The company, based out of Norman, OK, provided WSR-88D data in near-real-time to all of the Texas projects. The STWMA continued to run the WSR-74C radar at Pleasanton in tandem with the WDT feed, and the extra data collected may be analyzed at a future date and perhaps compared to the 88D data. Our neighboring project, Southwest Texas Rain Enhancement Association (SWTREA) moved their meteorologist from Cotulla to Pleasanton in early June. Then, in mid-July, a new meteorologist – Stephanie Beall – arrived in Pleasanton to work on behalf of SWTREA. There were some difficulties to start, mainly dealing with radio contact between the meteorologist and the pilots, but these were fixed over time. In addition, the two projects occasionally shared planes as well as meteorologists. We at STWMA look forward to continued camaraderie between the two projects as we move into 2005. We also look forward to another year of working with the EAA.
It was a busy year, with 54 days of seeding. One notable event occurred in July, when seeding of the outer rain bands of Hurricane Emily took place over the southern target area. This was the second time this has been done in the STWMA program Hurricane Bret was the first, on August 21, 1999.
Gonzales County joined the program in June. It was the busiest year as far as number of seeding days since the inception of the program, with seeding take place on 57 days.
The STWMA welcomed a new pilot – Robert “Butch” Card, who hails from near Kenedy. South Texas experienced several months of excessive rainfall that resulted in periodic suspensions throughout the summer, similar to what occurred in 2002. Record rainfall totals were reported for many areas. Due to the excessively wet conditions and the suspension periods imposed on the project, the number of seeding days was the second lowest since the program began, second only to 2002 during the extreme flooding in July of that year. The STWMA, in an agreement with the EAA, began an experiment within the EAA target area to conduct a randomized seeding experiment. The protocol was drawn up early in the season with some guidance from NCAR, but due to the unfavorable conditions, the first randomized missions did not take place until mid-August. Only five days of randomized missions took place during the latter part of the season. During the early part of the summer, two film crews came to Pleasanton to film pieces on cloud seeding. The Discovery Channel filmed a piece on cloud seeding for their program, “Can We Control The Weather?” which aired in August. A second crew from 4th Row Films did some filming for a documentary on weather modification which was projected to finish sometime in 2008.
The season’s first seeding flight took place on March 18th. This was the first flight for our new pilot, Matt Pope, who trained during the year with Craig Funke. The first few months were disappointing as convection was sparse, so seeding missions were few and far between. The heart of the seeding season, June-August was rather busy June saw a lot of small, short-lived convective cells that were treated. July and August were characterized by frequent intrusions of tropical moisture and associated convection. Hurricane Dolly affected the area on the 23rd and 24th, and although a reconnaissance flight took place, no seeding occurred. By September, convection began to wind down and few opportunities for seeding presented themselves. Hurricane Ike impacted the area as it made landfall at Galveston on the 13th, but instead of bringing us rains, the circulation around Ike brought scorching heat, with many locations in the target area topping out between 100-105°F. Our final day of seeding took place on October 14th, the only day of the month that operations took place. The NWS radar upgrade to Build 10 during the spring gave us some issues with TITAN as the older machines were not able to handle the significant increase in data stream size, so a new agreement was made with WDT and new machines were to be installed in February 2009 which would handle the super-resolution data. In October, the STWMA purchased a twin engine Aztec, which incidentally was the first plane that was used for seeding back in 1997 when the project first began. This plane will be capable of performing top seeding as well as night seeding, both of which will be attempted in 2009.
Season number 13 saw the continuation of the drought that began the previous year, with the vast majority of seeding opportunities on small, short-lived clouds. With the purchase of the Aztec last year, some nighttime seeding events took place. The summer was very hot with over 60 days of highs at or above 100°F. The onset of El Niño by September brought a dramatic shift in the overall weather patterns with much-needed rains falling across the state. WDT installed a new computer in February that would be able to easily handle the recently- upgraded Doppler radars to super-resolution. The computers were also assembled such that when the anticipated changeover to Dual-Polarized radar occurs in the next few years, they will be able to handle and process the data.
