re: #51 klys (maker of Silmarils)

Katrina had the time as a Cat 5 to build up the storm surge to bring with it. Those lag behind the intensity fluctuations, because it takes time for the wind to pile up that much water - and time for the piled up water to dissipate if the wind isn’t there to support it. When Katrina weakened shortly before landfall, that took down the winds but there wasn’t enough time for the storm surge to respond in kind.

Likewise, it’s very possible that the rapid intensification of Harvey has prevented the storm surge from building to the levels that would otherwise have been expected for a Cat 4 storm. My guess is a lot of the damage we’ve been seeing is wind-related, not from the surge.

And of course, the big hazard is really yet to come, in terms of the stall and flooding that’s going to happen in the days ahead.

Yes, but I’m not sure even the NHS has figured out why Katrina hit like it did. And of course at New Orleans she was a weak cat 2 at most. The disaster there had other causes.

And certainly you’re right that, if the predictions are anywhere close to correct, the greatest harm and destruction in the next few days will be from rainfall flooding.