Forecasting Algal Blooms the Way Meteorologists Forecast Hurricanes

A harmful algal bloom can be forecast much as a hurricane is. NOAA's Harmful Algal Bloom Operational Forecast System, working in the Gulf of America, tells officials whether a bloom is likely to contain a toxic species, where it is, how large it has grown, which way it is moving and whether it could get worse soon. The payoff is precision: with warning in advance, beaches and shellfish beds can be tested and closed more exactly, and for less time.

A boat cuts a green wake through a harmful algal bloom in Western Lake Erie. Credit: NOAA.

What goes into a forecast

The system draws on satellite imagery, observations in the field, computer models, public health reports and data from buoys. Forecasters combine them into a public report on bloom conditions that includes how likely people in the area are to suffer respiratory irritation.

NOAA oceanographers analyze the data and the models to write each bulletin, and every operational forecast is checked by a second reviewer before it is released.

Not just one coast

Harmful algal blooms are not confined to the Gulf of America, and the forecast system depends on people well outside NOAA — partner agencies and other organizations whose work and feedback keep it running. NOAA is working with local agencies in Maine, Massachusetts, Ohio, Washington, Oregon, California and elsewhere in the country to bring new forecasts into operation over the next five years.

Why a forecast beats a blanket closure

Without a forecast, the safe choice is to close wide areas for long periods whenever a bloom might be near. A forecast that says where the bloom is and where it is going lets officials act on the stretch of coast that is actually at risk — protecting people's health without shutting down more water than necessary.

Sources

Based on "How do we forecast harmful algal blooms?" from NOAA's National Ocean Service, a work of the United States government in the public domain.