The wet pattern that began in Fall 2009 continued through a good portion of 2010 with several months seeing well-above normal rainfall. There were a few excessive rain events that affected South Texas and these limited seeding operations due to the threat of flooding. Tropical Storm Hermine moved directly across the target area in September bringing heavy rains and gusty winds. The ongoing randomized seeding experiment within the EAA target area continued for its fourth year but only two suitable cases were realized during the season. The amount of cases acquired thus far falls well short of what is needed to conduct a reliable and acceptable analysis.
An intense drought plagued several southern U.S. states during the year, with the seeding season average rainfall at less than five inches in many parts of the target area. In addition, a record number of 100°F days were reported at Pleasanton (80). This affected operations, with a greatly reduced number of seeding missions compared to the long-term average. 2011 also saw the latest start to the program, with the first actual day of seeding not occurring until June 4. The pattern began to change in mid-September which allowed for several opportunities over a two-week period to conduct seeding operations.
At the beginning of 2016 Kendell LaRoche took over the position of Project Meteorologist for STWMA in Pleasanton. At this time 10 counties were part of the STWMA: Atascosa, Bandera, Bee, Bexar, Frio, Karnes, McMullen, Medina, Uvalde, and Wilson counties. 2016 had above average rainfall across most of south Texas, including the operational area. Most of the heavy precipitation took place in May, August, and September. The weather pattern across south Texas seemed to alternate back and forth between mostly sunny with no rain, to cooler with many consecutive days of rain during the season. The global weather pattern for 2016 started off with a strong El Nino, which decreased to a near neutral / very weak La Nina pattern by November. After October, there was a substantial decrease in number of rain events. The season began slightly later than usual on April 25, while the season ended much later than usual with 2 cloud seeding missions in November. During the season, flare dosage per storm was increased to see if more flares lead to a greater rain turnout. Overall, the yearly evaluation showed good results, with over 100 storms seeded, and cloud seeding activities bringing an additional 573,370 acre-feet of water during the season.
The same 10 counties from 2016 remained. The weather pattern begins the year with a near neutral / weak La Nina pattern. The winter months before cloud seeding began were spent repairing aircraft equipment, updating computer software, and exploring new research possibilities. A 'weather workshop' was held in San Angelo January 20-22. Topics included a 2016 summaries for each cloud seeding operation across TX, flare status and changes, and possible research techniques. March was spent testing aircraft and equipment for the upcoming season. During the end of March / beginning of April, the long time C-band radar at the airport, which use to be used for seeding operations, was dismantled and removed. The weak La Nina pattern began transiting to a more neutral pattern during late spring. The season began on April 11th as a weak cold front passed through the region. A few other cold front moved through the region throughout April, however these either did not cause any precipitation or the conditions were unsafe for pilots (low clouds, after dark). Representatives from STWMA, WTWMA, and Texas Tech attended the Weather Modification Association Annual Meeting in Boise near the end of April. Presentations were given by the meteorologist from WTWMA and STWMA on hygroscopic flare usage and Texas rainfall enhancement results from 2016. The first cloud seeding mission for 2017 occurred in early April, however beginning in mid April low clouds and rain occurred after sunset meant no other cloud seeding operations were conducted until the end of May. At the end of May a strong trough stalled over the Texas region, which sent many shortwaves into the region. These shortwaves, along with a stationary front, caused multiple days of showers and thunderstorms across the region. The trough eventually moved east and a strong ridge of high pressure sat over the region beginning in early June. The strong ridge persisted across southern TX until the last weekend in June, with a cold front stalled across the region, and brought 4 days of rain and cloud seeding. July began with another ridge of high pressure across the region, until about a week into July when morning and afternoon seabreeze thunderstorms became more