Indian monsoons influence hurricanes in the Atlantic: study

According to a study, the strong monsoons in the Indian Ocean can cause east winds that repel hurricanes from the Atlantic Ocean to the west, thus increasing the risks of landing. in the Americas.

The study, published in the journal Letters of geophysical research, found that in years when summer storms in India are stronger, Atlantic hurricanes move further west. In years with lower rainfall, hurricanes tend to bend north earlier and extinguish in the North Atlantic Ocean.

The newly discovered relationship could help scientists better predict the course of hurricanes, especially in late summer, as in September, when Atlantic hurricane activity reached a peak, according to the researchers.

"What surprises me is how precipitation near India can lead to significant changes in the Atlantic hurricanes," said Patrick Kelly of the North West Pacific National Laboratory of the Department. United States Energy. "This research is the first to establish the link between the hurricanes of the Atlantic and the Indian monsoon."

Hurricane Forecast

The Indian monsoon season has generally declined in September, but the weather forecast suggests that, under conditions of future warming, rainfall will increase, and that the monsoon season could end later in the year, indicated researchers. According to the study, as the climate continues to heat up, the monsoon could have an increasing influence on the trajectories of the Atlantic hurricanes.

"We do not have the habit of making hurricane forecasts on a seasonal time scale," said Benjamin Kirtman, a professor at the University of Miami. "What is deeply exciting about this job is its potential to improve seasonal forecasts and predict hurricanes."

Previous research has attributed changes in hurricane direction to ENSO (El Nino-Southern Oscillation), a periodic fluctuation in sea surface temperature and atmospheric pressure in the Pacific Ocean equatorial. Scientists have traditionally relied on the ENSO La Nina phase to make predictions about the strength of a particular hurricane season in the Atlantic, but have trouble predicting trajectories. of each hurricane.

"In the seasonal forecast of hurricanes, our biggest predictor of what will happen was La Nina," said Kirtman. "Unfortunately, seasonal forecasts based on La Nina have not been able to tell us much about the landing."

Simulations of hurricane traces

In the new study, Kelly and his colleagues wanted to know how the Indian monsoon, known source of climatic variability, had affected hurricane tracks, as the Indian monsoon had not yet been studied in the context of Atlantic hurricanes.

They conducted simulated hurricane trajectories with a model incorporating observed changes in monsoon intensity and found that hurricanes were moving significantly westward in response to strong monsoons.

The strong monsoons influence the direction of hurricanes by enhancing the effects of the subtropical high North Atlantic, high atmospheric pressure center in the Atlantic Ocean. As the subtropical peak increases, stronger winds arrive from the east and push the hurricanes to the west.

According to Kelly, La Nina and the Indian monsoon are correlated, but the strength of the monsoon influences the direction of hurricanes regardless of the fluctuations of La Nina, responsible for changes in the frequency of hurricanes. Fluctuations in La Nina could lead to more hurricanes in the Atlantic, but strong Indian monsoons direct them further west, making them more likely to land in the Americas, researchers said.