Bill Schintler
EF4
Chase target:
20 miles east of Stillwater, OK
Timing and storm mode:
Storms will develop from north to south across the area after 7 PM CDT, with a few supercells possible early in storm evolution. By early evening, storm mode will transition to linear.
Synopsis:
Another in series of upper-level systems will affect the Plains on Monday as a closed, cold-core H5 low tracks into NEB. Meanwhile, SFC cyclogenesis will take place in NERN KS; while a secondary low develops further S along an advancing CF in NCNTRL OK by late afternoon. A DL will extend S from this feature while serving as a focus for convection late Monday.
Discussion:
Moisture return appears problematic, with BL dewpoints in the mid-50’s FCST at best. 00Z models (WRF, GFS) are excessively bullish with LLVL moisture, as only mid-30’s dewpoints have verified in CNTRL/NCNTRL OK. The 15Z SPC SREF ensemble appears more in line with verification, and indicates dewpoints of 52-54 F by 00Z, 03/31. An SC deck will develop during the afternoon as the LLJ transports 10-12C H85 dewpoints into the region. Insolation will be inhibited by these low clouds along and E of US-377 during the afternoon hours; however, this should prevent mixing out of meager SFC moisture. A narrow axis of modest instability will develop ahead of the DL, with MLCAPEs AOB 1000J/kg as mid- and upper-level temperatures cool with the approach of the upper low and H8-H6 lapse rates increase. Capping will remain strong across the area, with SFC-90km CIN of 50m2/s2 at 00Z. Strong forcing arrives after 01Z, which should overcome inhibition. A short window of opportunity should exist for SFC-based convection providing that dewpoints increase to 55F.
Favorable kinematic parameters may somewhat offset weak instability with deep-layer shear in excess of 60 kts. Large clockwise hodograph curvatures are forecast, with SFC-1km SRH in excess of 200m2/s2. An SPC significant tornado parameter between 1 and 2 is forecast between 00Z and 03Z. Storm mode will transition into a line as forcing strengthens in an environment of increasingly weak instability.
- Bill
10:09 PM CDT, 03/29/09
20 miles east of Stillwater, OK
Timing and storm mode:
Storms will develop from north to south across the area after 7 PM CDT, with a few supercells possible early in storm evolution. By early evening, storm mode will transition to linear.
Synopsis:
Another in series of upper-level systems will affect the Plains on Monday as a closed, cold-core H5 low tracks into NEB. Meanwhile, SFC cyclogenesis will take place in NERN KS; while a secondary low develops further S along an advancing CF in NCNTRL OK by late afternoon. A DL will extend S from this feature while serving as a focus for convection late Monday.
Discussion:
Moisture return appears problematic, with BL dewpoints in the mid-50’s FCST at best. 00Z models (WRF, GFS) are excessively bullish with LLVL moisture, as only mid-30’s dewpoints have verified in CNTRL/NCNTRL OK. The 15Z SPC SREF ensemble appears more in line with verification, and indicates dewpoints of 52-54 F by 00Z, 03/31. An SC deck will develop during the afternoon as the LLJ transports 10-12C H85 dewpoints into the region. Insolation will be inhibited by these low clouds along and E of US-377 during the afternoon hours; however, this should prevent mixing out of meager SFC moisture. A narrow axis of modest instability will develop ahead of the DL, with MLCAPEs AOB 1000J/kg as mid- and upper-level temperatures cool with the approach of the upper low and H8-H6 lapse rates increase. Capping will remain strong across the area, with SFC-90km CIN of 50m2/s2 at 00Z. Strong forcing arrives after 01Z, which should overcome inhibition. A short window of opportunity should exist for SFC-based convection providing that dewpoints increase to 55F.
Favorable kinematic parameters may somewhat offset weak instability with deep-layer shear in excess of 60 kts. Large clockwise hodograph curvatures are forecast, with SFC-1km SRH in excess of 200m2/s2. An SPC significant tornado parameter between 1 and 2 is forecast between 00Z and 03Z. Storm mode will transition into a line as forcing strengthens in an environment of increasingly weak instability.
- Bill
10:09 PM CDT, 03/29/09
