Thursday, April 9, 1999

Chase Accounts

Marty Feely -- On our way home from the Des Moines Severe Weather Conference, my girlfriend and I visited Winterset,IA and the bridges of Madison County. At the Roseman Bridge gift shop, the owner bid us goodbye with, "Don't chase any of those through Madison County!" What are the chances that 12 days later I would watch a large tornado touch down just a few miles from the Roseman Bridge?
          At 2 p.m. Thursday I was in Osceola,IA and I had seen nothing but gray skies. It was depressingly cool. Then I got a call from Bobby Prentice saying that the latest information favored storms really going to town in SW Iowa as the warm front lifted north in the next couple of hours. Well that's what I'd been waiting for! I headed west on 34. Des Moines weather radio said "a line of tornadic thunderstorms" was moving NE across western Iowa.
          Just after 3 p.m. I was nearing Creston and I saw it - blue sky! And an anvil! A nice cumuliform anvil just to my west. There was my supercell. I turned north on 25 for intercept.
          Even though I was closing in, visibility was terrible in a misty haze, such that I could make out no storm structure. Bobby called again and confirmed that this was currently the biggest, baddest looking supercell in the line and that tornadoes had been reported on the ground.
          When I got to Greenfield at 3:35 the sirens were going off, with the storm just west of town. I didn't dare get in for a closer look, since there could be a rain-wrapped tornado in that mess. I parked east of town and waited. Another storm darkened the sky to the east. About 4 p.m. a new tornado warning was issued for Madison County. The radar-indicated tornado was near Macksburg and moving north at 45 m.p.h. "Hey, I can make that!"
          As I headed east on 92, a large, dark rain-free base became visible. The closer I got, the more "pregnant" it looked. It was ready to drop. At 4:17 I was 10 miles west of Winterset when a portion of the base started organizing into a cone about 3 miles to my NE. I slid to a stop on the muddy shoulder. With the car still in drive and my foot on the break pedal, I grabbed the camcorder and rolled tape as the cone rapidly descended and dropped a stovepipe to the ground. It moved north for 3 minutes, then lifted as a smaller "sister" funnel joined it just to the north.
          The line of storms blasted off to the east toward Illinois, too fast to keep up with. I gave up east of Knoxville,IA as a beautiful rainbow stretched across the eastern sky.

Jeff Piotrowski -- April 8, 1999 SW and C Iowa Long Tracked Tornado Chase Today was an anticipated chase day for both me and my chase partner Brian Stertz. The forecast models were trending for a tornado outbreak for the C.Plains during the earlier part of the week. Brian and I watched the models closely to see where the main activity would be focused. From Tuesday on, the models generally were in agreement in placing a bombing out surface low over Nebraska, while a strong negatively tilted 500 mb trough was expected to sweep across the C.Plains into the Middle Missouri and Mississippi Valley areas. The main challenge was predicting where the surface boundaries were going to setup by the afternoon hours on Thursday April 8. Brian was watching SW Iowa closely ; he and I thought this area was most persistent in placing the greatest tornado threat. Several forecast models (ETA,AVN,MM5 )kept pointing to SW Iowa regarding the best combination of tornado elements. North sector of dry line bulge, left front quad of mid-level jet max, warm front in proximity, and a pronounced axis of instability poking into that area were just a few of the favorable parameters that looked to be setting up by evening. The RUC model from the early morning hours on Thursday really bulls eyed our target area. A strong cap was expected to develop across much of Kansas , Oklahoma, and Missouri during the morning hours, this would allow for strong heating to take place south of the target area. Instability would not be extreme, but good enough to pop convection and sustain convection. The warm front was expected to lift slowly through Kansas and Missouri. Meanwhile, the dry line was expected to punch to the east and northeast in response to the approaching mid-level jet max. This would result in a pinching wedge of instability focused on E.Nebraska and W.Iowa. Our target area was chosen- SW Iowa or bust!! The Storm Prediction Center focused the greatest threat(high risk) of severe weather and tornadoes across much of Central and Northern Missouri, and portions of SE Iowa and C.Illinois. Our target area was