May 1, 1999     W.Texas Supercells

Today was looking like a repeat performance of the previous days of continued
severe weather in the Permian Basin area of West Texas. Extreme diffluent mid-
level flow remained over the area, and this coupled with the approach of a strong
shortwave, was expected to provide the potential for severe storms and tornadoes
by afternoon. The only negative factor was that the air mass had been extremely
worked over by the intense convection over the past few days. This did not overly
concern us though as this area is notorious for rapid recovery and destabilization.
We targeted originally the area around Lamesa TX as our chase spot. Both Brian
and I planned to chase today, and were going to be joined by Mike Morgan for
the long haul chase. Since it was looking like it would be an early show, we made
the decision to leave before sunrise in order to get down to our target area. This
was also to allow time to pick up Mike in Oklahoma City. Before we left, Brian and
I were able to look at the forecast models and the SPC severe storm outlook. Our
target area was still looking to be in line; however, the SPC indicated that the dry
line may not make it as far east as Lamesa before severe storms popped. The
area of greatest concern was between Hobbs and Fort Stockton. A slight risk for
severe storms was outlooked, but a few tornadoes were mentioned in the outlook
discussion. The RUC model indicated that the most vigorous and likely severe
storm was expected to develop in the Andrews Co. TX/Lea Co. NM area by mid
afternoon. This forecast trend remained consistent for 3 cycles and definitely
supported our target zone.

I drove my van and Brian followed in his car as we set off for Oklahoma City at
5:30am. We made it to Oklahoma City shortly after sunrise and Mike rode along
with me. Brian had to take his car as a safety measure in case he had to drive back for work on Sunday. We were in and out of Oklahoma City without much of
a delay, and started out on the 7+ hour journey to the Lamesa/Midland area. We
decided to take the southwest route through Wichita Falls to Sweetwater. This would allow us ample time to get to I-20 where we could blast west towards the target area. Overnight convection had weakened, but had spread a large area of mid and low level cloudiness over much of NW Texas. We were concerned that this would reduce the surface heating, especially with the coverage of the clouds.

We reached I-20 by 11:30am, and headed west for Big Spring where we could make the decision to go northwest towards Lamesa or southwest towards the
Midland/Odessa area. By the time we reached Colorado City TX, the new SPC
severe strom outlook was updated. The area between Hobbs, Big Spring, and
Fort Stockton was upgraded to moderate risk, and now strong tornadoes were
mentioned. We picked up the pace as the moisture convergence was increasing
dramatically to the west of Midland. We opted to continue sw towards Midland
as the dry line was really firming up between Carlsbad and Fort Stockton. The
surface low (which was now much deeper than what the forecast models were
showing) was developing near Kermit TX which is west-southwest of Midland.

Brian dropped his car off on the east side of Midland so we all could chase in my
van. Radar was starting to indicate isolated storms were just starting to develop
over SE New Mexico to the northwest of Hobbs. The storm was apparently developing along an outflow boundary in response to intense warm air advection.
No tornado watch was issued for another hour, even though the storm in New
Mexico continued to intensify and eventually indicated significant storm rotation.
A severe t-storm warning was issued for the storm, but for a while it looked like
a tornado warning should have been issued. Storm circulation was incredible,
and we were all convinced that if the storm turned right/moved east, a tornado
was quite likely. Other smaller storms were starting to take shape further south
along the dry line near Monahans and Fort Stockton. We were almost certain that
one of these storms would eventually become THE tornadic supercell of the day.
Just before 1 pm, a tornado watch was finally posted for W Texas and extreme
SE New Mexico. Rapid severe storm develoment was likely along the dry line
and further north along the outflow boundary. The cap still looked to be very
strong to the west of Midland, and appeared to be the strongest south of I-20. We
figured the best chance for the cap to be broken was near the developing surface
low over Winkler/Loving Counties TX. Now it was time to see if our prediction
would hold true.

