We measure the strength of earthquakes on the “Richter scale open at the top”, as it is always so beautifully called. And heat waves on the upwardly open Celsius scale. So why does the Saffir-Simpson hurricane scale stop at strength 5?
The reasons for this are historical: the strength scale served to warn the population of the expected storm damage. To put it in a nutshell: from strength 5 everything is broken anyway, so an even higher warning level seemed superfluous. This is how the Wall Street Journal argues against the introduction of a category 6.
On the other hand: from the perspective of science, for example to compile statistics on the frequency of different storm strengths, there is no reasonable reason to stop with category 5 – especially at a time of increasing tropical storm strengths in the wake of global warming. Moreover, a Category 6 storm would result in a significantly higher storm surge than a Category 5 storm, so that there is no sensible upper limit for storm surges even for warning purposes. For this reason, hurricane experts have been discussing for years whether the traditional Saffir-Simpson scale should be extended upwards. One of the best-known weather blogs in the USA has even called itself Category 6.
The world’s strongest hurricane to date, Patricia, would have even reached category 7 with winds of 345 km/h. The wind speed would have been 345 km/h. Fortunately, it only hit land in a weakened state as a Category 4 storm!