The January-February 1998 issue of STORMTRACK features the Lela, Texas Tornado on June 11, 1997.
A NEW SEASON
I. COMMENTARY by Tim Marshall
Ah, a new year and a new chase season. Now is the time to prepare. I will not speculate if this season will be good or bad. I am ordering my usual 100 ASA Fuji slide film and 10 Hi-8 tapes. No new cameras will be added this year, however, Iím quite impressed with the new digital camcorders by Sony and Canon. These cameras are still quite expensive, ranging in price from around $3,000 to $5,000. "One good tornado video could pay for it", I keep telling myself.
I suspect, there will be a lot of new chasers out there this year, especially toward the end of May in Oklahoma. I remained concerned about the number of people becoming involved in this sport and often stress education and safety. More and more people are turning out for spotter training. I urge anyone interested in storm chasing to attend such classes. There are a lot of new theories and new ideas out there. I am excited about EMWIN (Emergency Managers Weather INformation) which is a continuous data stream of weather information transmitted via satellite to your computer: ANYTIME-ANYWHERE. I am told the software and "black box" for the 9600 baud service will be available by March. Some cities are rebroadcasting this signal so you donít even need a satellite dish -just a scanner. Stay tuned to STORMTRACK online for further details.
Where are we and where we are going with respect to STORMTRACK? Since the movie TWISTER, the number of subscribers has risen 50% from a steady 600 (for many years) to over 900. It is possible that we will break the one thousand mark by the end of the year. Many of you have asked to keep the paper version going -and so it will for at least the next two years provided chasers continue to submit their chase accounts to STORMTRACK. I remain concerned that chasers will find it quicker to post their accounts on the internet. Donít ignore us! Simply send us your narrative via e-mail at email@example.com Printing your chase account in ST ensures that it will be preserved. Future projects include reprinting and binding the old STORMTRACKS and/or as making an indexed CD ROM. Online subscription eventually will occur and subscribers will be able to access the latest and past issues (as well as a ton of other stuff) via a personal password.
II. CHASER NEWS
MARCH 6-7, 1998: The College of DuPage, in association with the DuPage County Office of Emergency Management, hosted a Severe Weather Forecasting Conference, in Wheaton, IL March 6 and 7, 1998. The conference gave undergraduate meteorology students an opportunity to learn about cutting edge severe weather forecasting and analysis with nationally recognized experts. Although the conference was designed for undergraduates, the material presented at the conference also benefited graduate students, professional meteorologists and other interested weather enthusiasts. Speakers and topics included:
1) Dr. Chuck Doswell, Research Meteorologist, National Severe Storms Laboratory (NSSL),
2) Alan Moller, Lead Forecaster, NWSFO, Fort Worth, Texas "Multi-scale Analysis Workshop",
3) Roger Edwards, Outlook Forecaster, SPC "Pitfalls of Severe Storms Forecasting",
4) Ron Przybylinski, SOO, NWSFO, St. Louis, Missouri, "Using WSR-88D Data: Derechos and Supercells"
5) Greg Stumpf, Research Meteorologist, CIMMS "Radar Algorithm Development and Testing at NSSL"
6) Rich Thompson, Outlook Forecaster, SPC, "Evolution Of Pre-Storm Temperature And Moisture Profiles Through Sounding Analysis"
7) Dr. Erik Rasmussen, Research Meteorologist, CIMMS "Findings from VORTEX and SUBVORTEX"
MARCH 24, 1998: In celebration of the 50th Anniversary of the first tornado forecast, a one day tornado symposium will be held at the Meacham Auditorium at the University of Oklahoma campus in Norman, Oklahoma. There will be a number of speakers. Registration is limited to 350 people. The registration is $20 prior to March 1st and $25 after that. Remit check or money order payable to: COCAMS/NWA, c/o NSSL, 1313 Halley Circle, Norman, OK 73069, Attn: Tornado Symposium. Special tornado symposium T-shirts are available for $12 except for XXL which is $14. Remit check or money order to Bill Conway at NSSL.