Between 1pm and 2pm, the atmosphere started to transform rapidly. Clearing
skies and warm advection cumulus put a smile on our faces. The surface low
was now a full-fledged swirl on the streamline map from the Lubbock NWS web.
page. The dry line was also establishing strong convergence along a north-south
line to the west of Midland. Scattered storms were popping as the air became
more unstable over W. Texas. The strongest storms were over Lea Co. NM and
Ward Co. TX. Large hail and moderate to occasionally strong rotation was seen
on radar with these storms. Now it was time to play the waiting game. One thing
radar was indicating was that stronger winds aloft were entering W.Texas. The
storms were now accelerating to the north-northeast. Earlier, the storm motion
was on the order of 30-35 mph. The storms were now racing at 40-45 mph. This
would definitely mean that we would have to be on our toes today. Storms that
move this fast are chaseable; however, the road network in this area is sparce so
taking the right roads would be critical. We reached Monahans and the storm
was passing about 10 miles northwest of town. We had to carefully select the
appropriate road to follow the storm- we did not want to be left behind after the
long drive to reach W.Texas!!

The storm's track was going to be directly for the town of Wink and eventually
to the north of Kermit. We headed north from Monahans and plotted an intercept
point about 5 miles to the north of Kermit. After we reached this location, chasing
was going to be much more difficult in the desolate areas of N.Winkler and W.
Andrews Co.. This is the first time that sand dunes would dictate my chase plans!!
We continued north on TX-18 from Kermit and the storm was closing in on the highway. The storm was highly sheared but certainly severe. Radar was showing
a large boomerang hook. Visually, the updraft was well separated from the core;
the only problem was that there was also rain developing within the updraft area.
This usually does not bode well for continued rotation/tornado potential. At the
intersection of TX-18 and FM-874, we decided to pull over and watch the storm.
Rotation was very apparent and a substantial RFD was plowing into the updraft
from the west-southwest. The supercell was definitely on the dryline as there were
no clouds to the west of the storm. Very dry air was slamming into the storm, but
would there be enough low level winds to keep the storm from gusting out and
"choking" the updraft. This question would soon be answered.

Numerous low level moisture "feeder" bands were developing to the southeast
of the circulation area. It was now apparent that the storm was now becoming the
type of supercell that may produce a tornado. We watched the storm for about 15 minutes as it lifted quickly north-northeast into SW Andrews Co.. Further to the
southwest of this supercell, yet another storm rapidly developed and became severe. We headed northeast to TX-181 that would allow us the opportunity to
keep up with the fast moving Andrews Co. supercell. As the storm moved into
W.Andrews Co., the severe t-storm warning was upgraded to a tornado warning On the warning bulletin, a developing tornado was located 15 miles sw of the
city of Andrews moving n-ne at 40 mph. Certainly catchable but the road network was not too cooperative. The circulation was 5 miles to our northwest, but we would have to go all the way to Andrews in order to get ahead of the supercell. Over the next 15 minutes, we blasted north towards Andrews and the storm appeared as if it was going to pass closer to Frankel City than Andrews. This put
a huge monkey wrench into our intercept plans. The storm which erupted over Winkler Co. was also now showing rotation and was becoming a well developed supercell. When we made it to Andrews, the supercell was already crossing U.S. 385 near the town of Florey. Now it was decision time. The Andrews Co. supercell we could catch but it was going to later track across "no-man's land" with very few roads to follow the supercell. The Winkler Co. supercell was an easier intercept as it was going to track right for us. We decided that the Winkler Co. supercell was
the better choice as it was going to be easier to follow. Another factor which made
this the correct decision was that this supercell was in the diffluent mid-level jet
axis. This would allow for a tendency for the storm to turn more easterly and allow
for greater storm relative helicity/tornado potential.

