Study Shows Poleward Shift In Tropical Storm Peak Intensity
May 15, 2014

Peak Intensity Of Tropical Storms Shifts Poleward

Brett Smith for – Your Universe Online

A new report from a team of American climatologists has found that the latitude at which tropical storms reach their peak intensity is moving toward the poles – suggesting the term ‘tropical storm’ is slowly becoming somewhat of misnomer.

Published in the journal Nature, the new report found that the peak intensity of these storms is moving toward the poles at a rate of about 33 to 39 miles per decade.

"We've identified changes in the environment in which the deep tropics have become more hostile to the formation and intensification of tropical cyclones and the higher latitudes have become less hostile," said study author Jim Kossin, a scientist with the National Oceanic and Atmospheric Administration (NOAA). "This seems to be driving the poleward migration.”

The study team reached their conclusion through an investigation of 30 years of global tropical cyclone information. The term "tropical cyclone" describes an extensive class of storms that includes hurricanes and typhoons – typically massive, damaging storms that pull energy from warm ocean waters.

The results of the study are essential because they show that some regions, including populous coastal cities, could see greater risk as a result of large storms, as well as linked floods and storm surges, Kossin said. Areas closer to the equator could notice a decreased risk, and places far away from the equator could see a higher risk. The trend viewed by the study team is especially crucial considering the potential loss of life and property that can accompany a tropical cyclone.

While the study didn’t find a global trend in the frequency of tropical cyclones, it did identify a distinct poleward pattern in the latitude where storms are the most severe. While reports of storm strength varied in the study, the latitude where tropical cyclones attain their peak intensity is a more trustworthy measure of shifts in the way tropical cyclones act, Kossin said.

“(T)he more compelling aspect is that the rate of migration fits very well into independent estimates of the observed expansion of the tropics,” he said. Previous studies have noted the expansion of tropical zones and attributed that expansion to rising greenhouse gases, ozone loss, and particulate contaminants, all the result of human activity.

"The tropics are becoming less hospitable (to these storms)," Kossin told the Associated Press. "The higher latitudes are becoming less hostile."

"This is an important, very well researched paper that uncovers something that was unknown previously," noted Chris Landsea, a hurricane researcher at the National Hurricane Center who was not directly involved in the study.

Another study published this month by the Journal of Epidemiology & Community Health revealed one of the overlooked costs of powerful tropical storms – an increase in fetal mortality.

The study found hurricanes Katrina and Rita might have caused up to half of all recorded stillbirths in the areas hardest hit by the storms. Hurricane Katrina struck the state of Louisiana on August 29, 2005, and Hurricane Rita hit a month later on September 24. Using parish records and federal data, the study researchers found odds of a pregnancy ending in a stillbirth was 40 percent higher in parishes where 10 to 50 percent of housing stock had been damaged, and over twice as high in areas where more than 50 percent of the housing stock had taken a hit.