APRIL 3-5, 1998: The Iowa National Weather Association Severe Storms and Doppler Radar Conference will be held 3-5 April 1998 at the Holiday Inn Des Moines Airport (where it was last year) in Des Moines, IA. More than 200 are expected to attend second annual gathering! Reserve your room at the Holiday Inn for the special rate of $65 by calling 1-800-248-4013. The subject will be tornadoes, tornadoes, tornadoes. The conference will include a storm chasers video-fest (show and tell session). Additional conference details posted at: http://www.ecity.net/~iowanwa/ Registration before January 1 is $75.00, $50 for students, and $250 for vendors (includes 10 minute presentation). Registration should be mailed to: Central Iowa NWA, Box 7512, Urbandale, IA 50322. John McLaughlin. his email: firstname.lastname@example.org
APRIL 18, 1998: The Texas Severe Storm Association (TESSA) will host its annual meeting on April 18th at the Plano Municipal Center located at 1520 Ave. P in Plano, Texas. Featured speaker is Harold Brooks of the National Severe Storms Laboratory. The title of his presentation is "2000 years of Tornado History".
MAY 17, 24, 31 or JUNE 7: The ANNUAL STORMTRACK PICNIC and VIDEOFEST will be held at the editorsí house at 4041 Bordeaux Circle, Flower Mound, Texas 75028-7050. The party begins at 1 p.m. on May 17th unless there is a slight risk or better for the plains states. Alternate dates are the following week. For latest updates and changes, call my telephone recorder at 817-430-0517 after May 15th. Directions to the editorís house are shown below.
SEPTEMBER 14-18, 1998: The 19th Conference on Severe Local Storms will be held at the Radisson South and Hotel Tower in Minneapolis, MN. The week long conference will feature numerous presentations on tornadoes and other severe weather and will include a video/slide festival.
The ST Roster lists names, addresses, and brief biographies of those persons who are interested in or willing to correspond with others about storms and storm chasing.
Greg Grabijas, 6506 Beddo Court, Colleyville, Texas 76034, 817-352-1179. Looking for a chase partner around the Dallas-Fort Worth area for Spring 1998.
Russell T. Moody, 18400 NFS 524, Altoona, FL 32702, (352) 759-2111. Born in 1973 in Fairborn, Ohio and lived all of my life in Georgetown, KY. I am currently enlisted in the U.S. Navy and stationed at Pinecastle Bombing Range in Altoona, FL. I want to storm chase but do not have the experience required to be successful. With the right training and experience, I think my goal can be accomplished.
INTERNET DISCUSSIONS ABOUT THE LELA, TEXAS EVENT
Gene Moore email@example.com writes: "If it were not for the large outflow system in the TX Panhandle/NW Oklahoma I don't think there would have been a storm I would have wanted to be on west of I-35 that day. In fact I missed the day for that reason (a good day to buy a dryer for my wife, I thought) Well, obviously I choked on that one because I underestimated the impact of outflow boundary at 9-10AM in the morning....so it goes."
Jon Davies: firstname.lastname@example.org writes: "A supercell (non-tornadic) observed by chasers (and I believe the DOW crews) N of Jetmore KS at sunset still had roughly the same amount of CAPE available to it as the Wheeler/Lela TX large tornadic cell, was not particularly high-based (LCL well under 1000m). One interesting difference between the environments was the low-level shear... The background helicity in the Wheeler/Lela area appears to be roughly twice what it was in the DDC/Jetmore area on 6/11. Resulting EHI's are more than 4.0 for the Lela background environment, but only around 2.0 for the Jetmore background environment. So, this may have played a roll. Also, while there was an outflow boundary near the Jetmore supercell (from an earlier storm near Ness City), it appeared to move somewhat south and away from the boundary, which maybe robbed it of some local vorticity & helicity enhancement it would have needed to become tornadic re Erik Rasmussenís ideas). In contrast, it seems from satellite that the Wheeler/Lela cell had a NW/SE outflow boundary to work from during much of it's lifetime."
