• wildfire;
  • extreme events;
  • decadal variability;
  • Pacific Decadal Oscillation;
  • El Niño-Southern Oscillation;
  • fire weather


Low-frequency changes (decades to years) in precipitation related to the El Niño-Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO) are known to influence wildfire variability across the southwest United States. Little work has been done to identify whether daily fire weather variability, also important to wildfire activity, is influenced by these same climatic phenomena. This study identifies the synoptic climatological conditions associated with extreme fire weather events in the Southwest and constructs an extreme fire weather frequency data set for the period of 1958–2003 using a logistic regression technique. Interannual changes in extreme fire weather day frequencies are not linearly correlated with either ENSO or PDO, but do show significant deviations from expected values when grouped by PDO phase (positive or negative) and further subgrouped by ENSO state (La Niña, El Niño or neutral). A higher number of extreme fire weather days occur during the negative phase of the PDO, especially when accompanied by a La Niña event. Copyright © 2010 Royal Meteorological Society