Moisture which streamed into central California from the remains of Hurricane Elida and instability provided by a hot airmass over the area resulted in the development of afternoon thunderstorms on August 15. 95 inches of rainfall in one hour and resulted in the closure of several roads in the area around Pine Mountain Club.
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The episode as NWS HNX wrote it up.
Moisture which streamed into central California from the remains of Hurricane Elida and instability provided by a hot airmass over the area resulted in the development of afternoon thunderstorms on August 15. One slow moving thunderstorm produced heavy rainfall and flash flooding at Pine Mountain Club which measured 1.95 inches of rainfall in one hour and resulted in the closure of several roads in the area around Pine Mountain Club.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Hanford, CA wrote its last area forecast discussion before the first event at Aug 15, 12:51 PM PST, 3 hours 24 minutes earlier.
Area Forecast Discussion National Weather Service Hanford CA 151 PM PDT Sat Aug 15 2020 .SYNOPSIS... Excessive Heat will continue over much of the district for the next several days. Isolated showers and thunderstorms can be expected this weekend, primarily over the higher elevations. Otherwise, a few thunderstorms will pop up near the Sierra crest each afternoon through Wednesday. && .DISCUSSION...Oppressive heat, humidity, and thunderstorms are all a part of the weather picture over much of the central California today. Tropical moisture surged northward into the western third of the CWA earlier this morning equipped with showers and isolated thunderstorms. The richest band of moisture, as well as the heaviest thunderstorms, trained northward through Santa Barbara County and San Luis Obispo County. As the activity crossed over the coastal ranges, little if any rain fell from the thunderstorms, but they added more humidity to the atmosphere and slowed temperature rises a bit. The focus of convection will continue to be over the higher elevations of our CWA, the west side and south end of the San Joaquin Valley where isolated thunderstorms will remain a threat into early this evening. Any of these thunderstorms that are dry can ignite new fires over the mountains until convection dies around sunset. Otherwise, temperatures will remain much warmer than normal again tonight. The higher humidity will add to the discomfort. In the broader picture, a strong upper level ridge of high pressure will dominate our weather pattern for the next several days. It's currently centered over Arizona and New Mexico. This monster ridge will gradually build northward and westward and re-center itself over the Great Basin by Monday where it will remain anchored through at least the middle of next week. Until this ridge retrogrades into the Golden State, the window will remain open for more northerly influxes of tropical moisture. Indeed, the models bring another slug of mid level moisture into the CWA by Sunday morning. If so, we could see a repeat of convection in roughly the same areas as we did this morning. We've made adjustments to the forecast to add a slight chance of thunderstorms to the south end and west side of the San Joaquin Valley from late tonight through midday Sunday. The thunderstorm focus Sunday will probably again shift to the mountains during the afternoon and early evening hours. Much of this mid level moisture and atmospheric instability should diminish early in the week as the high pressure ridge builds more strongly into central California. If so, the thunderstorm threat will also decrease each day, but probably not end completely over the highest elevations of the Sierra where a few thunderstorms could pop up each afternoon through midweek. The big weather story during the next several days will be the extreme heat. Thermometer readings will top 110 degrees in some locations of the San Joaquin Valley and peak as high as 115 degrees in a few desert locales. Tuesday looks to be the hottest day, but honestly, each and every day will top 105 degrees in a large majority of these regions through Thursday. Perhaps a more significant health impact of this heat wave will be its longevity. This will be, by far, the longest stretch of triple digit in the valley, lower foothills and the desert yet this Summer. The persistence of this heat wave could take a stressful, life threatening toll on livestock, the elderly and heat sensitive individuals. The humidity will exacerbate the discomfort. Based on historical weather archives, this could end up being the worst heat wave to grip California since July, 2006. Records for maximum temperatures and high minimum temperatures will be challenged this week at several climate stations in the San Joaquin Valley. In the larger urban areas such as Fresno and Bakersfield, in addition to some desert communities, overnight lows will be at or above 80 degrees on consecutive nights this week. We advise people to stay indoors and in air conditioned buildings and not venture outdoors during the hottest part of each day. If you must be outdoors, limit your exposure, stay out of the sun, hydrate, and wear a protective hat, sunscreen, and light colored, loose-fitting clothing. Rivers are still