Patricia’s Promise: Storms to Come

by Ray Grigg

Hurricane Patricia struck the Pacific coast of Mexico at 6:15 pm on October 23rd near a town called Cuixmala, about 100 km northwest of Manzanillo. Fortunately, damage was minimized as the sustained winds of 297 km/h and gusts of 340 km/h quickly decreased over land. After deteriorating to a tropical storm, the remnant of Patricia caused a swath of flooding and mudslides along a narrow path through Mexico. In some areas of Texas and Louisiana its 50 cm of rain caused more flooding.

About a dozen major hurricanes have struck the Pacific coast of Mexico since 1955, the worst being Hurricane Mexico in 1959 and Hurricane Felix in 2007. Patricia, however, was unique because of the speed with which it arose from the warm band of ocean west of Central America. Within a day its winds had increased 160 kph to a sustained speed of 320 kph, with gusts over 400 kph. Patricia was noted as the most rapidly intensifying storm in the history of modern meteorology, and the strongest hurricane ever recorded in the western hemisphere — even exceeding Typhoon Haiyan which devastated the Philippines in 2013.

The hurricane season in the northern Pacific has been particularly active this year — Patricia is the 9th of category 4 or 5 storms, exceeding the old record of 8 set in 1997. Although an unusually strong El Niño event is a contributing factor, the major cause of such powerful weather is the continued greenhouse gas emissions that are warming our planet.

The climate models from the United Nations’ Intergovernmental Panel on Climate Change predict an increase in wind speed and rainfall rates in these storms as a hotter atmosphere and warming oceans amplify convection and evaporation. Although the frequency of these storms may not increase, their strength almost certainly will. The formation of Patricia can be traced precisely to that wide band of warm ocean west of the Yucatan.

This, of course, is an El Niño year so we might expect more active weather. But such years are becoming more frequent and lasting longer. And the science on climate change is unequivocal about the effects of a warming planet. As ocean and air temperatures rise, the two collaborate to produce storms of higher winds and heavier precipitation.

With about 500 times the mass of the atmosphere, the world’s oceans are somewhat slower to respond to the warming trend. But every unit of heat generated by greenhouse gas emissions is absorbed somewhere in the planet’s total warmth. The National Oceanic and Atmospheric Administration (NOAA) announced that July 2015 — typically Earth’s hottest month — had an average land and ocean combined surface temperature of 16.6°C, up from the 20th century’s average of 15.8°C and higher than in any previous July in the 135 years since records began in 1880.

Such heat gets translated into storm energy and weather anomalies. This year, for example, the Pacific Northwest had its wettest spring on record followed by its driest ever summer. Searing heat and uncontrolled forest fires plagued the region. Will this be our mildest but stormiest winter? All we know is that Patricia’s promise is for more extreme weather, and all we can do is reduce our greenhouse gas emissions and anxiously await her surprises.