Researchers quantify the trend toward increasing autumn wildfire danger in California

Autumn Days Fire weather index above 95th percentile
Fire Weather Index in California in September, October, and November since the 1980s. From the research paper.

Researchers have quantified some of the factors that have led to an increase in southern California large wildfires during the autumn months in recent decades.

Here are examples of late season fires that occurred in southern California in 2017 and 2018:

The study defines autumn as September through November.

But their analysis goes much farther back than just three years. Among other things, they found that rising temperatures, declining snowpack, and decreasing precipitation in autumn and spring have acted to extend California’s fire season in the shoulder seasons. They also determined that climate change has already doubled the frequency of extreme fire weather days since the 1980s (see the illustration at the top of the article).

The research also found a long-term trend toward more extreme fire weather conditions occurring in both southern and northern California at the same time.

The study was conducted by Michael Goss, Daniel L. Swain, John T. Abatzoglou, Ali Sarhadi, Crystal Kolden, A. Park Williams, and Noah S. Diffenbaugh.

NIFC releases prediction for wildfire potential, April through July

Wildfire potential weather July

Today there is a bit of good news for anyone worried about how firefighters will control wildfires during the current coronavirus pandemic. The wildfire potential outlook issued by the National Interagency Fire Center (NIFC) on March 1 predicted that the coastal areas of Central and Southern California would have above average conditions for April, but that changed in a new outlook released today. As you can see in the map above there are no areas in the United States with forecasts for above normal wildfire activity in April.

That is expected to change in May with enhanced potential in southeast Arizona and south Florida. Then in June portions of northeast California and the southern areas of Nevada and Utah will be added to the list. In July firefighters could be busy in Washington, Oregon, and northern California.

The outlook comes from the Predictive Services section at NIFC and represents the cumulative forecasts of the ten Geographic Area Predictive Services Units and the National Predictive Services Unit.

The temperature outlook from the National Weather Service for April through June predicts higher than average temperatures in the west, southwest, southeast, and east. Precipitation for the period should be normal, except drier in the northwest and more rain than normal in the east one-third of the country.

Below:

  • An excerpt from the NIFC narrative report for the next several months;
  • More of NIFC’s monthly graphical outlooks;
  • NOAA’s three-month temperature and precipitation forecasts;
  • Drought Monitor;
  • Keetch-Byram Drought Index.

“Mountain snowpack remained near to above average on the Continental Divide, along the Canadian Border, and across the Alaskan Interior. It was below average to well below average across the High Sierra, Southern Cascades, Great Basin, Sawtooth Mountains, Kenai Peninsula, and the Chugach Mountains. Snowpack melting rates will need to be monitored closely in these areas. Drought development and slight intensification was observed across California, Oregon, portions of the Great Basin, South Texas and Florida.

“Wildfire activity in April should continue to be light and focused in four areas. South Florida has been extremely dry. Fuels are receptive. Pregreenup activity may occur during warm and breezy periods along the Rocky Mountain Front as fronts pass. New Mexico begins to enter its season late in the month. In Alaska, hold over activity from the previous season can reemerge as the snowpack melts off. The potential for each in April 2020 is not expected exceed what is observed typically, except possibly in Florida.

“May is a transitional period. Fuels in southwestern areas dry, and fuels across northwestern areas enter peak greenup. The Southwest, California and Alaska begin to more fully enter fire season while other regions remain out of season. A normal transition into the Western fire season is expected. Areas of concern will be the middle elevations across much of California. In June and July, the West and Alaska enter their peak seasons. Activity across Oregon and Central through Northern California may be above normal. While overall Normal significant large fire potential is expected across most of the Southwest, some portions of the Great Basin and western portions of the Northern Rockies may experience elevated potential and activity as well. The Southwest and Alaska should transition out of fire season in July.”

Wildfire potential weather May Wildfire potential weather June Wildfire potential weather April

Temperature and precipitation outlook
Temperature and precipitation outlook for June through August, 2020.
Drought Monitor
Drought Monitor

KBDI

Scientists say climate change increased risk of extreme bushfires in Australia

The researchers found the climate models consistently underestimated the observed increase in temperatures in southeast Australia

bushfire in Victoria Australia
Photo of a fire in Victoria, Australia, by Forest Fire Management Victoria Forest Fire Operations Officer Dion Hooper. It was taken in January, 2020 on Wombargo Track looking towards Cobberas (north of Buchan in East Gippsland).

A group of scientists published a study that shows global warming led to warm and dry weather that created conditions favorable to large bushfires in Australia.

From the BBC:


…Global warming boosted the risk of the hot, dry weather that’s likely to cause bushfires by at least 30%, they say.

But the study suggests the figure is likely to be much greater. It says that if global temperatures rise by 2C, as seems likely, such conditions would occur at least four times more often. The analysis has been carried out by the World Weather Attribution consortium.

Co-author Geert Jan van Oldenborgh of the Royal Netherlands Meteorological Institute in De Bilt, The Netherlands, told the BBC even the study’s very conservative estimates were troubling.

