First, some history. The NY Times has an account of the last time a tropical storm hit California in 1939. (Full access via link)
The last time a tropical storm came ashore in the state was in 1939. It capsized boats, cut power and phone service and destroyed homes along the coast.
...The 1939 storm, which made landfall in Long Beach, Calif., tore through Los Angeles County and the surrounding area, destroying coastal homes, cutting power and disrupting rail and highway traffic, according to an article published in The New York Times the next day.
...More than a dozen boats were declared missing, and the wreckage of an 80-foot yacht washed up near Huntington Beach, a usually picturesque surf spot. Around 200 people had to be rescued from wrecked leisure and fishing boats. Twenty-three people drowned when a sport fishing boat capsized just 500 feet from a pier at Point Mugu, near Oxnard. And several bodies were recovered from the water, including those of a man and a woman that washed ashore.
In Los Angeles, 5.41 inches of rain fell in 24 hours, the heaviest September rain in the city’s history at the time. A deluge in the Coachella Valley washed out train tracks and destroyed 70 percent of the region’s date crop. The overall damage was
estimated to be around $2 million, the equivalent of around $44 million in today’s dollars.
The map above shows the storm weakening as it heads north, but it will still be delivering winds and rain.
with predictions for what the storm may do as it comes ashore.
...Primary threats are coastal flooding, heavy rainfall and flash floods across the southwest (southern CA, NV, UT, and western AZ), including desert areas, and tropical storm winds in southern CA and the Baja Peninsula, Saturday through Monday.
A Tropical Storm Watch has been issued for San Diego, Orange and Los Angeles counties and parts of Ventura county. Tropical storm warnings and hurricane watches/warnings are in effect for parts of the Baja Peninsula.
While the 1939 storm did a notable amount of damage, in 84 years the region has seen changes. In 1940 the population of Los Angeles County was 2,785,643. In 2020 it was 10,014,009. It has more than tripled, along with commensurate development. Even if Hilary is no less dangerous than the 1939 storm, there’s a lot more people and things in harm’s way.
I expect there are some very anxious people tonight trying to figure out how much water they should release from reservoirs to avoid overtopping and possible collapse. There is likely development in places that will become flood zones for the first time in living memory regardless of what happens with the dams. And if that’s not enough, there will be people trying to figure out if there will be enough water to get through dry months, so how much should they try to hang onto now?
have already been dispatched to California to fly missions into the storm with their specially equipped WC-130 Hercules aircraft.
WC-130 Hercules
...Satellites provide a lot of information about a storm; however, they don’t provide information about what’s happening inside of it. This is where the Hurricane Hunters assist the NHC.
The Pacific and Atlantic Oceans are data sparse environments due to the lack of radar and weather balloons, so 53rd WRS crews usually fly through the eye of a storm at about 10,000 feet four to six times to collect real-time information in the storm.
“By flying into the storm, crews are able to locate the low-pressure center of the storm and collect data that assists with movement and intensity forecasts,” said Lt. Col. Steve Burton, 53rd WRS mission commander for the weather deployment. “The data we collect can improve a forecast by anywhere from 15-25 percent.”
During a mission, the aircraft collects weather data such as temperature, wind speed, wind direction, humidity, and surface pressure. During each pass through the eye, they release multiple dropsondes at different areas in the storm, which collect weather data on its descent to the ocean surface, specifically gathering data on temperature, humidity, pressure, wind speed and wind direction. An automated data package is sent out every 10 minutes while manual observations, such as the dropsonde data, are sent as necessary.
Missions are already scheduled; here’s a couple of screen shots from the Weather Channel about the Hurricane Hunters schedule from earlier today, 8-18-23
Where Hilary is, and where Keesler AFB is, where the Hurricane Hunters are based. For this storm they’ll be operating out of Santa Maria Airport.
Expected Hurricane Hunter missions into Tropical Storm Hilary 8-18-23
Inside the cockpit of a WC-130, flying into Hurricane Ian 9-28-2022
Best wishes for everyone in the Path of Hilary, the Hurricane Hunter crews, and all of the emergency response teams getting ready for landfall.