Warm Ocean, Warm Air, Record Storms

On Oct. 23, 2015, Hurricane Patricia slammed into the west coast of Mexico. It had developed from a tropical storm into the strongest hurricane ever to make landfall on the North American continent, with wind speeds of 200 mph (330kp/h).

On Oct. 21, a storm system that originated in the warm Pacific waters off Baja California crossed the US southwest and hit Texas with drenching, record-breaking rainfall. One Texas town reported 20 in. (51cm) of rain in a 24-hour period. On Oct. 24, the remnants of Patricia added moisture to the Texas storm system, bringing even more heavy rain.

From Oct. 1 to 5, South Carolina was inundated with heavy rainfall that breached dozens of dams, washed out roads, and resulted in what was called a thousand-year flood.

What is causing these record-breaking storms that have been soaking and flooding the southern US and Mexico? A number of factors seem to apply. The air is warmer than normal due to climate change. The water in the Pacific Ocean is much warmer than normal due to a robust El Niño. The water off the west coast of Mexico stood at 87°F (30.6°C), 2 to 3° above normal, when Patricia grew from a 65 mph tropical storm into a 200 mph Category 5 hurricane in just 30 hours.

Not only do tropical storms form and grow in warm tropical water, but warm air causes greater evaporation, and warm air retains evaporated moisture in the form of highly saturated clouds. As one meteorologist put it, these have been very juicy storms, meaning the atmosphere is supercharged with moisture that comes down in the form of record-breaking rain.

Other meteorological factors contribute to conditions that favor powerful storms, such as the absence of vertical wind shear that, when strong, can disrupt tropical storm formation.

Climate scientists, for years, have been saying that global warming accelerated by unchecked burning of fossil fuels will bring bigger, stronger, and wetter storms. More destructive storms, rising sea levels, and more severe droughts all seem to be products of a warming planet.

The only way we can slow the global warming juggernaut is to replace our present fossil-fuel based economy with an alternative energy economy. The sooner we are able to switch from oil and coal to wind and solar, the sooner we’ll have clearer skies, cleaner air, gradually cooling temperatures, and less potent storms.