A Classic Case: the June 2 Intercept
Valuable data on two storms that produced violent tornadoes were obtained by VORTEX on June 2, 1995. The storms formed in a region of strongly backed low-level flow with modest westerly flow aloft, yielding strong deep shear. The target area for VORTEX for storm initiation was Clovis, New Mexico. Storms formed in this area (the boxed area below) in the late afternoon.Forecast Discussion for June 2, 1995
The first storms seemed somewhat disorganized. However, inflow quickly increased to 40-50 knots, so it was felt that the storms had a lot of potential for becoming supercells. The first target storm moved northeast along US 60 toward Friona, TX. When the storm was near Bovina, TX, inflow became so strong that visibility went to zero in blowing dust, and power lines were torn down at a distance of 15 kilometers southeast of the storm. Some surface teams were forced to turn away from the storm because of these conditions. The other teams that were closer to the developing mesocyclone reported winds of 30-50 knots flowing toward the mesocyclone from all directions. The mobile Doppler radar scanned the storm from a distance of 12 kilometers and observed very strong low-level horizontal shear. This information was reported in real-time to the field coordinator.
The first violent tornado formed just southwest of Friona, moved across the southern fringes of the community, and then across the eastside of town. It traveled for several miles further northeast to the area north of Black, TX. At Friona, a large grain elevator was destroyed. The airport was completely destroyed, with the most significant damage occurring to a large steel building. The anchor bolts holding the columns of this building were ripped out of the concrete slab, with part of the slab going with the bolts. The heavy beams were left in a twisted heap. One I-beam became a missile and was thrown about 100 meters. The cemetery just north of the airport was also heavily damaged, with trees missing most of their branches. A several-ton railroad boxcar that served as a storage building bounced through the cemetery, destroying monuments and gouging a two-foot deep hole through an asphalt drive into hard-packed soil. The boxcar traveled about 100 meters.
After the Friona tornado became rain-wrapped, attention shifted to a new mesocyclone just southeast of Friona. This mesocyclone was projected to move into a region with very few roads. Another mesocyclone was developing southwest of Dimmitt, TX. VORTEX targeted that storm. At times, more than a half-dozen mesocyclones were in existence over a few-county area, making the intercept very risky in terms of choosing the 'best' storm and staying safe.
VORTEX Communications Summary
As the mesocyclone approached Dimmitt, teams quickly converged on their correct storm-relative positions around Dimmitt. The mobile Doppler briefly scanned the near-ground mesocyclone region south of Dimmitt. A tornado developed quickly on the south side of Dimmitt, moving cyclonically about the mesocyclone to just east of Dimmitt, and then curved back towards the northeast. Mobile mesonet data were obtained in all quadrants of this tornado within 3 kilometers. Video was obtained from several sites. The mobile Doppler obtained tremendous data as the tornado moved in an arc around the Doppler position on the 3-kilometer range ring. The tornado debris cloud itself appears in the reflectivity data (below right).
When the tornado crossed TX 86, it removed the pavement in a 10 meter wide swath over a length of approximately 100 meters. The asphalt was thrown over 200 meters into the adjacent field. Power poles were snapped at the ground. Vehicles were totally destroyed, with reports of two truck trailers missing entirely.
The picture series below (in the form of a Java applet) shows the tornado as it passes US385.
Dimmitt Damage Track
NCAR Electra Flight TrackAs the Dimmitt tornado was in progress, another, less significant tornado was occurring about 10 miles north of Dimmitt, associated with the mesocyclone that formed southeast of Friona. The research aircraft were forced to fly on the west sides of these storms because of the wide-spread intense convection. The aircraft collected a large number of pseudo-Doppler volume scans that were at somewhat greater ranges than normal.
VORTEX obtained a rich data set on one significant tornado event, the Dimmitt tornado, and a good data set at Friona, although that event was sampled somewhat less thoroughly than the Dimmitt tornado.
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