We headed back down TX-115 to intercept the storm now moving into S.Andrews
Co.. Radar was showing increased circulation and was alomost certainly at the
threshold for a tornado warning. We had to punch the core in order to get to the
circulation, but fortunately the very large hail was going to remain west of the road.
The storm was now also increasing in size and intensity. Portions of 3 counties
were now being affected by this growing supercell- S.Andrews, NE Winkler, and
NW Ector Co. All 3 counties were under severe t-storm warnings for hail larger
than golfballs and 70 + mph winds. The original circulation had become rain and
hail wrapped to our east. A huge gust front extended to the southwest, and a new
storm updraft was rapidly developing at the intersection of this gust front and the
southwest flanking line. Radar was indicating strong rotation with the rain and
hail wrapped circulation; meanwhile, the newly developed updraft region was
also developing circulation. This rotation was probably being enhanced by the
outflow of the northern circulation. We pulled over near the town of Goldsmith as
did many other chasers and spotters. We watched a fully developed arcus cloud
(very menacing looking) approach us from the west. To the southwest about 5
miles, the new circulation started to indicate that it was starting to mean business.
Rain curtains developed quickly and swirled under the base of the wall cloud. We
were almost certain that the circulation was ready to produce a tornado. The rain
curtains quickly blocked our view of the base of the wall cloud so we headed east
on TX 158 to see if we could get a more unobstructed view. Fortunately, the move
paid off. Mike was watching the base closely when he finally saw the funnel. We
pulled over quickly and the funnel started to work down to the ground. A tornado
was now on the ground to the south of Goldsmith. Although the tornado appeared
to be weak( FO ), the funnel was well developed. We watched the tornado for a
good 5 minutes before it dissipated. I called it in on the local ham spotter net but
they wanted other confirmation of this by local spotters. Very quickly other chasers
and spotters confirmed the tornado. An interesting note was that most of the focus
of attention was on the northern circulation that was imbedded in the core and
very much outflow dominated. I guess it is a good thing to know a little bit about
meteorology and severe storm morphology!!

We continued to track the storm into Martin Co. from the Goldsmith area, but the
storm was hard to follow. Also the storm had the appearance now of a large but
outflow dominated HP supercell. We made a bad road choice thinking that an
oil field road was going to connect with the state highway. The map showed that
it did connect, but it connected through private ranchland that was gated/locked.
We lost valuable time as the storm was tracking northeast towards Tarzan. We did
not have our grapevines to swing from so we could not catch up to this storm very
easily!!! Tornado warnings continued with the storm as it was moving at 35 mph
across W. Martin Co.. We were a good 10 miles from the circulation when we were
able to make out the wall cloud. We heard the Martin Co. Sheriff report a tornado
just to the west of Tarzan, but we could not see this unfortunately. We now picked
up the pace and made it to TX-176 very near to where the tornado was reported 5 minutes ago. We could see that a strong RFD had just plowed into the storm but
searched for the circulation. The DOW(mobile doppler truck) unit was pulled over
and scanning the area to our east. We continued east and finally found the area
of circulation that had caused all of the excitement earlier. We were just a little
late in getting to the scene. The tornado had lifted and we searched the sky for the
remains of the tornado. Mike and Brian looked straight up and saw a beautiful
sight. The stretched out funnel was writhing overhead and was nearly horizontal
to the ground. We could not see any ground connection so it was now just another
pretty funnel cloud. This funnel appeared to just float in the sky before segmenting
and then dissipating. We followed the storm east for a while into Howard Co. but
it could never get another circulation established.

We headed south into Big Spring to I-20 where we headed back to Midland. We
were fairly satisfied with the chase, but we wondered why the storms did not have
larger tornadoes. When we reached the hotel where Brian dropped off his car, we
went inside and watched the Weather Channel. Radar more or less answered our question about why there were no large tornadoes. The storms moved n-ne and
did not have the easterly track that storms in the diffluent axis typically have. This
reduced the storm relative helicity quite a bit. Yet another factor which may have played a part was that the atmosphere was also attempting to recover from the
previous bouts of massive severe storms earlier in the week. Apparently the air-
mass did not recover fully from this. Brian had to decide if he was going to call in
to work or drive back with Mike. Mike had to get back to Oklahoma City so he
took Brian's car after he made the decision to chase on Sunday. We called it a day
and had a great bbq dinner in Midland. We were anticipating a chase on Sunday
near Abilene TX so we were in prime location for chasing. We stayed in Midland
and readied ourselves for the next day. We noticed that night a whirling dervish shortwave diving straight south along the Oregon coast. Brian turned to me and
said this compact system "meant business!!". We checked the forecast models
after seeing this and none of the models were overly impressive with this system.
Both Brian and I thought differently , and we simultaneously said " Watch out for
Monday!!".

May 2, 1999    NW Texas Chase....sort of....

