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

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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.

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Rising temperature trend in California, January through August

California, average temperature, January through August

California, average temperature, January through August

The NOAA data above showing the trend in temperature in California during the first eight months of the year, is impressive. The average temperature this year shattered the record. It illustrates that you should not get excited about the weather on one day, or one season, or even one decade. There is a great deal of variability. The long-term trend has the big picture.

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Fire Weather Outlook September 8 through 13

An upper level trough is crossing the western US Monday. This is enhancing the pressure gradient across central WA/OR this afternoon, generating gusty winds in excess of 35mph. Combined with very dry vegetation and relative humidity between 15-20%, red flag warnings have been posted. Weak cold front will cross the region overnight, weakening winds for Tues with slightly cooler conditions and higher RH. A few pockets of lingering gusty winds will persist for northern CA/southern ID/southern OR and the northern Great Basin on Tues. Southern ID will see the strongest winds with an enhanced fire risk. Farther west, very dry vegetation and RHs < 15%, especially for northern NV/north CA will promote fire growth as well, but winds are expected to be weaker. These conditions will still promote continued suppression difficulties of large wildfires in the region.
A disturbance will round the trough as it moves east, passing over the northwest US on Wed. In response, a strong high pressure is expected to develop on the backside of this disturbance across the northern Rockies. This will once again create strong easterly surface flow for much of the west. As winds flow downslope of the Rockies, warm/dry air will situate itself over the western states with above normal temperatures and dry conditions. Some localized breezy conditions are possible Thurs across WA/OR/ID, however they will dwindle Fri as the high moves east with a weakening pressure gradient. Upper level ridging builds back in across the western US this weekend and above average temperatures with very dry conditions are anticipated to continue into next week.
Heavy monsoonal rains (and moisture from ex-hurricane Norbert) will remain possible through Tues in the desert southwest and eventually diminish mid-week. Some very widely scattered dry thunderstorms possible in south/south-central CA. Drying trend will continue into the weekend before another round of monsoonal moisture pushes into NM/NV/UT/CA by early week. This may also be enhanced by another tropical system by mid-week.
Weather Highlights:
CA: Few isolated storms south Mon/Tues, otherwise continued above normal temperatures and very dry conditions. Isolated breezy winds Tues/Thurs for northern CA.
OR/WA: Red Flag Warning Mon. Breezy winds with critically low RH Mon with improving conditions into Tues. Another period of localized breezy conditions Thurs with a warming trend into the weekend. Expect continued very dry conditions, especially for southern OR.
Great Basin/southern ID: Heavy rain possible for the southern Great Basin through Tues. Enhanced fire weather Tues with gusty winds and low RH for northern Great Basin/ID. Dry and warm through the period.
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Fire weather outlook, September 3 through 8

Yet another upper level trough providing some active fire weather conditions today across northern CA/southern OR and most of WY/western SD. With this trough, a lack of mid-level moisture is preventing any thunderstorm activity across the northwestern US. However, very dry conditions (aggravated by drought in CA/OR) combined with windy conditions are developing critical fire weather conditions in both these regions. A surface cold front associated with the trough will slide southeast across the northern Rockies Wed evening and into Thurs. This front will increase humidity across WY/SD lessening fire danger and shifting winds to the north for Thurs.

The same cold front will push south/west across OR/CA overnight Wed. This front will continue mixing overnight with breezy winds and poor RH recovery-continuing elevated fire danger through Wed night. Through late week and into the early weekend, easterly winds will provide additional downsloping off the Rockies and continue increased fire risk with poor overnight RH recovery through Sun. With an off-shore trough developing late-week and weak ridging over the Rockies, temperatures will increase to 90F+ across much of CA/OR/WA. Very dry conditions and RHs at/below 20% will expand eastward/northward across the region and into the central Rockies through the weekend. Breezy easterly winds will continue through Fri for much of OR/northern CA/NV and gradually diminish overnight Fri. As the off-shore upper level trough approaches the West Coast Sun/Mon, westerly winds will increase for much of the northern CA/OR/WA/ID, which may develop widespread critical fire weather conditions. No precipitation is expected for northern CA/NV and WA/OR/ID through the period.

The other major weather highlight will be soon-to-be Hurricane Norbert near the California Peninsula. Current forecast model trends depict moisture streaming northward into the southwestern US by late weekend. Developing monsoonal conditions across AZ/NM/UT/CO late week will provide chances of scattered thunderstorms. However, much more widespread rains/storms could develop for portions of southern CA/NV and much of AZ/UT/CO with the influence of Norbert. Great uncertainty still exists on the exact track of this system, though confidence is increasing on widespread heavy rains late weekend/early next week.

WPC 5-day OPF

Quantity of precipitation forecast for September 3 through 8, 2014. Rains continue to avoid much of the Pacific Northwest and western US, with some much needed relief for southwest US. Image from the Weather Prediction Center.

