Should We Reclassify the Biggest CATs?

Typhoon Mangkhut, a Category 5 storm that ravaged the Philippines and China earlier this month, got us thinking about just how bad typhoons and hurricanes may become if the predictions of climate scientists continue to be proven accurate.  We’ve all seen the claims that a warmer atmosphere and warmer ocean waters will lead to stronger storms, higher winds, greater storm surge, and more rain and flooding.  Typhoon Mangkhut and Hurricane Florence seem consistent with those predictions, and Mangkhut may even call into question whether a new level of storm classification will be appropriate in the future.

The idea of a future Category 6 storm classification was the subject of a September 14, 2018 on-line article from the U.K.’s Daily Express, published when Typhoon Mangkhut was bearing down on the Philippines with wind speeds of an extraordinary 205 miles per hour.  That made Mangkhut a Category 5 by a wide margin, with the second highest wind speed on record (behind only 2015’s Hurricane Patricia, which had sustained winds of 215 miles per hour).

The existing five storm categories utilize the following sustained wind speed ranges:
Category 1: 74 to 95 miles per hour
Category 2: 96 to 110 mph
Category 3: 111 to 129 mph
Category 4: 130 to 156 mph
Category 5: 157 mph or higher
At Mangkhut’s 205 miles per hour and Patricia’s 215 miles per hour, these storms would be “off the chart” if not for the fact that the Category 5 classification has no top end.  Under the current classification system, Categories 1 through 4 each encompass a range of between 14 and 26 miles per hour (e.g., Category 4 spans 26 miles per hour – that is, 130 to 156 mph). However, the unbounded Category 5 includes storms with sustained winds of 50 or more miles per hour stronger than the threshold speed. 

Should there be a Category 6?  Will there be a Category 6 if these super-charged storms continue to occur?  Perhaps yes, although the U.S. National Hurricane Center’s description of the destructive force of a Category 5 storm makes it difficult to imagine exactly what a Category 6 would do that Category 5 storms don’t already have the power to do.  The National Hurricane Center summarizes the property damage and destruction to be expected in a Category 5 hurricane as follows:
. . . Almost complete destruction of all mobile homes will occur, regardless of age or construction. A high percentage of frame homes will be destroyed, with total roof failure and wall collapse. . . . Significant damage to wood roof commercial buildings will occur due to loss of roof sheathing. Complete collapse of many older metal buildings can occur. Most unreinforced masonry walls will fail which can lead to the collapse of the buildings. A high percentage of industrial buildings and low-rise apartment buildings will be destroyed. Nearly all windows will be blown out of high-rise buildings . . . Nearly all trees will be snapped or uprooted and power poles downed. . . Power outages will last for weeks to possibly months. Long-term water shortages will increase human suffering. Most of the area will be uninhabitable for weeks or months.
That comprehensive description would seem to apply to 200+ mile per hour storms as well.  Maybe a Category 6 classification would remove the qualifiers (“most,” “nearly,” “possibly”) and simply state that a Category 6 storm WILL result in these levels of destruction.

Whether we continue to classify all storms with sustained winds in excess of 156 miles per hour as Category 5, or we add a new Category 6 classification for storms exceeding a higher threshold (185 mph?/ 200 mph?), the insurance implications are the same.  More storms, stronger storms, higher winds, greater flooding – however you label them, these storms are a major threat to insureds and insurers worldwide. 

Posted by Dan Millea