Wind shear was negligible within the lowest of the atmosphere contrary to typical tornado outbreaks. Other metrics and indices used to diagnose tornado potential, such as the Energy Helicity Index, storm-relative helicity, supercell composite parameter, and the significant tornado parameter, were also lower than historically observed environments featuring tornadoes. For instance, the amount of storm-relative helicity within the lowest of the atmosphere—a common measure quantifying the amount of wind shear—was measured as 70&nbsp;m<sup>2</sup>/s<sup>2</sup> at Corpus Christi and reached 117&nbsp;m<sup>2</sup>/s<sup>2</sup> according to data from the Rapid Update Cycle computer model; values below 300&nbsp;m<sup>2</sup>/s<sup>2</sup> are correlated with weak tornadoes. A study published in Monthly Weather Review in 2007 described the environment as being "marginally favorable for supercells and unfavorable for significant, supercellular tornadoes."

Instead, the factors that enabled the eventual tornado outbreak may have transpired at a mesoscale involving several features becoming juxtaposed over Texas. The dry line delineating the boundary between the moist maritime air mass over East Texas and the drier continental air mass farther west remained nearly stationary in the region through the morning of May&nbsp;27. On the preceding evening, a mesoscale convective system developing along this dry line over eastern Oklahoma and Arkansas generated a well-defined gravity wave that traveled southwest across East Texas on the morning of May&nbsp;27. The development of new discrete supercells followed the advancing intersection of the cold front and dry line and the gravity wave as they continued southwest, The southwestward generation of storms brought them towards increasingly unstable air with higher CAPE, allowing the storms to acquire strong inflow and the requisite rotation to produce tornadoes.

There were at least three families of thunderstorms that developed as part of the initial southwestward-moving complex of storms, composed of at least 16&nbsp;distinct supercells; six of the cells formed along the cold front, five formed along the dry line, and five formed along the gust front imparted by previous storms. The gust fronts pushed outwards by the downdrafts of the thunderstorms served as foci for tornadogenesis; boundaries like gust fronts can provide low-level vorticity and rising air necessary for the formation of tornadoes. Some of the day's tornadoes were spun up by the gust front itself while others spawned from thunderstorms with preexisting mesocyclones aloft enhanced by the gust front underneath.

The day's first thunderstorm near Waco in McLennan County strengthened quickly in response to the highly unstable atmosphere. A severe thunderstorm warning—the first of the day—was issued for the county at 12:50&nbsp;p.m. Weather radars showed increasing rotation within the storm, prompting the issuance of a tornado warning at 1:21&nbsp;p.m. This storm produced the outbreak's first tornado southwest of Hewitt near Lorena. The same storm produced a second brief tornado near Bruceville followed by a third, intense F3&nbsp;tornado in southwestern McLennan County that lasted for 20&nbsp;minutes.

Farther south away from the southwestward-moving storm cluster, the cold front and dry line curved west, making them parallel to the advancing gravity wave; this triggered the development of numerous and intense storms between Austin and the Big Bend after 3:00&nbsp;p.m. when the gravity wave intersected the front. The parallel orientations of the wave and the other boundaries precluded these storms' rotation. A tornado watch was later issued by the SPC at 12:54&nbsp;p.m. for parts of eastern Texas and western Louisiana, citing the unstable airmass in place over the region. The Dallas/Fort Worth and Austin/San Antonio National Weather Service forecast offices also issued bulletins on the morning of May&nbsp;27 noting the potential for severe weather. However, these early outlooks focused more on the threat of wind and hail rather than tornadoes due to the low wind shear present over the region.

The Dallas/Fort Worth National Weather Service forecast office ultimately issued 10&nbsp;tornado warnings and 5&nbsp;severe thunderstorm warnings between 1 and 5&nbsp;p.m. on May&nbsp;27. The Austin/San Antonio office issued 8&nbsp;tornado warnings, 24&nbsp;severe thunderstorm warnings, and 10&nbsp;flash flood warnings during the afternoon and evening of May&nbsp;27, with 80&nbsp;percent of their issued products occurring after 5&nbsp;p.m. in connection with the widespread storms that developed later in the day separate from the initial tornadic storms. In one case, a media outlet's decision to manually activate the Emergency Alert System rather than allow weather warnings to automatically trigger it resulted in a 25–30&nbsp;minute delay in the dissemination of a warning. Interviews conducted by a National Oceanic and Atmospheric Administration service assessment team found that many watched the approach of tornadoes prior to taking shelter due to their slow movement and high visibility. In the case of the F5 Jarrell tornado, some fled while others took shelter. Due to the strength of the tornado, some who stayed behind were killed despite taking appropriate safety measures.

