Boundary Questions

I have several questions about things like outflow boundaries. I have some conflicting ideas about them from what I have heard and seen in the field. My understanding is that outflow boundaries can enhance tornadic potential in storms and also can produce more storms. However, I have seen both things happen. I have seen storms blow up on outflow boundaries, but I have probably more often seen storms fall apart when hit by outflow boundaries. I can see how both these can occur. Storms hit by cold outflow will fall apart, but the boundary can cause storms to rotate. What determines whether a storm explodes or dies when hit by outflow boundaries?
 
In my very limited understanding, I was under the impression that one factor was the thermodynamic profile of the outflow. Fresh outflow that is still relatively cool/cold will interact in a different manner, than will an older OFB that doesn't quite have as sharp a temperature gradient.

I wouldn't imagine that you'd want fresh, cold outflow.
 
Yeah now that I think about it, the storms that have blown up on those boundaries I have seen tended to be older leftover bondaries from things like a MCS that came through the night before while all the storms that died were on fresh boundaries. I can't believe I didn't notice that until now haha.
 
Outflow boundaries are generally good if they are old, but worse if they are newly generated. A fresh outflow boundary is generally bad for tornadoes for a couple of reasons. One, it has rain-cooled air on its upstream side that undercuts and weakens surface-based convection. New outflows are also moving faster, making it harder for a new updraft to root at the surface before being undercut. Usually, what you want is a strong outflow boundary to linger into the next day. These 'old' outflow boundaries that are able to 'bake' in the sun for several hours are the best for tornado potential, since 1.) they have unstable air on both sides and 2.) are not moving as fast, allowing a storm to 'anchor' on it. Orientation is important - you want a boundary to be set up to allow a storm that anchors on it to be deviant from the upper level flow. That is, if you have southwest flow aloft, an east-west outflow boundary would allow that storm to turn harder to the right, increasing its storm-relative surface and anvil level flow. A north-south boundary may not give a storm enough time to anchor on it before simply crossing it and moving off to the east.

That said, any mature storm that ingests an outflow boundary - new or old - shouldn't be ignored. Both are rich in vorticity, and even a cold-sided boundary can give a big supercell enough to produce.
 
So the "old" outflow boundaries are difficult to detect, right? It's obvious to identify new OFBs on radar because you can actually see the boundary rushing away from the storm. Also, you may see wind and temp changes at nearby weather ob stations. However, how are you going to detect the old OFB? The diffuse boundary wouldn't show up on radar a day later and the wind and temps would be extremely subtle, right? So how do you find it? Perhaps track it from the day before? Not sure how you would without a 10,000 frame radar loop :) although, I guess this is where archived surface data from NOAA or CoD comes in handy.
 
Sometimes you can detect old outflow boundaries on radar. Flying insects get caught up along outflow boundaries and sometimes produce a weak echo. You may have to track it for several minutes before it becomes obvious what you are seeing.
 
So do most chasers/forecasters use surface obs/maps to identify OFB by looking for subtle differences in temp, wind, dews and pressure?
You can often see them on visible sat images.

I pay special attention to the surface obs and visible sat on mesoscale analysis to see where the OFB will set up.
 
So the "old" outflow boundaries are difficult to detect, right? It's obvious to identify new OFBs on radar because you can actually see the boundary rushing away from the storm. Also, you may see wind and temp changes at nearby weather ob stations. However, how are you going to detect the old OFB? The diffuse boundary wouldn't show up on radar a day later and the wind and temps would be extremely subtle, right? So how do you find it? Perhaps track it from the day before? Not sure how you would without a 10,000 frame radar loop :) although, I guess this is where archived surface data from NOAA or CoD comes in handy.

Perhaps I should be ashamed to admit this, but even after 18 years of chasing I have trouble locating old OFBs and it has cost me dearly. I find it difficult to resolve with surface obs due to the very subtle changes in wind direction and possibly temperature, especially in areas where there are limited surface observation stations - after all, these are small-scale features that may exist within an area devoid of obs. I also find it difficult to use satellite imagery; unless the OFB is present in an otherwise completely clear sky, I find the resolution is not sufficient to discern an outflow boundary among other cloud features. (I use UCAR satellite, is there another site recommended for ability to zoom in on smaller areas and with greater resolution?)

If anyone is willing to go deeper into these topics, and perhaps can upload some examples of OFBs analyzed on surface maps or satellite, it would be most appreciated by me and I am sure others on here.

Jim
 
I agree with JamesCaruso, I struggle to see outflow boundaries, but am always looking for them. Sometimes they are clearly obvious, other times (more often than not) they seem invisible.
 
You must view loops of vis sat at 1km resolution. CoD has that, and I thought there were other sites, too, but now that I am rummaging through my bookmarks I'm not finding any others. GRL3 is also a great way to view vis sat, but as far as I know there is no way to run sat loops on GRL3.

Actually, and IDK for sure, but CoD is probably taking the same images from GOES-E that everyone else is using and just zooming in and calling it 1km resolution. You can zoom in using other sites. This is my favorite: http://mp1.met.psu.edu/~fxg1/ewall.html

CTRL++ may also do the same exact thing! (Hold the control key down and tap the + key repeatedly. CTRL plus "ZERO" to return to normal)
 
A lot of it is just knowing that one is there beforehand. If a big supercell or MCS is from the previous day dissipated in the area and sent out a OFB visible on radar at 10PM-1AM, you know there's an OFB there, even if it's not visible the next morning. In that case, sometimes it's just guesswork - if there are absolutely no signs of it on satellite/radar/surface obs the next day, you just target your best guess as to where you think it may be based on the radar loops from earlier (COD's 200-image loops are helpful here). Eventually, the OFB should start to become evident once cumulus fields begin to form, giving you enough time to adjust to its location before initiation. If that doesn't occur, sometimes it's just picking a storm where you believe the OFB is most likely to be. If it's there, the storm will "find it" for you. It gets tricky if surface flow is strong, in which case the OFB will eventually start to lift northward and/or just wash out. If someone knows of some other way to locate them, I'd love to hear it.
 
Meanwhile, in Amarillo....
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