Bill Schintler
EF4
Chase target for Friday, April 20
Chase target:
Wheeler, KS (20 miles north of Goodland).
Timing
Storm initiation 6 PM CDT.
Storm mode:
Isolated supercell storms with marginally severe hail and impressive storm structure. A bust is a definite possibility.
Synopsis:
UA analysis indicated a couple of closed H5 circulations embedded within deepening SRN stream WRN CONUS trough. The first, over SERN MT, was transitioning NWRD towards CAN while a secondary circulation was off the NRN CA coast. Strongest height falls over AZ and SRN NV indicate SWRD movement of this feature. At the SFC, the Pacific CF that had worked into WRN KS has essentially washed out as a result of the NEWRD progression of today’s S/WV along with the deepening WRN trough. Further S and E, ULVL ridging was present over TX into KS. The resulting lack of SFC forcing in KS in addition to significant H7 WAA from NERN NM contributed towards today’s bust there. Indeed, the 00Z DDC sounding indicated a strong inversion between 700mb and 600mb and a convective temperature of 81F – a long ways from the afternoon high of 76F in DDC. Also contributing to the CIN was the fact that the moisture layer was very shallow in this area. Despite SFC dewpoints in the low-50’s F, with a mixed-parcel the updrafts were unable to reach the LFC. As of 03Z, SERLY SFC flow has brought a nose of 55F dewpoints into NCNTRL KS, and this moisture layer should deepen with time as deeper moisture to the S is advected NWD. The 00Z OUN sounding indicates a moist layer depth of 100mb.
Discussion:
In all likelihood, the EWRD progression and eventual deamplification/breakdown of the current modified omega-block will unfold somewhat slower over the next three days then models are suggesting, perhaps 6 to 12 hours slower. Earlier model runs have indicated a slowing trend however the latest NAM is actually faster with the ejection of the H5 speed max from the main trough throughout the day Saturday which has obvious implications for the weekend weather in the Upper-Midwest. This most recent NAM performance, however, is most likely a deviation from the overall slowing trend we should see with future runs as the main energy is still off the PAC coast and is probably not sufficiently sampled by the models.
On Friday, SFC low pressure will strengthen and move towards NERN CO in response to a 60kt H5 max ejecting NE from the main trough. Meanwhile, a dryline will move slowly EWRD and approach the CO/KS boarder by late afternoon. This feature should provide the focus for convection. As was the case further to the south in SW KS today, mid-level temperatures will be warm, about 5C at 700mb. Additionally, afternoon temperatures will struggle to make it into the mid-70’s. A couple of S/WV’s embedded in increasingly cyclonic ULVL flow should provide the forcing to allow for initiation of isolated storms to take place. MLCAPE to 1000J/kG will be juxtaposed with favorable shear parameters including deep-layer (SFC-6 km) shear to 45 kts along with SRH (SFC-3 km) of 250m2/s2 to produce isolated supercells.
[FONT="]- bill[/FONT]
Chase target:
Wheeler, KS (20 miles north of Goodland).
Timing
Storm initiation 6 PM CDT.
Storm mode:
Isolated supercell storms with marginally severe hail and impressive storm structure. A bust is a definite possibility.
Synopsis:
UA analysis indicated a couple of closed H5 circulations embedded within deepening SRN stream WRN CONUS trough. The first, over SERN MT, was transitioning NWRD towards CAN while a secondary circulation was off the NRN CA coast. Strongest height falls over AZ and SRN NV indicate SWRD movement of this feature. At the SFC, the Pacific CF that had worked into WRN KS has essentially washed out as a result of the NEWRD progression of today’s S/WV along with the deepening WRN trough. Further S and E, ULVL ridging was present over TX into KS. The resulting lack of SFC forcing in KS in addition to significant H7 WAA from NERN NM contributed towards today’s bust there. Indeed, the 00Z DDC sounding indicated a strong inversion between 700mb and 600mb and a convective temperature of 81F – a long ways from the afternoon high of 76F in DDC. Also contributing to the CIN was the fact that the moisture layer was very shallow in this area. Despite SFC dewpoints in the low-50’s F, with a mixed-parcel the updrafts were unable to reach the LFC. As of 03Z, SERLY SFC flow has brought a nose of 55F dewpoints into NCNTRL KS, and this moisture layer should deepen with time as deeper moisture to the S is advected NWD. The 00Z OUN sounding indicates a moist layer depth of 100mb.
Discussion:
In all likelihood, the EWRD progression and eventual deamplification/breakdown of the current modified omega-block will unfold somewhat slower over the next three days then models are suggesting, perhaps 6 to 12 hours slower. Earlier model runs have indicated a slowing trend however the latest NAM is actually faster with the ejection of the H5 speed max from the main trough throughout the day Saturday which has obvious implications for the weekend weather in the Upper-Midwest. This most recent NAM performance, however, is most likely a deviation from the overall slowing trend we should see with future runs as the main energy is still off the PAC coast and is probably not sufficiently sampled by the models.
On Friday, SFC low pressure will strengthen and move towards NERN CO in response to a 60kt H5 max ejecting NE from the main trough. Meanwhile, a dryline will move slowly EWRD and approach the CO/KS boarder by late afternoon. This feature should provide the focus for convection. As was the case further to the south in SW KS today, mid-level temperatures will be warm, about 5C at 700mb. Additionally, afternoon temperatures will struggle to make it into the mid-70’s. A couple of S/WV’s embedded in increasingly cyclonic ULVL flow should provide the forcing to allow for initiation of isolated storms to take place. MLCAPE to 1000J/kG will be juxtaposed with favorable shear parameters including deep-layer (SFC-6 km) shear to 45 kts along with SRH (SFC-3 km) of 250m2/s2 to produce isolated supercells.
[FONT="]- bill[/FONT]
