July 14, 2009 chase account

Before I get into the account, take a look at the following skew-T plots and answer this question: If you wanted to see tornadoes, in the atmosphere of which of these skew-Ts would you target?

Mystery skew-T 1

Mystery skew-T 2

Mystery skew-T 3

Click on the images to see where they actually were. Now guess which one was associated with tornadoes. Guess which one was associated with no convection, and with no severe convection. (This little game is designed for those who don't know what happened or didn't chase this day.)

Now see which one won. See reports.

I nearly cap busted on this day, but technically saw convection before nightfall, although I didn't directly chase it. I had pretty much already given up on the day by that point.

This would mark my first chase in July. I chased in Iowa...in July...that already was a recipe for a cap bust. It damn near was one. 700 mb temps sat at 13-14°C along the most unstable area to along the western edge of the state all day. Just as forecast, though, shear wasn't the best in the area, and the best forcing was up north in Minnesota, where a few tornadoes did occur. I loved seeing the SigTor parameter light up in our area, but it was probably mostly due to the instability, not the shear. It didn't matter, though, because the cap squashed most of everything down in the area anyway.

What area? Well I and chase partners Adam and Ryan targeted west central Iowa, because we saw potential targets both to the north and to the south and couldn't decide which one to pursue. We saw the possibility for a sleeper event to occur to the south where instability would be huge, but the cap would be stronger, while the northern target had better shear, less cap, and better forcing, but not quite as much instability.

I need to learn that, in the warmer months of the year (i.e., chase season months minus April and early May), less instability does not mean insufficient instability. I completely overlooked northern Minnesota as a target because progged CAPE values were only going to be 1000-2000 J/kg. Oh well, wouldn't have been able to make it that far north anyway. We didn't leave until almost 2.

We spent most of the day near Council Bluffs, eating supper at the Taco Johns in the Mall of the Bluffs (see the June 26th chase account, caption on the first image, for an explanation on me and Taco Johns). Seeing no significant convection to the south in Kansas or Missouri, we headed up I-29 to go after the storms firing along the cold front near Sioux Falls. Before we could get there, we saw some towers go up almost right over us, but they couldn't fully develop, getting smashed down by the cap. Thus, we headed to Denison, looking to head home, while watching the storms come in from the northwest. One of them started to take on a hook shape when we were in Dension, but it didn't hold, and it was already 8:30 and getting pretty dark, so we just called it a day and headed home.

Such a sad chase I don't even have pictures! That cluster of storms did impact the Des Moines metro area later that night, even producing a 3" hail report!

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