Frequently unasked questions

[Tim Bond]

Hullo,

I hope this is acceptable to ask as a non-specific storm-related question.

Intrigued by the way my last question developed into an interesting discussion of many areas, I'm curious - are there common storm misconceptions which tend to catch novices like myself and, critically, which novices tend not know enough to ask questions about? I'm envisaging the scenario that I am standing in front of a storm watching with some awe and trying to understand what I'm seeing.

The distinction between an inflow-jet and convergence would be the key interesting point that hit me from the previous (striations on supercells) discussion. Are there other terms which are commonly misunderstood, or major visual-observation traps which frequently trap novice storm enthusiasts?

Thanks in advance for any education!

Tim

 

[Shane Adams]

Are there other terms which are commonly misunderstood, or major visual-observation traps which frequently trap novice storm enthusiasts?

The first thing that comes to mind is the difference between storm-scale rotation (mesocyclones, wall clouds) and gust front shear. Many times gust fronts will briefly take on the characteristics of a rotating wall cloud, as it's pushed out and encounters the outflow/inflow interface. This interface frequently causes chaotic, cascading type motions along the edge of the gust front that can give the appearance of rotation, when in fact it's simply convergence (this is probably the leading cause of false rotation/wall cloud reports). In an earlier post I stated how sometimes this area can actually develop true, cloud base rotation, but these instances are far fewer. The typical scenario with gust fronts is the "fake rotation" convergence.

Another one, and IMO this is especially true in landspout-prone areas like NE Coloado, is the classic "is that a rain shaft or a tornado?" situation. Landspout tornadoes (someone more knowledgeable will have to delve into these further as I have no experience with them) often appear "transparent" in the middle, which gives them an appearance very similar to a narrow rain shaft. From a distance, sometimes it's impossible to tell the difference. Also with landspout tornadoes, they will often-times form as only a debris whirl, and, because they can form from a visually-benign-looking cloud base, they are almost unrecognizable as a threat (benign cloud base and only dust on the ground beneath). But landspout tornadoes can be quite intense, so never under-estimate them.

Related to the above paragraph but on a larger scale is the classic "Is that a rain shaft or a rain-wrapped wedge?" Basically the same situation as above but a lot more and a lot bigger, LOL. Large or "wedge" tornadoes buried inside precipitation can look like heavy rain shafts, and vice versa. What you want to make sure of is that you never mistake the tornado for a rain shaft; the other way around you're disappointed but unharmed...the same cannot be said for the former.

 

[Tim Bond]

Thanks Shane! I'll bite on something from the first paragraph - what is 'cascading motion', and what's happening on the boundary to make it happen? I've heard this referred to in the field and on storm DVDs and never had much idea either where I was supposed to be looking or what I was supposed to be looking for.

Point very well taken on the 'is it rain or a tornado?' question - I will do my best to keep a wary distance from shrouds of precipitation or what appear to be innocuous dust whirls in Colorado!

Tim

 

[Shane Adams]

Thanks Shane! I'll bite on something from the first paragraph - what is 'cascading motion', and what's happening on the boundary to make it happen? I've heard this referred to in the field and on storm DVDs and never had much idea either where I was supposed to be looking or what I was supposed to be looking for.

I don't know if I can describe this very well, I'm pretty much a "visual" guy. Perhaps someone else can take this one with a more scientific approach?