![]() This is a numerical rating of the moisture content of surface litter and other cured fine fuels. The moisture codes reflect the nett effects of daily moisture gains and losses. The FWI System evaluates fuel moisture content and relative fire behaviour using past and present weather effects on ground level fuels. Ratings rise as fire weather becomes more severe. Low ratings indicate high moisture content, and ratings rise as moisture content decreases. The scales start at zero, and except for the Fine Fuel Moisture Code which has a maximum of 99, all are open-ended. Each code and index is a numerical rating related to likely fire behaviour. To interpret the system the three fuel moisture codes and the three behaviour indices need to be understood. The fire weather index calculation structure. ![]() The Fire Weather Index has six components: * Wind speed (at 10 metres above ground level for an average over 10 minutes) The FWI is based on weather readings taken at noon standard time and rates fire danger at the mid afternoon peak from 2:00 – 4:00 pm. The FWI was evaluated for several seasons before it was introduced for the 1980-81 fire season. It has proved to be a suitable fire danger rating system for this country. The Fire Weather Index (FWI) System is the first part of the Canadian Forest Fire Danger Rating System (CFFDRS) introduced into New Zealand in 1980. The Chandler Burning Index (CBI), Angstrom Index and Fire Moisture Index (FMI) are other Fire Rating Systems developed in North America and Scandinavia. * make decisions to close areas at high risk * determine fire suppression response and resources * assess the likelihood of fire occurring * determine appropriate fire prevention measures A fire danger rating system measures the variable elements which cause day to day changes in fire risk, and interprets the information gained. A fire danger rating system should supply an objective answer to the question: 'What is the probability of a fire starting, spreading and doing damage today?' It enables fire managers to properly assess the levels of preparedness and the suppression resources needed to keep fire losses to a minimum.
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