Thanks to NowCast, today is a good day for surfers who paddle out in Southern California’s prime wintertime waves and want to stay healthy.
For the first time, Heal the Bay staff scientists are running our NowCast water-quality predictions from December through March for a select few surf breaks.
NowCast predictions are the best water quality information available for beaches in California. They are made using machine-learning models, based on the most recent environmental conditions, and publicly available every single morning. By checking NowCast predictions before they go out, ocean users can reduce their risk of getting sick from polluted water.
NowCast predictions are now available each day by 7 a.m. for these very popular surf breaks:
- Venice Breakwater
- Manhattan Beach (near 28th Street)
- Redondo Breakwater
- Huntington Beach (near Beach Boulevard)
- Santa Ana River Jetties
We want people to catch a wave, not the stomach flu. You can find NowCast predictions on our Beach Report Card website and mobile app.
We have been running NowCast successfully for beaches in the summer months since 2015, predicting water quality before swimmers hit the shore. Last summer, we provided daily forecasts of predicted water quality for 20 beaches.
If you aren’t familiar with our NowCast system, here’s an FAQ about how we are continuing to improve water quality monitoring at California beaches.
What is the NowCast system?
The NowCast system provides information similar to a daily weather forecast, but this tool predicts good or poor water quality for the day at select beaches across California. NowCast predictions are made by statistical computer models that are calibrated on years of environmental and bacteria data to accurately estimate fecal bacteria levels in the surf zone.
Fecal bacteria levels can be affected by many environmental factors such as rainfall, tide levels, solar radiation, wind, and wave action. Water quality can even be affected by human-made factors such a stormdrain flow and the presence of piers or jetties. Because the effects of these factors on water quality varies from beach to beach, site-specific NowCast models are developed for individual beaches.
Predictions are made each morning by running the models using up-to-date environmental information, and are released by 7 a.m. When a model estimates that bacteria levels at a beach comply with the health standards, the NowCast result is shown as “Good”; however, if a model estimates that bacteria levels exceed health standards, the NowCast result is shown as “Poor.”
Why is the NowCast system important?
Currently, local health agencies use laboratory analyses of water samples collected at the beach to determine if it is safe for recreational use. Unfortunately, there is a long delay in this approach: It typically takes 24-48 hours to collect the samples, transport them to the lab, and analyze them. Meanwhile, water quality can change with environmental conditions. Additionally, most California beaches are sampled on a weekly basis (although there are some beaches that are monitored more frequently). As a result, health agencies currently rely on data that is days-old to make health protection decisions.
Predictive models like those used in the NowCast system can quickly and accurately provide daily water quality information based on the most recent environmental conditions at the beach. Local health agencies and organizations like Heal the Bay can then make public notifications of poor water quality in the morning before most people arrive at the beach.
Who created the NowCast system?
The NowCast system was created through a collaboration among Heal the Bay, Stanford University, and UCLA. The project is funded by the State Water Resources Control Board, and is supported by local health agencies throughout California. For more in-depth information on the research that went into creating the NowCast system, click here.
Will there be more NowCast beaches in the future?
Most certainly. This is our first season releasing predictions during the winter season, and our plan is to keep growing our winter system each season to more and more locations. We already release predictions during the summer for 20 California beaches, from Humboldt County to San Diego County.
Are NowCast predictions available during rain events?
No. When it rains in California, water quality typically plummets. As a result, beach managers (which include local health agencies and lifeguards) issue rain advisories. These warnings last at least 72 hours, and may not be removed from the beach until after water quality samples show that conditions have returned to safe levels.
Because rain advisories are the most conservative form of public notification, we do not release NowCast predictions when they are active. For information about water quality and rain advisories (and for another spot to check NowCast predictions), check the Los Angeles and Orange County health agency websites.