running cold and swift and are potentially dangerous places to seek cooling relief from the heat, no matter how great of a swimmer you are. Be sensible, and don't end up as a drowning fatality or the victim of a water rescue! Finally, there is some hope that our heat wave will ease up by the end of next week. The models forecast this high pressure ridge to weaken and shift back over Arizona on days 6 and 7. In doing so, the door to the tropics could swing wide open again. Indeed, both the ECM and GFS forecast another northward influx of tropical moisture into central California late Friday night into next Saturday. If so, parts of our CWA will see a renewed thunderstorm threat during this period. Don't get your hopes up too high if you're looking for a return to seasonable temperatures by then, however. We're still expecting high temperatures to be at or above the century mark in much of the San Joaquin Valley, lower foothills and the Kern county desert next Saturday. && .AVIATION... Isolated thunderstorms can be expected over mainly the higher elevations through 03z Sunday and again after 12z Sunday. VFR conditions will prevail elsewhere over the central California interior during the next 24 hours. && .AIR QUALITY ISSUES... On Saturday August 15 2020... Unhealthy for sensitive groups in Fresno... Kern... Kings... Madera and Tulare Counties and Sequoia National Park and Forest. Further information is available at Valleyair.org && .CERTAINTY... The level of certainty for days 1 and 2 is medium. The level of certainty for days 3 through 7 is high. Certainty levels include low...medium...and high. Please visit www.weather.gov/hnx/certainty.html for additional information an/or to provide feedback. && .HNX WATCHES/WARNINGS/ADVISORIES... Excessive Heat Warning until 9 PM PDT Wednesday for CAZ179>191- 198-199. && synopsis...Durfee public/fw...Durfee aviation/IDSS/PIO....JEB weather.gov/hanford
Special Weather Statement National Weather Service San Joaquin Valley CA 353 PM PDT Sat Aug 15 2020 CAZ189-196-197-199-152315- Fort Tejon CA-Kern County Desert CA-Tehachapi Area CA-Bakersfield CA- 353 PM PDT Sat Aug 15 2020 ...SIGNIFICANT WEATHER ADVISORY FOR SOUTH CENTRAL KERN COUNTY UNTIL 415 PM PDT... At 352 PM PDT, Doppler radar was tracking a strong thunderstorm near Golden Hills, or 32 miles southeast of Bakersfield, moving northwest at 15 mph. Half inch hail and winds in excess of 40 mph will be possible with this storm. Locations impacted include... Tehachapi, Stallion Springs, Golden Hills, Keene, Water Canyon and Bear Valley Springs. PRECAUTIONARY/PREPAREDNESS ACTIONS... Frequent cloud to ground lightning is occurring with this storm. Lightning can strike 10 miles away from a thunderstorm. Seek a safe shelter inside a building or vehicle. && LAT...LON 3515 11840 3499 11848 3511 11880 3536 11867 TIME...MOT...LOC 2252Z 112DEG 26KT 3511 11853 Dudley
Special Weather Statement
National Weather Service San Joaquin Valley CA
401 PM PDT Sat Aug 15 2020
CAZ197-152330-
Fort Tejon CA-
401 PM PDT Sat Aug 15 2020
...SIGNIFICANT WEATHER ADVISORY FOR SOUTHWESTERN KERN COUNTY UNTIL
430 PM PDT...
At 400 PM PDT, Doppler radar was tracking a strong thunderstorm over
Mount Pinos, or 25 miles north of Ojai, moving north at 10 mph.
Half inch hail and winds in excess of 40 mph will be possible with
this storm.
Locations impacted include...
Mount Pinos and Pine Mountain Club.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
Torrential rainfall is also occurring with this storm, and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.
&&
LAT...LON 3486 11924 3486 11928 3488 11928 3488 11930
3493 11932 3496 11903 3481 11903 3481 11924
TIME...MOT...LOC 2300Z 170DEG 7KT 3481 11915
abSpecial Weather Statement National Weather Service San Joaquin Valley CA 418 PM PDT Sat Aug 15 2020 CAZ179-182-160000- Western San Joaquin Valley CA-West Side Hills CA- 418 PM PDT Sat Aug 15 2020 ...SIGNIFICANT WEATHER ADVISORY FOR SOUTHWESTERN KINGS AND SOUTHWESTERN FRESNO COUNTIES UNTIL 500 PM PDT... At 417 PM PDT, Doppler radar was tracking a strong thunderstorm near Avenal, or 35 miles southwest of Hanford, moving north at 25 mph. Pea size hail and winds in excess of 40 mph will be possible with this storm. Locations impacted include... Avenal, Coalinga and Kettleman Hills. PRECAUTIONARY/PREPAREDNESS ACTIONS... Torrential rainfall is also occurring with this storm, and may lead to localized flooding. Do not drive your vehicle through flooded roadways. Frequent cloud to ground lightning is occurring with this storm. Lightning can strike 10 miles away from a thunderstorm. Seek a safe shelter inside a building or vehicle. && LAT...LON 3588 11996 3587 12018 3612 12033 3616 11998 TIME...MOT...LOC 2317Z 175DEG 50KT 3596 12009 Dudley
The Los Angeles radar (KVTX), 49 km away, was scanning. The volume nearest the first event began at 00:16 UTC.
1 flash flood. Local standard time, as filed.
A spotter reported flash flooding from a slow moving thunderstorm which made roads impassible in Pine Mountain Club. A nearby Acurite 5 in 1 weather station reported 1.95 inches of rain in one hour.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2020Every state in 2020This day in weather historyWarnings in California, August 2020
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 902569.