Monday, June 28, 2010

06/23/10 Squall line & Damage

Approaching shelf cloud near Woodhull, IL
entering an
extremely unstable environment

Last Wednesday, I ended up chasing after work as a strong cold front sagged south across west-central Illinois. The environment ahead of this cold front was rather ripe for severe weather. Extreme instability in place, plenty of shear, and a very moist boundary-layer with dewpoints near 80°F. I blasted north on IL Rt. 78 as I got off work targeting near the Geneseo, IL area. Storms began to initiate around 3:00pm which meant I was a little behind being an hour to the south. Anyhow, a tornado-warned storm organized near Muscatine, IA and headed east so I dropped south on I-74. I caught a view of a nice shelf cloud, but this once tornado-warned storm quickly went outflow dominate upon arrival. I continued south and than east to keep up with the developing squall line as it entered the very unstable environment to its south. Outside Galva, IL I noticed some rotation along the shelf with some meso-vorticies. At about this time, I got a phone call from home wondering "if that was just a tornado that went through?" At first I thought it was a joke, but quickly I understood the situation was definitely not a joke. It turned out this severe squall line produced 75mph straight-line winds at my residence which knocked out power, uprooted at least a couple trees, tore a roof off a storage shed, and completely obliterated another storage shed while at the same time taking down 70ft pine trees. This quickly ended my chase as I continued to drive back home on U.S. 34. Getting even home though proved quite difficult with one tree completely blown over/uprooted onto road 650E. I barely got through as this tree was blocking 3/4 of the road at this point. Once I finally got home I found lots of debris in the yard. After letting the storm pass off to the south and east toward Peoria, IL I proceeded to get a better idea of the damage. At first from family member accounts I thought this might have been a rain-wrapped tornado based off what they heard. Especially, when I noticed a hook signature on radar developing along the shelf cloud where our residence is located. This made me quite curious! After the storm passed I did my own damage survey around the area finding some inconsistencies with one of the 70ft pine trees stripped to its bark, uprooted trees, some trees only lost their top-half as well. With that being said however, I didn't find any "swirling" motion in any of the farm fields which is a tell tale sign of a tornado. It also appeared that even though there were some inconsistencies that didn't quite match up with straight-line wind damage most of the trees that did go down were oriented in the same direction. Overall, based on my assessment it looked like straight-line wind damage to me, but since I was chasing in another location I guess I'll never know. I've added some photos from the brief chase and damage photos from home below:

Shelf cloud traversing along the Illinois prairies
Gusty outflow moving overhead from a once tornado-warned storm
Mammatus clouds and sunset after the chaotic storm
One of my favorite local photo-op locations
will never look the same...
Pine tree snapped quite easily here...
Several of those 70ft pine trees down...
(note their orientation though as it's quite
important for damage surveys)

This was interesting as this tree had half of it
plucked and was tossed as well...

Tree blocking half of road 650E
Another tree blown-over onto the road
Next day photo showing how this storage
shed was obliterated

Storm ripped the roof off this other storage shed
providing a not so welcome skylight
Another view of our pine trees that couldn't withstand
Mother Nature's wrath Wednesday
What a mess...
Lots of clean-up that will forever change the
northwest skyline at our residence

Out of all of the chases this spring...this one was the least amount of fun. You always want storms close to home to make chasing easier, but on this day it was way too close and we ended up as one of the several damage reports across the state. The weather pattern responsible for the severe weather over recent weeks has finally shut-down though and we'll get a much needed break this week after a very active June across the Midwest.