5/27/97 Jarrell, TX et al chase by Lon Curtis


From: Lon Curtis (curtis@VVM.COM):

Started the day around 6:30am with the usual review of model output
from 00Z the night before, early morning SFDs and AFDs from
Texas forecast offices, and the ~06Z SPC SWODY1. SPC had put-up a
moderate risk for portions of eastern Texas, southern Arkansas and
northern Louisiana, but the western edge of the moderate risk extended
west into central Texas near Austin and Waco. The forecast soundings
for the afternoon looked very unstable and when I ran the 09Z RUC output
valid at 21Z through PC-GRIDDS, the results looked promising for deep,
intense convection, but forecast winds, both surface and aloft, looked
pretty weak. Instability was forecast to be extreme, with CAPES of 4000+
and LIs of -10 in central Texas by forecast time.

        My 11Z hand-analysis of surface data placed a weak surface low on a
dying cold front right at Dallas, with a trough extending southwest to
near Del Rio. An outflow boundary from overnight convection in eastern
Oklahoma and northeastern Texas had pushed across east Texas and was
draped from Fort Polk to Conroe to College Station to the low near
Dallas. Ahead of the front, surface winds were light southeasterly
except in areas impacted by the outflow boundary. North of the front,
winds were northerly with some evidence of a secondary front across
central Oklahoma. The most striking feature on the map was an area with
dewpoint temperatures 75 deg F or better which was to the right of a Del
Rio-Junction-Waco-
Palacios line.

        (Flow aloft was west-northwest to northwest.)

        I put on my work clothes (suit, dress shirt, tie, etc.) and went to the
office. During the morning, I watched the situation evolve via internet
sites. The first significant data to arrive was the 12Z soundings, which
I obtained from RAP-UCAR. Del Rio was showing CAPE near 4700 and LI=-12
(at 7am CDT!!!) while Fort Worth was CAPE near 3000 and LI almost -10.
(I didn't look at Corpus Christi but have been told it was almost 8000).
Such extreme instability before daytime heating took effect foretold
incredible instability for the afternoon hours. The 15Z SPC update of
SWODY1 continued a moderate risk of severe storms for portions of
central Texas eastward, but noted that the relatively weak wind fields
would mean that the primary threat was hail and damaging winds, with
only a chance for an isolated tornado. Experience and many hours of
reading research papers from AMS conference preprints told me to watch
for evidence of storm deviating in the extreme from the hodograph, which
suggested storm motions of ~300 at 12 knots.

        My 15Z hand-analysis placed the surface low nearer to Waco than Dallas,
suggesting that it had drifted southwestward. The outflow boundary to
the east was still visible on satellite imagery, as was the trough-cold
front to the west. The cooler air east of the OFB appeared to protrude
westward to near Corsicana, northeast of Waco, creating something
resembling a triple-point at Waco. I left at 11:30am for lunch so I
could drop-off film shot in south central Oklahoma Sunday for processing
(two tornadoes near Duncan Sunday afternoon), telling the secretary I'd
be back by 1:00pm. Lunch was from Chick-Fil-A in Temple and a large
cumulus tower to the north grabbed my attention and sent me home for a
quick look at data. I ate the sandwich as I drove.

        The ~12:40 SRM products off of KGRK and KFWS (thanks, Freese-
Notis!) both indicated strong shear suggestive of a developing
mesocylcone in the storm I'd seen visually, now located in southern
McLennan County. A quick look at a local television radar showed the
storm was developing a reflectivity pendant on the WNW side. I put the
SRMs and the pendant each together and went to put on my jeans and then
headed for McLennan County. The chase was "on"! Come on along! (All
times are CDT.)

