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)