outlooked for a moderate risk of severe storms, with the main emphasis on low topped supercells and a few tornadoes. We pondered our target area only briefly before we decided to head out from Tulsa. We geared all of the maps, scanner frequencies, etc. toward NW Missouri, S Iowa, and E.Nebraska. We had COMMITTED!!! Brian took control of the driving duties, while I called up data on my laptop. We headed up the I-44 turnpike to Joplin where we could get a decent road north to Kansas City and I-35. We reached the junction of I-44 and US 71 east of Joplin in great time. Elevated storms, a few severe, raced up the turnpike behind us and caught our attention briefly. The cap had control of these storms destiny, and these storms quickly fizzled into just showers. Another sign that told us get north!! We were still trying to analyze data when the new SPC severe weather outlook came across. The high risk was extended further northeast; however, the moderate risk was backed west well into C.Kansas. Apparently, the dryline had not yet started to punch northeast and was lagging back in C.Nebraska and C.Kansas. No doubt about it, the surface low was starting its rapid deepening phase. Our concerns were that maybe our target area was too far northeast. We had intense mind melting on this interesting nugget of information. Persistence is often the key to storm chasing, and in all of our years of successful chasing, sticking to a target area has yielded our best chases!! We reached Kansas City shortly before noon. Satellite photos started to show that dry slot convection was starting to firm up across C.Nebraska. Towering cu also outlined the dryline position well. The surface low was near N.Platte Nebraska , and the satellite had the scary looks of an inland hurricane(if such one existed). Distinct swirling bands surrounded the low pressure circulation. Two areas looked immediately threatening on the image. An arc of new convection extended in a negatively tilted orientation from NC Nebraska into SC/SE portions of Nebraska. A second area which looked potentially explosive was the dryline over NC Kansas and SC Nebraska. The Storm Prediction Center was monitoring this closely, and a mesoscale discussion indicated a watch may be issued in next 1-2 hours. We were in the Kansas City Metro at this time so we needed to decide on I-29 or I-35. We were extremely concerned that the dryline would blast northeast, and the storms would too so we opted for I-35. We noticed a marked change in airmasses between Kansas City and the Iowa border. The Kansas City area was under the influence of strong warm air advection both at low and mid levels. Further northeast on I-35(near Cameron). Large breaks could be seen in the cloud deck, but low level moisture was screaming back to the northwest. We were now in the low-level jet. We could see laminar clouds to the south, where the low level jet went up and over the warm front. Looking good!! As we approached the town of Cameron, the Storm Prediction Center issued a PDS tornado watch for E.Nebraska, W.Iowa, NW Missouri and NE Kansas. Long tracked strong tornadoes were mentioned. The dryline was starting to fire over SC Nebraska and NC Kansas, and a pronounced arc of dry slot supercells extended from near Valentine to near Grand Island. These supercells quickly went severe and started to rotate. We pressed on towards the border on I-35, but we were watching a severe storm(no rotation) north of St.Joseph MO. The storm was isolated but had capped/struggling look on radar, so we crossed into Iowa. WHO radio in Des Moines was coming in strong by now. Warm air advection continued to fire numerous severe storms over C.Iowa. Large hail and strong downburst reports were common. The storms were creating a strong rain cooled boundary along and just north of I-80 from south of Carroll to Des Moines. A supercell during the mid morning hours also tracked from SW Iowa into SE Iowa. We could not distinguish if this storm created an outflow boundary as well. Temperatures were not exactly favorable for tornadoes(55 in Des Moines), but we knew that intense warm air advection and the approaching warm front would assist in maintaining supercells. The low level shear was extreme(if not absurd). At the surface, east winds at 30-40 mph prevailed; while just above the surface, southeast winds at speeds well over 60 mph existed across C and S Iowa. Mid-level winds were expected to increase during the afternoon to speeds upwards to 100 mph from the s-sw. Speed shear deluxe!!! As we approached Des Moines, tornado warnings were being issued like parking tickets in Chicago!! Central and Eastern Nebraska was under the