New approach to improve hurricane intensity forecast

WASHINGTON: Scientists have discovered that physical conditions at the air-sea interface is a key component to improve forecast models, offering a new method to aid prediction of storm intensity of hurricanes.

"The general assumption has been that the large density difference between the ocean and atmosphere makes that interface too stable to affect storm intensity," said Brian Haus, from University of Miami (UM) Rosenstiel School of Marine and Atmospheric Science and co-author of the study.

"In this study we show that a type of instability may help explain rapid intensification of some tropical storms," said Haus.

Experiments conducted at the UM Rosenstiel School Air-Sea Interaction Salt Water Tank (ASIST) simulated the wind speed and ocean surface conditions of a tropical storm.

The researchers used a technique called "shadow imaging," where a guided laser is sent through the two fluids — air and water — to measure the physical properties of the ocean's surface during extreme winds, equivalent to a category-3 hurricane.

Using the data obtained from the laboratory experiments, the researchers then developed numerical simulations to show that changes in the physical stress at the ocean surface at hurricane force wind speeds may explain the rapid intensification of some tropical storms.

The research team's experimental simulations show that the type of instability, known as Kelvin-Helmoltz instability, could explain this intensification.

The study was published in the journal Nature Scientific Reports.