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Why do mesoscale convective systems reach their maximum at night?

  • Thread starter Thread starter Felix Welzenbach
  • Start date Start date

Felix Welzenbach

Hi folks!

I try to learn more about MCS's and their generation, but it remains still elusive to me why these systems (and also the larger MCC) reach their maximum (extent) during the night.

Ok, these larger multicell storms don't need thermal lift to persist, since the dynamic forcing is the critical factor for them. That is, the storms are independent on the boundary layer (which normally stabilizes overnight). Though, are there other parameters /processes being important? E.g., the low-level jet?

Thanks a lot for answers!

Best regards from Austria,
Felix
 
Timing. Cap usually erodes later in the day, so storms often have a late start. Then their cold pools gradually build and it's often night by then. I'd say that's the biggest thing to think about. Guessing the more severe types are actually during the day.
 
I'm not sure (don't call me an expert by any means) but I'd also think a modest low level jet would probably play a part as well. But I'd think getting a good cold pool generated would be important as well. I think Mike H hit the nail on the head with the first word, I think the timing is just what is crucial. Most of the key factors listed would most likely occur at night. Either way, as always I look forward to hearing more expert analysis on this!
 
Some current research now suggests that MCS can actually still ingest surface parcels long after the boundary layer has cooled significantly (see http://www.meas.ncsu.edu/mdparker/articles/parker.in.press.pdf. This research suggests that when the difference between the cold pool and the ambient environement becomes sufficiently small, then the system will begin to decay (which would be sometime during the night). Also, this study DID NOT include anything like a low-level jet which could maintain an MCS after the cold pool forcing had diminished.
 
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