Size Matters

i-e463dc7fe8373e4276e0411a5229e3fa-FloSept9.jpg

Flo is getting organized, finally. Maximum sustained winds are at 70 mph, and minimum central pressure is now 990 mb. By the next advisory this storm may be classified as a hurricane (if it isn't one already). The media, I'm sure, must be getting very excited.

Hurricanes run the gamut in size, and Florence happens to be a very large storm in terms of its spatial scale. And that makes a very big difference, as Jeff Masters notes:

Florence has a very large swath of tropical storm force winds that have been blowing for many days over a huge stretch of ocean. These factors, when combined with the storm's expected intensification into a Category 2 hurricane, will create very high ocean swells that will impact the entire Atlantic coast from the Lesser Antilles to Canada.

Indeed, variations in hurricane size can have a very big impact on how much damage the storms can cause--and yet they don't receive nearly as much attention as do variations in intensity. Part of the reason is that there's very little understanding of why hurricanes get really big, or remain really small. As Kerry Emanuel observes:

A fourth characteristic of hurricanes, their geometric size, has received less attention. The diameter of tropical cyclones ranges over nearly a factor of ten: the smallest observed storms can be placed entirely within the eyes of the largest. A storm whose radial dimension is twice the size of another will cause perhaps as much as four times the damage (all other things being equal) since the damage track will be twice as wide and each point within it will experience damaging winds for twice as long. The magnitude and area covered by oceans waves and the storm surge will also be greater. Katrina of 2005 is a grim example of a large hurricane. But so little is now known about the factors that determine the geometric size of individual storms that we are not able to discuss the matter here.

I'm not able to say much more about it either, obviously....but Bermuda could be in for a storm that has a greater impact than one would expect based upon merely considering its Saffir-Simpson category.

Tags

More like this