Phil Sherman: psherman@Adobe.com sends in his recipe: " "The Slow-Moving TX Panhandle Wedge Cookbook": regular ingredients are: (1) CAPE >= 4000 (2) 700mb wind > 20 knots (3) 500mb wind > 20 knots (4) possible minimum wind at anvil level (40 knots?) Special ingredients are: (5) mesoscale focusing mechanism (mesolow,dryline bulge) and (6) storm motion way off the mean wind vector (via a boundary or other means). Now put in the oven, and then you get (7) EHI >= 3.0, plus and (8) SRMLW >= 15 knots. Wait about 1 to 3 hours after 4pm and then you finally get (9) a slow-moving wedge." The real challenge is making this pattern stick out like a sore thumb amidst many other severe events (and stronger ground-relative wind parameters) in the same season. It's hard enough on the morning of the same day predicting the mesoscale influences that will arise later on (hats off again to Jim Leonard for seeing Lela 36 hours ahead of time)."
CHASE STRATEGY: JUNE 11, 1997by Tim Marshall
This morning, the main upper trough is still off the California coast with broad, flattened ridge over the plains states. Many weather features are weak to marginal for severe storms, but given the amount of surface moisture and instability, I feel isolated supercells are likely. There is a surface low near Dodge City with a wind shift line extending southwest of there west of Amarillo. This wind shift line has not manifested itself as a true dryline as dewpoint gradients are not strong. Amarillo and Dalhart still have 60+ dewpoints with southwest winds. I donít like this weakness in the moisture gradient or the northeast-southwest orientation of the dryline. The best surface convergence remains in southwest Kansas where the surface low is positioned. A fly in the ointment today is nocturnal activity which is moving southward from Kansas into Oklahoma. No doubt, there will be an outflow boundary in Oklahoma and I question whether Kansas air can recover in time for renewed convection.
As typical with late season severe weather events, the wind fields are weak especially at mid-levels. There is good low-level turning ahead of the windshift line, but not much speed shear. The stronger upper level winds are farthest north in Kansas. However, the most unstable air (high surface temperatures and dewpoints) remain in Texas and southern Oklahoma. SPC has issued a MODERATE RISK for most of Kansas today, but I think a slight risk would be more reasonable. My forecast today is southwest Kansas and northwest Oklahoma, west of Pratt to Woodward.
Chuck Brazell and I headed northwest from Dallas. We listened to KGNC radio, Amarillo, just in case something would develop in the Texas panhandle. We stopped at 6:30pm near Minneala, KS when KGNC reported a tornado in western Wheeler Co. in the Texas panhandle and watched The Weather Channel (TWC). The TWC radar loops did not even show an echo there which told me the radar information was old! Chuck and I dropped south and watched an LP storm develop and eventually die west of Shattuck, OK between 7 and 8p.m. We could see the Wheeler, TX storm to our southwest but it looked mushy and multicellular. We finally left the storm at Shattuck at 8pm and drove south arriving at the Wheeler, TX storm by 9 p.m. (donít ask me how!). By then, the storm evolved nicely and had a chunky anvil illuminated by the setting sun. We encountered very little hail while punching the core and found the power out in Shamrock. The storm had evolved into an HP by then. Our consolation prize was watching the storm wrap-up around Wellington; high mesocyclone winds caused several power flashes in town.
WESTERN KANSAS CHASE: JUNE 11, 1997by Mike Umscheid
First of all, I was supposed to go to the Royals game! Well, these plans were abruptly halted when I was up Tuesday night and happened to read the new 12Z severe weather outlook. I immediately called my chase partner, Jon Smith, and told him the situation. We knew there would be some interesting weather across the plains, but didn't know the magnitude. Local meteorologists seemed to downplay the severe weather situation.
We set out shortly after 1 p.m. from Overland Park, Kansas, hoping that we would only go as far west as maybe Salina. About 3 p.m., I gave Mark Hill a call to see what the latest situations were and we found out there was a red box issued for most of western Kansas to the Texas Panhandle. By 4:30 p.m., we were at Salina, thick in overcast. We had to continue west. About 25 miles west of Salina, we turned southwest on K-156 towards Great Bend. Convection had fired in the OK/TX Panhandles, but there was still nothing in Kansas that we could see. We refueled and ate in Great Bend and continued southwest on US-56. At 5:30 p.m., we still had no visual of convection to our west. With such high dewpoints, it was quite hazy, which limited our visibility toward the western sky. Jon and I continued west on K-156 past Jetmore, north of Dodge City (DDC). With the haze limiting our view, our view continued to be rather poor. Browsing through the AM radio, we somehow tune in to WIBW Topeka and learn that there was a tornado just 50 miles from where we lived and here we are over 300 miles from home with still no visual confirmation of convection. Jon and I were just puzzled. We stopped along side a farm road just north of K-156. Finally, around 6:30 p.m., towers fired southwest of Dodge City and a storm developed. About time!