Confirmed tornadoes

{| class="wikitable collapsible sortable" style="width:100%;"

|+ List of confirmed tornadoes – Tuesday, May 27, 1997

|-

! scope="col" width="3%" align="center"|F#

! scope="col" width="7%" align="center" class="unsortable"|Location

! scope="col" width="6%" align="center" class="unsortable"|County

! scope="col" width="6%" align="center"|Start Coord.

! scope="col" width="6%" align="center"|Time (UTC)

! scope="col" width="6%" align="center"|Path length

! scope="col" width="6%" align="center"|Max width

! scope="col" width="6%" align="center"|Damage

! scope="col" width="48%" class="unsortable" align="center"|Summary

|-

|bgcolor=# | F2

|W of Lorena

|McLennan

|

|18:21&nbsp;– 18:33

|

|

|

|Several large trees were uprooted and a mobile home was destroyed.

|-

|bgcolor=# | F0

|Eddy area

|McLennan

|

|18:44&nbsp;– 18:47

|

|

|

|Tornado reported by a sheriff deputy caused no damage.

|-

|bgcolor=# | F3

|E of Moody

|McLennan, Bell

|

|18:46&nbsp;– 18:59

|

|

|

|Most of the tornado's path occurred in McLennan County. A home and a barn were destroyed on Dowell Road after the tornado initially touched down in open terrain near Farm to Market Road 107; these structures received F3&nbsp;tornado damage. Another home nearby was also damaged and a pickup truck and car were displaced by several hundred feet. The tornado moved south-southwest, crossing the border between McLennan and Bell counties and traversing open country. There, numerous trees were uprooted. A local news station also captured this tornado and much of its life cycle as it passed within a few miles of their skycam and station.

|-

|bgcolor=# | F0

|WNW of Belton

|Bell

|

|19:16&nbsp;– 19:27

|

|

|

|Weak tornado remained stationary for much of its existence before dissipating.

|-

|bgcolor=# | F3

|N of Belton

|Bell

|

|19:27&nbsp;– 19:45

|

|

|

|The tornado began on the northern shores of Lake Belton at Morgan's Point Resort. A marina was destroyed on the lake's northern shores, leading to the capsizing of 100&nbsp;boats. Ten homes along the same shore sustained severe damage and trees were destroyed. The tornado then crossed the lake and moved ashore northeast of the community of Woodland, downing many trees and causing heavy damage to at least six structures. The tornado was on the ground for a third of a mile after traversing the lake before lifting.

|-

|bgcolor=# | F1

|SW of Belton

|Bell

|

|19:50&nbsp;– 19:58

|

|

|

|Brief tornado with unknown damage.

|-

|bgcolor=# | F1

|Blooming Grove area

|Navarro

|

|20:05&nbsp;– 20:10

|

|

|

|Brief tornado uprooted several large trees.

|-

|bgcolor=# | F2

|N of Jarrell

|Williamson

|

|20:25&nbsp;– 20:33

|

|

|

|First of two tornadoes that preceded the Jarrell&nbsp;F5 tornado.

|-

|bgcolor=# | F2

|NW of Jarrell

|Williamson

|

|20:35&nbsp;– 20:39

|

|

|

|Second of two tornadoes that preceded the Jarrell&nbsp;F5 tornado; classified as a multi-vortex tornado.

|-

|bgcolor=# | F1

|S of Dawson

|Navarro

|

|20:36&nbsp;– 20:40

|

|

|

|Brief tornado uprooted large trees.

|-

|bgcolor=# | F5

|W of Jarrell

|Williamson

|

|20:40&nbsp;– 20:53

|

|

|

|27 deaths&nbsp;– See article on this tornado – 12 others were injured.

|-

|bgcolor=# | F0

|SW of Hubbard

|Hill

|

|20:50&nbsp;– 20:53

|

|

|

|Brief tornado caused no damage.

