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How 2 US, European Satellites Are Studying Hurricanes During El Niño

✇NASA Breaking News
By: Stephen Carney
9 September 2026 at 12:00

5 min read

Preparations for Next Moonwalk Simulations Underway (and Underwater)

Category 5 Hurricane Melissa, one of the most powerful storms to strike the Caribbean in recent history, is pictured about 50 miles south of Jamaica in this photograph from the International Space Station as it orbited 262 miles above the Yucatan Peninsula.
Hurricane Melissa is seen 50 miles south of Jamaica in this photograph taken from the International Space Station on Oct. 28, 2025.
NASA

Last November, NASA and its European partners launched the Sentinel-6B satellite to improve hurricane forecasts, help protect infrastructure, and benefit commercial industries, including shipping. The satellite now is flying 30 seconds behind its predecessor, Sentinel-6 Michael Freilich. Both satellites are providing precise sea level height measurements during what oceanographers expect to be a historic El Niño, a naturally occurring oceanic phenomenon in which warmer-than-usual Pacific waters shift global weather patterns.

The two satellites make up the Copernicus Sentinel-6/Jason-CS (Continuity of Service) mission, the latest in a series of ocean-observing radar altimetry missions that have been monitoring Earth’s changing seas continuously since the early 1990s.

The data each satellite is collecting will not only allow scientists to better understand this year’s El Niño but will also help them create more accurate hurricane predictions.

“This El Niño was a late-bloomer,” said Josh Willis, Sentinel-6B’s project scientist at NASA’s Jet Propulsion Laboratory in Southern California. “It didn’t kick off until the middle of the year and is just now reaching a strength similar to what we’ve seen in the satellite record during significant El Niños in 1997 and 2015. We expect it to be big, and it’s already having big impacts.”

El Niños generally scramble weather patterns tied to rainfall and storms, including hurricanes. They also redistribute heat in the ocean, which affects sea level. Normally, Earth’s warmest ocean waters sit along the equator in the western Pacific. During El Niño, weakened winds, which usually blow westward along the equator, result in heat spreading east toward South America. The change in ocean heat shifts hurricane activity from the Atlantic to the Pacific Ocean.

Predicting hurricane strength

On July 15, Sentinel-6B began delivering low-latency data to scientists that could be used for weather predictions. That data will take some time to work its way into the research models on which meteorologists and climate scientists rely, but when it does, those improved models could save lives.

Data from Sentinel-6 satellite missions feeds into hurricane tracking algorithms used by federal and state agencies. Those predictions can activate disaster response efforts, mobilizing resources ranging from sandbag placement to National Guard activation. They also can lead to evacuation orders that require quick but well-informed decisions about logistics at a local level. More severe events may require engaging larger organizations, such as the Federal Emergency Management Agency.

A tropical storm can take a week or more to become a hurricane and make its way to a coastline, but a hurricane can rapidly intensify in the 48 hours prior to landfall, leaving planners little time to prepare.

“Hurricanes have been known to speed up quickly at the last moment, so the window in which to decide what to do is short,” said Deirdre Byrne, an oceanographer and altimetry expert with the National Oceanic and Atmospheric Administration (NOAA). “The goal is to forecast how much and how rapidly intensification will happen so that officials can make the right calls.”

Byrne oversees one of the country’s most crucial hurricane forecasting algorithms, NOAA’s Satellite Ocean Heat Content Suite, which has been operating since 2012.

Each Sentinel-6 satellite measures ocean height, as well as the size of waves and marine wind speed, using a radar altimeter, which bounces thousands of radar pulses a second off the crests and troughs of waves. Ocean height varies from place to place and provides insight into the ocean’s heat content, since warm water expands. That, in turn, helps forecast how fast hurricanes will grow.

The satellites each carry a second instrument, called the Global Navigation Satellite System – Radio Occultation (GNSS-RO), which measures atmospheric properties, such as humidity, pressure, and temperature.

Among the measurements Sentinel-6 is gathering, Byrne is most anticipating the ocean height data, which she plans to begin incorporating into the current Satellite Ocean Heat Content Suite algorithm by the end of the year.

“In terms of data quality, the Sentinel-6 missions are unparalleled,” Byrne said.