At first, this storm was really looking good, but by around 7 p.m., it just croaked. Around this time, we could see a collapsing cell north of Garden City. East of that, the towering cumulus looked more and more interesting, I told Jon, "well, let's go after it. It's either this or nothing at all." We figured that, like the other cells, it would collapse as soon as it would develop. So, we headed north on K-23 in Finney County. The towering cumulus, now west of us, had enormous cauliflower tops. About 15 minutes later, Dodge City National Weather Service issued a severe thunderstorm warning for Ness County. At about 730 p.m., we continued east on K-96 at Dighton. There were two separate storms going nuts, one directly to our east, and one to our east-southeast. Between the towns of Beeler and Ness City, we were getting closer to the cells. We had to find a south road to keep behind the storm. We found a fairly decent farm road to take. Several minutes later we stopped to take a look at a lowered base from the northern storm. There was a lot of instability and motion in the clouds, but no rotation. We continued south and east on the farm roads until we got to US-283 a couple miles south of Ness City. We got the chase vehicle (white Ford Taurus) a little dirty, but nothing a little core punching can't get off. The back side of these storms was beautiful! We could see two separate hail shafts and there were three or so suspicious updraft regions with occasional lowerings. We pulled off along a farm road by US-283 to sit and watch, since the core was only a couple miles south of us. We were monitoring an updraft base west of the main core to our south. But what was more beautiful was the awesome Cb structure directly over us. It was incredible. We had thought, since there was a lot of earlier development in The Texas and Oklahoma panhandles in the late afternoon, that we would be one of very few on this storm. Wrong! There were many chasers on this storm including the Doppler on Wheels (DOW) and a few other chasers I recognized, but can't match names with. As we passed under the turbulent base, the cloud motion was incredible, and for a moment, looking straight up, the clouds were rotating rather rapidly for a brief moment! I found that very interesting, as it wasn't even part of the main updraft base we were watching. Between 8 and 9:30 p.m., we traversed along US-283 north and south a couple miles to keep away from the core. As the sun was setting, a well-defined wall cloud formed to our southeast. We stopped along the road to view it. The Doppler on Wheels was also there scanning the storm. As the view darkened, the wall cloud slowly diminished. We arrived at Jetmore close to 10 p.m. We continued east along K-156 passing through the core of the storm for only five minutes or so.
At US-183, we went north and viewed an incredibly awesome storm around the Hill City area about 90 miles north of us. A tornado warning was issued for Graham County near Hill City. The storm was moving southeast toward Hays, at the same time we were moving north toward Hays. Hmm. We refueled in LaCrosse and continued the chase. The time was around 10:30 p.m. The lightning to our north was constant and we had an awesome view of the storm. Shortly before entering Hays, we noticed a lowering in the clouds almost directly over Hays. The constant lightning helped our view and we arrived at I-70 before the core, and continued east. There were awesome scud clouds from the storm to our north and east near Russell. Around Russell, we finally entered core and encountered very heavy rain and pea to quarter size hail. This lasted about 15-20 minutes. We eventually got home around 4 am. My e-mail address is: email@example.com
WHEELER COUNTY, TEXAS STORM: JUNE 11, 1997by Rob Slattery
The atmosphere over the eastern Texas panhandle was very unstable on this day! A dryline was poised over eastern New Mexico and was expected to mix eastward during the afternoon. A cool front had moved south of the Texas panhandle on the 10th and was located over the eastern counties as a warm front by 7 p.m. that evening. The Bulk Richardson Number (BRN) and Energy Helicity Index (EHI) at Amarillo were 31 and 3.67, respectively. These data indicated to us that thunderstorms would likely develop later in the day and that once developed the storms would have a high probability of producing severe weather. In fact, this was one of the most unstable soundings that I have seen this year.
