Local Storms (SELS) Unit amended the convective outlook issued
earlier to include "Isolated thunderstorms with large hail
expected in High Plains of West Texas east of Pecos late afternoon
and early evening"
pm: SELS Unit advised that the air mass in the high country
of West Texas was unstable, isolated thunderstorms would be severe,
and that "local areas should be monitored for this possibility"
pm to 5 pm:
Warm and dry conditions dominated Lubbock, with temperatures climbing
from the middle 80s into the lower 90s and dewpoints holding steady
pm: Towering cumulus clouds began developing in the
6:30 pm: First radar echoes
appear south of Lubbock on the Amarillo WSR-57 scope.
Lubbock radar detected a moderate thunderstorm 15 miles south
of the Lubbock Airport or about 5 miles south of the Lubbock city
limits near the community of Woodrow.
pm: Cumulonimbus clouds (Cb), which are dense, vertically
developed clouds, reported by the Lubbock Weather Bureau (located
at Lubbock Municipal Airport). Also, the following statement was
transmitted over the weather wire: Moderate thunderstorm with
a diameter of 10 miles indicated by Lubbock radar at 6:55 pm.
pm: Forecasts were revised to include thunderstorm activity
for Lubbock and vicinity, and transmitted over the weather wire.
pm: The following statement was transmitted over the
weather wire: The Lubbock radar detected a moderate thunderstorm
10 miles south of the Lubbock Airport near southern city limits;
thunderstorm increasing in intensity.
pm: Lubbock forecasters called the Amarillo Weather Bureau
Office (WBO) on the Federal Telecommunications Service (FTS) and
talked to the radar operator. Amarillo radar indicated cloud tops
near 46,000 feet and increasing. The 7:00 pm sounding observation
at Amarillo indicated a tropopause of 48,000 ft, an increase of
7,000 ft since the 7:00 am observation.
pm: Severe Thunderstorm Warning Bulletin until 9:00 pm
for Lubbock, Crosby, eastern Hale, and Floyd counties transmitted.
Emergency Action Notification Signal (EANS) requested. Long form
of Severe Thunderstorm Warning Bulletin with specific details
sent near 8:00 pm. Also, Civil Defense was given warning by telephone.
The switchboard operator was requested to notify Mr. Payne, the
Civil Defense Director.
pm: The Texas Department of Public Safety (DPS) reported
to the Lubbock WBO on marble-size hail in the 1300 block of 58th
Street (southeast Lubbock).
pm: Radio Station KFYO used EANS to alert other radio
and television stations that a special warning message is coming
over the network. No "commercials" given by KFYO from
this time until 7:30 am, May 14th.
pm: Public reported golf ball-size hail 3 miles south
of Lubbock city limits.
pm: Severe Weather Statement transmitted reiterating
warning and advising of golf ball to egg-size hail south of town
8:10 pm: Funnel cloud, associated
with the first tornado, reported by an off-duty policeman 7 miles
south of the airport.
golf ball- to grapefruit- size (4.00 inch diameter) hail was reported
from Lubbock Downs (about 2 to 3 miles south of city limits).
Lubbock WBO checked with Amarillo radar personnel on severe storm
just south of Lubbock and found that cloud tops had increased
to 55,000 ft. Additionally, another Severe Weather Statement transmitted
reiterating the warning and advising of grapefruit-size hail 5
miles south of the city.
pm: Baseball-size hail reported by the public in southeast
pm: Tornado Warning Bulletin issued until 9:00 pm for
Lubbock, western Crosby, eastern Hale, and Floyd counties transmitted
on the Weather Wire. The warning noted the funnel cloud report
along with a hook echo developing in that same location on the
Lubbock WBO Weather Service Radar (WSR)-1 radar, apparently moving
northeastward. The warning was transmitted on the weather wire
and relayed by phone to the Civil Defense Director.
pm: First tornado touches down near Broadway and Quirt
Avenue (now Martin Luther King Jr. Blvd) on the east side of town.
pm: Baseball-size hail reported to the Lubbock WBO by
the public about 5 miles south of the airport.
pm: Severe Thunderstorm Watch Bulletin Number 225 issued
by the national Severe Storms Forecast Center (NSSFC) for all
of the South Plains valid until 2:00 am CDT Tuesday morning.
