Bill Schintler
EF4
Chase target:
Ida Grove, IA (between Denison and Storm Lake).
Timing:
Renewed convection will develop in the target location at 6 PM CDT.
Comments:
Ongoing convection in western IA will weaken and move out of the area by early afternoon. Supercell storms will be likely late in the afternoon with large hail to golf-ball size and a tornado or two. Storms will evolve into an MCS by mid-evening, which will track ENE through NRN IA. By that time, severe weather potential will transition to that of wind and heavy rainfall.
Discussion:
A SE/NW-oriented outflow boundary, currently located along an YKN/OAX line in NE, will lift NEWRD today and provide the focus for renewed convection as the RRQ of a 45kt H7 speed max lifts through the area. Late afternoon appears to be the best time for surface-based convection as localized forcing becomes sufficient to overcome convective temperatures in the low-100’s F. A window of time will exist when storms should lift over to the NE side of the OFB where a more backed SFC flow and cooler temperatures will be in place from rain-cooled air along with a partial cloud cover. Very high instability, with SBCAPE’s to 4000J/kg, will be juxtaposed with modest but adequate shear parameters. SRH (SFC-1km and SFC-3km) should locally exceed 200m2/s2 while deep-layer shear (SFC-6km) should reach 40 kts. A 45kt LLJ will maintain storms into the overnight hours, when very heavy rainfall totals will be likely where storms train in an area with precipitable waters in excess of 2.5†along with NWRD advection of a 16C H85 airmass into NCNTRL IA.
- bill
Ida Grove, IA (between Denison and Storm Lake).
Timing:
Renewed convection will develop in the target location at 6 PM CDT.
Comments:
Ongoing convection in western IA will weaken and move out of the area by early afternoon. Supercell storms will be likely late in the afternoon with large hail to golf-ball size and a tornado or two. Storms will evolve into an MCS by mid-evening, which will track ENE through NRN IA. By that time, severe weather potential will transition to that of wind and heavy rainfall.
Discussion:
A SE/NW-oriented outflow boundary, currently located along an YKN/OAX line in NE, will lift NEWRD today and provide the focus for renewed convection as the RRQ of a 45kt H7 speed max lifts through the area. Late afternoon appears to be the best time for surface-based convection as localized forcing becomes sufficient to overcome convective temperatures in the low-100’s F. A window of time will exist when storms should lift over to the NE side of the OFB where a more backed SFC flow and cooler temperatures will be in place from rain-cooled air along with a partial cloud cover. Very high instability, with SBCAPE’s to 4000J/kg, will be juxtaposed with modest but adequate shear parameters. SRH (SFC-1km and SFC-3km) should locally exceed 200m2/s2 while deep-layer shear (SFC-6km) should reach 40 kts. A 45kt LLJ will maintain storms into the overnight hours, when very heavy rainfall totals will be likely where storms train in an area with precipitable waters in excess of 2.5†along with NWRD advection of a 16C H85 airmass into NCNTRL IA.
- bill
