The Modification of the Daily Fire Danger Categorization Basis (DFDR) for Guam

Guam is a tropical-climate based island in the northwest Pacific Ocean with latitude and longitude at 13.4° N and 144.8° E. Guam fire services receive the Daily Fire Danger Rating (DFDR) from the National Weather Service (NWS) Weather Forecast Office (WFO) in Tiyan based on the Keetch-Byram Drought Index (KBDI) to determine if an area has an increased potential for fires to start. The Keetch-Byram Drought Index is a mathematical formula based on the prior days’ maximum temperature and 24 hour rainfall total. The KBDI is frequently (or often) used in fire danger assessment across the US, but the KBDI is less effective in tropical areas than in mid latitude areas. Guam, and its neighboring low-latitude islands across Micronesia experience heavy amounts of annual rainfall, but often experience short-term droughts in the dry season (ranging from December-June). The extent and severity of these droughts are heavily influenced by the El Nino Southern Oscillation (ENSO). This investigation searches for a revision of the Daily Fire Danger Categorization Basis (DFDR) for the tropics, specifically Guam, using weather data collected from July 1996 to July 2019. The current DFDR has four categories: Low, Moderate, High and Extreme. The revised DFDR would have five categories: Low, Moderate, High with low winds, Extreme with high winds, and Extreme (solely based on high KBDI values). The revision includes a wind component because the intensity of the wind directly affects the potential for fires to spread rapidly, and increases the difficulty of containment by conventional fire suppression tactics. Ultimately, the investigation supports that a new, revised, version of the DFDR for Guam is possible. However, further investigation is needed to determine if the revised DFDR can be used elsewhere in the tropics and other Pacific Islands.