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Fire Danger Background

General References

Fire Danger ratings are an effective part of daily risk rating and operational preparedness for fire management agencies across the world.  Chapter 10 (Preparedness) of the Interagency Standards for Fire and Fire Aviation Operations outlines processes and resources applied in the development of standard Fire Danger Operating Plans in the United States.

Included in Fire Danger Operating Plans are:

  • Specification of fire danger ratings
  • Identification of climatological thresholds for administrative purposes. Default thresholds include the 90th and 97th percentile values for key indices in the applied system. The Bureau of Land Management (Department of Interior) uses the 80th and 95th percentiles instead.
  • Communication of those danger ratings, including both internal and external forms.

Some valuable links:

A variety of fire weather systems are applied in danger rating around the US. There are primarily two systems used in fire danger operating plans.

US National Fire Danger Rating System (NFDRS):

First introduced in 1964, NFDRS has been updated in 1972, 1978, 1988, and now 2016 to integrate newer science and improved processing. This guide will compare important aspects of the 1978, 1988, and 2016 versions, detail important outputs, and describe primary components and indices. More information about the system and the latest update to it can be found at:

https://www.wfas.net/nfdrs2016/index.php/en/

https://www.nwcg.gov/committees/fire-danger-subcommittee 

CFFDRS Fire Weather Index (FWI) System

Introduced in Canada in 1970. Implemented in Alaska and the lake states of Michigan, Minnesota, and Wisconsin in the early 1990s. Details about CFFDRS are included a separate section of this guide. These websites provide data access

Other tools, formulations, and applications are used locally across the country. Some examples are highlighted later, in section 4.5

78/88 Version NFDRS Structure


2016 Version NFDRS Structure 

NFDRS Version Comparison

Category

78 Version

88 Version

2016 Version

Fuel Models and Settings

20 NFDRS specific fuel models

Grass identified as annual or perennial

Shrub type not detailed

Specific revisions to 3 of the 78 Version fuel models (C, E, and N)

Grass identified as annual or perennial

Shrubs identified as evergreen or deciduous

Reduction to 5 new 2016 Version NFDRS specific fuel models

(V, W, X, Y, Z)

Grass identified as annual or perennial

Shrub type not detailed

Climate  Class

Used to determine dormant 100h, 1000h, and live fuel moistures

Used to specify duration of greenup process and influence curing rates

Used to determine dormant 100h, 1000h, and live fuel moistures

Station Catalog identifies location as “Humid” with on/off toggle.  Influences Max SC & Moisture of Extinction

Manual Inputs

Observation type

Snow Flag

Wet Fuel Flag

Greenup/Freeze Flag

State of the Weather

Observation type

Snow Flag

Wet Fuel Flag

Season

1h = 10h?

Daily Herb & Woody Greenness Factor

State of the Weather

Snow Flag

1h & 10h

Fosberg-71 Model

Fosberg-71 Model

Nelson Model

100h & 1000h

Fosberg-71 Model

Fosberg-81 Model

Nelson Model

Herbaceous and Woody Fuel Moisture Content

Herb fuels classified as dead when dormant.

Transition from dormant/dead fuel moisture to live/full greenup based on climate class in spring

1000hr based live moisture trend and load transfer

Herb fuels classified as dead when dormant.

Season/Greenness factor based live fuel moisture trend/load transfer unless fuels declared dormant.

Herb fuels classed as dead when dormant.

Growing Season/Live Fuel Index based moisture trend and load transfer

Drought Fuel Load Transfer


KBDI used to signal initiation and amount of fuel load transfer KBDI used to signal initiation and amount of fuel load transfer

SC, IC, ERC, BI

Models unchanged.  Outputs will vary based on differences from new fuel moisture models and new fuel model definitions.