Unlocking the ocean’s role driving hurricanes

New research focuses on the place where ocean meets the atmosphere

It’s no secret among forecasters that the reliability of hurricane intensity forecasts or the strength of sustained winds has been harder to improve than track forecasts. Tropical cyclones with strengthening sustained winds are dangerous, damaging, and happening more frequently. Improving our ability to predict rapid intensification of hurricanes would help emergency planning and preparedness. 

Scientists at NOAA’s Atlantic Oceanographic and Meteorological Laboratory are now focusing on what happens where the sea meets the atmosphere to help solve the hurricane intensity problem. The place right above where the air meets the sea is called the planetary boundary layer. The ocean drives global weather. By building on past research, scientists have determined that factors in the boundary layer and underlying ocean such as salinity, temperature, currents, precipitation, and wave and wind patterns are crucial to understanding the energy that fuels a hurricane. “The more we understand about how the ocean fuels tropical storms, the better the forecast will be,” said Frank Marks, director of NOAA AOML’s Hurricane Research Division.”

“The more we understand about how the ocean fuels tropical storms, the better the forecast will be.”

-Frank Marks, Director of the Hurricane Research Division at AOML

Real-World Observations Improve Forecast Models

While models have improved for predicting intensity, up until recently they have lacked key observations from the boundary layer, mainly because it has been difficult and dangerous to obtain them from this area where the winds cause turbulent waves. AOML is now deploying a growing number of ocean-observing platforms that provide real-time satellite-transmitted data to capture pre-storm and hurricane conditions. Hurricane Gliders measure down to half a mile below the ocean surface, providing sustained observations to understand how ocean conditions fuel the storm. Global Drifters observe wind, waves, and surface currents to determine how air-sea interactions influence the evolution of a storm, and Saildrones measure the upper ocean and the atmosphere in the boundary layer to reveal how the atmosphere changes in a hurricane. In addition, new air-deployable technology has just been approved for the 2021 season that allows for targeted ocean data collection directly in front of a storm. This multi-pronged observing strategy will help us gain more insight into how the ocean drives hurricanes to improve intensity forecasts. On the atmospheric side, NOAA and partners have successfully tested new uncrewed systems that will provide more detailed data from within the hurricane’s eyewall. Scientists liken this to a movie was compared to the snapshots of data provided by dropsondes.

Detecting Changes at Every Spatial Scale

Observations are invaluable, but making sure they are integrated into the models and that storms are forecasted correctly is an ongoing process. That’s why AOML has teamed up with experts in other laboratories to figure out exactly what is happening in the turbulent, sometimes-vapor-sometimes-water layer under a hurricane. AOML scientists have published new research looking at how everything from the structure of ocean eddies to ocean temperature and salinity, wind-caused heat transfer, and precipitation in the storms affect hurricane intensity. Hurricane modelers have recently experimented with different ways to streamline the models by comparing multiple prediction algorithms in the models and coupling ocean and atmospheric data to improve accuracy. With recent model upgrades, scientists at AOML are now able to track the inner core of a storm in high-resolution as it progresses.

Solving Intensity Forecast Error Makes Storm-Prone Areas Safer and Better Prepared

Understanding the dynamics that fuel tropical cyclones is paramount to producing better forecasts and keeping our coastlines and coastal communities better prepared when hurricanes hit. By running model simulations, studying past hurricanes, and collecting real-world data on what goes on inside the storm with new instruments, AOML continues to push forward the scientific literature on the boundary layer and extreme weather. AOML works with NOAA’s National Weather Service National Hurricane Center and Environmental Modeling Center, NOAA’s Aircraft Operations Center, Earth Systems Research Laboratories, and other NOAA labs and offices to gain diverse perspectives that will help our community solve the hurricane intensity forecast problem. Greg Foltz, Research Oceanographer at NOAA AOML said, “Based on what we are learning with new research, we suspect that a big part of the answer lies in the boundary layer.”