Remnants of tropical storm pause fire season in Southern California

Nine weather stations in San Diego County recorded more than 4 inches of precipitation

Above: Mt. Laguna Observatory in Eastern San Diego County at 8 a.m. PST November 21, 2019. HPWREN.

On Tuesday the remnants of tropical storm Raymond hit Southern California and the next day merged with a cold storm that formed in the Gulf of Alaska. The result was two waves of rain, lightning, wind, and in the higher elevations, snow.

Nine weather stations in San Diego County recorded more than 4 inches of precipitation. The highest total was at Lake Henshaw with 4.68 inches. Some of the moisture became snow at Mount Laguna 6,100 feet above sea level.

Precipitation recorded Southern California
Highest totals of precipitation recorded in Southern California during the 48-hour time period ending at 8 a.m. PST Nov. 21, 2019. NWS.

Many other locations in San Diego County received more than an inch, but farther north Riverside, San Bernardino, and Los Angeles Counties had less.

This of course will pause the fire season in these areas and may be the season-ending weather event in the locations that were dumped on with multiple inches of precipitation.

Precipitation recorded Southern California
Precipitation recorded in Southern California during the 48-hour time period ending at 8 a.m. PST Nov. 21, 2019. NWS.

Meanwhile in Northern California it was dry and very windy Tuesday and Wednesday. On Monday in the Sacramento area the Hot Dry Windy Index is predicted to be above the 95th percentile again but there is a chance of rain in the area the next day, November 26.

Hot Dry Windy Index Sacramento weather wildfires
Hot Dry Windy Index for the area 25 miles west of Sacramento, CA. Generated November 21, 2019.

Forests in many areas of California are just waiting for a spark

The Energy Release Component is at or above record levels in some areas of the state

Energy Release Component wildfire fire central sierra California
The Energy Release Component (or flammability) of the vegetation in the Central Sierra area is the highest recorded for this time of the year. (Click to enlarge)

The forests and brush lands of many areas of California are ready to burn. The effects of precipitation received in the winter and spring have been negated by relentless warm, dry, and occasionally very windy weather. The recent Kincade and Maria Fires were examples of wildfire potential during strong winds.

The Energy Release Component (ERC) is a measure of the heat produced within the flaming front of a vegetation fire and is largely influenced by the moisture in the live and dead fuels. In other words, it reflects the flammability of the vegetation. The weather in the last few months in California has resulted in many areas having record or nearly record high ERCs in recent days, including the Southern Mountains, Bay Marine, Central Coast, South Coast, Central Sierra, and Santa Cruz Mountains.

The data in these ERC charts shows the most current levels being above the 97th percentile for any date and close to or above the maximum ever recorded on November 5. (Charts for more areas in California)

Energy Release Component fire wildfire California mountains southern
The Energy Release Component (or flammability) of the vegetation in the Southern California Mountains is the highest ever recorded for this time of the year.

One thing that is striking about this information is the ERC in the Central Sierra, an area where the wildfire danger usually drops quickly after September. The conditions we are seeing now are similar to or perhaps more extreme than in 2017 and 2018 before the Camp, Woolsey, Thomas, and North Bay Fires that combined destroyed over 29,000 structures in October, November, and December.

This is not normal. The fire seasons are longer than they were a couple of decades ago.

The fuel is ready now. The only things lacking are very strong winds and an ignition source.

 Santa Ana wind events per month
The mean number of Santa Ana wind events per month. The dark bars refer to NCEP–DOE reanalysis and the clear bars refer to the CFS climate run. (Charles Jones, Leila M.V. Carvalho, and Francis M. Fujioka in Monthly Weather Review, December 2010)

There are no forecasts for very strong winds within the seven days in California, but wind is difficult to forecast and can sneak up on you. There is a possibility for an off-shore flow around November 15.

The three months with historically the most Santa Ana wind events are November, December, and January. The forecast for California in November is for higher than average temperatures and precipitation that is at or below average.

outlook probability precipitation temperature
One-month outlook for probability of precipitation and temperature, made Oct. 31, 2019, valid in November, 2019.

Potential for wildfires in California predicted to be high in November

It will remain high in southern California through December

wildfire potential November

The Predictive Services section at the National Interagency Fire Center has issued their Wildland Fire Potential Outlook for November through February. The data represents the cumulative forecasts of the ten Geographic Area Predictive Services Units and the National Predictive Services Unit.

If NIFC’s analysis is correct the only area with above average potential for wildfires during the four-month period is California in November and December. According to the prediction most of the forested or brush-covered lands in the state will have enhanced potential in November. That area will shrink in December to just the southern two-thirds of California.


  • An excerpt from the NIFC narrative report for the next several months;
  • More of NIFC’s monthly graphical outlooks;
  • NOAA’s three-month temperature and precipitation forecasts;
  • Drought Monitor;
  • Keetch-Byram Drought Index.

From NIFC:

“Entering the outlook period, most states will remain out of fire season in November. Exceptions to this will continue to be California, Colorado, and possibly Texas where drier than average conditions will continue. Expect periodic increases in fire potential and activity during wind events that not only bring strong winds but also drier air that lowers humidity levels to critical levels. The occurrence of such events should begin to diminish in frequency later in the month as the seasonal transition begins to end. Medium range data suggests that conditions across the Southeast will continue to show improvement as the frequency of moisture events continues to increase.”

wildfire potential December

wildfire potential January
Continue reading “Potential for wildfires in California predicted to be high in November”

Elevated fire danger to continue on Friday in southern California

UPDATED at 7:38 a.m. PDT November 1, 2019

Hot Dry Windy Index wildfire
Hot Dry Windy Index for the Santa Clarita area, created October 31, 2019.