pm: Severe Weather Statement issued by Lubbock WBO included
numerous reports of large hail reported in Lubbock area in past
30 minutes. The WSR-1 radar indicated hook at 8:40 pm, 5 miles
south-southeast of the airport.
pm: Tornado Warning Bulletin continued for persons in
Lubbock, western Crosby, southern Floyd, and southern Hale counties
valid until 10:00 pm.
pm: A small tornado takes a roof off a barn located about
8 miles north of Crosbyton.
pm: Texas DPS informed Lubbock WBO of golf ball-size
hail about 6 miles southeast of the airport.
pm: Public reported to Lubbock WBO baseball-size hail
at Holiday Inn East and Mackenzie State Park about 4 miles south
of the airport.
pm: Bulletin issued advising of latest radar report,
recent reports of large hail in the Lubbock area, and reiterating
the continuation of the tornado warning.
pm: Lubbock WBO advised the Texas DPS in Lubbock to notify
Idalou police (10 miles east of Lubbock) to sound tornado warning.
pm: Lubbock WBO advised the Shallowater Fire Department
by telephone of severe storm 5 miles south of their area.
pm: 2.00 inch diameter hail observed at the Lubbock Airport.
Second larger and more destructive tornado touches down near 19th
Street and University Avenue. The Lubbock WBO WSR-1 radar indicated
a tornado about 7 miles southwest of the airport near 19th and
Brownfield highway. This information was relayed by two-way radio
and telephone to Civil Defense. Sirens were sounded at 9:35 pm
(this was the time that a patrolman reported a funnel in this
part of the city). Also, the Texas Zone Forecasts for Lubbock
and vicinity are issued, including the severe thunderstorm watch.
The remainder of the amended forecast was going to be issued after
10:00 pm, but because of the tornado hitting downtown Lubbock,
loss of communications at 9:49 pm prevented transmission.
pm: Power failure at Civil Defense Headquarters.
pm: The last communications between Lubbock WBO and Lubbock
Civil Defense reported that "hooks" were indicated on
radar around 9:45 pm about 5 miles southwest of the airport.
pm: Lubbock WBO lost all communications. Power to the
WSR-1 radar failed when the emergency generator died.
pm: Lubbock WBO personnel abandoned the WBO to take cover
from the approaching tornado.
pm: 77 knot wind recorded at the Lubbock Airport.
pm: Second tornado passed over the Lubbock WBO.
pm: Lubbock WBO, using the two-way Lubbock Fire Department
radio, relayed tornado warnings to the Abernathy, new Deal, and
Petersburg areas. Sirens were sounded in Petersburg at an unknown
time. Tornado warning was valid until 11:00 pm and included Lubbock,
western Crosby, southern Hale, and southern Floyd counties. Message
relayed by Fire Department operator.
pm: Lubbock WBO relayed information to EOC by two-way
radio that the tornado warnings were officially cancelled for
all areas as storms had decreased to moderate intensity in the
The thunderstorm that spawned the
Lubbock tornado was unique in that it formed on a retreating dryline.
The dryline is a narrow boundary between dry continental air to
the west and moist air from the Gulf of Mexico to the east. It
is often present across the high plains of the U.S. during the
springtime and is especially common in the south plains of West
Texas. When there is not a strong storm system bringing winds
that will overwhelm the dryline, the dryline will move east (advance)
during the day as the air heats up and then will move back to
the west (retreat) during the evening. While thunderstorms often
form along advancing drylines during the afternoon and can produce
large hail and even tornadoes, thunderstorms that form along retreating
drylines are much less frequent, and only rarely produce tornadoes.
This is due in part to the air becoming more stable (air temperature
decreases less rapidly with height) as the air cools near the
ground after the sun sets.
The figures below show the atmospheric
conditions that existed leading up to and during the Lubbock tornado.
These are common maps that meteorologists use to examine the state
of the atmosphere. In the 1970s, the only ways to collect information
from the atmosphere above the surface was to use weather balloons.
For more information on these balloons please click
Series of surface weather maps
on May 11, 1970. The maps, from left to right, are at 4 pm CDT
(2100 UTC), 7 pm CDT (0000 UTC), and 10 pm CDT (0300 UTC).
