Backside of the Supercell

[Greg Blumberg]

For a long time, I've been shown photos, videos, and conceptual models of the supercell seen facing towards the northwest. It's been frustrating for me to try to picture the supercell in it's entire beautiful, complete 4D entity, as it seems very 2D-ish in my mind due to constantly seeing photos from that northwest facing vantage point. I do understand that this typical supercell vantage point is the safest, but I want to know what the backside looks like, especially when the RFD carves into the updraft and tornadogenesis occurs.

Does anyone have any pictures or video of these processes occurring from this different observational point or any other point for that matter? Seeing the full occlusion cycle of the supercell from this different vantage point would immensely help this storm chaser better visualize and understand the storm.

Thank you very much!

 

[rdale]

http://www.nws.noaa.gov/om/brochures/adv_spotters.pdf

 

[Stephen Locke]

Position southwest of the storm. RFD cutting into updraft.
Aurora, NE 6-17-09

 

[Skip Talbot]

Greg, from the backside a supercell retains most of its characteristic identifiers including the updraft tower and anvil. You can get dramatic views of convection if there is a dry punch behind the storm that clears out the low clouds. Underneath the storm, however, there is often rain and hail wrapping around the hook which makes viewing from the back of the storm difficult. However, here's a shot I got while underneath the clear slot, looking east and straight up as the RFD cuts through the tower:

This is the southern portion of the horseshoe shaped base you get when the RFD cuts through the rain free base. You can see the clouds curling around on the end in a place where you get anticyclonic rotation and anticyclonic tornadoes are possible. On the left or north side of the image, out of the frame, is where you'd be more likely to see tornadoes and where the precipitation core is.

 

[Greg Blumberg]

Thanks very much! This will help my problems!

 

[Bill Tabor]

June 4th 1999 - I had a chase near Valentine, NE (almost to SD) partly night chase. I was approaching the supercell from the sw headed north and east. Some of these views are from the south. I have a lot of the footage but only conveniently have it publicly at the moment as a music video which has snippets of the feature you are curious about. I recommend you check out the video. That storm showed the most dramatic example of rear flank downdraft leading to tornadogenesis I have ever seen, or seen examples of. I watched as the RFD carved out the backside like a canyon, pulled the cloud material toward the ground, and then wrapped around the inflow producing a tornado! I've never seen such a good example and actually I should provide it to SPC and NWS for study of origins of tornadogenesis IMO. You will have to stop the video at the proper times to see the back of the supercell / RFD / tornado but I have the time stamps they are:
20, 40, 52, 1:26, 1:33, 2:16, 4:10, 4:34 (tornado), 5:21 (tornado).

This is compressed and smaller screen than the full quality version and I suppose it will never be as clear and dramatic as what I witnessed in person the storm produced a number of tornadoes. Video link here:
http://www.tornadoxtreme.com/Chases_By_Year/1999_Chases/1999_chases.html

Click the Music Video link toward the bottom of the page..scroll down.

 

[James Langford]

Position southwest of the storm. RFD cutting into updraft.
Aurora, NE 6-17-09

Stephen, that is an incredible photo! That is probably the clearest example of an RFD slot that I have ever seen, even showing the blown dust. Awesome.

James

 

[Bill Tabor]

I agree..a nice shot. Different from my video in that the slot is displaced from the area of the funnel / tornado developing...at least as far as I can tell in the photo from this angle. In my video they seem to be coincident...in other words the tornado develops directly in line with and as a part of the cloud material that get dragged toward the ground by the RFD. This would be good study stuff to see the different ways it can happen.

 

[Charles Kuster]

On July 13, 2009 I chased a supercell that moved south southeast out of South Dakota and into Nebraska. Due to the road options, I had to approach the storm from the west (behind it) which gave me a pretty good view of the backside of the supercell.

<O</O

This picture was taken at 5:53pm CDT from about 4 miles south southwest of Parmelee, SD and is looking to the southeast. Unfortunately, the picture does not show much, but it is looking towards the “hook regionâ€￾ of the supercell.

This radar image is valid 7 minutes after the above picture was taken.

 

[Bill Tabor]

Greg, keep in mind that how a supercell appears looking northwest is also dependent on the orientation of the supercell. Based primarily on the wind field at 850mb to 500mb determines the direction a supercell moves. Technically they can move in any direction. Probably the most common movement is to the ne though a supercell can turn right into the storm relative wind or attach / follow a boundary. The direction of flow at all levels also determines which position a supercell is oriented (different from movement). Sometimes in northwest flow (where the mid level wind ~500mb is coming from the northwest) what you would normally consider to be the rear flank of a supercell (what you are interested in) can actually be on the northwest side of the cloud. It can be potentially disorienting. In other words the inflow area can be on the nw side. Supercells can also be oriented conventionally rear to S or SW but go 'backwards' - move to the SW. The Jarrell parent supercell moved in this way in 1997 by backbuilding along a boundary. This is an amazing thing to see on animated visual satellite imagery. Upper jets 300mb and up determine where the anvil goes downstream.

 

[Mike Hollingshead]

Replying more about motion relative features than views from west.

It seems to me storm features are almost always very much the same, regardless if the storm is moving northeast or due south or anything in between. Even north or nw movement too.