|-

|bgcolor=# | F3

|Cedar Park

|Williamson, Travis

|

|21:05&nbsp;– 21:15

|

|

|

|This tornado moved south through Cedar Park before crossing into Travis County and lifting just northeast of Mansfield Dam. The thunderstorm that spawned the tornado developed along the flanking line of the storm that produced the F5&nbsp;tornado in Jarrell. It initially touched down in an open area, causing minor shingle damage to a house and damaging a few trees. Before moving into Cedar Park, the tornado caused F1 and F2&nbsp;damage. Localized F3&nbsp;damage occurred within Cedar Park's business district. Most of the roofing on an Albertsons grocery store was torn away; the store's walls and doors were also severely damaged or destroyed. At least seven people were injured in the store and one person was hospitalized, though additional injuries were mitigated by the sheltering of customers in the store's refrigeration units under the direction of the store's manager. Several businesses were damaged along US-183; one business lost most of its roof, though damage to most other businesses was minor. Near the highway, a historic steam locomotive, Southern Pacific 786, was struck by the tornado with superficial damage, and its oil tender was flipped over and thrown a short distance from it. The tornado then moved into the Buttercup Creek subdivision in southwestern Cedar Park, inflicting F1–F3&nbsp;damage to 136&nbsp;homes. Some homes sustained significant roof loss and severe structural damage; eleven were destroyed. It then curved towards the southwest into Travis County and downed ten percent of trees in a wooded area before lifting north of Lake Travis. Fifteen people were injured by the tornado.

|-

|bgcolor=# | F1

|NW of Four Points

|Travis

|

|21:15&nbsp;– 21:15

|

|

|

|Brief tornado with minimal damage.

|-

|bgcolor=# | F4

|W of Lakeway

|Travis

|

|21:50&nbsp;– ?

|

|

|

|1&nbsp;death&nbsp;– The tornado touched down near the shore of Lake Travis, destroying a marina and most of the watercraft at the docks. Trees in the area were contorted and uprooted, though other nearby structure sustained minor damage of F0&nbsp;severity. Numerous structures sustained varying degrees of damage as the tornado moved westward and later southwestward, including a Southwest Bell telephone building on Bee Creek Road that was destroyed and a home across the road that had several collapsed walls. The destruction of the well-constructed telephone building warranted an F4&nbsp;rating. The tornado then made a turn towards the southwest roughly from Lake Travis, bringing it across a hill where buildings and trees were destroyed. Further southwest, a steel tower carrying high transmission power lines was destroyed. Additional site-built homes, mobile homes, and other buildings were either heavily damaged or completely destroyed in the Hazy Hills subdivision, leaving many uninhabitable. This included well-built homes within the subdivision. One person was killed following the destruction of his mobile home and vehicle, though investigators could not establish whether he was in the home or attempting to evacuate when the tornado struck. The tornado crossed Texas State Highway 71, entering another subdivision near Lick Creek and causing as high as F2&nbsp;tornado damage to structures in the area, including the complete unroofing of one house near Pedernales Drive. Throughout the tornado's path, numerous trees were downed and 25&nbsp;homes were destroyed; five people were injured.

|-

|bgcolor=# | F1

|N of Kyle

|Hays

|

|22:38&nbsp;– 22:45

|

|

|

|Trees and power lines were knocked over.

|-

|bgcolor=# | F0

|S of Utopia

|Uvalde

|

|00:00&nbsp;– 00:03

|

|

|

|Tornado remained over open country.

|-

|bgcolor=# | F0

|NW of Sisterdale

|Kendall

|

|00:30&nbsp;– 00:32

|

|

|

|Tornado remained over open country.

|-

|bgcolor=# | F0

|NE of Moore

|Frio

|

|01:20&nbsp;– 01:23

|

|

|

|Tornado remained over open country.

|-

|}

Jarrell, Texas

This violent and slow moving tornado began within the Williamson County line north of Jarrell as a narrow and rope-shaped funnel swathed in large amounts of dust when it touched down at 3:40&nbsp;p.m. The Texas Highway Patrol also stopped traffic on both sides of the interstate under the expectation that the tornado would cross the highway; it ultimately moved parallel to Interstate&nbsp;35. Tracking south-southwest, the tornado quickly intensified and grew to a in width, changing from its initial thin and white appearance to a blue and black color. Some of the most extreme damage at this location was inflicted to a small metal-framed recycling plant that was obliterated, with little left of the structure besides a few twisted structural beams.

left|thumb|The Double Creek Estates subdivision was pulverized by the tornado, with many homes swept off their foundations and disintegrated. This photograph shows one remaining foundation with plumbing pulled out of the concrete.|alt=Black and white photo of the remaining foundation of a destroyed home.

