Ice Capping? Column Collapse?

[mikef]

OK, The Cedar Fire was about 3 days old when the Santa Anas were replaced by onshore flow. On 28 October 2003 a very brief pulse of deep pyroconvection occurred. This happened soon after sunset. We were able to track the exhaust from this "pyrobubble" into the Great Plains the next day.
The plume got to ~11-13 km altitude! This is very impressive for a SoCal fire and implies some very distinctive fire behavior. Just what happened late that
afternoon I am still unsure. Maybe someone here does?

Here is the GOES loop. IR only because of time of day.
This shows the fires as white; pyrocloud as black. Looks like a UFO!
http://rammb.cira.colostate.edu/proj...03/ch2loop.asp

[Mellie]

It would be very interesting to have this kind of video for all the fatality fires that seemed to have something like this occurring.

Thirty-mile comes to mind. One report I heard after 30mile said firefighters described the fire as going up the facing mountain slope across the river as very hot and fast, then it collapsed back toward them. There were only 10 feet between those that died and the burned effects of the edge of the energy pulse coming back down if I recall correctly.

I wonder if it's possible to take some of these time lapse sequences, video/ infrared loops, and firefighter reports of what's happening with the fire on the ground and correlate them.

Mellie

[Redfire]

Here is a very good Time laps of the station fire "white capping" posted by xna2200. It shows what i belive you are asking about. If you watch the top of the smoke youll see it "white cap" then collaps back into the cloud. This at times can cause very high winds in all directions on a fire. Hope this helps.

Red

http://brandonriza.com/Video/HTML/Ze...Contained.html

[stringtown]

I like the progression of column build and collapse in this link posted on theysaid, it's the video clip in the middle (image 18); it looks like it was shot from San Bernadino some where, viewing the south side of the fire on 8/30 right at sunset.

http://www.flickr.com/photos/anosmic...th/3864982760/

[mikef]

Syncing up satellite views of extreme fire behavior with ground data is my research quest, and current priority. Pinged Brandon Riza and got his date/time of time lapse. Stay tuned for the GOES loops. Will share ASAP.

Re. 30-mile and other cases of interest, just say the word. Give date, location, and fire name and we will make the satellite loops. Satellite data
go back to 1979, so only fires newer than that are candidates. Practically speaking, GOES data are patchier the farther back you so...we'll take
what we can get.

FYI, we have a catalog of these pyroCb events that is ever growing.
Some fires of interest may already be documented. E.g. Hayman, Tripod, Derby, Jasper... Happy to share what we know.

[smeise]

That sounds awesome Mike can't wait to see it.

[mikef]

OK, Brandon Riza's time lapse (http://www.brandonriza.com/Video/HTM...Contained.html)
is from 29 August, ~14:05 - 16:17 PDT (~21-23 UTC).
His vantage point was Marina del Ray.

Here are GOES loops for 29 Aug, 18:30 UTC - 29 Aug 01:45 UTC (sunset local).
*vis* is the visible image
*ch2* is shortwave IR, sensitive to fire hot spots
*ch4* is the thermal IR (what they use for cloud images on TV).
Note the red x. That is Brandon's camera's vantage point.
http://rammb.cira.colostate.edu/proj...09/visloop.asp
http://rammb.cira.colostate.edu/proj...09/ch2loop.asp
http://rammb.cira.colostate.edu/proj...09/ch4loop.asp

Credit for these and all GOES loops offered here goes (ahem) to Dr. Dan Lindsey of NOAA Ft. Collins.

See the fleeting capping Cu in the vis. These are accompanied by colder
clouds (ch4). They may disappear due to collapse OR simply evaporation.
There is evidence that the smoke left behind after the disappearance is at
a higher altitude than other parts of the plume.

Enjoy!

[abercrombie]

From the Ab account:

I’m going to wonder out loud about collapsing columns:

I had the fortune to attend a 30-mile lessons learned style review, by the FBA from Okanogan country. He described a collapsing column of a different kind then we normally talk about. When he interviewed on-site several of the survivors of the 30-mile fire at the entrapment location. The FBAN said they described a scenario like the Montana Elk River photo. It was really hot as it went up the hill across the river. Then it lost energy and 'fell' back down toward them. That was what caused the spotting across the road and the entrapment, the heat coming back down the hill. In an earlier post on this thread Mellie references this event with a similar description.
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I remember reading a paper by Haines et al from the early 1990’s as I recall. THE Donald Haines described different types of Plume Dominated fires. The worst one was what he called a 1-A or A-1 where the fire was fed by wind at the ground level but the vertical component needed for a plume was available at mid and high levels.
It was the worst of both worlds – wind and plume combined.