Due west at a supercell moving due south to ssw. Mid-level flow mostly out of the west but real weak getting to nw aloft. http://www.extremeinstability.com/04-7-12.htm

Due west at a supercell moving due north and even hooking nw. Mid-level flow southerly. http://www.extremeinstability.com/07-3-28.htm

Looking west again. I think this one was more solidly nw flow in the mid-levels but not certain. I do know it was moving nearly straight sw at points. http://www.extremeinstability.com/july_24,_2000_n._central_nebraska_tornadoes.htm

I'd say if the storm is solidly surface based, features will look very much the same regardless of motion. Left splits would be more apt to have the inflow on the nw/n side.

The only time I felt "back-assward" watching a storm was on a ne to e mid-level flow odd summer day. Strong high and there was a good jet out of the ne or ene over instability here. Storm formed and moved due west. Now that thing was backward with the inflow truly on the west side. Beavertail thing was going wsw down the road at me, on the south side of the base, north of the core... as I looked east at it.

To be more thread related here is one from the west.

From west all you usually see is an updraft tower first, then rain. To see anything again sometimes you just have to punch east into that rain and hopefully pop out with a view before being "too close" to something. Then structure wise you can usually just follow the "coil" of the flanking line/gust front out ahead and to the se on north and around back to where you are. Can kind of do that on the above.
http://www.extremeinstability.com/04-5-22.htm

That whole chase was from the west, not where I wanted or ever really want to be.

June 7 last year on the west side. Again, first all one saw was a big updraft tower. Then drive into its rain. Punch through the rain/hail and come out to that just east of you. Al this one was from the west too...
http://www.extremeinstability.com/09-6-7.htm

Another from the west. Get a wall cloud and usually you have the clear slot viewable. Can see it is drier on the left/nw and trying to cut/dry in on this side of the wall cloud.

Same storm short bit later. Clear slot grew as did wall cloud though it was more strung out now and less organized at this point. Just cycling a larger area or rotation.

 

[Bill Tabor]

Greg, after reading Mike's comments I realize he brings up some good points concerning supercell orientation. I was thinking inflow positioning may be related to northwest flow but actually I think it is likely more related to warm, moist surface winds and those almost always in the US Plains come from the south. In other words if the warm, moist air is on the south side then likely it makes sense the inflow region is south. I almost never chase northwest flow events...I usually don't like them, so no experience with. I guess what I was trying to remember was a situation (that I thought was related to NW flow, and it may have been) where chasers found themselves dealing with bizarro orientation of the supercell features. This was back 8-10 years. As I recall Shane Adams was one of the chasers - so perhaps he could elaborate. Anyway, in that case I think it was a cold core, low topped supercell chase and they were all hanging out near or behind the surface low which was occluded. The direction of mid level flow (including nw vs sw) will affect the direction the supercell moves however. Anyone willing to explain supercell orientation rules chime in. On the other hand supercell type such as HP or not should affect what you see. If only for the difference in the amount of precipitation it is easy to see around an LP. HP is typically very large and the inflow region is somewhat wrapped toward the Forward Flank Downdraft FFD region in what is called a 'notch'. Because of this occlusion it makes it difficult to see a tornado in an HP. What I said before about movement is still true. Supercells can move odd directions such as backbuilding (tail first) to the sw which is opposite of the most common movement direction ne.

 

[Mike Hollingshead]

I can think of just one oddity regarding nw flow types and things being to the nw burried behind the rain(not wrapped, just nw of a core). Often with nw flow you can end up with too much turning with height. Take nw aloft and se surface and things will suck. What you'll get is a more pulse type of chase, as an updraft vents into its own inflow. So boom, goes up with good air, then it sucks in rain cooled air. Perhaps it can deviate some/enough for a little while. But it never seems to do well for long. And what can happen with those is getting a quick tube or something back to the nw of a core where the updraft was. Even that I can barely think of a single time I've felt a need to get on the nw side of things.

I just remember some of the best viewing location topics of the past, on storm motions. As time has gone on, I've noted best viewing location really doesn't change with storm motion. My favorite is always due east or even ene of the base, granted depending on the storm you might be in some rain. Mostly a storm topic, not a tornado one as all bets are off on best tornado view.

 

[Greg Blumberg]

Bill, Charles, and Mike, thank you for your contributions!

Bill, that's a very interesting point you bring up regarding the storm structure orientation to the compass rose and the storm motion. I suppose I should have mentioned that instead of generalizing the SW to NE motion. I have never had any luck with NW flow events, and I tend not to chase them for the same reasons Mike mentions above.

I did see your video and checked out the individual frames at those times you mentioned. I noticed that it looked like two separate updrafts with a notch (the RFD?) slightly dividing them. Is that what you were describing? Are you planning on uploading the full video anytime soon? (You've got me very curious.)

Mike, thanks for the description of the storm when approaching from the west. That was very helpful.

 

[Bill Tabor]

Yeah, it's pretty weird video. it could have been two towers that were merging. That's what I was thinking at the time, but at the same time it appeared to be one supercell and yes, I believe the notch carved down the back in between the two was the RFD..in other words could have been one supercell and that's just what the RFD did to it from top to bottom. It was a crazy thing to see from that perspective. The reason I believe it's RFD is because the cloud material was pulling out directly below the vertical gorge (whatever you want to call it) from the base. I watched this continue to pull and then become a tornado.

The video was on old Hi 8mm. Guess I should grab it and post for educational reasons. Probably some smarter than myself can actually figure out the dynamics of what is happening here, but on a basic level it does seem to be RFD directly leading to / affecting tornadogenesis.