New climate study signals faster moving hurricanes for Texas

Climate change will intensify winds that steer hurricanes north over Texas in the final 25 years of this century, increasing the odds for fast-moving storms like 2008’s Ike compared with slow-movers like 2017’s Harvey, according to new research.

A group of climate researchers publishing their findings after examining regional atmospheric wind patterns that are likely to exist over Texas from 2075-2100 as Earth’s climate changes due to increased greenhouse emissions.

“So we started the work the day that Harvey made landfall,” said study lead author Pedram Hassanzadeh of Rice University. Dr. Hassanzadeh moved to Houston just before Harvey hit, dropping historic amounts of rain on the Texas coast.

Rice University researchers riding out the storm began collaborating with colleagues from Columbia University’s Lamont-Doherty Earth Observatory (LDEO) and Harvard University to explore whether climate change would increase the likelihood of slow-moving rainmakers like Harvey.

“We find that the probability of having strong northward steering winds will increase with climate change, meaning hurricanes over Texas will be more likely to move like Ike than Harvey,” said Dr. Hassanzadeh.

Harvey caused an estimated $125 billion in damage, matching 2005’s Katrina as the costliest hurricane in U.S. history. Ike was marked by coastal flooding and high winds that caused $38 billion damage across several states. It was the second-costliest U.S. hurricane at the time and has since moved to sixth. Ike struck Galveston around 2 a.m. Sept. 13, 2008, crossed Texas in less than one day and caused record power outages from Arkansas to Ohio on Sept. 14.

Hassanzadeh, a fluid dynamicist, atmospheric modeler and assistant professor of both mechanical engineering and Earth, environmental and planetary sciences, said the findings don’t suggest that slow-moving storms like Harvey won’t happen in late 21st century. Rather, they suggest that storms during the period will be more likely to be fast-moving than slow-moving. The study found the chances that a Texas hurricane will be fast-moving as opposed to slow-moving will rise by about 50% in the last quarter of the 21st century compared with the final quarter of the 20th century.

“In climate science when you look at regional changes in wind, many times different models will give you different answers,” explained Dr. Hassanzadeh. “Some of them will say the wind will slow down, some of them might say the wind will become faster because it’s just a complicated problem, but over Texas we saw this very robust increase in the northward wind.”

“These results are very interesting, given that a previous study that considered the Atlantic basin as a whole noticed a trend for slower-moving storms in the past 30 years,” said study co-author Suzana Camargo, LDEO’s Marie Tharp Lamont Research Professor. “By contrast, our study focused on changes at the end of the 21st century and shows that we need to consider much smaller regional scales, as their trends might differ from the average across much larger regions.”

“It doesn’t happen a lot, in studying the climate system, that you get such a robust regional signal in wind patterns,” said Dr. Hassanzadeh.

So what seems to be changing in out atmosphere as we head toward the end of the 21st century? 

Two big atmospheric processes were identified in this study. First, the Bermuda High, located well east of Houston, Texas. This clockwise circulation, according to these findings, will likely strengthen and expand west. The other process is the North American Monsoon. It also spins clockwise at a high altitude in Earth’s atmosphere over Mexico and the southwestern United States. Climate models used in this study show this process weakening. These signals, combined, will likely increase the northward steering wind over Texas.

Steering winds are strong currents in the lower 10 kilometers of the atmosphere that move hurricanes.

Dr. Hassanzadeh said the increased northward winds from both east and west “gives you a strong reinforcing effect over the whole troposphere, up to about 10 kilometers, over Texas. This has important implications for the movement of future Texas hurricanes.”

“It’s important to do these {climate studies} regionally because how the hurricanes and impacts might change over Houston and Texas coast might be different from how they might change over Florida or other regions,” said Dr. Hassanzadeh.

The full study can be found by clicking here.