Iowa Tornado Outbreak - 04-09-2011

Incredible cyclical tornadic supercell over western and northern Iowa Saturday afternoon and evening...we're still reviewing video to determine how many tornadoes we actually saw. We know for sure that we saw at least 10, with possibly more than that.

To set the stage...it became increasingly obvious throughout the day on Saturday that there was a significant threat of tornadoes - and that any tornadoes that did develop could be strong. Mike Brady, Roman Totten, and I left Peoria at 6 AM, targeting Onawa, IA.

A low pressure center over western NE was forecast to move northeast, and deepen throughout the day. Backed SE surface winds intensified ahead of the low, and brought unseasonably warm, moist air north into IA/NE. Record to near-record temperatures reached the upper 80's, with dewpoints just below 70 by 4 PM. This created a very unstable convective environment, with surface based CAPE reaching well in excess of 3000 j/kg by 21Z (4 PM CDT). The wind fields near the warm front/triple point in western Iowa were extremely favorable for tornadic development, with Surface-3 KM Storm Relative Helicity of 391 m2/s2 (per OAX 21Z sounding). Hodographs were large, and curved clockwise, as clearly shown by the aforementioned sounding.

A few blips started to appear on radar before 5 PM, and one started to become dominant. It started moving northeast, but as the mesocyclone's rotation increased, it began to turn right, and slowing down. By the time the storm crossed the river, it was moving ENE at 35 MPH.

We moved east of Onawa, and parked up under the meso. After getting hit with golf-ball sized hail for a bit, and seeing several funnels, the rotation and motion under the meso started to ramp up rapidly. A small, non-condensated tornado touched down briefly about 200 feet down the road, and dissipated after about 30-45 seconds.

We raced east after the tornado had lifted, and tried to navigate some terrible terrain/soupy dirt roads as fast as we could. We missed the 3/4 mile wide tornado that struck the town of Mapleton (video from my friends Skip Talbot and Mike Boik), and entered the town minutes after the tornado went through. After a quick stop to make sure that people were ok, we got through, and continued after the beastly supercell.

The inflow into the storm at this point was incredible - easily 50 MPH, backed to the SE. This continued for about the next 5 hours...when inflow into a storm is that strong, it's not a matter of if it'll put a tor down. but when.

As we got east of Mapleton, we noticed that a new wall cloud was developing outside the rain curtain. Then, the fun began...

Tornadoes just started dropping. One, after another, after another. Beautiful stovepipes. A multiple-vortex. Several ropes. Power flashes. We found tornadoes in our video that we didn't even notice that night because we were focused on bigger tornadoes elsewhere. And, we were on what could be the largest tornado in recorded history - a final number hasn't come in yet, but the path width was measured between 2 and 3 miles wide. Here's some of our video still captures...

Most of these tornadoes were between a quarter and half mile wide at some point in their life cycle, and EF-2 to EF-3 in strength - they would drop, strengthen, and then either become rain-wrapped, or get ingested by the 3 mile monster.

After about 5-6 hours of dropping tornadoes, the storm weakened, and we drove to Mason City, IA for the night. An absolutely incredible storm, and an absolutely unreal night.

#1 lesson learned...backed SE winds can do anything.

Here's our video from damage in Mapleton, and some more stills from the tornadoes...

Never understood how people could forget how many tornadoes they saw until tonight. Saw at least 8 tornadoes, including 2 on the ground at one time, a multiple vortex, and an unbelievable cone/stovepipe. Got video, not sure how it'll turn out since it was all after dark. Prayers go out to people affected - these were large tornadoes that caused major damage.

Tornado outbreaks possible today and tomorrow...

...and I'm leaving for N IA/S MN in 20 minutes. Chase partners Mike Brady and Roman Totten - the next two days have the potential to be absolutely incredible. Live stream at www.chasertv.com under either my name or Mike's.

From DMX AFD for Sunday: "THESE PROFILES AND SOUNDINGS SUGGEST A LINE OF SUPERCELLS WILL EXPLOSIVELY DEVELOP WITH VERY STRONG LOW LEVEL HELICITY VALUES AND LOW LCL HEIGHTS. THE POTENTIAL AND CONFIDENCE FOR A TORNADIC OUTBREAK IS INCREASING AND WILL CONTINUE TO HIGHLIGHT."

Chase Potential - Saturday/Sunday

Saturday is currently looking like the first major tornado threat of the year. Still tough to lock down the details, due to timing differences between the models, but it looks like the target area is centered over eastern IA/western IL/northern MO attm.

Storm motions are currently holding at 30 kts. CAPE is forecast to be over 3000 j/kg. EHI at the surface is over 4, with over 7 aloft. Shear may be veered from the SE, and is running at 60 kts. Hodographs are showing large, clockwise curvatures. Capping doesn't look to be an issue...it could be a huge day.

I'll be out in the field with Mike Brady...stay tuned for what could be a historic day!

4-3-11 Eastern IA/NW IL Wall Clouds/Hail

Tough forecast yesterday paid off big dividends with a couple of rotating wall clouds, and hail up to quarter size....amazing structure!

Because of my proximity to the chase zones of interest, I was able to stay at home in Peoria til a little after 3 PM. My main point of indecision was whether to target the triple point in NE IA/SE WI, or further south, along the cold front. I decided to go with the 4 KM WRF model, which showed decent initiation around 23-00Z (6-7 PM local time).

A bit before I hit Burlington, IA, the SPC issued an MD saying that a watch would be issued soon...based on this, I decided to head a bit further north than I had initially intended. I hit Mt Pleasant and blasted north as storms erupted, going from blips to massive supercells in under 20 minutes. I initially targeted the northernmost storm because of its proximity to the low pressure head.

About 10 miles out from the northernmost cell, near Iowa City, a large lowering became evident. As I got closer, medium rotation became evident, and the wall cycle several times. At one point, it tried to drop a funnel, but it wasn't meant to be.



I pulled off north of Iowa City, and let it go right over me. Absolutely fantastic motion, and it's always great to feel the winds changing at the surface under an area of rotation...ended up getting blasted by 35-40 MPH rear-flank downdraft, and, as the wall cloud became rain-wrapped and started to crumble, I decided to bail and head back south towards another supercell that was starting to show the makings of a hook.

I was able to get onto the southern storm, get onto the wall cloud (which was another beauty), and let that go right over me, as well. Got behind Mike Brady as the RFD blasted us, and ended up tailing him home...not before we core-punched a few hail cores, though. Best we got was a fairly heavy bout of quarters.

Navigation was pretty tricky without a co-pilot, but I managed to pull it off without too much of a problem. Also, I'll need to get a camera of some sort...taking pics with my phone while blasting down the interstate is a supreme pain.

Some good shots of the southern storm/second wall cloud from my friend Brandon can be seen here. Here's one of the shots of the wall cloud he took, not too long before I let it go overhead...

Chase later today

THE TORNADO THREAT MAY BE GREATEST NEWD ACROSS NRN MO INTO WRN AND NRN IL WHERE THE STORMS WILL HAVE ACCESS TO GREATER LOW-LEVEL SHEAR. IF DISCRETE ROTATING STORMS CAN PERSIST INTO THE EARLY EVENING WHEN THE LOW-LEVEL JET IS FORECAST TO STRENGTHEN...THEN AN ISOLATED STRONG TORNADO WILL BE POSSIBLE.

Nice tor threat in my backyard...can't pass that up. Updates to follow!