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On 2 June, VORTEX obtained much-needed data on two storms which
produced violent tornadoes. The storms formed in a region of
strongly backed low-level flow with modest westerly flow aloft,
yielding strong deep shear. CAPE was larger then 3500 J/kg.
The target area for VORTEX for storm initation was Clovis, New
Mexico. Storms formed in this area in the late afternoon.
The first storms seemed somewhat disorganized. However, inflow
quickly increased to 40-50 kt, so we felt that the storms had a
lot of potential for becoming supercells.
The first target storm moved NE along US 60 toward Friona, TX.
When the storm was near Bovina, inflow became so strong that
visibility went to zero in blowing dust, and power lines were
torn down at a distance of 15 km SE of the storm. Some surface
teams were forced to turn away from the storm because of these
conditions. The other teams which were closer to the developing
mesocyclone reported winds of 30-50 kt flowing toward the
mesocyclone from all directions. The mobile Doppler scanned the
storm from a distance of 12 km and observed very strong
low-level horizontal shear and reported this information in
realtime to the Field Coordinator.
The first violent tornado formed just SW of Friona, moved across
the southern fringes of the community, and then across the east
side of town. It traveled for several miles further NE 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 being 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.
There, trees had most of their branches removed. A several-ton
railroad boxcar which served as a storage building bounced
through the cemetery, destroying monuments and gouging a 2-foot
deep hole through an asphalt drive and into hard-packed soil.
The boxcar traveled about 100 meters.
At this time, VORTEX is reluctant to establish an F-scale rating
because of the usual problems with this rating system. In much
of the VORTEX region, the probabilities are miniscule of
tornadoes striking areas with residential/business structures
from which damage ratings can be obtained. I can say that the
visual impression of the damage northeast of Friona is
consistent with other damage swaths I have seen that were rated
high-end F4. Officially, I would have to say that this tornado
was a significant, violent tornado, and assign it the rating of
F-unknown. Of course, I don't speak for all of the VORTEX
investigators in this informal information statement.
After the Friona tornado became rain-wrapped, attention shifted
to a new mesocyclone just SE of Friona. This mesocyclone was
due to move into a region with very few roads, and yet another
mesocyclone was developing SW of Dimmitt, so 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).
As the mesocyclone approached Dimmitt, teams quickly converged
on their correct storm-relative positions around Dimmitt (kudos
to all participants!). The mobile Doppler scanned the
near-ground mesocyclone region south of Dimmitt briefly. A
tornado developed quickly on the south side of Dimmitt, moving
cyclonically about the mesocyclone to just east of Dimmitt, and
then curved back northwestward. Mobile mesonet data were
obtained in all quadrants of this tornado within 3 km. Video
was obtained from several sides.
The mobile Doppler obtained tremendous data as the tornado moved
in an arc around the Doppler position on the 3 km (!) range
ring. The tornado debris cloud itself appears in the
reflectivity data. It is largest in the boudary layer, with
high reflectivities all the way to the axis. The debris cloud
narrowed above the boundary layer, and the core had very low
reflectivity. Higher up, the tornado widened. The tornado
reflectivity contained a number of fascinating asymmetries,
including a high-reflectivity "inflow band" in the boundary
layer. Doppler velocities are strong (folded two or three times
with a 16 m/s Nyquist velocity), and the flow is smooth enough
that the velocity data can be unfolded easily.
This tornado was also a violent tornado, with the same F-scale
assignment problems as discussed above. Where structures were
damaged, the damage (tentatively) was rated F3. However, when
the tornado crossed TX 86, it removed the pavement in a 10 m
wide swath over a length of 100 m (don't quote me on those
dimensions... a real damage survey report will be forthcoming).
The asphalt was thrown over 200 m into the adjacent field.
Power poles were snapped at the ground. Vehicles were totally
destroyed, with reports of two truck trailers missing entirely.
Once again, my personal opinion is that the "honest" F-scale
rating, as with most Plains tornadoes, is "F-unknown".
As the Dimmitt tornado was in progress, another, less
significant tornado was occurring about 10 miles north of
Dimmitt associated with the mesocyclone (noted above) which
formed southeast of Friona.
The research aircraft were forced to fly on the west sides of
these storms because of the widespread intense convection. A
large number of pseudo-dual Doppler volume scans were collected
by the aircraft at somewhat greater ranges than normal.
In summary, VORTEX has obtained a rich data set on one
significant tornado event (Dimmitt tornado). Data were obtained
which will allow us to document the entire life cycle from
genesis through the rope-tornado demise. We obtained a good
data set at Friona, although that event was sampled somewhat
less well than the Dimmitt tornado. We believe these data sets
will compliment the many rich data sets we have for non-tornadic
supercells, as well as those representing tornadic storms with
weaker tornadoes.
To those of you who intercepted either storm who aren't
associated with VORTEX: VORTEX is very interested in obtaining
copies of any video footage or other photographic material you
may have. Contact me via email at rasmussen@nssl.noaa.gov, or
by phone at 405-366-0560.
Erik Rasmussen
Jerry Straka