“Last year the fire prevention system in Australia, which is extremely well prepared for bushfires, was straining. It was at the limits of what it could handle, with volunteers working for weeks on end,” said Prof van Oldenborgh.

“As the world warms, these events will become more likely and more common. And it’s not something that we are ready for.”

During the 2019-2020 fire season in Australia, record-breaking temperatures and months of severe drought fueled a series of massive bushfires across the country. At least 33 people were killed and more than 11 million hectares (110,000 sq km or 27.2 million acres) of bush, forest and parks across Australia burned.

Although it makes sense that human-induced global warming is likely to have led to more bushfires, assigning a figure to that increased risk is complex. That is because other factors not directly related to climate change may also play a significant role. These include increased water use making the land drier, urban heating effects or unknown local factors.

Nevertheless, Prof Jan van Oldenborgh and 17 fellow climate scientists from six countries gave it their best shot. “It was by far the most complex study we have undertaken,” he told the BBC.

The researchers found the climate models consistently underestimated the observed increase in temperatures in southeast Australia and so could not pinpoint a figure for the increased risk from climate change. They were, however, able to tease out a minimum risk.

“We show that climate change definitely increases the risk of the extreme weather that makes the catastrophic bush fires (that south-east Australia has experienced) in the past few months more likely by at least 30%.

“But we think it could be much more. We don’t know how much more. It could be a lot more.”

Prof van Oldenborgh is among those attempting to find out if the current climate computer models really are underestimating the influence of global warming – and if they are, working out how to correct them.

Above average wildfire potential predicted for coastal areas of Central and Southern California

NIFC’s prediction for March and April

March wildfire outlook

The Predictive Services section at the National Interagency Fire Center has issued their Wildland Fire Potential Outlook for March through June. The data represents the cumulative forecasts of the ten Geographic Area Predictive Services Units and the National Predictive Services Unit.

If NIFC’s analysis is correct the only area with above average potential for wildfires during March and April will be the coastal areas of Central and Southern California.

Below:

  • An excerpt from the NIFC narrative report for the next several months;
  • More of NIFC’s monthly graphical outlooks;
  • NOAA’s three-month temperature and precipitation forecasts;
  • Drought Monitor;
  • Keetch-Byram Drought Index.

Entering March and continuing through April, the prolonged periods of dry conditions across Southern California may lead to periods of elevated fire potential during days experiencing offshore winds. However, a muted greenup should initially limit activity. Normal to Below Normal significant large fire potential is expected along the Rocky Mountain Front during the pre-greenup period due to sufficiently wet or snowy conditions experienced during late winter.

Both the Southwest and Alaska will gradually transition into fire season in May with both regions peaking in activity by late June. Overall Normal significant large fire potential is expected during the period except possibly across northern and western portions of Arizona and across portions of South Central Alaska including the Kenai Peninsula where conditions were drier than average over the past winter.

[…]

[In Southern California] well below average rainfall and above average temperatures are expected to continue through April. Due to the lack of significant rainfall, fine fuels are curing rapidly across the lower elevations and will be completely cured by the middle or end of March. There will be an above average potential for large fires across the lower elevations of the Central Coast and Southern California due to the early curing of fine fuels. A near average amount of offshore wind events will most likely continue to occur through April. These winds will fan any new ignitions and rapid rates of spread and long range spotting will be likely in continuous dead fuel beds. The potential for large fire development will become Normal across all of Central and Southern California May and June as the interior warms up and the offshore wind season comes to an end.

April wildfire outlook May wildfire outlook June wildfire outlook

90-day Precipitation Temperature forecast
90-day Precipitation & Temperature forecasts for March, April, & May, 2020.
Drought Monitor
Drought Monitor

KBDI

February brought record low precipitation in parts of California

February Precipitation record low California map

From Daniel Swain of @WeatherWest:

“Well, it’s official: most of California just experienced driest February on record. Locations like Ukiah, Sacramento, Redding, & San Francisco recorded no rain *at all* during a month at peak of the rainy season. Wildfire concerns are elevated this week.”

Rain stops some of the bushfires in Australia

A number of locations have received 100 mm (almost four inches) of precipitation

Precip Observed
Observed precipitation observed during the seven-day period ending February 7. The darkest green color indicates 100 mm (almost 4 inches) of precipitation.

Many areas in New South Wales, Victoria, and Queensland have received multiple inches of rain over the last seven days with a number of locations recording about 100 mm (almost four inches).

A heavy rain could come close to putting out some fires but a light rain, depending on the fuel (vegetation), might just pause the spread for a while. And some regions have received little or no rain.

NSW Rural Fire Service commissioner Shane Fitzsimmons says the rain is “breaking the back” of the bushfire season. “The rain is good for business and farms as well as being really good for quenching some of these fires we’ve been dealing with for many, many months,” the commissioner told ABC TV on Friday.

The forecast for Sydney, on the NSW coast, calls for nearly 100 percent chance of precipitation every day over the next eight days.

Precipitation forecast for Sydney, Australia
Precipitation forecast for Sydney, Australia. Generated Saturday February 8 local time.