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)

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)

Now the pre GCK storm is the western end of a squall line moving southeast with a dominant cold pool.

Craig’s considering removing the current hail threat area for the western cell. Maybe they’ll consider dropping probabilities.

Craig would issue a severe warning for the entire line for the wind threat but would consider keeping hail threat more cellular based.

Greg suggests at 0056 UTC to create new threat area for the cell to the east so that they can practice polygon threat areas.

Overview: The warning valid times are still equivalent to legacy polygon warnings. There’s considerable uncertainty about when to think multicell-based threat area vs. individual cell. When to transition is a big question.

Jim LaDue (EWP Weekly Coordinator, 5-9 May)

Brian wanted to add an interior, enhanced probability hail threat area but we’ll stick with simpler issues for now.

The storm is now more merged with the line to the east and is now nor N-S oriented.

There’s a storm to the east in the line with enhanced MESH. Bill’s wondering whether to add a new threat. For now he’ll want to keep it simple.

Updating western, pre GCK, storm which acquired a N-S dumbbell configuration. Do they go with a second threat for the south dumbbell? Bill sais the VIL’s continuing downward and they’re satisfied with the drop in probability trend from earlier. Brian thinks the inflow is weakening the storm and there’s contamination.

Greg asked if they feel confident the probability will be zero by the end of warning time? Bill sais no. Brian agrees. But now at 0048 UTC the MESH dropped further. So Brian’s going with 30 min validation time. Initial prob =70% lowering to 45%. The storm’s out of the previously created threat area and so they just saved at 0050 UTC.

Jim LaDue (EWP Weekly Coordinator, 5-9 May)