May 25 1996 Southern High Plains Tornadoes
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Detailed Tornado Cases for Amarillo and Lubbock
Brief Overview
Storms
developed along the dryline in eastern New Mexico and far west Texas.
The first storm developed soutwest
of Tucumcari
around 11 am to 1130 am MST. This was probably the storm that
moved north-northeast, producing
several
tornadoes after crossing an outflow boundary northeast of Tucumcari. A
brief tornado occurred 15 miles
southwest of
Amistad. Another tornado occurred with this storm near Sedan with barns
and irrigation piping damaged.
Another
tornado occurred near Texline(apparently with this storm) and a final
tornado occurred near Felt, OK with
roof, power
pole and tree damage. The tornadoes with this storm were in very rural
country.
Another
storm developed along the Texas/New
Mexico border to the southeast of Clovis and moved north-northeast,
producing several tornadoes. Most of the tornadoes were
fairly brief. The last tornado did some property damage in this
very rural area. A map of the storm locations can be found here.
I tried to
roughly estimate the storm motion based on storm spotter
locations/times and tornado reports. I came up with
30
mph for the storm
motion. This is slower than one would expect based on the 00z AMA
sounding that showed 50kts
at 850mb, 60
kts at 700mb
and 75kts at 500mb. I think that the mid level flow must have been
at least 10 kts weaker
where the tornadic storm
was located. I don't think the 00z AMA sounding was contaminated.
Sam Barriclow,
Gilbert Sebenste, Chuck Doswell, Al Moller and myself were all chasing
on this day. I managed to miss
the tornadoes.
Chuck Doswell has some tornado pics from this day on his webpage.
Synoptic Sequence of
events
The key to
this event was an outflow boundary that stretched from just south of
Lubbock northwest to just east of Clovis in the
afternoon. To
the west of this boundary, T/TD spreads were fairly high. Immediately
east of the boundary T/TD spreads were
lower and
CAPES were around 3000 j/kg. There was a narrow corridor on the cool
side of the boundary with strong instability.
T/TD around
Friona were around 80F/65F. Further east it was too cool and CAPES were
much lower. Of course this
is very
typical. Storms developed near the dryline and then crossed an outflow boundary as they moved north-northeast.
One negative on this day may have been the fairly strong mid level
flow. Storms did not stay in the favorable corridor for
very long
before moving into stable air. The 00z Amarillo sounding and a modified
sounding for Friona can be found here. The
pressure of
870mb was used for Friona(elev. 4000ft compared to 3600ft at Amarillo).
But then again, the good shear on this
day was partly
due to the strong mid level flow.
Surface charts:
21 UTC May 24
00 UTC May 25
03 UTC May 25
06 UTC May 25
09 UTC May 25
12 UTC May 25
14 UTC May 25
16 UTC May 25
18 UTC May 25
21 UTC May 25
500mb charts:
12 UTC May 25
00 UTC May 26
250mb charts:
00 UTC May 26
700mb charts:
00 UTC May 26
Similar West Texas Events
A
special surface pattern often develops on days with significant
tornadoes northwest of Lubbock or the general area
between
Lubbock and Clovis including Hockley, Lamb, Bailey, Lubbock, Hale and
Parmer counties. I have discovered
this while
exploring case after case of tornadoes for the United States. One of
these situations occurred on June 2, 1995
and was
documented by the project VORTEX crew. A low level thermal gradient
often develops in this part of west
Texas from
several mechanisms, namely outflow boundaries, upslope cooling and warm
fronts. I believe that the upslope
cooling
mechanism operates in many of these cases. An excellent example of a
boundary developing near Lubbock from
upslope
cooling north of Lubbock occurred on May 10, 1991. When southeast low
level flow is in place across west
Texas and the
panhandles, cooling occurs between Lubbock and Amarillo. This is due to
the very sharp elevation gradient
in west Texas.
Note in this topo map how rapidly the elevation drops off ne/e/se of
Lubbock. This elevation gradient is
not as
pronounced in western Kansas and southwest Texas. Upslope flow north of
west Texas warm fronts also creates
a low level
thermal boundary with very high dewpoints advecting westward on the
cool side of the boundary. Very
Very high
dewpoints can be achieved on the cool side of these boundaries since
vertical mixing is not as strong.
Obviously the
shear profile is greatly enhanced since the winds tend to be very
backed on the cool side of the boundaries.
LCL heights
are also lower on the cool side. From the many cases I have looked at, I believe that the west Texas
tornado environment is special and different from
other parts of the country. I think that there is a local tornado
maximum around
the Olton, Littlefield, Muleshoe, Friona area. One could argue that
this is due to population density but
I still think
that this is a local hot spot for tornadoes. Some other cases like
these include:
June 11, 1964 Outflow boundary(tornado in Parmer county)
Apr
17, 1970 warm front(tornado outbreak)
April 21, 1957 outflow from previous MCS and upslope flow reinforcing boundary(meridional mid-level flow with NW moving violent tornadoes)
May 24, 1957 warm front(tornado outbreak)
May 10, 1991 upslope driven surface boundary ( meridional mid-level flow with NW moving tornadoes in Bailey and Parmer counties)
May 31, 1968 outflow boundary(tornadoes west of Lubbock and near Kress)
June 02, 1965 outflow boundary(killed tornado north of Lubbock)
May 29, 1990 warm front enhanced by outflow(tornado in Lamb county)
June 02, 1995 outflow boundary(Friona and Dimmitt tornadoes)
June 03, 1989 outflow boundary(Muleshoe tornado)
May 29, 1987 outflow boundary(Wolfworth tornado)