        About 1:00pm I left my house in far western Temple and traveled north
on SH317 to Moody. Called the office to report I'd be a little late
getting back. Severe thunderstorm watch issued for the McLennan Co.
storm at 12:50 ("rapidly developing thunderstorm near Woodway"). Passing
Moody, I hear the DPS dispatcher at Waco asking a trooper to check the
"back side" of that cell near Woodway. I take FM2113, which will take me
right into the rear of the storm. The sky darkens. FM2113 passes through
farm and ranch land broken by several small streams, and about 5 miles
northeast of Moody, I come up out of a valley and around a curve and
there, a mile or two in front of me, is tornado #1. After several
photographs and a chance to observe the very slow motion of the storm, I
creep up toward it. Additional photos are shot from ~1/2 mile away. The
tornado is undercut by outflow and dies. I go down Mackey Ranch Rd to
see if help is needed; a mobile home has been blown-away but no one was
hurt. This tornado moved from ENE to WSW over a distance I would
estimate to be a couple of miles. Path width was probably 75 yards or
less. Reports were made to NWSFO/FTW when the tornado was spotted and
when it dissipated.
        At this point, I make one of only two mistakes in the afternoon chase
which is about to evolve. Hearing a tornado warning being issued for
Falls County, southeast of my location, I continue on to Hewitt and then
south on IH35 toward Eddy and Falls Co. In the process, I almost miss
seeing tornado #2. Approaching Eddy, it is obvious that to get back
south of the storm, I've got to punch the core, because the storm is not
moving southeast, it's going almost due south. Most motorists have
abandoned the interstate as I barrel south at the speed limit or better
with golf ball hail everywhere and smaller hail beginning to cover the
highway. (Perhaps that explains why I've never worried about repainting
the chase truck where the hood is peeling and rusting!)
        The scanner is absolutely full of spotter and law enforcement reports
of a new tornado bwtween Moody and Troy. Passing through Troy, I take
FM1237 back west toward Pendleton and SH317. Topping a hill near
Pendleton, I can see tornado #2 off to the northwest. I watch for
several minutes as until it becomes rain-wrapped and disappears. I'm low
on gasoline and I radio the Belton Fire Dept. to watch the area near
Moffat and Morgans Point for new development (southwest of the last
tornado) as I stop for fuel near SH317 and SH36 just west of Temple.
        I head on south on SH317 and while crossing from Temple into Belton,
hear that a new tornado (#3) is on the ground at Morgans Point. I turn
west of FM439 and from the south side of Belton Dam, shoot several
photos of the large tornado that is roughly 3 miles away. I decline to
cross the dam and approach the tornado for fear that a traffic accident
or sightseers will obstruct my only path of escape. Instead, I
reposition to US190 at FM1670, west of Belton, in time to
see that #3 is rain-wrapped. I shoot one photo with aid of a telephoto
lens as it emerges from the rain and ropes-out. I radio to the F.D. that
we will need to watch the Lake Stillhouse area for new development, and
I head for Stillhouse Hollow Dam on FM1670. While crossing the dam, I
glance left and see a funnel cloud extending earthward; looking down
into the valley east of the dam, I see that there is a condensation
funnel forming and debris flying; tornado #4 is developing, but soon
dissipates. I continue on south on FM1670, and radio Belton F.D. to
notify the Salado F.D. to be particularly alert; I expect the next
threat to be from near Youngsport (west of Salado on FM2484) to Salado
itself.
        I pass through Salado southbound on the IH35 westside frontage road. On
a hill south of Salado at the FM2268 overpass (one of my favorite
'spotting' locations), I see a funnel cloud to me southwest. I continue
south on the frontage road and about MP282 on the interstate, just south
of a rest area, stop to watch tornado #5, a thin rope-like tornado as it
wanders around in a pasture about 3/4-mile away. After several minutes
of observing little movement other than 'wandering', I move-up on the
tornado, eventually closing to ~0.3 mile, documenting with more photos.
I realize maybe I'm getting a little bold, and retreat to the Exit 280
overpass and make several more photos, as the pencil-like tornado
suddenly begins to move southward and accelerates.
I take the eastside service road southbound and turn my back to the
tornado for about 2 minutes. Halfway to Jarrell, I stop for another
quick series of photos. I am amazed ... my "pencil" is now a
multi-vortex tornado and growing rapidly in size. (Later surveys and
interviews with residents show that the "pencil' likely dissipated as
the multi-vortex tornado formed (tornado #6).
        I rush southward to Jarrell (another 2 miles or less) and notice that
what looks to be most of the residents are outside watching the tornado
grow and move toward their city. Just prior to observing this fact, I
radio the Belton F.D. to have them notify Jarrell F.D. that a large
tornado is approaching from the north. I stay with the eastside frontage
road through Jarrell and take a position 0.4 mile south of the center of
town. (Time 3:30pm) I begin to photograph the tornado again, now a large
cone which becomes a wedge, and continue to do so until debris falling
from the storm make my position untenable.
        Turning to "flee" (the chaser is beginning to feel like the chased), I
am confronted with the sight of another tornado (#7) on the ground about
3 miles to my southwest. My last view of the Jarrell wedge is as it
becomes rain-wrapped. Subsequent survey leads me to believe that it was
entering the Double Creek subdivision at that time.     I move on south on
the frontage road and about 3 miles south of Jarrell, stop to 'shoot'
the large tornado as it emerges from the rain and slowly begins to
rope-out. (#7 turns out to be thankfully brief.)
        I now begin to try to get south of the parent thunderstorm, which has
overtaken me near Jarrell, so that I can stay ahead of it. As I turn
northwest on SH195 north of Georgetown, Bruce Haynie calls from Austin
(it is 3:55pm, give or take a minute) and wants to know where I am and
where he should go. I tell him to head northwest, out US183, toward
Cedar Park and Liberty Hill. Bruce gets out in time to catch the next
tornado at Cedar Park, but I'll let him tell that story himself. I
continue to Cedar Park, hoping perhaps to get on the west side of the
storm again, but to no avail. The traffic jam caused by the tornado
there and the hail and rain put an end to my chase at roughly 4:30pm.
I buy two beers (among the best I've ever had), and visit with the
convenience store customers and clerks about the events I've just
witnessed.

Lon Curtis
Belton, TX

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