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Team 2, Craig and Brian, continue to issue low prob hail swaths for the small multicell northwest of LBB and the SW-NE axis of multicells southeast of LBB. They consider the northern storm swath to not be worthy of a legacy warning (max prob<50%).
Jim LaDue (EWP Weekly Coordinator, 5-9 May)
Kristen and Bill discussed what happened to the probability swath when they put 30% initial, 70% max, a storm motion of 17kts with an 8kt uncertainty. The swath wound up showing 70% over just about the entire area. How does a user visualize the really low initial probabilities when the storm motion is so slow?
Jim LaDue (EWP Weekly Coordinator, 5-9 May)
Team 1 just issued a hail swath for the second storm behind the monster south of MAF (in Crane County). Craig started at 20% and raised it to 70%. The lead storm in Upton county is too obvious with 100% and 100% hail probs. Craig wouldn’t issue a legacy warning yet.
Jim LaDue (EWP Weekly Coordinator, 5-9 May)
Team 2 has reconsidered adding a low probability hail swath for the small multicell northwest of LBB. Max probability – 30%. They don’t consider it for a current warning.
Jim LaDue (EWP Weekly Coordinator, 5-9 May)
we have two teams including a cognizant scientist, warning forecaster, and a third volunteer coordinator.
team 1 in the center of the room includes Craig, Kristen and Dave. They’ll be focusing on the storm south of Midland that has a tornado warning and big hail signature.
Team 2 working the PAR workstation have converted to a probwarn station focusing on the LBB area and in particular an isolated small multicell forming up on the dryline, outflow bndry triple pt.
Both teams are working tornado and hail threats.
Jim LaDue (EWP Weekly Coordinator, 5-9 May)
Today features a long north-south dryline from the Rio Grande southwest of MAF to western Nebraska. A northern stream shortwave is setting off strong convection embedded in strong deep shear though with relatively high dewpoint depressions. A jet exit region extending over west TX is setting off convection in the MAF area with a little better shear and moisture. We’ll be targeting the MAF and LBB CWAs and focusing on tornado and hail threats.
Jim LaDue (EWP Weekly Coordinator, 5-9 May)
This evening featured a supercell with large hail near GCK that merged with a line to the east and became an outflow dominated multicell event. The hail threat decreased as largescale wind threat increased. This team consisting of Bill, Craig, Cynthia and Brian focused on hail threats given their unfamiliarity with the probwarn software.
The big difficulty today is going from single to large multicell mode. Craig wonders how much longer a probabilistic warning should continue after a legacy warning expires? Bill’s worried about how to transition from isolated to large multicell threat areas? This storm underwent such a transition and they kept the single cell mode for a long time after merger began.
The team consisted of one member operating the familiar D2D for radar base data analysis while another team member operated the probwarn software. Two other team members contributed to the discussion. This setup appeared to work very well with lot’s of interaction.
Given the probabilities, what do they mean? Bill sais he’s comfortable with them because he associates high probability to his thinking when he’s doing warning decision making in the current way.
Jim LaDue (EWP Weekly Coordinator, 5-9 May)
Does the team want to keep the threat area inclusive of multicells or drop the southwestern cell and focus on the bigger cell? They pulled in the threat area.
Bill wants speed uncertainty up to 10kts. Initial probability is set at 50, marginal. Bill’s thinking 50% is worthy of a warning.
Jim LaDue (EWP Weekly Coordinator, 5-9 May)
So now the multicell is beginning to accelerate southeast and it’s leaving their threat area out. Brian, Cynthia and Bill think the hail threat is small now. They’re thinking of adding a wind threat using the same threat area already done for hail. BTW, the Brian’s got the hail threat area elongated along the line axis encompassing multiple cells. We’ll stick with hail for now.
Somehow the valid time hail threat went to zero.
Greg asked whether there needs to be changes in how probabilities are computed. Brian wonders if there should be a membership function? What should the ending probability be? Craig thinks the ending probability will be below his warning threshold. Craig wonders how hard it would be for users to understand that some low probability swaths will not be associated with warnings.
Jim LaDue (EWP Weekly Coordinator, 5-9 May)
Hail polygon’s being created for the DDC cell within the multicell. Brian’s adding numbers to the new warning. Bill’s not confident there’s hail in there. We purposely ignored this cell before now.
0105utc: Bill’s learning storm motion creation in WDSS-II. Done in < 1 minute.
Initial prob hail of 75%, trend probability= 65%, a little lower. Bill and Brian are worried about new stuff forming ahead of the line along that prestorm boundary. They’re deleting the old threat area.
Jim LaDue (EWP Weekly Coordinator, 5-9 May)
