Gliders Rode Beneath a Super Typhoon to Sharpen Forecasts

Beneath a Super Typhoon, two autonomous gliders kept working in the dark water below a raging storm, collecting the first measurements of their kind for forecasters in that part of the Pacific. The machines travelled under Typhoon Choi-Wan near Guam in early October, gathering temperature and salinity readings before, during, and after the storm passed overhead. According to the United States ocean observing program that coordinated the effort, no comparable underwater glider data had previously been gathered for forecasters directly below a major storm in that region.

The result matters because a tropical cyclone draws its power from warm water, and forecasters still struggle most with sudden strengthening. Satellites can watch clouds and winds from above, and aircraft can fly into a storm, but neither can easily measure how heat is stored and mixed in the upper ocean where a storm feeds. The gliders filled that gap by diving and surfacing on their own, sending back a profile of the water column while the storm churned overhead. That kind of detail can help models judge whether a storm is likely to intensify quickly, giving coastal and island communities earlier and clearer warnings.

How the underwater mission worked

The vehicles are torpedo-shaped robots that change their buoyancy to glide up and down through the water, rather than using a propeller for most of their movement. Each dive produces readings that are relayed when the craft returns to the surface, so scientists can follow changing conditions almost as they happen. In this case, the pair stayed on station through the storm passage, which meant the record covers the ocean before the winds arrived, at the height of the disturbance, and in the cooling and mixing that followed. That continuous view is far more useful than a single snapshot, because storm intensity depends on how the ocean responds over hours, not just on the warmth measured on one day.

The mission grew out of a partnership that has run since the late twenty-tens, bringing together naval operators, federal forecasters, and regional observing groups. According to the observing program, the naval partner has supplied gliders for hurricane-season work in American waters for years, while the observing network has made the data available for forecasting. This autumn, the partnership expanded into waters around Guam for the first time, and the milestone arrived in that very first season. The timing was fortunate and instructive: planners had put the tools in a place where a powerful storm was likely to pass, and the storm obliged.

Why forecasters want more ocean data

Rapid intensification remains one of the hardest problems in storm forecasting, and it is also one of the most dangerous. A storm that strengthens sharply overnight can leave little time for evacuations, port closures, and preparations for flooding and wind damage. Better ocean measurements do not remove that risk, but they reduce one source of uncertainty by showing how much energy the storm can draw on and how the sea surface cools as winds stir deeper, colder water upward. Forecasters can then test their models against real underwater evidence, rather than relying only on estimates from satellites and ships that must stay clear of the worst weather.

There are limits to what a single mission can prove. Beneath a Super Typhoon, conditions are extreme, and two vehicles can only sample a narrow slice of a vast storm. Researchers will need to compare the new readings with satellite observations, aircraft data, and model output before they can say how much the forecasts improved. Still, the first success changes the planning question for future seasons. Instead of asking whether gliders can survive and report from below a major storm in this region, teams can ask where to place them next, how many are needed, and how quickly their data can reach forecast desks during a live event.

For readers in Guam and the wider island Pacific, the practical payoff is straightforward: earlier signals of a strengthening storm, and warnings grounded in measurements taken where the storm lives. For the rest of the world, the lesson travels, because the same approach could be used in other basins where storms form far from shore. The ocean has always been part of the forecast; now, thanks to a pair of quiet machines that rode out a storm from below, forecasters can see more of it. Related coverage of a warming ocean includes a recent look at glaciers thinning in a record heat year, while another recent story follows a new race to return to the Moon. Sources for this story include the ocean observing program report on the glider milestone.