Bill Schintler
EF4
Chase target:
Roseville, IL (20 miles east of Burlington, IA).
Timing and storm mode:
Mini-supercells and possibly a brief tornado will affect the area between 3 and 4 PM, CDT. Storms will track slowly to the northeast at 10 mph.
Synopsis:
At the surface, low pressure was centered in far NWRN MO with an ill-defined warm front extending east of this feature along the IA/MO border and into IL. Weak pressure falls were noted over SERN IA and visible satellite animation indicated the low was tracking slowly towards extreme SERN IA. Partial clearing was taking place over the warm sector in MO and IL, where moderate instability has developed despite weak lapse rates. Weak flow existed aloft, with compact H5 circulations existing over WRN KS and NWRN MO within broader cyclonic flow. Ambient vorticity was maximized over NWRN MO. Convection has initiated over much of the warm sector, especially E of the Mississippi.
Discussion:
The favored area is along the WRN extent of the instability axis where moderate MLCAPEs AOB 1500J/kg will be juxtaposed with weak but sufficient deep-layer shear. This area is also within the WRN periphery of a 20kt LLJ. Ambient vorticity within the SFC-H8 layer will slowly increase throughout the afternoon as the low drifts to the east, which may also aid in rotating updrafts. The chase target may also be at the southern extent of an arc of convection ongoing just W the Mississippi between SUS and UIN, where a “tail-end Charlie” may form.
- Bill
12:30 PM CDT, 05/26/09
Roseville, IL (20 miles east of Burlington, IA).
Timing and storm mode:
Mini-supercells and possibly a brief tornado will affect the area between 3 and 4 PM, CDT. Storms will track slowly to the northeast at 10 mph.
Synopsis:
At the surface, low pressure was centered in far NWRN MO with an ill-defined warm front extending east of this feature along the IA/MO border and into IL. Weak pressure falls were noted over SERN IA and visible satellite animation indicated the low was tracking slowly towards extreme SERN IA. Partial clearing was taking place over the warm sector in MO and IL, where moderate instability has developed despite weak lapse rates. Weak flow existed aloft, with compact H5 circulations existing over WRN KS and NWRN MO within broader cyclonic flow. Ambient vorticity was maximized over NWRN MO. Convection has initiated over much of the warm sector, especially E of the Mississippi.
Discussion:
The favored area is along the WRN extent of the instability axis where moderate MLCAPEs AOB 1500J/kg will be juxtaposed with weak but sufficient deep-layer shear. This area is also within the WRN periphery of a 20kt LLJ. Ambient vorticity within the SFC-H8 layer will slowly increase throughout the afternoon as the low drifts to the east, which may also aid in rotating updrafts. The chase target may also be at the southern extent of an arc of convection ongoing just W the Mississippi between SUS and UIN, where a “tail-end Charlie” may form.
- Bill
12:30 PM CDT, 05/26/09
