STORM2K

Hypothetically you have a category 1 hurricane which is twelve hours from landfall in the GOM headed toward a large metro area. It itensifies in twelve hours to a category 4 before landfall. Would you begin massive evacuations in that short time span or tell people to stay where they are? What are the rules governing evacuations with this scenario?

Hard question. We all know that an evacuation with the scenario you have presented is not possible.

There is only one answer I can think of......

"Do the best you can, with what you have, in the time you have left." (Mother Theresa)

That is a very tough call right there. That's also the worst case scenario as well. A Category 1 hurricane is about the make landfall and voluntary evacuations are ordered and overnight it explodes into a massive Category 5 hurricane. If they call for evacuations for a Category 1 hurricane, it's probably not a bad idea to evacuate.

If I saw the possibility of explosive development, I would just evacuate.

Have to be clear on your terminology. Landfall = the center of the hurricane crossing the coast. Tropical storm-force winds could reach the coast greater than 12 hours prior to landfall of the center, making it impossible to evacuate safely. If you're in a surge zone you should plan for a hurricane 1-2 categories higher than is forecast. Forecasting intensity is always harder than forecasting the path. Bottom line is that if you're in the surge zone for ANY hurricane (1-5) you should consider evacuation if a hurricane is heading your way. We saw how quickly hurricanes can develop (Rita from 65 to 165 mph in 36 hours, Wilma did it in 24 hours, Charley Cat 2 to Cat 4 in 6 hours). Forecasters won't be able to say for sure whether such rapid intensification is possible from 3 days before landfall when you have to make your decision to stay or leave.