Langdon ND area Fire Tornado,
24 October 2011.

Area Map | Fire Tornado Photos | Weather Discussion | References

Possible "Fire Tornado" near Langdon ND, this past Monday.
By Gregory Gust, NWS Warning Coordination Meteorologist.

A grassland/slough wildfire southwest of Langdon on Monday afternoon, October 24th, 2011, appears to have spawned one of the fire-weather world’s more interesting and obscure phenomena... a Fire Tornado.


Figure 1. The approximate location of the grassland/slough burn area is about 5 mi. due north of Loma ND, or 8 mi. west- southwest of Langdon, in Cavalier Co, as indicated in the shaded area of the map.

The whole fire whirl/fire tornado event was likely short-lived, occurring between 2:55 and 3:05 p.m. CDT. Langdon area photographer and SkyWarn storm spotter Kelly Schwartz reported the event to the National Weather Service office in Grand Forks, and supplied the following photographs, taken between 3:02 and 3:04 p.m. CDT.

In the following photos, the direction of view is to the south, from near Dresden towards Loma.

The direction of the smoke plume is towards the northeast, from the area north of Loma towards Langdon.

Surface winds reported in the area were light from the east-southeast, turning west-northwest following the event. Three to ten thousand foot winds aloft were turning from southwest to west, blowing the smoke plume northeastward, into the Langdon area, and temporarily restricting visibilities at the airport.


Photo 1. View of fire/smoke plume and rapidly building pyro-cumulus cloud @3:02 p.m. CDT. View of smoke plume and building pyro-cumulus cloud

Photo 2. View of fire/smoke plume with well articulated tornadic rope @3:04 p.m. CDT. View of tornadic rope in smoke plume

Photo 3. Close-up of the tornadic rope, extending from the ground to the cloud base. Close-up of the tornadic rope

Photos and locations are courtesy by Kelly Schwartz of Langdon ND.


Why did this "Fire Tornado" occur?

A Fire Whirl generally forms when superheated air near the surface of a large fire zone rises rapidly in an airmass where sufficient horizontal or vertical vorticity is also present. Much like a dust devil or whirlwind, the rapidly rising air above a wildfire can accelerate and turn the local vorticity into a tight vertical vortex, now composed of fire instead of dust. Whereas the dust devil will often mix out its local temperature discontinuity and the vortex dissipate rather quickly, over a few minutes or less, the wildfire zone can help maintain a fairly long-lived fire whirl lasting for several minutes or more.

A Fire Tornado would be a much more extreme example, and involve a Fire Whirl that had stretched vertically from the ground up to the base of developing cumuliform clouds. In our case, the vortex extended nearly 3900 feet high.

What's the Meteorology behind all of this?

A below listed article by Mike Umscheid, with the NWS office in Dodge City KS, has a great meteorological explanation and example of how this process initiates.

Our detailed analysis of the Langdon event will take some time to complete, but preliminary information suggests that similar ingredients are present as follows: 1. the fire zone heating produced the rapidly rising air, 2. the lower level winds had enough environmental shear to induce a vertical vorticity near the surface and get the fire whirl going, and then sustain it.

In addition, we suspect that at least two additional factors were in play, as follows: 3. low level moisture was sufficient to rise, cool, condense and form the pyro-cumulus cloud deck, and 4. the lifted condensation level (LCL) was close enough to the level of free convection (LFC) so that the developing pyro-cumulus quickly became a towering cumulus... which may have increased the overall up draft speed and vertical vorticity to such an extent that the near surface Fire Whirl stretched into a Fire Tornado.

The 2:55 p.m. CDT report from the Langdon Airport listed winds at 3 mph from the east, with visibilities reduced to 1.25 miles in haze, and lowest cloud heights of 3700 to 3900 feet AGL. The next published observation, at 3:15 p.m. CDT, listed winds as calm, visibilities as unrestricted (10 miles or greater), and skies as overcast at 3900 feet AGL.

According to local observers, the pyro-cumulus cloud developed quite quickly above the fire zone as the ascending smoke plume then took on its whirl.

What's a pyro-cumulus Cloud?

Pyro-cumulus clouds are like most any other clouds, made of water droplets or ice crystals, and caused by moist air which rises, cools, and condenses. The difference is in the reason the air is rising… which is due to the extreme heating of the near surface air mass caused by a local fire zone.

