• The odds show a slight tilt towards below normal temperatures and a slight to moderate tilt towards above normal precipitation for the January – April 2024 period.
• The odds tilt towards above normal dead fuel moisture to occur for the majority of the forecast period.
• The odds tilt strongly towards El Niño conditions to persist for the entirety of the forecast period.
Weather Discussion
December 2023 was overall a warmer and drier month for much of Southern California (Figures 1 and 2). Most areas were between 2-6 F above normal with respect to temperature. For precipitation, there is a much larger variance across Southern California due to recent wetting rains across coastal areas that did not produce as much precipitation farther in land. The driest anomalies were areas along the southern South Coast (Orange and San Diego Counties), the lower and eastern deserts as well as the high desert and areas east of the Sierra Crest. The wettest anomalies were along the northern South Coast (Los Angeles County northward), Western Mountains and along the Central Coast as these areas received several inches of rain on December 21st and 22nd. The current state of the El Niño Southern Oscillation (ENSO) shows the early stages of a shift between a traditional East Pacific El Niño to a Central Pacific El Niño Modoki. This means the core of the warmest sea surface temperature anomalies in the equatorial Pacific is shifting westward from the east Pacific off the coast of South America into the central Pacific. There has been a consistent cooling trend over the past month of Niño 1+2 region (Figure 4) while at the same time, a warming trend across both Niño 3.4region (Figure 3) and Niño 4 region. For reference, Niño 1+2 region is the eastern most region in the equatorial Pacific right off the South American coast while Niño 3.4 region is located in the central equatorial Pacific and Niño 4 region in the western equatorial Pacific.
Fuels Discussion
Latest U.S. Drought Monitor indicates zero areas in drought status across Southern California (Figure 5). Moreover, live fuel moistures remain above normal with a large load of live fuel present (Figure 6). Larger dead fuels also have above normal moisture content in addition to the live fuel from recent wetting rains across Southern California (Figure 7).
The 6 Predictive Services Areas (PSAs) that show near-normal or below normal dead fuel moisture have a very small load of 1000-hr dead fuel (Figure 7). Live fuel makes up the overwhelming majority of the fuel load in those PSAs.
There is a strong tilt in the odds that live fuel moisture continues to remain above normal for the January – April period and a slight to moderate tilt in the odds towards dead fuel moisture remaining above normal for most of the forecast period as well
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SOUTH OPS OUTLOOK
Current sea surface temperature analysis combined with climate models suggest the westward movement of the core of the warmest water from the eastern Pacific towards the central Pacific (Figure 8). However, El Niño conditions are highly likely to continue during this period with some modest weakening towards the end of the forecast period as the current projections suggest a transition into a neutral ENSO state by the later spring months. This pattern suggests a slight tilt in the odds towards cooler than normal temperatures across Southern California and a slight to moderate tilt in the odds towards above normal precipitation (Figure 9). Therefore, as mentioned in the fuels discussion, there is a high probability the live fuel moisture remains above normal since the live fuel moisture has remained anonymously high for several months and a slight to moderate tilt in the odds in favor of the dead fuel moisture remaining above normal for the majority of the January – April period.
In conclusion, the odds tilt in favor of large-fire potential to remain near normal for all 16 PSAs with the climatological normal for large fires being zero across all 16 PSAs for this time of the year. The combination of above normal fuel moisture for larger dead fuels and live fuels coupled with the El Niño pattern and absence of drought support this tilt in the odds for the January – April 2024 4-month period.
Source: Predictive Services
