LA Times supercell explanation

[Jody Radzik]

Today I encountered this graphic in the Los Angeles Times with this explanation:

Unstable conditions produce an updraft of warm, moist air. As the storm forms, <b>cooler air wrapping in from behind causes the rising air to spin.</b> This is called a mesocyclone. As the mesocyclone intensifies, it may produce violent rotating winds at the surface — a tornado.​

Please correct me if I'm wrong, but I thought that the rotation of a mesocyclone begins after vertical windshear has started a rolling horizontal packet of air along the ground which then gets picked up by rising air, combining with this to form an updraft. Thanks for your help.

 

[Jody Radzik]

The confusion here is their making the RFD as the sole source of rotation for the mesocyclone rather than a source of additional momentum.

 

[Bob Hartig]

You've got it right and they've got it wrong. The thunderstorm updraft stretches streamwise vorticity into a vertical orientation to produce the mesocyclone. The RFD has nothing to do with this process that I'm aware. Rather, its is vitally linked to producing the actual tornado, and a relatively warm RFD is likelier to do so than a cooler one, which simply undercuts surface-based buoyancy.

 

[Hannah.Taylor]

more proof you can't believe anything you read in a newspaper or from a media source as FACTUAL.

 

[Jeff Duda]

This sounds like the industry standard explanation given to people who you wouldn't expect to understand the real meteorology. yes, it is misleading to say, since all the vorticity present in a mesocyclone is generated from the storm's inflow (be it from deep layer shear or boundary layer rolls etc.), which would have to still be warm and moist lest the storm die.

 

[JanelleHelling]

more proof you can't believe anything you read in a newspaper or from a media source as FACTUAL.

Wow.

Retired journalist here. An editor in CA probably had minimal knowledge about severe storm meteorology, and needed to explain a breaking story quickly. Either a canned graphic or one prepared by someone who also had minimal knowledge of severe storms was used. (Not all sources of reference material are created equal. internet anyone?) Someone not familiar with a subject would have no way to know if it's accurate or not. If a tornado just leveled a town in the midwest, it's probably mid to late afternoon. If your paper comes out in the morning, the pages are due in prepress at 4 or 5 pm (or the pressroom is holding for a breaking story -- due 20 minutes ago), you don't have time to check the details.

Jody didn't specify in the original post where the story was seen. Per the LATimes e-subscription link: "Sometimes articles are combined or separated for print or Web. Different versions of a wire service story may be displayed. Photos, headlines, graphics and other related materials may be different ... " So it might not have even been on their end.

 

[Jake Orosi]

Wow.

Retired journalist here. An editor in CA probably had minimal knowledge about severe storm meteorology, and needed to explain a breaking story quickly. Either a canned graphic or one prepared by someone who also had minimal knowledge of severe storms was used. (Not all sources of reference material are created equal. internet anyone?) Someone not familiar with a subject would have no way to know if it's accurate or not. If a tornado just leveled a town in the midwest, it's probably mid to late afternoon. If your paper comes out in the morning, the pages are due in prepress at 4 or 5 pm (or the pressroom is holding for a breaking story -- due 20 minutes ago), you don't have time to check the details.

Canned explanation. That graphic is actually one of the best and most lifelike storm diagrams I've seen and only needs to be paired with a correct explanation to be extremely useful.

 

[JanelleHelling]

Canned explanation. That graphic is actually one of the best and most lifelike storm diagrams I've seen and only needs to be paired with a correct explanation to be extremely useful.

"Unstable conditions" seems to be their only acknowledgment of wind shear, dry line, moisture and frontal systems. I certainly agree that additional information would have been better. The point I was making was that an editorial staff in California either wouldn't know this, or wouldn't have the time or resources to find out. (I would expect a more accurate interpretation by a news staff in one of the plains states.) The story was posted on the 21st, so they had less than one day to put it together after the event in Moore the previous day.

Which explanation are you saying is "canned"? Canned is a term used for material not produced in-house. Press releases, wire service news, syndicated material ... that sort of thing. It's actually a good thing, because any given newspaper production staff often doesn't have the time or resources to prepare complex material on a short deadline.