Together, the missions are also extending a precise dataset deep into its fourth decade. This record of sea level observations traces back to the TOPEX/Poseidon mission, which launched in 1992, and continues through to the present day with Sentinel-6 Michael Freilich. Sentinel-6B will take over for its predecessor as the reference satellite for global sea level measurements later this year.

“The key is consistency, measuring the same way, every time,” said Severine Fournier, Sentinel-6B deputy project scientist, JPL. “That’s what lets us predict hurricanes, and, in turn, protect coastal communities and infrastructure.”

More about Sentinel-6B

Sentinel-6 Michael Freilich, named after a former director of NASA’s Earth Science Division, is one of two satellites that compose the Copernicus Sentinel-6/Jason-CS mission.

Sentinel-6/Jason-CS, a part of the European Union’s Earth observation program called Copernicus, was jointly developed by ESA (European Space Agency), EUMETSAT (European Organisation for the Exploitation of Meteorological Satellites), NASA, and NOAA, with funding support from the European Commission and technical support on performance from the French space agency CNES (Centre National d’Études Spatiales). Spacecraft monitoring and control, as well as the processing of all the altimeter science data, is carried out by EUMETSAT on behalf of the European Union’s Copernicus Programme, with the support of all partner agencies.

NASA JPL, a division of Caltech in Pasadena, contributed three science instruments for each Sentinel-6 satellite: the Advanced Microwave Radiometer, the GNSS-RO, and the Laser Retroreflector Array. NASA also contributed launch services, ground systems supporting operation of the agency’s science instruments, the science data processors for two of these instruments, and support for the United States members of the international Ocean Surface Topography Science Team.

For more about Sentinel-6B, visit:

https://science.nasa.gov/mission/sentinel-6B

-end-

Media Contacts

Andrew Good / Andrew Wang
Jet Propulsion Laboratory, Pasadena, Calif.
818-393-2433 / 626-379-6874
andrew.c.good@jpl.nasa.gov / andrew.wang@jpl.nasa.gov

2026-060

NASA Data Feeds River Forecasts as Snow Drought Effects Linger

✇NASA Breaking News
20 August 2026 at 10:12
This map, derived from NASA’s GEOS (Goddard Earth Observing System), shows an atmospheric river reaching Washington state in December 2025, during a winter marked by extreme rainfall and too little mountain snow.
NASA’s Scientific Visualization Studio

As the effects of the 2026 snow drought in the western United States carry into summer, NASA Earth data is feeding machine-learning forecasts that inform decisions about water, power, and public safety in Washington state.  

Tacoma Power, a Washington public utility, is using a U.S. technology company’s river-flow forecasts during a year of water extremes on the Cowlitz River. The utility’s largest hydroelectric project uses water stored behind Mayfield and Mossyrock dams to generate enough electricity to serve more than 151,000 homes each year.

Upstream Tech’s HydroForecast combines weather forecasts and river measurements with NASA-produced satellite data on snow cover and vegetation conditions to predict river flow from hours to days ahead. Updated every two hours, the forecasts are used by reservoir managers, hydropower producers, water utilities, and government agencies to prepare for storms, plan reservoir water releases, and navigate dry periods.

“Part of NASA’s mission is to make the view from space useful on the ground,” said Erin Urquhart, manager for NASA’s Water Resources program at the agency’s headquarters in Washington, D.C. “When an American company incorporates NASA’s freely available data into forecasts that help water managers prepare for floods, generate power, and steward water supplies, that’s NASA delivering practical value to the nation.”

Year of water extremes

During the winter of 2025-26, unusual warmth meant a larger share of precipitation fell as rain instead of snow across much of the West, while below-normal precipitation deepened deficits in some areas. January, February, and March each had the lowest Western snow cover for that month in the NASA MODIS (Moderate Resolution Imaging Spectroradiometer) satellite record since 2001.

On the Cowlitz, those conditions produced a season of extremes. In December 2025, a powerful atmospheric river brought a long, narrow band of Pacific moisture into the region, causing one of the largest one-day inflow surges ever recorded at Tacoma Power’s hydroelectric project. Across the season, that rain-heavy pattern sent water downstream quickly instead of building mountain snowpack that would melt and release water steadily into summer. Snowpack remained at just 20% to 50% of normal levels.