At 2:33 p.m., the Storm Prediction Center (SPC) issued tornado watch number 402. Convective updraft towers which developed around 4:15 p.m. over Gray county had vertical wind speeds in the updrafts that were so strong the top of the storm became separated from lower portion of the storm. I was fairly apprehensive about traveling underneath this tower and the numerous other towers that were shooting up over eastern Gray county between Alanreed and Lefors along highway 291 and encountering hail. I cautiously traveled east on FM 1321 and saw a developing wall cloud that was slowly moving southward. I had time to pull over along highway 273 for a few pictures. It wasn't long before Warren Faidley passed by heading south honking that trumpet sounding horn on his fancy chase mobile. That was about the time I sensed I was really getting into something.
I made sure I stayed on the south or inflow side of this mesocyclone as it continued to intensify while it traveled southeastward at about 15 mph. I traveled east to the intersection of FM 2473 and FM 1443 around 6:30 p.m. Inflow winds were very strong and were picking up debris and dirt into the storm. Winds at this point were probably around 40 mph or higher but I can't be sure. The lightning was getting closer and the clouds were really beginning to spin. Then a long funnel cloud developed from the very well developed mesocyclone which nearly twisted to the ground. At this time, the Doppler radar in Amarillo detected the first of three Tornadic Vortex Signatures (TVS) at a range of 60 miles. Winds at this point were really howling and I was grateful when I came upon FM 1443 which headed south to I-40 between Lela and Mclean Texas.
By this time I had crossed into Wheeler county. As things turned out, I took too much time taking pictures of the massive wall cloud along FM 1443 and the storm "got the jump on me" as it traveled nearly due south along the warm frontal boundary. This motion is opposite of the surface winds and practically perpendicular to the westerly mid level winds. The southward motion rapidly intensified the storm relative helicity. When I reached I-40 the storm was really bearing down on the Lela and Shamrock area and it really became apparent that I would not be able to reach highway 83 south of Shamrock without getting pounded. Road construction along this section of I-40 also made things even more tricky. As I looked toward Lela I remember seeing a large obscured looking dark grey thing which I can describe as a hybrid between a large vortex and a large rain shaft. I turned around and went west a mile or so and got out of the way of the storm. I feel that turning around at that point in the chase was the smartest thing I did that day. The Doppler radar in Amarillo detected the second TVS along I-40 just east of my position at a range of 64 miles.
I photographed a few small funnels trying to organize but the main brunt of the storm was rain wrapped and directly east of me by a few miles. Large towers were shooting up near Mclean but I felt these would not be too explosive since the previously mentioned storm would take most of the available energy since it was off the cap rock at a lower elevation. This did not turn out to be the case, and radar shows the storms near Mclean would not be denied as all the storms slowly traveled into Collingsworth county, where the third TVS signature at a range of 74 miles appeared at 10:22 p.m.
I decided that I better start getting back to Amarillo because I was due in on the midnight shift in about 4 hours and thirty minutes! On the way home to Amarillo along I-40, I saw five emergency vehicles from several different panhandle communities heading toward the storm area. From the parking lot of the photo developing store in Amarillo, I noticed the MEDIVAC helicopter was flying in for a landing at Northwest Texas Hospital. To date, this was the largest storm I ever chased successfully. A remarkable point about the three distant TVS signatures is that all were confirmed by storm spotters with tornadoes on the ground.
JUNE 11, 1997 TORNADO CHASEby Robert Allison
Well, I took one look at those clouds last night and couldn't pass it up. At about 6:00p.m. I headed east towards the impressive 'lone wolf' supercell that was dropping tornadoes around the Kellerville area. Spotter reports indicated high-based clear areas on the west side of the storm, so I figured I was ok as long as I stayed on the fringes. The latest reports showed the storm on a south track at about 10mph, with some back-building going on, so I plotted an intercept course on I-40, figuring I would catch it somewhere around McLean.