Perhaps with enough energy there doesn’t need to be as perfect a mid and upper level atmosphere. I’m sure many of you have seen this and if you look at the time lapse by Mr. Brandon Riza. I think this is what is happening here, at least at times in the film.
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It occurs that these columns on the 29th could be collapsing due to their placement out in front of any support by the main fire. Would this create just downdrafts like a T-cell or include heat being pushed down also like the description of the 30-mile fire?
{Is anyone aware of any descriptions of T-cell ice caps collapsing?
Not the virga associated downbursts.}

For the good of the order:
Is it possible that Camp 16 faced collapsing columns in front of the main fire that contributed to not understood net rates of spread and energy release?
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Station Fire:
Fuel driven, (per Doug Campbell discussion) that is combined with
wind driven to create an also
plume fire with
collapsing ice caps?
Any thoughts?

Fuels Guy

[mikef]

This is a fascinating topic for this fire outsider. I hope to learn as much as I can from the folks closest to the fire behavior.

But I have a few caveats re. interpretation of pyroconvection in terms of column collapse.
1. There is built-in optical illusion to time lapse photos like we've seen.
The best shots of the column are still not ideal. Obviously, the vantage point is at ground level. Plus, they are usually upwind
of the plume (because that's where the best ground visibility is). So the combined result is that plume/cloud movement away will look like movement down. Both are probably occurring to some extent but it is nearly impossible to give proper attribution based on the photo animation.
2. The way convection occurs routinely involves buoyant bubbles overshooting their level of thermal equilibrium and subsequently descending in the process of achieving that equilibruim with the environment. But that is mostly restricted to a relatively small altitude range and does not routinely involve descent all the way back to the ground. It's more of a rippling about the level of neutral buoyancy. What is going on to cause the manifestations on the ground described as column collapse is, to me, still out there in the frontier to be nailed down.
3. In our studies of pyroconvection from space, we now know that downwind smoke is found at the altitudes that the convective columns/anvils achieve.
E.g. if the pyro-anvil gets to the tropopause, the smoke gets that high. So it seems that to some extent the convection column acting akin to a chimney is a reasonable (albeit incomplete) model of the column behavior.

Thoughts? Corrections? Arrows?

[norcal]

This is a great discussion. I am no "space scientist" just a chopper and squirter with an interest in the weather. Three things come to mind;1.) Topography,Fuels, and Pressure.

Topography- As the fire is making its run upslope and the column is lifting, the column will eventually be pushed off away from the fire. If the terrain is sustained then perhaps the column is allowed to remain elevated longer and any downdrafts will be limited or experienced beyond the fires perimeter?? The natural updrafts may also be strong enough to counteract any downdrafts? If a column were build on a steep ridge and drift off over a flat plain, then there might be a "blast" effect. The other option is what you described earlier about the downdraft experiencing a steep slope and being forced back down into a draingage, where its effects are enhanced.

Fuels- Are not always continuous, even a large timber stand when viewed from across a valley may seem continuous, but when walked shows open areas or rocky areas etc. As the fuel is fed into the column, it experiences pulses that allow different release rates. Those release rates reinforce the bubbles of hot air that are rising and help the available moisture push higher. Once that bubble of air reaches equilibrium, it is eventually forced up again by the next bubble of air from a large run.?????

Pressure- Just as a wind moving over ridges will create a wave form, could the downdrafts be doing something similar? Such as wind shear, where a bubble of air has suddenly become less bouyant and then rapidly pushes down towards earth. It never makes it, because it is broken apart and some of it returns upward, but for the time that it existed it displaced another parcel of air that interacted with the ground. The parcel of air displaced another parcel that was allowed to interact with the surface. Think of an invisible "Mamato Cumulous" cloud. But rather than containing moisture, it contains debris from the fire.

Someone also mentioned that grass fires cannot create these types of clouds. During large VMP burns in the spring on the central valley floor, we have been able to have small versions of these develop, because of the available moisture in the air and the condensing effect when the column reaches the magic altitude.

Here is another interesting observation from last summer. During the Butte Lightning Complex in Northern California the Camp Fire made a run on a downslope wind event and pushed into some big timber as the fire burned downslope. The winds were in the 15-25 mph range with higher gusts, blowing downslope. When viewed from the valley floor the column would build and be blown towards the west out from over the fire, it would "collapse" and a new column would form. On the ground there was an obvious general downslope wind pattern, but there was excessive fall out of large chunks of bark and branches, Most of the roof tops are metal in that area. There was the constant sound of large objects striking these roofs. Someone even commented that it was the "artillery" softening us up. There did seem to be a "pressure" that existed in the general direction of the fire. But there was no straightline winds that were in excess of the normal gradient- "Jarbo Winds" of that area.
Just some random thoughts on this topic.