As winter became spring, the rain tapered off, and on April 8, Washington state placed every watershed, including the Cowlitz, under a drought emergency. From April through June, peak daily inflow into the project was among the lowest on record, leaving Tacoma Power with less incoming water to replenish its reservoirs ahead of summer demand, said Saul Villarreal, Tacoma Power’s senior hydro operations manager.

Tacoma Power’s Mayfield Dam and powerhouse sit on the Cowlitz River in southwest Washington, where forecasts using NASA data support reservoir operations and hydropower generation.
Tacoma Power, used with permission

Turning satellite data into river forecasts

NASA turns observations collected by the VIIRS (Visible Infrared Imaging Radiometer Suite) instrument on the Suomi-NPP (Suomi National Polar-orbiting Partnership) satellite into data products that provide information about snow cover and vegetation greenness across entire watersheds, including where ground monitors are sparse.

To train HydroForecast, Upstream Tech collects and archives years of those NASA products alongside weather forecast data and actual river-flow measurements. Using records from hundreds of watersheds, the models learn common patterns in how water moves through the landscape and apply them in new locations.

Tests across multiple basins found that including snow and vegetation observations increased forecast skill, said Dr. Laura Read, director of technical and federal partnerships for HydroForecast at Upstream Tech. “NASA’s data gives us the reliability, global coverage, and consistency we need,” said Read. “Our short-term models run every two hours, so those inputs have to show up when we need them. Though we have stopgaps in place, any interruption to our operational pipeline is a huge deal.”

Tacoma Power uses HydroForecast alongside stream gauges, snow stations, and operator judgment. During the December storm, the NASA-informed, short-term forecast helped the utility anticipate how much water would reach the project and prepare for dynamic river conditions, while meeting operating requirements and keeping public safety at the forefront, Villarreal said.

NASA’s GEOS (Goddard Earth Observing System) maps an atmospheric river, a ribbon of water vapor, before Washington’s January-April 2026 snow cover is compared with a historical median.
NASA’s Scientific Visualization Studio

As spring approached, the operational challenge reversed. Tacoma Power used HydroForecast’s seasonal model to track the growing risk of weak runoff and began keeping its reservoirs higher than usual to preserve water for summer. That left less space to contain another large storm, so operators continued checking the short-term forecast “to play defense,” and remained ready to adjust operations if another atmospheric river developed.

“The earlier we understand how conditions might change, the more effective planning we can do to manage our reservoir and balance the many demands of our system throughout the season,” said Villarreal.

Tacoma Power entered summer 2026 with reservoir levels near average despite the dry spring. The stored water supports reliable hydropower, required river flows to support fish and aquatic habitat, and public recreation. It also gives the utility more flexibility to meet electricity demand during heat waves or unexpected outages and, when possible, support the wider regional power system.

From forecasts to drought assessments

Tacoma Public Utilities’ Cowlitz Hydro Project is just one example of NASA science supporting water decisions across the West.

NASA also has partnered with the U.S. Department of Agriculture’s Natural Resources Conservation Service to bring satellite-based snow and groundwater information into machine-learning water-supply forecasts.

The National Oceanic and Atmospheric Administration’s Colorado Basin River Forecast Center uses MODIS and VIIRS data to adjust snowmelt rates in its model. The Bureau of Reclamation uses NASA and NASA-derived snow data, alongside other sources, for reservoir operations in California’s San Joaquin Basin.

NASA data and research have long informed the U.S. Drought Monitor, the weekly assessment used by farmers, water managers, and public agencies. NASA became a formal partner in 2026, expanding its role from providing information to helping produce the assessment. The agency took its first turn authoring the Drought Monitor during the week of Aug. 17.

About the Author

Emily DeMarco

Emily DeMarco

Writer/Editor (IV), Earth Science Division

Emily is a science writer and editor with NASA’s Earth Science Division, with more than 10 years of experience in science journalism and communication. A former deputy news editor at the magazine Science News, she holds a master’s in environmental science and management from UC Santa Barbara’s Bren School, where she specialized in water resources management and science communication.

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