gun!! Supercells were spawning not just a few, but many confirmed tornadoes there. The interesting item of note was that the supercells appeared to be building southeast along the occluded front or negatively tilted lobe of energy(probably both). The supercells were very small but intensely rotating on radar moving north-northwest at 55-60 mph. The storms seemed to be more intense the closer the storms got towards the Lincoln/Omaha area. Tornado reports were bombarding the radio news guys in Omaha. We switched our radio over to Omaha to monitor the progress of the new storms that were starting to explode across SE Nebraska. We figured these would be the storms we would have the best chance to intercept. The speed of the storms was not exactly conducive for a controlled chase, but it certainly will make it a fast and furious one!! We headed west on I-80 and figured this would be the quickest way out to the target zone in SW Iowa. We enjoyed listening to the Omaha radio station's broadcast of the tornadoes in and around Omaha. Several tornadic supercells passed on the west and north sides of the city limits of Omaha. The station had many spotters out and about town. The strongest tornado, from what we could gather from the radio reports , was the tornado which passed northwest of Omaha near Yutan. A cluster of rapidly developing supercells was near near Hamburg and Sidney in SW Iowa, and near the town of Tarkio in NW Missouri. Now it was time to "pick" a storm to intercept. There was very little doubt as to whether the storms would produce a tornado; keeping up with the storms another story!! As we headed west on I-80 near Earlham, 3 distinct supercells were now organizing quickly over extreme SW Iowa and NW Missouri. Supercell #1 complete with an intensifying circulation was near Sidney IA. Supercell #2 was exploding near the town of Shenandoah. Supercell # 3 (the meanest of the bunch) was already rotating impressively on radar near Tarkio MO. We opted to chase either supercell #2 or #3, depending on how each evolved later. We could not help to notice the low bank of clouds marking the rain cooled air just north of I-80. This would be a critical factor later....stay tuned..... As we approached Stuart (please refer to May 27,1995 storm historians), the supercells were already developing major hooks on radar. The strongest of the 3 supercells continued to be the one near the Atchison/Nodaway county line in NW Missouri. Extremely large hail was also accompanying this strongly rotating storm. The time was now 2:15pm, and tornado warnings were issued for Fremont, Page, and Montgomery counties in SW Iowa, as well as, Nodaway Co. in Missouri. Tornadoes were soon reported near Shenandoah IA and near Westboro MO. I turned on the tv and was able to pick up KCCI in Des Moines. John McLaughlin KCCI Chief Meteorologist started almost continuous severe weather coverage from this point on. He was advising that he was very concerned about the SW Iowa area, and was giving preparedness information for the viewers to prepare for these tornadic supercells. We were near Casey when we heard reports of strong tornadoes on the ground near Essex and College Springs. Radar indicated these tornadoes well and the storms were actually intensifying and growing larger at this time (2:25pm). We reached Highway 148 when we decided to stop going west and head south now to intercept one of the supercells. As we left the town of Anita, a strong tornado was approaching Red Oak. At the same time, another very damaging tornado was passing west of Clarinda IA. The tornadoes were just 30 miles to our southwest and approaching at 50 mph. I watched radar very closely, and the Clarinda storm was definitely the strongest. We plotted an intercept near Corning for this circulation/tornado. Local radio reports indicated "significant damge" on the west side of Red Oak. That strong tornado was expected to approach the small town of Elliott and later, Griswold IA. Tornado reports soon were also broadcast on the storm we were most interested in near Montgomery/ Page county line. Decisions, decisions..... We remained focused on the tornado that was going to pass near or west of Corning IA. As we approached Massena, drizzle and fog quickly appeared and limited our view to the west and southwest. Both Brian and I have seen this drizzle/fog combination before tornadoes in the past, and this is not a good sign for the general public!! Visibility was shot so we had to turn to "ifr" guidance/radar. The rotation was extreme on both storms, but more impressively with the tornado approaching Corning rapidly. Just after 3pm, the tornado was approaching the town of