About 7:10p.m. I pulled off I-40 at the first McLean exit. A distinct wall cloud was visible just to the southeast of McLean, so I headed south on FM 273. Five or so miles later brought me to a nice clear section just off the caprock. I pulled off the side of the road and watched. A couple of small funnels dropped out, and soon a large funnel started to form about 1.5 miles east of me. Contact with the ground was made about 7:25p.m., and I had my first Panhandle tornado of the year. About 7:26p.m. I had to abandon my position, as the debris was starting to track toward me. I caught glimpses of the storm in my rear view mirror as I headed back up tothe top of the caprock, where I pulled over to get a view. The storm was starting to rope out at this point (you'll love the pictures). At this point my roll of film ran out. I went to grab another roll out of the bag and realized that there was none! For the rest of the chase I could only watch the storms. After the tornado dissipated, I headed back into McLean, where I saw another funnel form again to the south. At this point I was watching three distinct areas of rotation. The storm was backbuilding to the west again, So I pulled out and went back towards Alanreed on I-40.
Just south of Alanreed off the main highway I drove about one mile east on a dirt road that left me on a rise with a good view of the action to the East. In the distance I saw another tornado on the ground to the southeast of McLean. I soon had to once again abandon my position, as a wall cloud was forming directly above me. A brief funnel started to form overhead as I beat it out of there. I drove back to I-40, and heard reports of a good area just north of McLean, so I decided to head east again and see what was going on. Lucky for me I used the access road, because about three miles out of McLean it became obvious that I was going no further, due to the ink black sky in front of me. I turned around and decided to head for home.
At this point I was in the only rain I saw of the evening. It was heavy, and visibility was really spotty. Suddenly a spotter called in to report a tornado on the ground just north of I-40 between McLean and Alanreed. Just at that moment I broke into the clear and saw a pick-up truck with a ton of antennas pulled off to the side of the road right in front of me. I then looked to the north and saw a large tornado about a half mile away. It was a couple hundred yards wide at the bottom, and looked like it was heading my way. I swear you could hear the roar of the wind. I honked my horn at the spotter to tell him to get out of there, and floored it. At this point I had one eye on the road, one on the funnel, and one on a good ditch to jump into. Soon I saw the storm was lifting, and continued west. The rest of the chase was spent driving west a couple of miles, pulling over to watch the storm for a couple of minutes, and then driving west a couple miles more. Everywhere you looked there was rotation. I finally left the storm for good about halfway between Alanreed and Groom. What an evening. I wish I had somebody with me though. email: RTALLISO@ipgate.actx.edu
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BIZARRE CHASER NEWS:
Marty Feely sent in excerpts of a newspaper article by Chris Olson from the Omaha World-Herald dated October 2, 1997. "Paris has the Eiffel Tower. St. Louis has the Gateway Arch. Seattle has the Space Needle. Now, Robert Hogenmiller Jr., an Omaha commercial artist, proposes a 610 foot-high stainless-steel Tornado Tower for Omaha. The tower, at an estimated cost of $35 million, would include a restaurant, a tornado museum, a virtual-reality theater depicting a tornado, an educational-conference center on tornado safety, and an amusement ride to the top of the vortex with observation decks. At night, lasers would give the tower the illusion of spinning counter-clockwise like a tornado, said Hogenmiller, who doesnít yet have the financial backing for his idea." Should we take up a collection?
Andy Kula submitted a news report from the Des Moines, IA register: "A flying cow and a Doppler Radar tower are among the features unveiled on September 14th at a dedication ceremony for Eldora, Iowaís latest recreational area: TWISTER PARK. The 12,000 square foot area became the home of usual jungle gyms and swings, along with unique playground equipment including a "Dorothy" and a flying truck. The parkís wooden structures have the appearance of a ravaged community. The park was financed through private donations. Cost: $70,000.
