Sunday evening's MRF run already showed signs of an impressive shortwave trough entering from SW Canada which was progged to be in the Midwest by Thursday afternoon. After Tuesday's negative tilt trough and associated HIGH risk bust in MN, model data still looked good for Thursday. Despite SPC downgrading the area to slight on the Day 1 (later upgraded to MDT at 3pm) and me only getting 2 hours of sleep, Mike C. and myself were still convinced that something was going to happen. We left Milwaukee around 1pm after having targetted the area west of Madison. Temps in this area were in the low/mid 80s with Tds in the mid 60s and ~20 knot south winds. After we had passed through some ACCAS fields and scattered, elevated convection with showers, we caught the tornado watch for the entire area until 8pm. We stopped at a Madison library for the latest obs and radar and to our delight isolated SVR cells were in progress in northeastern IA. The most impressive featured a tight reflectivity gradient and pendant shape...NWS-LaCrosse issued a TOR for this cell. We headed west and then south for an intercept (passed local media chasers) and the rest is what you see below. The storm motion was 271/35 and we soon fell in the FFD of the decaying HP supercell in northern Lafayette county. The precip here was light compared to the dense, circular shaft to our west courtesy of the RFD meso occlusion. NWS-Sullivan continued the TORs for obvious reasons, but this was the only cell of major interest. A brief rotating cell ensued near Cuba City, WI (see radar note below) and moved over Gratio, WI with golfball sized hail. Once the primary cell collapsed, scattered non-SVR cells exploded left and right behind this zone (via possible outflow boundaries). Though picturesque, their updrafts failed to keep up with the strong speed shear. A blue box was issued around 7:45pm for linear convection along the cold front. Severe reports with this squall line were minimal.
As is often the case, the warm front usually has
more direct storm relative inflow and today's case was no exception...at least 4
tornadoes, all short-lived, in northcentral WI. The fcst sndgs revealed
nice helicities in that area, but the thermodynamics weren't as nice and this
yielded EHIs <1.5...though low LFCs would compensate a bit for that. So the potential for rotation was very real up there, though I'll have to say we made a good decision to play SW WI (see radar for evidence!). The primary supercell that we witnessed initiated as a multicell ~80 miles west of Dubuque and took on supercellular characteristics near Dubuque. All in all, a fun day considering I skipped all of my classes!
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Ahhh...clearing |
Young mammatus in Madison |
Circular precip core from meso |
Explosions above us |
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Compact cell to our west (note inflow band at lower right) |
Anvil and new convection |
A little better structure |
Distant Cb at sunset |
