Inversion traps smoke over prescribed fire

Sequoia Kings Canyon National Park

Smoke is trapped by an inversion in Sequoia Kings Canyon National Park. NPS helitack photo.

In this photo taken Wednesday, smoke is attempting to break through an inversion over the Mosquito prescribed fire in Sequoia Kings Canyon National Park in California.

Normally, as you rise in altitude, the temperature decreases due to the changes in air pressure. In a weather (or temperature) inversion, instead of getting cooler at higher temperatures, it is actually warmer higher up.

weather inversion

Cool air trapped under a warmer layer, creating an inversion. From Fortair.org.

Share

Monitor near-real time Red Flag weather conditions in LA area

Observations from weather stations in the Los Angeles area

Observations from weather stations in the Los Angeles area that “flirt with” or meet Red Flag criteria. (Click to enlarge.)

The National Weather service has developed an excellent site for monitoring the near-real time weather conditions in the Los Angeles area, and how those observations from weather stations “flirt with” or meet the criteria for Red Flag conditions. It is a very useful site, refreshing automatically every five minutes. It includes the following parameters: RH, wind speed, gusts, duration for meeting the Red Flag criteria, fuel moisture, temperature, and elevation.

When you visit the site, hovering your mouse pointer over a station brings up the last 12 observations at that station.

Other areas in the country should develop similar sites. If you are aware of more, let us know in the comments below.

Share

Wildfire potential, October through January

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

If their predictions are accurate, California will be the only area with above normal wildfire activity.

Here are the highlights from their outlook.

October

September wildfire outlook

  • Above normal fire potential continues across some portions of northern, central and southern California. Long term drought coupled with increasing potential for offshore winds will keep potential elevated through October.
  • Below normal fire potential is expected for central Texas as well as the southern Atlantic Coast.
  • Elsewhere normal fire potential is expected as many areas transition to out of season conditions for the winter.

November

November wildfire outlook

  • Above normal fire potential will be alleviated in the north, leaving central and southern California as the only areas with continuing threats from dry fuels coupled with offshore flow.
  • Below normal fire potential will expand to include an area stretching from Texas to the Atlantic Coast.
  • Most other areas are out of season during November.

December and January

December January  wildfire outlook

  • The last remaining areas of above normal potential in California will transition to normal during December, leaving only normal to below normal conditions.
  • Below normal fire potential will continue from Texas to the Atlantic Coast.
  • Most other areas are out of season December through January.
Share

U.S. Forest Service launches new tool for fire preparedness

Santa Ana header

RIVERSIDE, September 17, 2014 — The USDA Forest Service, in collaboration with San Diego Gas & Electric (SDG&E) and UCLA, today unveiled a new web-based tool to classify the fire threat potential of a weather phenomenon unique to Southern California — the powerful, hot, dry Santa Ana winds that can turn a spark into an inferno.

The Santa Ana Wildfire Threat Index, which includes four classification levels from “Marginal” to “Extreme,” will be used to help fire agencies, other first-responders and the public determine the appropriate actions to take based on the likelihood of a catastrophic wildfire fueled by high winds.

“Given the current state of fuel conditions, we have the potential to see devastating fires this fall should significant Santa Ana winds occur,” said Forest Service Meteorologist Tom Rolinski. “This tool will directly benefit fire agencies by allowing us to better anticipate what kinds of resources may be needed, as well as where and when we could face the greatest challenges.”

Since the 2007 wildfires in San Diego County, SDG&E has been a partner in enhancing local fire preparedness and has taken major steps to strengthen its overhead electrical system – changing out wooden power poles for steel – to make the grid more wind- and fire-resistant. The utility also hired in-house meteorologists and installed 150 weather stations across its service area to gather real-time information about the impact of weather on utility equipment – all to improve situational awareness during emergencies.

SDG&E’s Dave Geier, vice president of electric transmission and system engineering, considered other ways to leverage this significant amount of weather data and to share it broadly.

“I asked my team to come up with something similar to the categories to rate hurricanes that could be used to classify Santa Ana wind events based on their potential to spread a major fire, which would help us in making operational decisions to protect our system and our customers,” said Geier. “The goal was to develop a uniform and recognizable system that also could be used to alert fire agencies and communities in time to prepare and take appropriate action.”

As luck would have it, Rolinski already had been working on a similar concept and was eager to share ideas and information. Initially, SDG&E’s meteorologists compiled hourly weather data for the last 30 years in Southern California — information that was used as a basis for the models that eventually led to the four-level wildfire threat index. The utility reached out to regional fire agencies, including the Forest Service and CAL FIRE, along with universities in Southern California, to partner in the development of the index. SDG&E also provided funding for state-of-the-art computing hardware and software to help turn the raw data into a manageable tool.

The actual “number crunching” was done by a team from UCLA, led by Dr. Robert Fovell, Ph.D., chair of the university’s Department of Atmospheric and Oceanic Sciences, who applauded SDG&E’s weather network for “its unprecedented station density and uniformity.”

“We not only have a new, deeper understanding of how the San Diego-area terrain influences weather, especially wind, which is crucial to SDG&E’s operations, but we also have been able to make improvements in weather modeling that will benefit forecasters worldwide,” said Dr. Fovell.

The threat index includes four levels of increasingly severe fire potential:

Santa Ana legend

The National Weather Service (NWS) is the agency that issues a Red Flag Warning when weather conditions indicate the development of a strong Santa Ana. Forecasters look at fuel moisture, humidity levels, temperature and topography, as well as wind speed, to determine whether to declare a Red Flag Warning, which typically means high fire danger with increased probability of a quickly spreading vegetation fire in the area within 24 hours.

“This index will help forecasters to quantify a Red Flag Warning and the public to better understand the risk,” said Roger Pierce, director of the NWS in San Diego. “We believe this new tool will support and complement our forecasts and provide even more information to help the public to be better prepared.”

The Santa Ana Wildfire Threat Index is intended to be used by fire agencies, emergency responders, the media and the public. The Forest Service “owns” the tool and is the agency responsible for determining and issuing the alerts, which can be found on the agency’s website at: www.santaanawildfirethreat.com

“Each of the levels includes recommended ‘calls to action’ that escalate as the chance of a catastrophic fire becomes more likely,” said Rolinski.

Recommended actions for the public include closely monitoring fire conditions, making sure cell phones are charged and vehicle gas tanks are full, as well as reviewing emergency evacuation plans at work and at home and registering phones to receive reverse-911 warnings for the latest information about an emergency.

Share