pnw long-term outlook for fire season 2015 - frames...1 pnw long-term outlook for fire season 2015...

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PNW Long-term Outlook for Fire Season 2015

Date: August 26

Analysts: Rick Stratton ([email protected]) and Josh Chapman ([email protected])

Background & Purpose

It has been a long and challenging season. It started early with fires throughout the Pacific Northwest—Coos Bay BLM, border fires with Canada and the Colville and Okanogan-Wenatchee NFs, the Mt. Hood NF, and a little later with the Columbia-River Gorge Scenic Area, the Deschutes NF, and Rouge-River Siskiyou NF. It was symptomatic of the fuel moistures and the weather (dismal snowpack and dry spring). We now have several large fires in SW, central, and eastern Oregon and Central and NE Washington. The purpose of this outlook is to provide information about the potential duration of the fire season, by predictive service area (PSA), short-, mid-, and long-term.

Predictive Service Areas in PNW

PSAs are sub-geographic areas of similar climate, fuels, and topography defined by Geographic Area Coordination Center (GACC) Meteorologists for forecasting purposes. They are similar in definition to Fire Danger Rating Areas (FDRA), but generally encompass a larger area. Ideally, a PSA would be a conglomerate of one or more FDRAs. In PNW, there are 12 PSAs; note the large fires in each area.

mailto:[email protected]

mailto:[email protected]

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Fire Danger: Current vs. Historical (ERC & 1000-hr)

Energy Release Component (ERC) is a measure of heat release at the flaming front. It is a good indicator of intermediate and long-term drying. Below are ERC charts for the PSAs with ongoing large fires. Note that the ERC is above the 90th percentile, near or at all-time highs (max), and at levels where large fires have occurred.

Thousand-hour fuels are those larger than 3” in diameter. It is a good metric as to the moisture content in large, dead woody debris. Note how low 1000-hr fuel moistures are and how early they dipped below the large fire threshold. Graphics are courtesy of Northwest Coordination Center (NWCC) and local dispatch centers.

NW08 (Lower Chelan Complex; Twisp; Lime; Funk)

NW05/08 (Wolverine)

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NW09 (Kettle, Colville, and Kaniksu Complex)

4

NW05 (Cougar)

5

NW11 (Grizzly Bear Complex [FDRA 6] and Eagle [5/6]; Canyon Creek Complex [4/5])

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Short-term Weather Outlook (Next 7 days)

Terry Marsha is a fire weather meteorologist at NWCC and issued the following statement about the fire potential in the coming days (Aug. 26).

Below is the 7-day significant fire potential product from Predictive Services.

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Mid-term Weather Outlook (1 month)

The National Weather Service Climate Prediction Center forecasted temperatures to be above average and equal chances for precipitation (i.e., no clear signal either way).

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Long-term Weather Outlook (3 Month)

The 3-month forecast is for a dry fall with above normal temperature and below normal precipitation. With a strong El Niňo currently in the Pacific Ocean, it is possible that northern Oregon and Washington will have a warm and dry winter.

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Probability of Large Fires, Fire-slowing, and Season-ending Events

Below are column charts for each PSA based on the probability of getting another large fire, a fire-slowing event, or a season-ending event. Large fire occurrence data was obtained from T. Marsha for an 8-year period. A large fire differs in size based on the PSA, so think of this as the probability of a fire requiring a type 1 or 2 team.

Season-slowing information was obtained through a query of the PSA Special Interest Groups (SIG)—a group of remote automated weather stations (RAWS). A ¼” of rain was selected as a fire-slowing event, as several forecast areas use this criteria as a “wetting rain.” Fires that receive approximately a ¼” of precipitation are likely to see fire movement pause for 3 to 5 days.

A season-ending event consists of a fire-slowing event followed by a persistent combination of environmental factors that end the fire season. NWCC develops waiting-time distribution functions—or TERM events—for each PSA by using a SIG. Season-ending estimates were constructed from the Predictive Services 7-day significant fire potential product from 1994 to 2012. The product determines the probability of a significant fire occurring based on historical dryness and fire occurrence. The analysis results assume end of season when three or more consecutive “green” days occur (1% probability of a significant fire event). For more information, go to the NWCC website (http://gacc.nifc.gov/nwcc/predict/fban-ltan.aspx). The season-ending charts are also available on the PNW Long-term Analysis Library (http://maple.ordvac.com/event/map/).

http://maple.ordvac.com/event/map/

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16% 17%22% 23% 22%

57%

86%89% 89%

100%

50%

75%

90%

99% 99%

0.0%

10.0%

20.0%

30.0%

40.0%

50.0%

60.0%

70.0%

80.0%

90.0%

100.0%

Aug 15-31 Sep 1-14 Sep 15-30 Oct 1-14 Oct 15-31

Prob

abili

ty

Analysis Period

NW01

Probability of a fire-slowing event (≥0.25" rain)Probability of no large firesProbability of season-ending event