Click on the maps for larger views.
above series of surface weather maps concentrate on the dryline
location throughout the late afternoon and evening of May 11,
1970. The dryline initially made its way east of Lubbock during
the early afternoon, with winds shifting from south to west and
dewpoints, which are a measure of the moisture in the air, dropping
from lower 60s at 10 am CDT to mid 30s by 1 pm. Click
here to view the hourly observations taken at the Lubbock
Airport on May 10, 11, and 12, 1970.
However, as the 4 pm surface map
and observations show, the winds quickly
switch back around to the south at the airport, preventing the
moisture and dryline from advancing far from Lubbock. Although
surface observations in West Texas were sparse in 1970, they did
manage to pinpoint the area of confluence (air coming together)
associated with the dryline to be located between Reese AFB, with
a light west wind and the Lubbock airport, with a south wind.
Temperatures had also warmed nicely, under sunny skies, into the
lower and middle 90s.
Three hours later, at 7
pm, the surface map continued to depict the dryline, and related
confluence, between Reese AFB and the Lubbock airport. This extended
period of confluence near Lubbock aided in the development of
clouds and eventually thunderstorms as the warm and increasingly
moist air that was coming together at the surface was forced to
rise. Additionally, the 7 pm observation at the airport indicated
that cumulonimbus clouds, which are dense, vertically developed
clouds that produce thunderstorms, were visible to the south and
distant northeast of the airport. The surface map indicates the
approximate locations that the isolated thunderstorms had developed.
Finally, the 10
pm surface map reveals that the dryline had continued its
retreat more rapidly off to the west, with moisture and southeast
winds returning to southeast New Mexico, Reese AFB, and Amarillo.
The thunderstorms that were developing at 7 pm were now mature,
feeding off of abundant low-level moisture supplied by strong
Upper-level weather maps at 7
pm CDT on May 11, 1970 (0000 UTC). The left image is the 850 mb
map, with dewpoints over 10 C (50 F) shaded in lighter green and
dewpoints over 15 C (59 F) shaded in darker green. The right image
is the 500 mb map, with winds over 30 knots shaded in blue.
Click on the maps for larger views.
The maps above are examples of maps
meteorologists put together using the weather balloon data from
May 11, 1970. These maps are called constant pressure maps because
instead of measuring altitude in height, they measure it in pressure
(recall that air becomes less dense with altitude. Air pressure
also decreases with height because there are less air molecules
above to exert downward pressure).
On a constant pressure map, high(low) elevations
correspond to higher(lower) than normal pressures at any given
altitude. In this way, meteorologists can track high and low pressure
systems as they move across the world.
The 500 millibar
map shows how the atmosphere looks at around 18,000 feet (5400
meters). The map shows a trough of low pressure across the northwest
United States (heights decrease from 5880 meters over the Gulf
of Mexico to 5460 meters near California and Oregon. In addition,
look at the 5820 (labeled 582 on the map) line. You can see two
small waves - one over Oklahoma and one moving through West Texas.
This second wave trough (waves have ridges and troughs) is labeled
with a red dashed line. Sometimes, subtle waves like this can
provide just enough lift (thunderstorm development requires moisture,
instability and lift) to get thunderstorms going. The stronger
area of winds shaded in blue centered near Midland are also an
indication of this wave. Winds in the atmosphere are created by
pressure differences, which in turn are caused by temperature
differences. Areas of higher winds at this altitude are often
caused by sharp temperature contrasts. This enhanced temperature
contrasts means that there may be a pocket of cold air aloft (cold
air aloft provides the energy for instability and lift).
The 850 millibar
map shows how the atmosphere looks at only a few thousand
feet above the ground. At this level, meteorologists look for
areas of high moisture, the strength and direction of the winds,
and any fronts that may be present. You can see on this map that
there is a trough of low pressure stretching from a low pressure
center in central Colorado south through New Mexico into northern
Mexico. The green shading shows areas of deeper moisture with
the darker green shade show very high moisture levels. You will
notice that at 7 pm, the deeper moisture was located off to the
southeast of Lubbock. However, the winds over central and southern
Texas were from the south and southeast, and were bringing the
moisture north and west. This moisture return coincided with the
lift from the approaching wave that is depicted on the 500 millibar
chart to greatly enhance the severe thunderstorm potential.
