While chasing today in the US is most likely going to involve chasing some sort of QLCS or MCS or something, we will be sending out a chase car to see if we can bag a tornado during the middle afternoon hours before everything goes to H-E-double hockey sticks. I describe some advantages and disadvantages below, and note that this discussion is brief and very casual, so if you want to comment more on it go for it, that's what this blog is all about baby:
Chasing Advantages:
Wisconsin located in the warm sector, near the triple point of the deep low pressure system. An occlusion will develop, with the warm sector branching from the twin cities clockwise to Madison and into Illinois. Warm, moist air will be advected from the Gulf of Mexico region into the upper Midwest, and this along with daytime heating will allow for the breaking up of a very weak (if at all even one) EML and morning cap over eastern Iowa and into south-central Wisconsin and destabilize the atmosphere this afternoon. SBCAPE values will reach 1500-2000 J/kg this afternoon. In terms of shear, the region exhibiting maximum helicity (both 0-1 km and 0-3 km) occurs near the warm front, which will push northward into eastern MN and central WI by 1800-1900 UTC. This, along with strong upper level forcing associated with the approaching upper level trough will allow for development of some respectable convection, and hopefully some discrete cells will fire between the triple point and near the warm front starting ~4 pm local time (2100 UTC).
Also, we'll be in Wisconsin, so the home crowd is on our side (that means wear the red AOS "home" jerseys and khaki shorts or else...)
Chasing Disadvantages:
Well, the shear profile is not the best in terms of chasing tornadoes today. Wind speeds remain southerly throughout the lower and middle troposphere east of the cold front (Illinois, southern Wisconsin, southeastern Iowa, south from Illinois towards the Gulf of Mexico), and bulk shear and helicity values (according to the 1200 UTC NAM and HRRR) are not favorable except near the warm front by I90/I94 during the afternoon hours. Since CAPE values are favorable east of the cold front and within the warm sector near the triple point, my guess is that any storms that fire will become linear and form some sort of squall line (with respect to the upper Midwest). Hence, chances of chasing tornadoes safely and accurately are not too high, except for near the warm front and triple point.
OUR GO ZONE: Tomah, WI. It will be just south of the warm front and south-east of the triple point, and is also near the I90/I94 interchange. If we get there by 1830 UTC (1:30 pm CDT), this will give us plenty of time to check out cumulus fields via satellite data (and our eyeballs) and see where to go from there. HRRR is showing lots of scattered convection and cells starting around 2100 UTC. I'm not trusting the HRRR completely, since it overestimated the strength of this morning's MCS and made the one in central Illinois look more epic than it really was. While are chances at seeing a tornado are very small, this will give us a chance to catch any supercells early on before they either die off or possibly congeal and kill our chasing chances for the evening.
Peace out,
Helicity and friends
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