Villisca near the 4 county corner area(Montgomery/Adams/Page/Taylor Counties). Radio reports now indicated "major damage" to 2 towns the tornado struck, College Springs and Villisica IA. the tornado was next in line to approach the town of Carbon. This is where our chase takes off, so strap in and enjoy the ride!!! We were at the intersection of Highway 148 and County Rd N-28 when the real chase began at 3:05pm. We were approaching Carbon from the east. The tornado was approaching Carbon rapidly from the south. We could see only the lowered part of the wall cloud as a hill obstructed our view. The fog and drizzle was now completely gone. Visibility was well over 5 miles ,and we pressed on towards Carbon. At 3:08pm, the large tornado was now coming over the hill and looked to be heading right for Carbon. The tornadoes width looked to be in the 200-300 yard range, possibly in the F-2 to F-3 appearance. We were on the east side of Carbon with trees blocking our view slightly, but the tornado remained definitely on the ground. I called the 911 dispatcher to advise them that the tornado looked to be headed for the town of Carbon. The person seemed startled when I told her how close the tornado was to town. We opted to head a little west of town to see if we could get a clear view of the tornado. We were just east of the Middle Nodaway River at 3:10pm on County Rd N-28. Brian saw the tornado was bearing down on us from the south, so we pulled over at a clearing(probably should have been just a little more west) to video the impressive tornado. Brian did the video camera, while I shot "still" photos of the tornado. Hard to keep still when you have a tornado bearing down on you at 50 mph!! We watched the tornado widen to a quarter mile, and then move on a more north- northwest track/heading. A squirrel ran in front of us on the road, probably responding to the drop in pressure. My ears popped first and then Brian's did too. We got back into the van and headed a little more west- about 1/4 mile to be precise!! The tornado bore down on the road to our west at 3:14pm. We watched the tornado in awe as it intensified dramatically right in front of us. The tornado struck a stand of hardwood trees on the bank of the Middle Nodaway River before it crossed the road (5 telephone pole spreads from us). The tornado was audible and the RFD was so strong from the south that Brian was not able to get his door open(even leaning full force on it). I shot some great video as it moved across a pre-season corn field. The tornado moved rapidly north and we shot video for about 3 minutes before we headed back east and then north. Brian's Cardinal's hat that he wore for nearly 12 years was last seen blowing in towards the tornado on a jet band. We're sure it will end up with a corn stalk growing through it by July!! I guess you have to sacrifice to the storm gods sometime!! At 3:15pm, we headed back east through Carbon to get back to Highway 148. The tornado was on a track that would take it to near Massena and/or Bridgewater. The tornadoes intensity and width was growing at this point. We had a cedar tree/bush fall down from the sky and blow across the road just east of Carbon. At least it wasn't a cow!! Anyway we reached the intersection at 3:18pm and headed north towards Massena. A wedge tornado was seen swirling to the n-nw of Carbon. Width of the tornado by now appeared to be in the 1/2-3/4 of a mile and the position of the tornado was about 5 miles west of Mt Etna (not Sicily) Iowa. We closed on the tornado quickly and at 3:22pm, we watched the tornado approach a farmstead on Highway 148. The tornado looked very similar to the Spencer SD tornado of last year(May 30), although probably not as intense. The whole storm tower above the tornado was rotating at similar speed. We approached the wedge tornado from the south, so wrapping rain was becoming a problem. At 3:26pm, the large tornado (multiple vortex) swirled directly for the farmstead, but appeared pass a little south of the farm house. The barn disintegrated before us and other large debris blasted across the road in front of us about a half mile. Power poles were broken off and power lines were on the road. We maneuvered through the lines and debris on the road to continue our chase. The farm house was spared but everything else to the south of the farm house was destroyed/blown away. We believe that the tornado's strength was in the F-3 category as it crossed the road. The width of the tornado was impressive as it headed more northeast into Adair Co. At 3:30pm, the tornado approached but missed Bridgewater. We had to go north to Massena to get a road east IA Highway 92. The