7/13/06 NOW: NE / SD / ND

[nickgrillo]

I'd think the activity north of OAX could become surface-based as it pushes further east into lower CINH (for a surface-based parcel). RUC mesoanalysis shows 0-6km shear has increased +10kts in the past hour in some spots in response to the approaching shortwave perturbation aloft at 500mb (evident in moisture channel imagery) which is increasing the midlevel kinematic profiles. I wouldn't be surprised to see the MDT risk verify based on hail reports given the extreme > 4000j/kg MLCAPE and low wet-bulb zero levels across much of the area. WRF showed a large-scale convective line stretching from the Dakotas southward into the MDT risk zone on last night's run -- which is likely given the degree of capping and deep shear. Nonetheless, I wouldn't be surprised to see some significant wind/hail reports, especially with any embedded supercells or bow echo structures in the line (or ahead of the line). I'm glad to see the >70 tds have held despite the strong insolation / sfc diabatic heating (which has weakened CINH while incresing CAPE and still maintaining relatively-low LCLs). I'm thinking that large hail and damaging winds would be the biggest threats given the weak low-level shear.

 

[Adam Atkins]

Damaging winds is right...check out the lowest tilt velocity from OAX. Looks like theres a hint of an inflow notch on that HP beast too, and I agree it has probably become surface based.

 

[Jeff Snyder]

That's an impressive (though relatively-small) bow echo complex just west of OAX. Widespread area of greater than 71kt wind on the lowest base velocity tilt (the center of the beam is about 600m AGL). It looks like the leading edge of the outflow (i.e. the OFB) is beginning to surge out ahead of the convection a little, so the maximum winds may decrease a little in time (at least temporarily). Very high CAPE characterizes much of the area, which is certainly help drive this storm complex. There have been a couple rotational couplets visible from time to time as well. It looks like the strongest winds (like near or a little above 80mph IMO) is occurring right along Hwy 30 about 10 miles WNW of Cedar Bluffs. This, not coincidentally, it also where the gap between the leading edge of the outflow and the leading edge of the convective precip is the most narrow (in this case, there is no gap).

EDIt: Latest BV1 imagery indicating that the highest winds remain about 6 miles behind the leading OFB. This storm complex is moving rather quickly to the ESE, so Omaha will be at risk in about 50-60 minutes.