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

Meta Title: Sentinel-6 Satellites Track Hurricane Seas During El Niño
Meta Description: NASA and European Sentinel-6 satellites measure sea-surface height and waves to improve hurricane forecasting, shipping safety, and coastal planning during El Niño.
URL Slug: sentinel-6-hurricanes-el-nino-sea-level
Excerpt: NASA’s Sentinel-6 Michael Freilich and Sentinel-6B satellites are designed to provide highly precise ocean measurements, including sea-surface height and wave conditions that can support hurricane forecasting. Flying close together, the missions offer a valuable comparison of ocean data during changing El Niño conditions.

# Sentinel-6 Satellites Are Watching Hurricane Seas During El Niño

Hurricanes are powered by warm ocean water, but the ocean conditions that influence a storm are more complicated than a single sea-surface temperature map. Water depth, currents, sea-level patterns, wave heights, and the amount of heat stored below the surface can all affect how a tropical cyclone develops and intensifies.

NASA and its European partners are using two closely related ocean-monitoring satellites to improve those observations. According to the NASA source item, Sentinel-6B is flying about 30 seconds behind Sentinel-6 Michael Freilich, its predecessor, allowing scientists to compare measurements from both spacecraft over nearly the same parts of the ocean.

The mission is especially useful during periods shaped by El Niño, a large-scale climate pattern that changes ocean temperatures, winds, rainfall, and hurricane activity around the world.

While satellite altimeters cannot predict hurricanes on their own, their data can help forecasters and researchers understand the changing ocean environment that storms encounter.

## What Sentinel-6 Measures

The Sentinel-6 missions are primarily satellite altimetry missions. They use radar instruments to measure the distance between the spacecraft and the ocean surface with exceptional precision. Combined with careful calculations of the satellite’s orbit, atmospheric conditions, tides, and other factors, those measurements reveal sea-surface height.

Sea-surface height is not simply a measure of coastal flooding or long-term sea-level rise. Small differences in ocean height can also reveal information about currents, eddies, and the distribution of heat in the upper ocean.

Warmer water expands, which can slightly raise sea level. In many regions, higher-than-average sea-surface height can therefore be associated with deeper layers of warm water. This matters for hurricanes because a storm’s winds churn the ocean. If warm water extends farther below the surface, the storm may be less likely to cool the water enough to weaken its own energy supply.

The satellites also provide information that contributes to wave-height observations. Large waves are dangerous to ships, offshore platforms, coastal infrastructure, and emergency responders. During hurricanes, observations of the sea state can supplement data from weather satellites, aircraft reconnaissance, ocean buoys, drifting instruments, and numerical forecast models.

## Why Two Satellites Flying Close Together Matter

The NASA item says Sentinel-6B is following Sentinel-6 Michael Freilich by roughly 30 seconds. This close formation is valuable because both instruments can observe very similar ocean conditions within a short period.

A paired-satellite period can help mission teams compare the measurements made by the two radar altimeters. Scientists can identify small differences between instruments, check calibration, and ensure the long-running record of global sea-level observations remains consistent.

Continuity is one of the main goals of the Sentinel-6 program. Oceanographers need measurements spanning years and decades to separate short-lived weather events from seasonal variability, El Niño and La Niña cycles, and the long-term rise in global mean sea level.

For hurricane science, the close satellite timing is also useful because storms can rapidly reshape the ocean surface. A hurricane can generate major waves, push water toward coastlines, alter surface mixing, and interact with ocean eddies. Near-simultaneous observations provide a sharper picture than measurements separated by days.

Still, there are limits. Sentinel-6 satellites follow fixed orbital tracks and do not continuously hover over an individual storm. They offer highly accurate snapshots along their paths, rather than constant storm surveillance. Geostationary weather satellites, hurricane-hunter aircraft, buoys, and model systems remain essential parts of operational hurricane forecasting.

## El Niño Changes Hurricane Risk, But Not Everywhere in the Same Way

El Niño is the warm phase of the El Niño-Southern Oscillation, or ENSO. It occurs when sea-surface temperatures in parts of the central and eastern tropical Pacific become warmer than average, accompanied by shifts in atmospheric circulation.

Its effects on tropical cyclones vary by basin.

In the Atlantic, El Niño often increases vertical wind shear — a change in wind speed or direction with height. Strong wind shear can disrupt the organized circulation of developing storms, making an active Atlantic hurricane season less likely on average.

But “less likely on average” is not the same as “no danger.” Individual storms can still form, strengthen, and make landfall during El Niño years. Other factors, including local ocean warmth, atmospheric moisture, Saharan dust, and weather patterns over Africa and the Caribbean, can influence the season.

In the eastern and central Pacific, El Niño can shift areas favorable for tropical cyclone development and may support more activity in some locations. The consequences can extend to Pacific islands, Mexico, Central America, and the western coast of North America.

For this reason, describing an El Niño period as simply good or bad for hurricanes would be misleading. The risk changes geographically, and communities should rely on forecasts tailored to their basin and location.

## Sea Level Is Important for Coastal Hurricane Impacts

One of the most direct links between Sentinel-6 data and hurricane risk involves coastal water levels.

Storm surge occurs when powerful hurricane winds push seawater toward shore. The danger from surge depends on many factors: storm size, intensity, forward speed, angle of approach, coastline shape, tides, waves, and the water level that already exists before the storm arrives.

As baseline sea level rises, a given storm surge can begin from a higher starting point. That can allow damaging water to reach farther inland, particularly in low-lying coastal areas.

Satellite altimetry is not a replacement for local tide gauges, which provide direct measurements at specific coastlines. However, satellite observations are critical for mapping broader ocean patterns and tracking global and regional sea-level trends. Together with tide-gauge records and coastal models, they support better assessments of long-term infrastructure exposure.

Ports, roads, wastewater systems, power facilities, coastal homes, and industrial sites can all be vulnerable to flooding. More accurate information about ocean conditions can help planners evaluate risks before a storm arrives and guide longer-term adaptation decisions.

## Benefits for Shipping and Offshore Operations

The source item highlights potential benefits for commercial industries, including shipping. That connection is practical.

Hurricanes and large ocean swells can force vessels to alter routes, delay port calls, reduce speed, or avoid affected regions entirely. Offshore energy facilities and marine construction operations also depend on reliable information about waves and sea conditions.

Satellite altimeter data feed into broader ocean and weather-monitoring systems. These systems help forecasters estimate significant wave height and improve models used by mariners and coastal operators.

No single satellite can provide every detail needed for route planning. But accurate ocean-height and wave observations add to a larger network of information that supports safer decisions at sea.

## What Is Known — and What Still Requires Context

The supplied NASA item reports that Sentinel-6B was launched in November and is now operating close behind Sentinel-6 Michael Freilich. It describes the two satellites as providing precise sea-level-height measurements during El Niño conditions.

The broader scientific rationale is well established: satellite altimetry supports sea-level science, ocean-current research, wave monitoring, and weather and climate models.

However, satellite measurements should not be interpreted as a direct hurricane forecast on their own. Hurricane intensity and track forecasts depend on a broad observing system and complex computer models. Also, El Niño does not determine the outcome of an entire hurricane season by itself.

The significance of the Sentinel-6 pair is its ability to preserve and strengthen a high-quality ocean record while providing measurements useful to scientists studying the ocean conditions behind coastal hazards and severe weather.

## A Long-Term Ocean Record With Near-Term