April 22, 1999      NE Oklahoma Supercells

Today was promising for severe storms, but tornadoes were a big question mark.
A weak front was expected to drop south into NE Oklahoma and surface low was
expected to track along the front from NE Oklahoma into SW Missouri. The cap
was quite strong so there were lots of uncertanties if the cap would break. If in
fact the cap did break, then there would be explosive convective development in
NE Oklahoma. Very unstable air was in place over NE Oklahoma and SE Kansas.
CAPEs were in the 3000-4000 range so instability was not a problem. The shear
profiles were favorable for supercells as there was good veering of the winds with
height. Brian Stertz and his friend Tom Zeitinger from St. Louis were more or less
on standby all day to chase with me later. One thing that was certain was that it would be very late afternoon before any development would occur.

By late afternoon, the airmass over NE Oklahoma looked primed for explosive
supercell development. A weak trough/dry line was moving into E.Oklahoma and
a weak surface low was forming east of Stillwater OK, or west of Tulsa about 45
miles. Shortly after 3pm, a cluster of storms formed along the frontal boundary
over N.Osage Co. to the west of Bartlesville. Eventually, the storms organized
into 2-3 separate cells and a few had large hail. Since these storms were along
the cold front, I did not give these much notice. Brian and Tom returned from running errands around town and noticed the sharp anvils and one exploding
storm to the northwest of Bartlesville. A severe t-storm warning was issued for the storm which rapidly intensified. The storm was tracking e-se at 35-40 mph and
was heading across Washington Co. when radar indicated slight rotation in the storm. I called Brian and told them to get ready to chase, and that I would swing
by and pick them up in 5 minutes. I wanted to get out of Tulsa before the rush
hour traffic kicked in. The severe t-storm warning was extended into Nowata Co.,
and very large hail was expected. The overall storm structure transitioned to a
well developed supercell on radar and a small hook was developing about 5
miles northeast of Bartlesville. A tornado watch was quickly issued!!

By the time I reached Brian's apartment, the storm over W.Nowata Co. was now a
full fledged supercell. Moderate rotation was developing on the southeast inflow
side of the supercell. We figured our best chance for an intercept was to scream
up I-44 and get ahead of the quick and rapidly changing supercell. Our target
zone was originally Vinita OK. The storm was tracking for Vinita, and this would
give us better road options later. We were due south of the storm when a tornado
warning was issued for Nowata Co.. A developing tornado was near the town of
Childers and was moving e-se at 35 mph. We stuck with our plan to get ahead
of this monstrous supercell. We reached Vinita and it was appearing that the main
circulation was going to pass well north of Vinita. We decided to go on to the exit
for Afton on I-44. We could then take U.S. 69 north and position us directly ahead
of the advancing circulation. Radar was indicating fairly strong rotation as it was
moving to the north of Vinita. Tornado warnings continued and were extended
into Craig and Ottawa Counties. We were now in great shape to get this one!!

By the time we reached the Afton exit, the original circulation had gusted out in a
big way. However, a new circulation was forming much closer to us near the town
of Bluejacket. We headed north on U.S. 69 and we could see inflow bands to our
north pointing to the new circulation. Radar was also indicating very large hail to
the north of Bluejacket so there was little margain for error in our intercept!! We
wanted to close some distance on the circulation which was about 5 miles nw of
Bluejacket. With time, the circulation tracked more southeasterly, and were now
in the direct path!! Storm relative velocities increased significantly when the main
circulation turned to the southeast. We took a dirt farm road west and immediately
west of us we could see a broad wall cloud. Our chase now went into overdrive
and we got all of our cameras ready.

The wall cloud was continuing to tighten up to our northwest about 2 miles. The
wall cloud was closing in rapidly so we pulled over and started taking video of
the tightly wound circulation. Intense cloud to ground strikes around us told us
that it was definitely intensifying. A strong RFD was punching into the wall cloud
from the west and visually rotation was becoming vigorous. We thought that a
tornado would soon appear as ther was now lots of vorticity overhead and to our
immediate west. We held our position as the wall cloud passed less than a mile
to our north. As the wall cloud passed to our north, the RFD blasted us with 45-50
mph winds...hail cooled air!! We realized that this was not a good sign especially
since the large hail core was bearing down on us. We were so close and yet so
far from seeing a tornado. This storm was lacking the hot dry westerly RFD that
usually gets things going!!