Weather Highlights:

WY/western SD/northern CO/NE Panhandle: Critical fire weather Wed with breezy westerly winds, RH’s <20%, and warm conditions. Cold front crossing region tonight increasing RH and winds increasing and turning northerly post-front. Becoming very dry/warm Sun/Mon with increasing fire weather threat.

OR/northern CA/northern NV: Critical fire weather Wed through Thurs with breezy northerly wind, turning easterly Thurs AM. Very warm/dry with poor overnight RH recoveries expected through Sat with continued enhanced fire weather conditions. Additional critical fire weather conditions possible Mon/Tues with breezy westerly winds.

WA/ID/MT: Increasing fire weather threat as temperatures warm into the weekend with breezy westerly winds possible late weekend. Continued dry conditions with no precipitation expected (with exception of northern ID/MT Wed/Thurs).

AZ/UT/NM/southern CO: Monsoonal flow returning Thurs/Fri/Sat with scattered thunderstorms, rain becoming more numerous over the weekend, especially across AZ/UT with flooding possible.

Southern CA/southern NV: Very dry and warm through late week. Increasing showers/storms Sun/Mon with flooding possible.

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Wildfire potential, September through December

The Predictive Services section at the National Interagency Fire Center has issued their Wildland Fire Potential Outlook for September through December, 2014.

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, firefighters could be busy in Washington and Oregon through October, and busy in southern California into December. The fall fire season in the southeast looks like it will be normal or slower than normal.

September

September  wildfire outlook

  • Above normal fire potential will remain across southwestern Oregon through September for lingering dryness and potential dry, east winds.
  • Fire potential will remain elevated across portions of California. Continued dry fuels will couple with potential offshore winds.
  • Below normal fire potential is expected to continue for some portions of the eastern U.S. and the Hawaiian Islands.

October

October  wildfire outlook

  • Above normal fire potential will persist across California as fuels will remain dry and off shore flow season arrives in earnest. Northern and central California will return to normal potential by the end of the month.
  • Below normal fire potential is expected to continue for some portions of the southern Plains, Florida, and Hawaii.

November and December

(Note: there was a technical problem in getting a good copy of the image below.)

November December wildfire outlook

  • Above normal fire potential will persist across southern California as offshore flow potential continues. Expect a return to normal potential from north to south beginning in late November through December.
  • Below normal fire potential is expected to continue for the Gulf and Southeast Coasts, and Hawaii.
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Fire weather outlook, August 29 through September 2

An upper level trough will cross the northwest Pacific states Fri/Sat and eject into the central Plains on Sun. This will bring periodic windy conditions across the western US and cooler weather for the northwest. No critical widespread critical fire weather is expected, although some areas will have enhanced conditions that will aid in fire spread, especially with drought conditions across the west. Continued heat is expected for the southwest with dry conditions prevailing.

The primary fire threat across the US will focus on warm temperatures and low RHs in the western Great Basin Fri and Sat. Breezy westerly winds are expected Fri/Sat especially across much of NV due to the approaching upper level trough. As the trough shifts eastward, wind conditions will move across northern UT and southern WY/northern CO into Sun/Mon. Dry conditions over much of WY/CO will provide an increased fire risk with these strong westerly winds.

The southwestern US will remain dry and hot through the period. Portions of central/eastern CA/NV/AZ will have poor RH recovery overnight. Though no windy conditions are expected across this region, above average temps and below average precipitation will lead to conditions conducive to human caused fire starts and challenges for suppression

A cold front crossing WA/OR will bring breezy conditions Fri, however, temperatures are expected to remain cool and RH is expected to remain above critical levels. A lack of upper level moisture will prevent any thunderstorm development, however some light rains are possible along western slopes. A stable post-frontal air mass will provide quiet conditions for the Pacific Northwest and eastward with the front’s advancement through the weekend. Cooler weather is expected to continue through the period for WA/northern OR/MT/northern ID with warming conditions likely Tues in advance of the next system.

Long term into mid-week, a summer type pattern looks to return for the central US with another trough pushing into the west. This may develop enhanced fire weather conditions across the western US mid-week and central Rockies mid-to-late week and should be monitored.

Five-day precipitation outlook

Five-day precipitation outlook, issued August 29, 2014.

Weather Highlights:

Eastern CA/NV: Breezy westerly winds Fri/Sat with low RH and warm temperatures. Locally critical fire weather is possible, otherwise generally enhanced fire weather is expected across the region. Winds will be decreasing Sun.

WA/OR: Breezy conditions are likely today across central portions of OR/WA on the eastern sides of the Cascades. Moderate temperatures and RH should prevent any increased fire risks. Warming with decreasing RH across southern OR late weekend and moving northward into next week.

Southern WY/northern CO/northern UT/southern ID: Developing strong westerly winds Sun/Mon. Combined with warm and dry conditions, this will lead to an enhanced fire threat continuing into mid-week.

Southern/central CA/AZ: Continued warm and dry with poor RH recovery. Some breezy winds Fri in eastern CA, otherwise no significant winds/thunderstorms.

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