Still image from PBS Weathered. “Firenado: when two of nature’s deadliest forces combine.”
PBS has published a 10-minute video (below) about how fire whirls and fire tornados form. Here is how they summarize it:
A fire tornado, or “firenado,” is exactly what it sounds like: a tornado made out of fire… and it is truly the stuff of nightmares. The most famous example occurred when the 2018 Carr Fire spawned an EF3 fire tornado with estimated wind speeds of 143 mph! And as climate change drives increasing wildfires around the planet, it only makes sense that we see more fire tornadoes as well.
Tune into this episode of Weathered to learn what the latest science can tell us about these rare but dangerous phenomena as well as about the surprising ability of burnt forests to store carbon and mitigate climate change.
Weathered is a show hosted by meteorologist Maiya May and produced by Balance Media that helps explain the most common natural disasters, what causes them, how they’re changing, and what we can do to prepare.
Fire whirls, much like dust devils, are not uncommon on a fire when the atmosphere is unstable, and are much smaller than fire tornados. In 1978 a researcher for the National Weather Service in Missoula, David W. Goens, established parameters for the two.
He said the average size of a fire whirl is usually 33 to 100 feet, with rotational velocities of 22 to 67 MPH.
But a fire tornado dominates the large scale fire dynamics. They lead to extreme hazard and control problems. In size, they average 100 to 1,000 feet in diameter and have rotational velocities up to 90 MPH.
The fire was mapped Wednesday night at 859,000 acres
8:55 a.m. PDT Sept. 2, 2021
Map of the southeast side of the Dixie Fire, 3-D map looking northwest at 7:30 p.m. Sept. 1, 2021, showing the escarpment above Highway 395. The blue areas are previous fires.
The southeast side of the Dixie Fire grew substantially to the northeast Wednesday pushed by 10 mph winds gusting up to 20 mph while the relative humidity was in the single digits. During a 7:30 mapping flight Wednesday night it was 2 miles west of Highway 395, threatening to cross the road again. There is already a 5 mile-long fire scar where it reached the highway a few weeks ago, crossing it in several places near Honey Lake south of Buntingville.
The fire is approaching the edge of the escarpment where the terrain drops rapidly 2,500 feet down to Highway 395, seen on the 3-D map above. Firefighting on that steep slope would be very difficult.
Dixie Fire map, southeast side, 7:30 p.m. Sept. 1, 2021
“It’s almost to the escarpment now,” said CAL FIRE Operations Section Chief Tony Brownell. “We’ve moved a lot of engines and personnel around, we are down around 395, concentrating on structure protection. So when it does come off that hill we are going to be there to catch it and keep it out of structures the best we can.”
To see all articles on Wildfire Today about the Dixie Fire, including the most recent, click HERE.
The fire has also reached the north edge of Lake Davis eight miles north of Portola which is on Highway 70.
The extreme fire behavior witnessed Wednesday is predicted to continue due to persistent winds and dry fuel conditions — near red flag warning criteria. The forecast for Thursday is for 7 to 13 mph winds out of the west-southwest gusting late in the afternoon up to 21 mph with the relative humidity in the teens.
Dixie Fire map, 7:30 p.m. Sept. 1, 2021. The blue areas are previous fires.
On the northeast side, which is still active about a mile south of Highway 44, approximately half of Lassen Volcanic National Park has burned.
The fire was mapped Wednesday night at 859,000 acres. At least 696 residences and 586 other structures have been confirmed as destroyed. Suppression costs have reached $432 million since it started near a PG&E power line July 14. Wednesday evening 4,039 personnel were committed to the incident.
Predicted to be above normal in Northern California through November
The forecast for wildland fire potential issued September 1 by the National Interagency Fire Center predicts that the potential for wildfires in Northern California will be above normal September through November. Northern Minnesota and the northwest one-quarter of the country will also be above normal in September. Hawaii and Wyoming could be busy in September and October. The southeast Atlantic coast states may experience above normal fire activity in October and November, but December looks to be pretty average in all 50 states.
The data from NIFC shown here represents the cumulative forecasts of the ten Geographic Area Predictive Services Units and the National Predictive Services Unit.
Below:
An excerpt from the NIFC narrative report for the next several months;
Additional NIFC monthly graphical outlooks;
NOAA’s three-month temperature and precipitation forecasts;
Drought Monitor;
Keetch-Byram Drought Index.
“Climate outlooks indicate warmer than normal conditions are likely for much of CONUS through fall. Wetter than average conditions are likely across western Washington for the fall with below normal precipitation likely across the Southwest, Great Basin, central Rockies, and much of the Plains. The Southeast is forecast to have near normal precipitation through October but turn drier in late fall and early winter.
“Much of Southern Area and areas south of the Ohio River are likely to have below normal significant fire potential in September, but much of the southeast US and Mid-Atlantic is forecast to have above normal fire potential in October and November. Normal significant fire potential is forecast for Alaska along with most of Eastern Area through the period. The entire US is forecast to have normal fire potential in December.
“Above normal significant fire potential is forecast to continue for September across much of the Northwest and portions of the Great Basin, Northern Rockies, and Rocky Mountain Geographic Areas. Most of these areas will return to normal fire potential in October and November except for portions of Wyoming, northwest Colorado, and the Black Hills, which will remain above normal into October. Much of northern California is forecast to have above normal potential through November with leeside locations in Hawaii likely to have above normal significant fire potential into October.”
Fuel treatments, Lake Tahoe area, and perimeter of the Caldor Fire Sept. 1, 2021.
For decades land managers and some residents in the Lake Tahoe area have been anticipating the Caldor Fire that has been burning since August 14. The blaze has blackened more than 204,000 acres as it rages to the northeast. It passed through the south edge of Meyers six miles south of the lakeshore and the head of the fire Wednesday morning was four miles from the lake.