We wanted to get ahead of the hailcore so we dropped back south towards I-44
to the north of Afton. The Ottawa Co. Sheriff was perched along the farm road we
headed south on. He was concerned about the storm that was tracking right for
the town of Fairland. We told him that the storm had just collapsed and that the
biggest threat would be the hail and 70 mph winds. Radar showed the collapse as well so we had to rethink our chase plan again. Another severe storm with very
slight rotation was heading for Vinita. We positioned ourselves ahead of this
storm just in case the rotation increased. This storm also collapsed in the same
manner as the first storm we chased- too cold of an outflow. We turned our sights
on yet other storms 50 miles to our southwest developing in the Tulsa Metro area.
Several of these storms had become severe along the dry line. Brian and I put
2 and 2 together and figured out that these storms would have a better hot dry
RFD component if they started to rotate. We picked out the strongest cell and
plotted an intercept to the south of Claremore. A very large storm was tracking
east across SE Tulsa Co. near Broken Arrow very close to where I live. We knew
that we would have to haul to get ahead of this storm. We decided to head for
U.S. 412 as the developing inflow notch was going to track very close to Inola on
that highway.

The storm exploded just to the east of Tulsa and became every bit the supercell
the storm over Nowata Co. was earlier. A severe t-storm was abruptly replaced
by a tornado warning for Rogers Co.. The circulation had nearly doubled over
a span of 15 minutes while we were en route for intercept. Inola was listed to be
in the direct path of the circulation. We beat the storm to Inola, and it was now
appearing as though the circulation was going to pass just south of town. Several
inflow bands arced back to the southwest into the circulation that was just 2 miles
from Inola. The circulation was starting to turn southeast and velocities were very
much on the increase. We knew we would have to core punch a little with the
southeast movement now of the supercell. I took over driving for Brian and he
plotted a difficult but direct route on farm roads south of Inola. We had to really
watch several things now. The roads were unmarked so that was one issue. The
biggest issue was the advancing hailcore. We were right on the edge of at least
golfball sized hail and extremely heavy rains. The winds were now gusting hard
out of the north. The circulation was still south...but how far?

We drove through intense core that did not seem to relent. The heavy rainfall did
eventually let up, but hail slightly smaller than golfballs started to pound us. We
knew it was time to ready our cameras as we were now very close to the north
wall of the circulation. The rain and hail abruptly stopped and we could see a
large wall cloud to our southeast about 2 miles. We slowed down and we could
see a vapor tube extending from the wall cloud to the ground. A very brief debris
swirl appeared in the vicinity of this wild looking vapor tube. We had a tornado
now 2-3 miles southeast of Inola near the Wagoner Co. line. The tornado was
obcured quickly by a thick rain curtain that surrounded the circulation. We zig-
zagged across the back roads of SE Rogers Co. and finally reached U.S. 69
about 1 mile north of Mazie OK. The rotation was still very intense so we kept
right along with the circulation(we could not see the rain obscured wall cloud).
We knew that this was our last shot.

The storm was heading right for the Fort Gibson Lake area and we would soon lose the storm. We headed east on a rough but paved road to the lake's edge.
The circulation was less than a mile to our southeast. We knew this because the clouds above us were racing to the southeast. Large hail (up to golfball sized) intermittently fell on us on the back side of the wall cloud. Radar was confirming that circulation was still extreme and there was a very large hook crossing Fort Gibson Lake into Cherokee Co.. Not surprisingly, the tornado was extended into Cherokee Co.- a developing tornado was near Peggs moving e-se. We had lost this one, but we had fun watching hail up to tennis ball sized ricochet through the large oak trees above us. Brian eventually got nailed in the back by an large, and undetermined size hailstone-  we got out of there quick!!

Our chase focused on yet another storm entering Okmulgee Co. with moderate
rotation. We plotted an intercept near Muskogee in 45 minutes so we headed
south on U.S. 69. This storm had great rotation the further east it moved; we just
made it to the storm a little late. The storm wound down as it moved towards
Muskogee from the west. After watching the slow death of this storm, we called
it a chase and headed back to Tulsa. I like these close by chases- hopefully
there would be more of these this spring. The total miles driven today were the
equivalent of 1/4 of a normal chase day. We headed back into Tulsa for dinner
and a few beers!!