Soundings taken at 7 pm CDT on May 11, 1970
(0000 UTC). The soundings, from left to right, are Amarillo, Midland,
and Abilene.The low-level thermodynamics (temperature and
dewpoint) for the Amarillo sounding were modified to better represent
the conditions experienced at Lubbock. Click on the soundings
for larger views.
soundings display all the data gathered from the weather balloons,
at a particular site, after they have ascended through the atmosphere.
The solid red line in each image is the temperature recorded as
the balloon ascended, while the dashed red line is the dewpoint.
The wind speed and direction can be seen on the right hand side
of each sounding. Additionally, a light green line, which shows
the temperature air from the surface would have if it was lifted
through the atmosphere, is drawn on each sounding. Whenever the
air lifted from the surface is warmer than the environmental air
at a given height, the lifted air is inclined to continue to rise,
since warmer air is less dense than cooler air. Each sounding
is shaded pink whenever the air lifted from the surface would
be warmer than the environment around it. This pink area in each
sounding is thus a measure of the amount of instability present
in the atmosphere.
each sounding, significant amounts of pink area are present, indicating
that the atmosphere on the evening of May 11, 1970, has plenty
of instability to work with. This instability, coupled with the
increasing moisture at the lower levels, confluence and lifting
of air along the dryline, and the weak disturbance at 500 mb,
conspired together to produce a couple of very intense thunderstorms
across West Texas. Additionally, the change of the wind direction
from southeast at the surface to southwestly aloft, among other
factors, provided sufficient spin in the atmosphere to make the
stronger storms rotate, and produce tornadoes.
Series of images taken from the
Amarillo radar on the night of May 11 and early morning of May
12, 1970. Click on the image for a larger view.
Lubbock is located approximately 4 range rings south of the radar
(second range ring on the images where the range rings are less
dense). Dots are located on the 8:30 and 9 pm images, at the location
of the first tornado, and again on the 9:45 and 10 pm, at the
location of the more destructive second tornado. Time is in CDT.
(Image courtesy of Weatherwise magazine)
above series of pictures taken from the Amarillo radar depict
what meteorologists in Amarillo would have seen on their radar
scope on the night of May 11. The radar, located in Amarillo,
is centered in the middle of the range rings toward the top left-hand
side of each image. Lubbock is located almost due south of Amarillo
on the fourth range ring (second range ring on the images where
the range rings are less dense). The bright white blobs are radar
returns, or radar echoes. These radar echoes can represent many
things found in the atmosphere, including rain and hail produced
by thunderstorms. However, many of the radar echoes found close
to the radar are "ground clutter" - caused by the reflection
of energy back to the radar from trees, buildings, and other ground-based
objects, and are not meteorological features of interest.
series of images show no radar echoes at 6 pm. The first storm
starts off as a small radar echo south and southwest of Lubbock.
Over time, this echo grows as it slowly moves off to the north
and east. Then, at both 8:30 and 9 pm, the largest radar echo,
located over the city of Lubbock, is associated with the first
tornado that touches down on the east side of town (the location
of the first tornado is plotted with a dot at both times).
thunderstorm over Lubbock continues to build over the city from
9 to 10:30 pm as it merges with smaller echoes that approach and
get absorbed into the massive storm from the south and southwest.
The location of the second more destructive tornado is plotted
with a dot on the 9:45 and 10 pm images. After 10:30 pm, the storms
generally decrease in areal coverage and organization as they
move off to the east and northeast.
seen from the above images, the Amarillo radar perspective was
helpful in identifying storm location, but less helpful in seeing
the details of the storm, primarily because the radar was located
so far away. Although not pictured here, radar images as seen
from the radars located at Reese AFB and the Lubbock airport both
depicted greater detail of the storm, which aided in the issuance
of timely warnings. In particular, both nearby radars detected
a hook shaped radar echo (known as a hook echo), which is a feature
that is sometimes produced by a rotating storm, and can be a signature
associated with the development or presence of a tornado.