There’s been a lot of blather about the “category” of Hurricane Florence, currently inflicting itself on the Carolinas of the United States (South and North, about which many political jokes could be made, but out of respect for their travails of the day, I shall desist), but as someone at work pointed out, it may not be as useful for predicting the impact of a Hurricane as one might wish. For those with a taste for technical details, the Category of a hurricane is a measurement of the sustained wind speeds in the hurricane, and the metric is known as the Saffir–Simpson scale. See the link for more details.
Hurricane Harvey (Wikipedia)
Not that I’m dissing the dangers of the wind, of course, but remember Hurricane Harvey, which afflicted Houston, TX, in 2017? For all that the wind did damage, the major part of the damage was inflicted by the rainfall, as nearly 40 inches of rain fell in some areas around Houston.
Did we have a clue it was going to be that bad? No. Now, perhaps the NWS (National Weather Service) didn’t have a clue, either, but it seems to me that when they do, they should find a way to inform the public of the expected characteristics of the storm[1]. But it’s not enough to claim that they’ve worked up forecasts and made them easily available to the public. This is especially true as it becomes apparent that the characteristics of hurricanes are changing such that the “Category” isn’t as important as its expected rainfall.
And, finally, given the relative success of the Category system of classifying hurricanes, it should not be thrown out – it should be extended.
I think it should be extended so that, iconically, it looks like this
Category<wind-speed ind>,<expected heaviest rainfall>,<area of substantial impact>
As suggested, we keep the wind-speed indicator, as most folks know what it means or how to look up the mappings from the symbolic 1-5 values to wind speeds.
The expected heaviest rainfall value, which I suggest be in inches only because I live here in the States[2], should be obvious. However, I argue for the heaviest expected rainfall, not average, because the difference between average and heaviest may be so large as to be misleading, and the go-to statistical alternative to average, which is median, has no meaning in this context. Best to be prepared for the expected worst.
Finally, area of substantial impact, probably best measured in square miles[3], would describe the expected coverage of the weather event over the geographical territory it is most likely to hit, as constrained by substantial impact. I would limit this to dry land, since land is typically far more densely populated by humanity than is the ocean.
One more refinement is that the latter two measurements, unlike the first, would be predicted values, not current values. That is, they are the expectations as of the moment the categorization is issued of the amount of rain still to fall, over the specified area. As a hurricane hits a land mass, dumps its rain, and loses energy, these latter two values would fall (as would the first, in most cases, as winds need energy to blow). So we might see Harvey, before making landfall, and assuming the meteorologists saw this coming, as a
Category 4,40,1660
40 inches was the worst rain rain Houston saw, and, while I don’t know how much of the Houston and non-Houston area Harvey impacted, I decided to substitute, for the purposes of this example, the metropolitan area of Houston, which is roughly 1660 miles2.
This approach, I think, will encode this brief, predictive, and descriptive categorization of a Hurricane into the public consciousness, and will hopefully lead to more thought about the potentially disastrous effects of any given hurricane. It may even lead to more easily understood comparisons, and perhaps some intrepid data visualization people can use these for graphing purposes.
And now I look forward to some reader telling me that the NWS is already doing this. Still, I hope this pushes them forward on this useful pursuit.
1New readers may not know that I live in Minnesota, which, in the United States, is just about as far as you can be from any hurricanes. That should explain any ignorance I’m displaying in this post.
2Call us barbarians if you must.
3See note 2.