The weather in southern California will be dry and breezy on Friday and Saturday but not to the extreme levels seen earlier this week. There are no Red Flag Warnings, but in Santa Clarita where the Tick Fire occurred for example, the forecast calls for 10 to 14 mph northeast winds gusting at 16 to 29 off and on into Friday night. Through Saturday the relative humidity will remain below 10 percent during the day with no recovery at night.

The Hot-Dry-Windy Index will be above the 75th percentile on Friday and Saturday.

Friday morning the chart below was revised to add the red “Critical” area that was not in the version issued Thursday. That is where the Maria Fire started at 6:15 p.m. Thursday east of Ventura, California.

Elevated Fire wildfire Weather for November 1, 2019
Elevated and Critical Fire Weather for November 1, 2019.
Weather forecast fire wildfire Santa Clarita
Weather forecast for the Santa Clarita area for the 48-hour period beginning at 4 p.m. PDT October 31, 2019.

There are no Red Flag Warnings in the medium-range weather outlook for southern California, but it is supposed to be dry.

Nominee to oversee NWS wants to privatize weather forecasting

Barry Myers is the former CEO of Accuweather

NOAA NWSThe person that has been nominated to run the National Oceanic and Atmospheric Administration, which includes the National Weather Service, thinks the NWS should reduce or eliminate the weather analysis and forecasting products it makes available to taxpayers. Barry Meyers resigned from his CEO position at Accuweather, a company founded by his brother Joel, in order to improve his chances of being confirmed by the Senate and Congress to run NOAA. The executives at Mr. Meyers’ family business would like to continue receiving weather data at no charge that NOAA and the NWS collect from weather stations and a constellation of satellites. They would then sell it back to taxpayers and private companies with little or no competition from the NWS.

Mr. Meyers was first nominated to head NOAA in October, 2017. He was approved by the Senate Commerce, Science, and Transportation Committee but his appointment has not been voted on by the full Senate. If finally confirmed he would be only the second head of NOAA that served without having a science degree.

Of the three elements that affect wildland fire behavior — weather, fuels, and topography — weather is the one that changes by the minute, hour, and day and is the most difficult to analyze and predict. Firefighters can see the vegetation and topography in front of them, but they can’t stand on a hill and predict with accuracy humidity, wind speed and direction for the next 72 hours.

It remains to be seen how privatizing weather forecasting would affect wildland fire management. Which company, if any, would issue Red Flag  Warnings for the United States? The Weather Channel, Accuweather, or WeatherUnderground? Would Incident Meteorologists that are deployed to a fire with an Incident Management Team be employees of one of those companies?

The video below from “Last Week Tonight with John Oliver” explores the concept of a businessman with conflicts of interest taking over NOAA and the NWS. Mr. Oliver briefly expresses his opinion about a politician, but the video is predominately about the concept of a former CEO of a weather company running NOAA. Warning: it contains crude language.

This is not the first time that privatization of weather forecasting, Accuweather, and one of the Myers brothers have been mentioned in the same conversation. Check out an article by Kelly Anderson in Wildland Firefighter in 1998.

Analysis of wildfire danger during the California wind event using Hot-Dry-Windy Index

Hot-Dry-Windy Index
The Hot-Dry-Windy Index for an area 15 miles northwest of Santa Rosa, California.

Weather forecasters expect the wildland fire danger in some areas of  California to be extreme Tuesday night and into Thursday.  Strong north to northeast winds accompanied by low humidity has triggered Red Flag Warnings putting land managers on edge. PG&E is so worried it is proactively turning off the electrical power to 600,000 addresses in nearly 30 northern, central, coastal, and Bay Area counties.

We consulted a fairly new fire danger forecasting tool to see how it analyzed what firefighters will be faced with for  the next few days. The Hot-Dry-Windy Index (HDW) is described as being very simple and only considers the atmospheric factors of heat, moisture, and wind. To be more precise, it is a multiplication of the maximum wind speed and maximum vapor pressure deficit (VPD) in the lowest 50 or so millibars in the atmosphere.

The products, displayed as charts, show the index for the preceding 10 days and the forecast for the next 7 days. For the current and following days you will see results of the Global Ensemble Forecast System (GEFS), which is a weather forecast model made up of 21 separate forecasts, one control (in red) and twenty perturbations. The reasoning for showing 21 different forecasts is to quantify the amount of uncertainty in a forecast by generating an ensemble of multiple forecasts, each minutely different, or perturbed, from the original observations.The HDW only only uses weather information – fuels and topography are not considered by HDW at all. If the fuels are wet or have a high live or dead moisture content it will not be reflected in the data.

At the top of the page is the HDW forecast for an area about 15 miles northwest of Santa Rosa in the Bay Area of California. It predicts the Index will be above the 95th percentile on October 8, above the 90th percentile on October  9, and back up to the 95th percentile on October 10.

Below are HDW predictions for other areas in California.

Hot-Dry-Windy Index Susanville
Hot-Dry-Windy Index, Susanville

Hot-Dry-Windy Index Lake Tahoe
Hot-Dry-Windy Index for the area 30 miles south of Lake Tahoe near the Caples prescribed fire.

Hot-Dry-Windy Index Bakersfield
Hot-Dry-Windy Index for the Bakersfield and Lancaster area.

Hot-Dry-Windy Index San Diego County
Hot-Dry-Windy Index for eastern San Diego County