Indian monsoon pushing Atlantic hurricanes westward

Strong Indian monsoon wind pushes Atlantic Ocean hurricanes westward, increasing the likelihood of the storms making a landfall in the Americas, says new research.

A new study finds that in years where India experiences stronger summer rain storms, Atlantic hurricanes move further westward towards the land.

In years where the rains aren't as strong, hurricanes tend to curve northward earlier and fizzle out in the north Atlantic Ocean.

This newly-discovered relationship could help scientists better predict the path of oncoming hurricanes, especially in late summer months like September, when Atlantic hurricane activity peaks, according to the study.

“What amazes me is how rainfall near India can drive important changes to Atlantic hurricanes half a world away. This research is the first to draw the connection between Atlantic hurricanes and the Indian monsoon." said Patrick Kelly, an atmospheric researcher at Pacific Northwest National Laboratory in Richland, Washington and lead author.

Asked whether the observational data matches the findings, he told DH, “The short answer is 'yes'. My work finds a connection between the monsoon and the tracks of Atlantic hurricanes in the observed post-satellite historical record (years 1970-2016).”

“Results from a model experiment agree well with the observed relationship, lending greater confidence that the Indian monsoon causes a westward shift of Atlantic hurricane tracks,” said Kelly. The findings were published last month in Geophysical Research Letters.

Currently, forecasting of a hurricane's landfall is a gray area and not generally attempted. “The thing that is profoundly exciting about this work is its potential to improve seasonal forecasting and predict land-falling of hurricanes,” said Benjamin Kirtman, a professor of meteorology at the University of Miami who was not involved in the research.

Kelly and his colleagues conducted simulations of hurricane tracks with a model that incorporates observed variations of monsoon intensity and found that in response to strong monsoons, hurricanes shifted significantly westward.

Strong monsoons influence hurricane steering by enhancing the effects of the North Atlantic subtropical high, a center of high atmospheric pressure in the Atlantic Ocean. When the subtropical high increases, stronger winds come from the east and push hurricanes westward.

“This work suggests that the state of the monsoon may serve as a useful predictor of landfall probability on monthly to seasonal timescales. Incorporating the monsoon as an additional factor in monthly to seasonal hurricane outlooks may prove beneficial and warrants further investigation,” concurred Kelly.