Fire Weather Index (FWI) Calculator

The Fire Weather Index (FWI) is a numerical rating that indicates the likelihood of wildfire ignition and spread based on weather conditions. It is widely used in wildfire management to assess fire danger levels.

Historical Background

The Fire Weather Index is part of the Canadian Forest Fire Weather Index (CFFWI) System, developed in the 1970s. It is now used globally to monitor fire risks and inform decision-making in wildfire-prone areas. The index is influenced by factors like temperature, humidity, wind speed, and precipitation.

Calculation Formula

The Fire Weather Index (FWI) is derived from multiple components. A simplified calculation is:

\[ FWI = 0.5 \times \text{Temperature (°C)} + 0.1 \times \text{Humidity (%) } + 0.3 \times \text{Wind Speed (km/h)} - 0.2 \times \text{Rainfall (mm)} \]

This formula gives a rough approximation, with more complex models incorporating fuel moisture, drought codes, and other advanced parameters in professional use.

Example Calculation

For example, if the temperature is 30°C, humidity is 40%, wind speed is 20 km/h, and rainfall is 5 mm, the calculation would be:

\[ FWI = 0.5 \times 30 + 0.1 \times 40 + 0.3 \times 20 - 0.2 \times 5 = 15 + 4 + 6 - 1 = 24 \]

Importance and Usage Scenarios

The Fire Weather Index is critical for predicting wildfire risk. It helps fire agencies, foresters, and governments take preventive measures, allocate resources, and inform the public about fire dangers. It’s particularly useful during fire seasons in areas like Australia, Canada, the Mediterranean, and the western United States.

Common FAQs

1. What factors affect the Fire Weather Index?

   • Key factors include temperature, humidity, wind speed, and rainfall. High temperatures, low humidity, and strong winds typically increase the index.

2. How often should FWI be calculated?

   • It is typically calculated daily or multiple times per day in fire-prone regions, especially during the fire season.

3. What is considered a high Fire Weather Index?

   • An FWI value above 20 is considered moderate to high, and above 30 indicates severe fire danger.

This Fire Weather Index calculator offers a practical tool for approximating fire risk, helping communities stay prepared and manage wildfire threats effectively.