The last couple weeks have brought rain to the majority of California, but unfortunately, most of the state remains in a rainfall deficit. With the exception of the San Diego area, which is above normal, the rest of the state gets progressively drier as you move north.
Reservoirs are Full but Northern California is Still in a Deficit
The state’s largest reservoirs are located across Northern California and the Sierra Nevada Mountain range. These reservoirs are currently at or above historical averages for this time of the year, but the snow pack that feeds these stockpiles are measuring just over half of their normal levels for the season. Across the rest of the state the story is similar. San Francisco, for example, has only received about 50% of the normal rainfall for the year. April precipitation is not expected to alleviate this deficit, with most forecasts predicting a dryer than normal month. This does not bode well for some of the dryer portions of the state trying to catch up. Many areas need triple digit increases in the average rain totals to make up for the shortfall. San Jose tops this list, requiring an almost 500% increase in rainfall before the end of June, just to breakeven.
What Does This Mean for Wildfire Season?
The recent rains may help to stave off an early start to the 2020 wildfire season but may actually fuel wildfires moving forward. In areas that have experienced prolonged drought conditions, rains often lead to an explosive growth of new vegetation. Much of this vegetation growth is in the form of native and non-native grasses. Moist fuels are an ideal fire retardant, but these grasses are very susceptible to drying out after just a short period of low humidity and high temperatures.
The March storms failed to break California’s drought so the fuel moisture of this vegetation is going to be a concern as temperatures begin to rise across the state. Once dried, these “fine fuels” are easy to ignite. Something as small as an errant cigarette butt is a sufficient catalyst to spark a wildfire. When active, these wildfires can move rapidly and are prone to “spotting”. Spotting occurs when embers are blown to nearby fuels and cause multiple ignitions, making the wildfire difficult to contain.
Despite the trend of unprecedented wildfire destruction and the predictions for another above average potential for significant wildfire activity, the 2019 wildfire season was significantly less destructive. 2018 recorded over 49,000 fires for a total acreage of just of 4.5 million. The total acreage burned was almost half that of the previous 2 years and short of the 10 year average by more than 2 million acres.
Just sixteen miles south of last week’s Saddleridge Fire, the Palisades Fire burned 40 acres between Palisades Dr and Charmel Ln in steep terrain yesterday afternoon, quickly spreading and prompting evacuations of a neighborhood of Pacific Palisades. Fortunately, hard work from air and ground crews saved the 200 homes that were threatened from damage or destruction and all have since been repopulated. This morning’s incident briefing portrayed a mop-up and perimeter-control day ahead of the crews. A direct ground attack is the main plan for the two divisions, with dozer(s) cleared to improve a nearby fire road, and an Structure Protection Group working the previously evacuated neighborhoods.
Below are summaries from the National Significant Wildland Fire Potential Outlook, provided by the National Interagency Fire Center, for the period of October 2019 through January 2020. The full outlook can be located here which will give more in depth picture of US fire weather projection.
Fall Means Santa Ana Winds
Annually, the onset of the fall and winter seasons brings the highest chance for Southern California’s famed Santa Ana winds. Historically, the worst fires in Southern California in terms of speed of growth and destruction are linked to these hot, dry wind events. The last two years, a strong and persistent Santa Ana event was a major player in the spread of both 2017’s Thomas fire in Ventura and Santa Barbara and last year’s Woolsey Fire in Malibu.
Tropical Storm Imelda quickly organized, formed, and made landfall all today. Imelda was the ninth named storm of the 2019 Atlantic Season. As it’s set to creep slowly north, the storm could drop a dozen or more inches of rain in Houston and Galveston this week. As a result multiple areas are under TS and Flood Warnings and a Flood Watch.
Tropical Storm Dorian is moving WNW over islands of the Caribbean, bringing winds and rain for Puerto Rico Dominican next. The storm is forecast to stay a Tropical Storm force over the next several days with the long term path over the Bahamas and towards Florida by the weekend.