tornado moved n-ne once again and crossed IA-92 at 3:34pm. Iowa state troopers were also watching the tornado. Once the tornado crossed the road, the tornado seemed to weaken and then re-organize. The process of vortex breakdown happened about a mile north of the road. We and the Iowa trooper kept following the tornado, but it's northward movement was hard to keep up with. The trooper stayed on IA-92, but we decided the only way to stay with the tornado was take an unmarked gravel road north. The tornado's speed had to be approaching 60 mph at this point. We had picked a good road that's for sure. The road crossed the damage path once again. By now the tornado was 4 miles to our north and leaving us behind. At 3:38pm, we came up over a hill and got a good view of the tornado. We were so transfixed on the tornado, that we almost did not see the large tree debris the tornado left behind on the road. To continue the chase, we had to clear large tree limbs off the road. Unfortunately, this was our last glimpse of the tornado. We headed north to I-80 at 3:50pm. The storm looked severely blown out, and the storm was crossing the rain cooled boundary (mentioned earlier). We now had to focus our chase to yet another tornadic supercell heading northeast from the Creston IA area. We got back on to I-80 and headed east. The supercell was approaching Winterset from the Macksburg area at 4:10 pm. Numerous tornado reports were broadcast on local radio with this storm. The circulation was going to pass to the west of Winterset, but the town of De Soto was in the projected path. De Soto(birthplace of John Wayne) is right on I-80, so this would be an easy intercept. We were only 15 miles from DeSoto. At 4:20pm, we were at the Earlham exit on I-80. Spotters reported a tornado on the ground northwest of Winterset moving northeast at 55mph. De Soto was the next exit past Earlham, so it looked like we would be in the mix to see another long tracked tornado. Radar indicated intense rotation at all levels and a tornado was definitely on the ground. Local radio reports confirmed this. At 4:24pm, we passed through the town of DeSoto that was scrambling to prepare for a tornado. Sirens were sounding in town and the streets were emptying. We headed south plotting an intercept somewhere along US 169. Radar indicated that the tornado was paralleling the highway so we would have to see it soon. We rounded a slight bend in the road (about 5 miles south of DeSoto) and there it was!! The tornado was starting to intensify right as we pulled over. The vortex structure changed very rapidly from stove-pipe to wedge appearance as the tornado tracked north at nearly 60 mph. We shot video of the charging wedge to our northwest about 2-3 miles between 4:28 and 4:33 pm. Large structural debris was seen centrifuging out from the tornado. A spectacular RFDwas also seen coming in behind the tornado-extreme sinking motion/cloud evaporation. Since the tornado(now nearly a mile wide wedge)was up against the dark core, we decided to head to the north towards De Soto. The tornado was tracking towards De Soto as well, but might pass just a little west of town. We reached the intersection of US 169 and County Rd G14 at 4:36 pm. The tornado started to rope out at this time, but still doing damage on G14 immediately to the southwest of DeSoto. The tornado passed about 1/2 mile west of DeSoto and weakened to F0-F1 intensity as it crossed I-80. Fortunately it did weaken because there were alot of clueless motorists on I-80. The tornado was gone from view as it started to dissipate in Dallas Co. to the south of Adel at 4:48pm. The chase from her on was a struggle to keep track of supercells and where these would cross I-80 between Des Moines and Iowa City. The tornado threat appeared to leave S.Iowa with time, and re-focused further southeast in Missouri and W. Illinois. A very stressful but highly successful chase. The next day we surveyed the damage, most in the F-2 to F-3 range. A few isolated spots had lower end F-4 damage, particularly between Carbon and Fontanelle ( Adams, E.Cass , and W.Adair counties). The maximum damage intensity corresponds well with the widest phase of the tornado. Brian even tried a search and rescue of his hat, but not found within half mile of the road. Fortunately, advanced warning prevented any serious injuries or fatalities, especially with regards to the speed of the tornadoes 50-60 mph!!

Tornadoes in Adams & Adair counties. Copyright 1999 Jeff Piotrowski

Tornadoes in Adams & Adair counties. Copyright 1999 Jeff Piotrowski

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Radar data provided courtesy of Weathertap, Inc.