11 JUNE 1997 FORECAST DISCUSSION by Paul Janish and Greg Stumpf
A developing dryline, increasing low-level moisture, steep mid-level lapse rates, and moderate shear suggested a potential for severe thunderstorms and supercells across portions of western Kansas and the Texas/Oklahoma Panhandle on the afternoon of 11 June 1997. Our initial forecast was based on the 12 Z Eta model that morning. Low-level moisture was forecast to increase with surface dewpoints in the upper 60s across the eastern Texas Panhandle and mid 60s into southwestern Kansas ahead of a weak dryline by 00Z. Mid-level lapse rates were forecast to become increasingly steep which suggested an axis of CAPE exceeding 3000 J/kg from western Texas into western Kansas. Although a low-level jet was forecast to develop across the area by late afternoon and vertical wind profiles showed considerable veering with height, 0-3 km shear was marginal with winds of 15-20 knots expected at 700 mb. A band of west-northwesterly 500 mb flow greater than 30 knots was forecast across the area with strongest winds through 300 mb (greater than 50 knots) across west-central and northwest Kansas creating a more favorable deep shear profile there. A 50-60 knot westerly subtropical jet at 200 mb was forecast across the Texas Panhandle. Storm relative wind profiles were forecast to be most favorable for supercells and tornadoes across west-central and northwestern Kansas given an expected supercell motion of 290/16 knots.
There was no organized upward vertical motion forecast at mid-levels and 850-700 mb winds and Q-vectors suggested sinking motion and divergence over western Kansas with some low layer rising motion and weak convergence across the Texas Panhandle. Our primary question of this day was whether the Eta under forecast the structure of the dryline and if localized low-layer convergence would develop in the vicinity of the forecast dryline position near the Caprock in the Texas Panhandle or in the vicinity of thunderstorm induced outflows near the Kansas border. The Storm Prediction Center issued a moderate risk across central/western Kansas and slight risk southward across western Oklahoma and the Texas Panhandle at 15Z.
Since the capping inversion was expected to be rather strong over northwestern Texas and considerably weaker further north our initial target area prior to 18Z (see "TARGET 1" on our 18Z and 21Z maps) was near Medicine Lodge, KS, coincident with thunderstorm outflows, axis of greatest instability, and strongest mid/upper level storm relative flow. However, convection developed by mid-morning across our target area and northwestern Oklahoma which pushed an outflow boundary into the extreme northeastern Texas Panhandle and west central Oklahoma.
By 18Z clear skies, rapid destabilization, an intensifying dryline in the central Texas Panhandle, and the expected position of the outflow boundary, re-defined our target area further south and west near Canadian, Texas (see "TARGET 2" on our 18Z and 21Z analyses). Trends in surface fields suggested a possible dryline bulge across the northern Texas Panhandle which was not forecast by the Eta. Our 18Z analysis depicts the dryline convergence zone, which is east of the moisture gradient; the moisture directly behind the dryline was shallow and mixing out. With increasing convergence and a focus for development across this area, SPC redefined it's moderate risk to include parts of western Oklahoma and the eastern Texas Panhandle at 19Z. Later, our 21Z analysis (completed after our chase) depicted a developing low pressure area in the N TX and W OK panhandles, and an apparent increase in the dryline bulge.
11 JUNE 1997 CHASE SUMMARY, by Greg Stumpf and Paul Janish
We (accompanied by Paul's wife Janelle) left the NSSL parking lot at 1:30 p.m. to head west on Interstate 40. As we approached Elk City OK, we noticed a developing line of towering cumulus along the outflow boundary, aligned east-southeast to west-northwest passing over Elk City (these towers never developed into thunderstorms). The boundary appeared to be "pointing" toward Canadian, Texas, which was where we were heading. From Elk City, we drove northwest to near Durham, OK and spotted several convective areas. One large thunderstorm was visible to our distant northwest with a backsheared anvil and small overshoot. This was presumably the storm that was warned for in Texas County Oklahoma, that turned LP (low-precipitation) and died later (we suspect it moved into lower CAPE air, and the capping inversion choked it off). We could see some very distant cirrus anvils way to the north (north of Dodge City?) and way to the south (northwest of Lubbock). But our attention was grabbed by one isolated tower developing to our west-southwest, we thought, somewhere east of Pampa TX, south of Miami, west of Mobeetie. We headed through Allison TX, to Mobeetie to greet an LP supercell. The storm was medium-high based, producing a small left split, and had beautiful rounded striations on the east side of the updraft.
The initial tornado reports west of Mobeetie appeared to be false to us. The storm base and ground was clearly visible from our vantage point as we heard a spotter claiming ground contact of a tornado. There was no funnel nor dust seen by us (from about 5 miles east). However, inspection of WSR-88D radar data from Amarillo shows a nice tight mesocyclone at this time. We are still perplexed.