Under the concept of reducing the fire threat to structures in the Lake Tahoe Basin, the US Forest Service and other organizations have been conducting hazardous fuel treatments. Since 1997, over 2,000 acres of landscape underburns and over 8,000 acres of prescribed pile burning has been completed on the Lake Tahoe Basin Management Unit (LTBMU), a division of the USFS that manages much of the land near the lake. In these areas, surface fuels have been reduced and smaller live trees thinned. The USFS says this “creates a zone where a damaging crown fire is less likely, which provides a safer environment for firefighters.”
The map above shows the fire on the morning of September 1 and completed hazardous fuel treatments. The green areas represent mechanical methods, such as thinning by hand or by using machines such as dozers or feller bunchers which can rapidly gather and cut a tree before felling it. Then the cut vegetation is piled. The purple areas represent locations where piles were burned. Some of the projects shown were completed in the last few years and others are older. This map shows very few areas (in yellow) that were treated with prescribed broadcast fire.
The USFS web page for the LTBMU politely says that budget restraints limit the number of acres that can be treated: “Increasing the annual number of acres treated with prescribed fire will challenge our future capacity.”
USFS engine crews on the initial attack of the Caldor Fire, August 14, 2021. USFS photo.
The hope is that reducing the flammable vegetation will reduce the chances of structures being destroyed when a fire like the Caldor Fire burns into the area. Thinning trees and removing brush will not stop a fire, but in a best case scenario under benign weather and fuel conditions it might reduce the intensity of the fire and the number of firebrands landing on and near structures. If a fire does dramatically slow down when entering a treated area, it may make it possible for firefighters on the ground, perhaps aided by firefighters in the air, to stop the spread. That is, unless the wind is too strong and the vegetation moisture is historically low like we have seen this summer in California. As we wrote on August 22, under these conditions, “There is no possibility of stopping the forward spread of the fire. There is no number of 747 air tankers or firefighters on the ground that could be effective against the flaming front of this raging inferno.” This will continue to be true until something changes — some combination of cooler more humid weather, less wind, and vegetation with higher moisture content — or until it runs out of fuel at high elevations or spreads into agricultural land.
The Caldor has been lofting burning embers into the air that have landed a mile ahead of the flaming front, starting new fires, called spot fires by firefighters. When that is occurring fuel reduction projects a half mile wide around a community will not necessarily keep structures from burning. We could pave the forest paradise and put up a parking lot but if a fire a mile away can ignite residences we need other solutions.
The Home Ignition Zone (HIZ) is what home owners need to concentrate on. If it is welcoming to an ember storm, then the structure could burn no matter how much forest management is done. The HIZ must be maintained so that burning embers will not start a fire on the structure or ignite nearby vegetation which creates a fire that spreads to and ignites the building.
This is called Living With Fire. We can’t stop fires from burning, but we can stop homes from igniting when the inevitable fire occurs.
The best way to prevent homes from being destroyed in a wildfire is not clear cutting or prescribed burning a forest, it is the homeowner reducing flammable material in the HIZ. This includes spacing the crowns of trees at least 18 feet apart. The envelope of the structure itself must be fire resistant, including the roof, vents, siding, doors, windows, foundation, fences, eaves, and decks. A FEMA publication (13 MB) has excellent detailed recommendations. Headwaters Economics found that the cost of building a fire-resistant home is about the same as a standard home. When implemented, Chapter 7A of the California Building Code, regulates these features.
Here is an excerpt from an article written by Jack Cohen and Dave Strohmaier:
Uncontrollable extreme wildfires are inevitable; however, by reducing home ignition potential within the Home Ignition Zone we can create ignition resistant homes and communities. Thus, community wildfire risk should be defined as a home ignition problem, not a wildfire control problem. Unfortunately, protecting communities from wildfire by reducing home ignition potential runs counter to established orthodoxy.
UPDATE September 3, 2021:
In a live briefing Sept. 3 about the Caldor Fire near South Lake Tahoe, California, East Side Incident Commander Rocky Oplinger complimented the land owners and managers for the fuel treatments that have been accomplished over the years. He said the 150-foot flame lengths dropped to about 15-feet when the fire entered the treated areas. This allowed hand crews and engines to take an aggressive approach to suppress the fire and prevent structure loss. The video of the briefing is on Facebook; Mr. Oplinger’s comments about the fuel treatments begin at 34:10.
Caldor Fire, looking northeast from Armstrong lookout, August 29, 2021. AlertWildfire.
A firefighter on the Caldor Fire suffered serious burns and is being treated in the burn unit at UC Davis Medical Center, the Modesto Bee reports.
Richard Gerety III of Patterson was on a four-person engine crew from West Stanislaus Fire when he fell into burning material. It was his tenth day on the fire. He suffered third-degree burns on his arms and hands and second-degree burns to his legs, said his wife, Jennifer Gerety. The burns account for about 20 percent of his body.
She said he will undergo skin grafting surgery Wednesday and recovery is expected to take up to a month.
Thanks and a tip of the hat go out to Kelly and Dan.
Forecast for wildfire smoke at 12:01 a.m. PDT Sept. 1, 2021.
Above is the forecast for the distribution of smoke from wildfires at 12:01 a.m. PDT September 1, 2021.
Below is the current air quality status, obtained at 2:22 p.m. PDT August 31, 2021 from AirNow.gov. There is not much pollution in the East, due in part to Hurricane Ida.
Air quality (Ozone, PM2.5, & PM10) at 2:24 p.m. PDT Aug. 31, 2021. AirNow.gov