common. July consisted of mostly afternoon seabreeze showers and storms which would dissipate with the loss of daytime heating. There were multiple days with no rain, however a few times a weak low pressure would form west of the border in Mexico and move north along the Rio Grand Plains, helping showers and storms develop. Also weak troughs would move into central TX and occasionally as far south as San Antonio and hill country. In mid July Archie, weather modification researcher, visited STWMA to offer guidance and test computer evaluation programs on the computers. By the end of July/beginning of August a strong trough/cold front moved through then stalled across the region, bringing multiple days of isolated and scattered showers and storms. A weather modification workshop was held in San Angelo August 8-10, with discussions on season results, new technology, and modification of seeding techniques. After August 10, a strong high pressure system developed over the Gulf, and pushed all moisture further east to eastern TX, and Louisiana while leaving south TX dry. The end of August saw hurricane Harvey impact the coast near Corpus Christ, dumping tremendous amounts of rain mainly east of the I-35 corridor. Cloud seeding was suspended for multiple days while the region dried out. Cloud seeding resumed in early September, however other than Sept. 4-5 the region was dominated by high pressure and slightly cooler temperatures. Near the end of September a strong high pressure stalled over the southeastern US, which brought warm and humid conditions to south TX. Chance of rain increased the last 2 weeks of September, with isolated to scattered showers and storms. A few rain chances extended into early October, however seeding only took place on Oct. 3. Most of October then became dry with a few cold fronts which pushed through the region. However most of these cold fronts were either took weak, or too dry to generate significant rainfall. The only strong front to generate rain on October 31 produced stratiform rain with low visibilities. Pilot was launched and attempted to investigate, but low ceilings and poor visibility made even getting close to the rain dangerous. The beginning of November was similar conditions, with warm and dry conditions. Seeding operations ended by end of the first week in November. The Pacific Ocean temperatures were near-to-below average by the time seeding in early Nov. The yearly results were excellent with 250 seeded storms, precipitation increased by 10.3% above the yearly average, and 855,485 acre-feet of additional water added to the operational area.
No changes to the participating counties for 2018: Atascosa, Bandera, Bee, Bexar, Frio, Karnes, McMullen, Medina, Uvalde, and Wilson counties. The year began with a slightly cooler than average temperatures in the Pacific. January was spent finishing the previous year annual report and working on future projects. The STWMA and WTWMA meteorologist attended the 98th American Meteorological Society Annual Meeting in Austin. The meteorologist worked with the Weather Modification Association to host a booth about weather modification during Weatherfest. The meteorologists provided information and answered questions on weather modification. Both meteorologist also attended multiple presentations during the Conference for Weather Modification. A summary of the 2017 season was presented to the Weather Modification Advisory Committee in Austin in early February.


Humberto Vivanco joined the STWMA in April as a pilot based out of Uvalde, TX. His main counties include Bandera, Medina, Uvlade and Bexar. These counties collectively make up what the STWMA calls the EAA (Edwards Aquifer Authority) counties. Humberto also manages the STWMA airplanes in Uvalde and helps relocate other planes, parts and flares as needed.


In June of 2021 Bria Hieatt took over the position of Project Meteorologist for STWMA in Pleasanton. At this time 10 counties were part of the STWMA: Atascosa, Bandera, Bee, Bexar, Frio, Karnes, McMullen, Medina, Uvalde, and Wilson counties. 2021 had above average rainfall across most of south Texas, including the operational area.


John Lorbach joined the STWMA in March as a pilot based out of Uvalde, TX. The same 10 counties remained from 2021. The 2022 season started out in a La Nina and the entire target area was in drought ranging from a category D2 (severe drought) to a category D4 (exceptional drought). In April, the project meteorologist Bria Hieatt attended the Weather Modification Conference in Corpus Christi, TX where the Distinguished Service Award for Pilot/Technician was presented to Mr. Craig Funke by the Weather Modification Association for his 20+ years of service.