The tornado then slowly entered the Double Creek Estates subdivision where it exacted its most catastrophic impacts. Concurrently, the tornado expanded further to its maximum width of . The mostly wooden-framed residences, some well-built and anchored, were completely obliterated and swept away, leaving behind concrete slab foundations swept clean of all debris.

The tornado turned slightly towards the south-southwest after traversing Double Creek Estates. Some of the damage to the trees suggested that the tornado may have been a multiple-vortex tornado, which was documented by Scott Beckwith, receiving a nickname as a “dead man walking”. Shortly after entering this forested area, the path of damage left behind by the tornado ended abruptly, with the National Centers for Environmental Information indicating that it lifted at 3:53&nbsp;p.m. after remaining on the ground for 13&nbsp;minutes and . Kelly Air Force Base in San Antonio registered a gust of at 8:03&nbsp;p.m. Gusts reached in Del Rio and overturned a plane at an airport near Seguin. The Southwestern Insurance Information Service estimated that the totality of the storms' effects inflicted $25–40&nbsp;million in insured losses; most insured claims originated from Cedar Park.

Aftermath

thumb|The memorial at Jarrell Memorial Park naming the victims of the 1989 and 1997&nbsp;Jarrell tornadoes|alt=A granite memorial with victims' names

Law enforcement officers from the Texas Department of Public Safety, four municipal police departments, and two county sheriff's offices aided search-and-rescue efforts in the aftermath of the Jarrell tornado. The Texas National Guard and other volunteers from around Central Texas joined in the search. The Jarrell Volunteer Fire Department organized a temporary morgue; Although a death toll of 30&nbsp;people was initially reported, that figure was later revised to 27; the inflated count was attributed to the dispersion of remains that led some fatalities to be tallied twice. The Federal Emergency Management Agency elected not to provide federal aid, citing the contributions from private and state sources. The U.S. Congress approved a relief bill allocating $5.4&nbsp;billion for 35&nbsp;states affected by natural disasters, including Texas. However, the bill also included other provisions that led President Bill Clinton to veto the bill. A drive-through donation line was established at Auditorium Shores in Austin. Local musicians organized and performed at a benefit concert at Austin Music Hall, attracting an audience of 2,800 and raising about $94,000. Businesses also donated to the relief efforts. Vouchers were distributed by the American Red Cross to storm victims in the Buttercup Creek subdivision for clothing, food, and other supplies. The events and survivor accounts of the tornado were profiled in television documentaries such as the 1999 episode of HBO's America Undercover series titled "Fatal Twisters: A Season of Fury", the 1999 BBC television series titled Twister Week (also known as Tornado Diary in the United States) in an episode titled "Tornado Alley", the seventh episode of the Discovery Channel program Storm Warning, produced by GRB Entertainment, and the 2006 documentary Ultimate Disaster (also known as Mega Disaster) on National Geographic Channel.

See also

  • List of North American tornadoes and tornado outbreaks
  • 1922 Austin twin tornadoes&nbsp;– also featured southwestward-tracking tornadoes that struck the Austin, Texas, area
  • Tornado outbreak of April 6–9, 1998&nbsp;– produced the official first F5&nbsp;tornado after the Jarrell tornado
  • 1953 Waco tornado&nbsp;– the deadliest tornado in Texas history

Notes

References

Bibliography

  • Aerial Damage Survey of the Central Texas Tornadoes of May 27, 1997 (PDF) (National Weather Service), includes discussion and map of the tornado's track
  • Texas Tornadoes (National Climatic Data Center)
  • Satellite imagery (University of Wisconsin–Madison)
  • Stormtrack Magazine Nov/Dec 1997: Jarrell, Texas Tornado Expanded Edition (PDF)