Do We Need a Category 6 for Hurricanes?

[Randy Zipser]

Don’t the NHC surge maps encompass these factors, via the color scale of surge inundation?

They might, in broad, general terms. But the idea behind creating a new WRAS is to assign a specific scale number to the anticipated landfall location and surrounding coastal region, similar to the SSHWS for wind risk (Category 1-5). Coastal residents might respond with more evacuation urgency to numbers than just to "broad-brush" color-scale schemes on maps.

Admittedly, the downside to having both wind- and water-risk scales is that both wind and water start with the letter "W," so the messaging might cause confusion with the public (at least at first). One way to resolve that messaging problem, however, would be to have a "W/S" [Wind/Surge] scale designation. For example, instead of Category 4, public hurricane warnings would say "W4/S3" [or "Wind 4/Surge 3"] where both scales have 5 levels of severity (because the public is already used to a 5-level scale). So, there may be no need for a Category 6 after all...

 

[Randy Zipser]

Lastly, the direction (onshore vs. offshore) of winds relative to the coastline due to the direction of approach of the tropical cyclone would have a huge impact on the storm-surge potential.

...to have a "W/S" [Wind/Surge] scale...

It would be possible to have a W5/S1 event, which makes a huge difference as to how the potentially-affected residents would prepare/respond in terms of evacuation.