Thread by @pmarshwx

Thread time!

As we enter what appears to be another multi-day severe weather event, I want to take a moment to caution people against taking composite parameters at face value from convection allowing models. And, yes, what follows is slso s reminder to me.

In CAMs, models explicitly simulate some of the convective processes, allowing for numerical-based responses/feedbacks into the near-storm environment. This includes modifying near-storm wind fields and moisture fields.

A consequence of this is that composite parameters (such as STP) can max out in bullseyes in the immediate vicinity of convection. This can lead to the false impression of a more favorable larger/mesoscale environment than actuall exists.

This also leads to widespread PDS Tornado soundings in SHARPpy.

The problem is that all of the studies that determined/calibrated the composite parameters were based on the background/larger-scale/mesoscale environments -- not the immediate near-storm environment.

We do not know what an impressive STP value is in the immediate inflow of a weak/'ordinary'/massive supercell. This is at least one of the reasons the SPC Mesoanalysis is still run at 40-km and not say 3 -- we want to be sure to sample the environment and not individual storms.

So, my unsolicited advice -- and your mileage will vary -- is to evaluate composite parameters (and soundings) in the non-contaminated environment and not in the vicinity if model convection. (Easier said than done, I know.)

Oh, and get off my proverbial lawn, too. 😉