Can inflow into updraft of a tornado come from ALL directions? (360 degrees) or ??

[Carol Sidofsky]

That great video of the Mass. tornado going across a river, seemed to show inflow coming from all directions (360 degrees). Was I seeing that correctly? If yes:

How does this relate to other tornadic storms' inflow bands? Do all tornadoes have inflow coming in from all directions, or was that unusual?

Does inflow usually come from a more limited direction, going toward (or being pulled in) toward the updraft area?

How does low level wind direction relate to the Mass. seemingly multi-directional inflow into the updraft of that Springfield, MA tornado?

How does low level wind direction generally relate to inflow directions into updrafts in general?

 

[rdale]

I think you have two concepts running together... You have an updraft into the thunderstorm, which is coming from out ahead of the cell (if it's going to last long.) You have the winds coming into a tornado itself (not the "updraft" really) which would come from all directions I would imagine.

 

[Greg Blumberg]

Carol, those are some great questions. I'll try to answer them to the best of my ability, but I'm willing to bet that others here will be able to fill in where I lack in knowledge.

A tornado can be broken up in to several regions. Near the surface, where the inflow for the tornado is, you do get inflow from all directions. I do believe that you were observing the air flow near the surface correctly.

Now, compared to the tornado, inflow directions for a mesocyclone is different. We have to think about what scale of inflow we are talking about, which is even more complicated considering that to understand a supercell's processes, we need to think three dimensionally. What is commonly called "inflow" into a supercell is the result of different ways the storm generates a low pressure center. By generating a low pressure center, the storm induces a pressure gradient force which serves to accelerate air towards the center from all sides. It's like sitting in a bathtub, then taking a bunch of water out with your hands. Water from the sides rushes into the center to fill the gap. This is similar to what happens when you induce a low pressure center in a supercell. Air rushes into the sides. Our experience of this air is what we call "inflow." See the black arrow in the graphic below for the common direction of inflow:

http://www.wikinfo.org/upload/4/43/Supercell-above.png

Now personally, I don't think that this is the only direction of inflow in a supercell. I think it occurs on all sides of the updraft, and it's just difficult to identify because a.) the updraft is usually surrounded by the forward-flank downdraft and the rear-flank downdraft and b.) that it's more difficult for the updraft to draw in the rain-cooled air that the storm has precipitated out because it's less buoyant than warm, moist air out ahead of the storm (where you see the black arrow in the graphic).

Regardless, the updraft of a supercell can still draw in rain-cooled air. This often happens when the supercell develops a wall cloud. The updraft lifts rain-cooled air from the forward-flank downdraft to saturation. Additionally, the updraft can lift air from the rear-flank downdraft.

Some of your questions are tough to answer because the term "low level wind direction" can mean multiple areas when you're talking about the interface between supercells and tornadoes. If you're talking about a specific wind direction that you can see on a map, then the answer is that there isn't one direction that you can identify that relates to updraft inflow. Air flow around a supercell and tornado is difficult to talk about because there are so many different scales of air motion that we have to consider.