Quite often, the smoke plume from a fire zone or from a large industrial chimney will induce the formation of a cumuliform cloud above that heat source, assuming sufficient low-level moisture is also available. In very intense and widespread fire zones, the building clouds can develop from more humble cumulus, to towering cumulus, and even to cumulonimbus (thunderstorm) scales.

A great example of a fire zone contributing to the formation of a pyro-cumulonimbus cloud can be found in this web article by the NWS office in Duluth MN, regarding the Pagami Creek Wildfire in Extreme Northeast Minnesota, which occurred from mid-August into September of 2011.

Is a Fire Tornado a real Tornado?

The phenomena viewed in these photos does appear to meet the standard definitions of a tornado (see AMS Glossary of Meteorology definitions below), which is a violently rotating column of air, in contact with the ground and pendant (attached) to a cumuliform cloud.

The Glossary doesn’t contain a specific entry for either a Fire Whirl or a Fire Tornado, however it does make mention of another colloquial expression used for a non-supercell tornado which occurs over land, called the landspout (see AMS definitions below). Meanwhile, Wikipedia indicates that Fire Tornado is one of a few colloquial terms used for the Fire Whirl.

Is this considered a serious storm event by the NWS?

A Fire Tornado is something which is not yet well explained in the scientific literature. Both the Fire Whirl and Fire Tornado are mainly forced by the thermodynamics within the fire zone, and are not considered a strictly meteorological phenomena, therefore they aren’t something that is typically reported to the NWS, nor are they something which would typically warrant an NWS warning. It is possible for a Fire Whirl or Fire Tornado to become large enough and strong enough to produce damaging winds apart from the actual fire damages, but those damages would generally be confined to the fire zone.

Hypothetically, a Fire Whirl could develop in an atmosphere with a pre-existing deep layer of vertical vorticity in the near vicinity of a developing supercell thunderstorm. In such a case, a resulting Fire Tornado could possibly grow to more typical tornado scale intensity and result in higher tornado scale wind damages.  There are reports of large wildfires producing damaging fire winds of EF1 or EF2 strength or greater (86 to 135 mph, Enhanced Fujita Scale), with or without Fire Whirls present.   

We would normally expect a Fire Whirl or Fire Tornado to quickly dissipate once it moved off the fire zone, but if sufficient supercell thunderstorm forcing was still present such an event could evolve into a more classic long-lived tornadic event – much as a waterspout or landspout tornado might occasionally evolve into a long-lived supercell tornado.

I’m still waiting for evidence of this to occur!




Photos and locations are courtesy by Kelly Schwartz of Langdon ND.

Definitions:

From the American Meteorological Society Glossary of Meteorology:

tornado- 1. A violently rotating column of air, in contact with the surface, pendant from a cumuliform cloud, and often (but not always) visible as a funnel cloud.

landspout- 1. (Rare.) A tornado. 2. Colloquial expression describing tornadoes occurring with a parent cloud in its growth stage and with its vorticity originating in the boundary layer.

nonsupercell tornado-  A tornado that occurs with a parent cloud in its growth stage and with its vorticity originating in the boundary layer. The parent cloud does not contain a preexisting midlevel mesocyclone. The landspout is an example of the nonsupercell tornado.

 

External *Links:

Fire Whirl definitions, from:
http://www.forestencyclopedia.net/p/p471

Tornado definitions, from:
http://amsglossary.allenpress.com/glossary

Fire Whirl and Fire Tornado definitions, from:
http://en.wikipedia.org/wiki/Fire_whirl

Meteorology examples, from:
Umscheid, M., Monteverdi, J., & Davies, J. (2006). Photographs and Analysis of an Unusually Large and Long-Lived Firewhirl. E-Journal Of Severe Storms Meteorology, 1(2). Retrieved October 26, 2011, from:
http://www.ejssm.org/ojs/index.php/ejssm/article/view/6/11

Pyro-cumulonimbus and Pagami Creek Wildfire examples, from:
http://www.crh.noaa.gov/news/display_cmsstory.php?wfo=dlh&storyid=72987&source=2

*Note: NOAA’s National Weather Service provides a link to these external Web pages because they may contain related information of interest to you. These links do not constitute an endorsement by the NWS of any information, products or services on these external Web sites. The NWS does not own or operate these sites and is not responsible for site maintenance or data accuracy. Use this data at your own risk.


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