Corfidi, et al – convection where air parcels originate from a moist absolutely unstable layer above the PBL. Can produce severe hail, damaging surface wind and excessive rainfall well removed from surface-based instability. Frequently located near (north of) a warm or stationary front. Not synonymous with accas as these clouds can also arise from surface-based convection. These storms evolved into supercells which produced a tornado in northwest MO (25 June 1994)

Moore, et al East-west quasi-stationary front South-southwesterly LLJ directed nearly normal to the boundary Moisture convergence within the left exit region of the LLJ helps to initiate deep convection in the unstable layer along or above the frontal zone. Maximum θe advection nearly centered over the MCS centroid

Moore, et al

Lower 50s surface temperatures near storm Supercell moving into a region of surface temperatures in the mid 40s with dewpoints in the upper 30s

Widespread wind damage with winds to 78 knots in Lawrence and baseball size hail in Lawrence and Kansas City

Lawrence

MUCAPE – 600 J/kgMUCAPE – 2800 J/kg Favors elevated supercells with very large hail  rich low level moisture near top of sharp surface-based inversion  nearly dry mid trop layer with nearly dry adiabatic lapse rates atop inversion  strong vertical wind shear through lower half of storm depth  Large DCAPE > 900 J/kg supports strong saturated downdrafts originating in the dry, steep lapse rate layer above the surface-based inversion

Gilmore and Wicker, 1998: The influence of mid- tropospheric dryness on supercell morphology and evolution. Min theta-e within 100 mb thick layer Descend this theta-e min down moist adiabatic Area between this trace and T profile = DCAPE Continue this for every obs. layer up to 400 mb DCAPE = largest area

 East of Rockies - identify severe reports 1 degree latitude (111 km) on the cool side of a surface front (excludes convection which may occur above a surface-based nocturnal inversion  129 severe storm cases….1066 reports: 58% hail (3/4”)…..37% wind…..4% tornado  Focuses on the occurrence of severe wind events ……(tornadoes are rare and forecasting large hail not as significant of a forecast challenge)

Shallow near surface stable layer (< 100mb thick) Relatively deep moist layer above the inversion Dry air at mid levels (allows for evaporational cooling which can enhance strong downdraft potential DCAPE) Occurred north of east-west front 4 of 5 cases warm sector MUCAPE > 2000 J/kg Weak e to se near surface winds Vertical wind shear- sometimes quite strong