11% 12%19%

26%33%

39%

70%

95%100% 100%

50%

90%

99%

0.0%

10.0%

20.0%

30.0%

40.0%

50.0%

60.0%

70.0%

80.0%

90.0%

100.0%


Prob

abili

ty

Analysis Period

NW02

Probability of a fire-slowing event (≥0.25" rain)Probability of no large firesProbability of Season Ending Event

12

11% 11%

20%26%

32%

42%

69%

84%89%

100%

25%

50%

75%

99%

0.0%

10.0%

20.0%

30.0%

40.0%

50.0%

60.0%

70.0%

80.0%

90.0%

100.0%


Prob

abili

ty

Analysis Period

NW03


13% 11%

22% 22%

32%33%

62%

84%

100% 100%

25%

50%

90%

99%

0.0%

10.0%

20.0%

30.0%

40.0%

50.0%

60.0%

70.0%

80.0%

90.0%

100.0%


Prob

abili

ty

Analysis Period

NW04


13

8%15% 16%

21%

40%

67%

86%

94%100% 100%

25%

75%

99%

0.0%

10.0%

20.0%

30.0%

40.0%

50.0%

60.0%

70.0%

80.0%

90.0%

100.0%


Prob

abili

ty

Analysis Period

NW05


13%8%

15%21%

42%

60%

89%92%

100% 100%

50%

90%

99%

0.0%

10.0%

20.0%

30.0%

40.0%

50.0%

60.0%

70.0%

80.0%

90.0%

100.0%


Prob

abili

ty

Analysis Period

NW06


14

15%10%

21%14%

40%

75% 78%

89%

100% 100%

25%

90%

99%

0.0%

10.0%

20.0%

30.0%

40.0%

50.0%

60.0%

70.0%

80.0%

90.0%

100.0%


Prob

abili

ty

Analysis Period

NW07


25%

11% 14% 17%

34%

72%

95%100% 100% 100%

25%

50%

90%

99%

0.0%

10.0%

20.0%

30.0%

40.0%

50.0%

60.0%

70.0%

80.0%

90.0%

100.0%


Prob

abili

ty

Analysis Period

NW08


15

15% 17%22%

16%

29%

43%47%

57%

82%

100%

25%

75%

90%

99%

0.0%

10.0%

20.0%

30.0%

40.0%

50.0%

60.0%

70.0%

80.0%

90.0%

100.0%


Prob

abili

ty

Analysis Period

NW09


15% 13% 15%21%

36%

64%

89%

99% 100% 100%

50%

75%

99%

0.0%

10.0%

20.0%

30.0%

40.0%

50.0%

60.0%

70.0%

80.0%

90.0%

100.0%


Prob

abili

ty

Analysis Period

NW10


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16% 13%

21% 21%

30%

67%

84%

99% 100% 100%

25%

50%

90%

99%

0.0%

10.0%

20.0%

30.0%

40.0%

50.0%

60.0%

70.0%

80.0%

90.0%

100.0%


Prob

abili

ty

Analysis Period

NW11


13%9%

23% 23%

32%

94%100% 100% 100% 100%

25%

90%

99%

0.0%

10.0%

20.0%

30.0%

40.0%

50.0%

60.0%

70.0%

80.0%

90.0%

100.0%


Prob

abili

ty

Analysis Period

NW12


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Below is the PSAs colored by season-end date. The top is the 50% probability of a season-ending event by the given date. The bottom is the 75% probability.

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Discussion and Implications

• This weekend a significant amount of rain is forecasted west of the Cascades, particularly in Washington. It is not likely that the precipitation will be as widespread or heavy in eastern Oregon. Once the storms pass, we will have a better feel for which fires will still have the potential to impact areas of concern. Those fires that meet that criteria will be candidates for additional long-term analysis.

• Frontal passages are often associated with strong outflow winds. It is possible that we may see rapid rates of spread followed by moisture terminating the sudden run. In areas of little or no rain, these winds are of particular concern (e.g., Canyon Creek).

• There is over a thousand miles of active fire line in moderate to heavy fuels. We are likely going to live with fire on the landscape for several more weeks. Less moisture over a longer duration has more of an impact on halting fire spread than a larger amount of precipitation at one time. This is particularly true this year given the very dry live and dead fuels.

• If the predictions hold for a drier fall and winter, it is likely a few of these fires will smolder into the winter months and possibly into spring. This has been the case the past couple years in areas with large fires in heavy fuels.

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