We decided to head south noting that the storm was beginning to severely turn to the right. We stopped along FM 2473 about 3 north of "Magic City" (hmmm...no city here...must have disappeared!), and shot some photographs (e.g., Fig. 1). We eventually ended up at FM 2473 and FM 453 about 4 miles east of Kellerville and watched the storm very slowly move to the south-southeast. We were in and out of dime to quarter sized dry hail in the forward flank precipitation area. The beautiful striations and beaver's tail continued as the storm slowly grew larger and began to evolve from an LP storm to a classic supercell.
In the next 20 minutes, this storm evolved quickly into a beast of a classic supercell about 3 miles away from us (see WSR-88D image). Along with a well-developed beaver's tail cloud extending from the southeast into the updraft base, a lower ragged tail cloud began to quickly develop extending from the northeast. Rapid upward motion and motion toward the center of the updraft base became very evident, and a rear-flank downdraft (filled with some precipitation) began to wrap around the south and the southeast side of a developing low-level mesocyclone (Fig. 2). We also noticed that the storm had a very laminar front edge to its updraft, and no flanking line. Within about 10 minutes, the low-level meso became completely surrounded by the RFD (rear-flank downdraft) and rotation became very rapid in a diameter of about 2 miles wide. At 644 p.m., we noticed the first hints of dust whirls under this "blender" of a low-level mesocyclone, and then wisps of condensation grew rapidly to a multiple-vortex tornado (see cover) and then a stovepipe, and then the condensation briefly disappeared. It returned soon, and the tornado quickly grew larger, and then became a wedge (Fig. 3). The motion in the sub vortices at the base of the wedge suggested to me that the tornado was violent (compared to other violent tornadoes I've seen). We stayed at our position (about 7 miles north of I-40 on FM 453) for about 12 minutes before retreating south.
As we retreated the tornado became increasingly rain-wrapped and very large (twice as wide as it was tall) (Fig. 4). At one point, we thought we saw another smaller (but still large) vortex on the southwest side of the wedge. The south edge of the updraft remained laminar and "flank-less". By the time we reached I-40, the rain was completely obscuring the tornado. We bolted east 5 miles to Lela, and then south. Soon, another storm to the southwest began to precipitation into the inflow of our original storm, and we could no longer see the rain-wrapped mesocyclone. This mesocyclone (and tornado) crossed I-40 about 1.5 miles west of Lela and overturned many vehicles and sending 7 to the hospital.
Later, the new storm became a supercell, and we witnessed twin vortices develop on the forward flank gust front and move to the southwest about 3/4 mile away from us (Fig. 5). One vortex lasted about 2-3 minutes, had no visible condensation funnel (but rotation at cloud base), and died as outflow overtook the vortex (I think it transformed into a gustnado). As the daylight wore to twilight, this storm had a nice beaver's tail (Fig. 6), absolutely beautiful laminar structure (Fig. 7), still no apparent flanking line, and LOTS of meaty cloud-to-ground activity (too dangerous to be outside for a long time).
The next day, Greg was the driver for the subVORTEX FC van. We ended up chasing another storm that developed N of Kellerville! Along the way to that storm, we crossed the 11 June tornado damage path on I-40 and FM 453. The damage was 0.75 miles wide at I-40, and estimated damage at F3 or F4. About 3 miles north of I-40 is where the southern end of the damage path was on FM 453 (the path was rather wide on FM 453 as the tornado was moving from about 340 degrees). I estimate damage on FM 53 to be about F2. At the location where we photographed the tornadogenesis, the field about 2 miles to the west appeared scoured of vegetation.
Some questions we still ponder:
* Was there a tornado W of Mobeetie while the first supercell was in its LP stage? Does anyone have photographs of video of that tornado?
* Did the storm initiate on the dryline and then move off, possibly interacting with the outflow boundary in the eastern Texas Panhandle? We don't think the outflow ever actually intersected the dryline but perhaps as the storm moved off, the boundary may have played a role.
* Our initial forecasts of storm relative winds were based on a supercell storm motion of 290/16 knots (actual mean wind vector was 260/20). Our storm moved at about 340/20, which would greatly improve the storm-relative profiles, making them much more favorable for supercells and tornadoes.