After a good night's sleep in Midland we were refreshed and ready for more
action today. The forecast models were indicating that today's activity was going
to be more isolated than yesterday. However, almost all of the models were
pointing to severe storm development near Abilene TX by afternoon. Strong mid-
level winds remained over W Texas and the dry line was expected to mix out to
Abilene and San Angelo by late afternoon. Nearly every storm chasing day has a
limiting factor or two. Today's big issues were the cap and fairly persistent t-storm
activity from S Oklahoma into N Texas. The cap was much stronger today so the
severe storm activity would develop much later today. The overnight convection further to the northeast created a strong outflow boundary that was sagging into
N Texas. This boundary was good and bad for the afternoon severe storm and
tornado potential. First the good. The boundary created a wide fetch of east to
northeast winds across much of N Texas. This would create a great low/mid level
shear environment for the development of mesocyclones and tornadoes. Winds
at mid levels were w-sw so there would be significant veering with height. Now the downside to this situation. The outflow boundary was more or less acting like
a true cold front as it had a strong southward push. This would drive the e-ne flow
of surface winds and rain cooled air into the less capped area along/north of I-20.
As a result, the instability would be greatly diminished so the balance of shear
and instability would be shot. Our forecast area for any severe storms was near
and immediately east of Abilene by late afternoon.

We headed east on I-20 for Abilene by late morning. We finished up our forecast
mind melt and we stuck to the target zone. The dry line was already on the move
and was now punching out towards Sweetwater and San Angelo. We plotted up
a quick surface map, and the surface features were starting to look very favorable
for severe storms very near Abilene. Dew points remained in the upper 60's and
the surface temperatures were rising very quickly into the 80's. Also, there was a
pronounced moisture convergence max setting up right over Abilene- probably
in relation to the intersection of the punching dry line and the outflow boundary.
We watched the weather data and satellite imagery really close as we closed in on the Abilene area. The cap was very strong as most of the towering cumulus
cloud development was suppressed from taking off. Instability was increasing
significantly by early afternoon as li's were in the -8 to -10 range. We noticed the
winds at Abilene were starting to veer to the sw so this concerned us a great
deal. We ate lunch in Abilene and then made the decision to shag a little more to
the east. Winds at Abilene were now s-sw and the dew point was dropping. The
moisture convergence shifted to the east along I-20 as well.

We pulled over at the town of Baird in the vicinity of the moisture convergence
maximum. The outflow boundary remained to the north of our location and we could see the dry line to our west (marked by very capped cumulus clouds). We knew we were in the right spot as the low level cumulus clouds were rolling from the extreme low level shear. Instability was also fairly good right now but would it
last. The airmass immediately south of the outflow boundary was "hell capped"
but very warm and unstable. To the north of the boundary, the air was warm ( in
the lower 80's), but surface obs were showing cooling from the e-ne. For nearly
2 hours we held our spot near Baird and still no development. The cap was just
too strong and it did not appear that the cap would be weakened with any cooling
aloft. The cap strength was increasing along I-20 but was slightly weaker to the
north towards Wichita Falls. After a period of "wishcasting", Brian and I decided
to call it day and started back to Tulsa. We were very impressed by the strong
e-ne winds along and north of the boundary. If only the cap had been weaker!!

The low level shear was tremendous north of the outflow boundary which was
now extending from near Mineral Wells to near Albany TX. We crossed the outflow
boundary and the surface winds were gusting hard from the northeast. Thinking
ahead, we were convinced that tomorrow was going to be a major day when the
intense shortwave approached. This boundary was definitely going to be the
major player as it returned north as a "pseudo" warm front- especially with the
strength of the east-northeast winds. While today was not going to be promising
for severe storms, tomorrow certainly was!! We headed north through Graham
and a storm struggled to get through the cap to our north. We watched this storm
just in case, but the cap won out. The storm tried hard to establish itself near the
town of Olney. The storm even had long inflow bands for a while poking into the
storm from the east. No problem with shear today, just a nasty cap!! We drove
on back to Tulsa through rain cooled air over much of Oklahoma. This airmass
would need to go through rapid recovery/warm advection if Oklahoma was going
to be the play on Monday. STAY TUNED!!!