I think this discussion is getting to the point where it is more about what you think the NWS should do in warning situations. Should the NWS use call to action statements in warnings? Why or why not?
This brings into question how people respond to warnings. Is there a perceived threat that if people do not act on the warning, their lives could be at stake? Not let's think about this for a moment. If there is a tornado warning, the first thing we(weather geeks, chasers, etc) do is fire up the laptop with GR3 and start looking at the storm. Then we make a decision to go chase or not. Hopefully if we see it is coming for our house we have the video camera ready and then ready to run for cover.
Other people get the warning, go outside and look for the storm. They want more information on the threat. Do I need to be concerned? Others may blow it off thinking this is just another tornado warning, I live in OK and yet to be hit, so this will just be another storm or non event. There are others that have had their houses removed by an EF4 so they head for the storm shelter regardless. The idea behind these call to action statements in warnings is to provide additional information so that you act upon the warning and usually time is of the essence.
Now with storm surge and hurricanes, you hopefully have a lot of time to get going when the evacuation is started. Evacuations started before the hurricane warning was issued for Ike, and then expanded when the warning went out. For whatever reason, people were slow to respond to the situation. There is more time to think about it and rationalize it. Afterall, evacuating is not on everyone's priority list. It is expensive with high gas prices, hotel costs, food, etc. People make excuses to stay for whatever reason. Some still want to see that this thing is going to hit, and by the time they figure out that it is, it is too late. So with that, what is going to motivate you to get out of surge prone areas? Your only option is to run to higher ground. This is where the certain death type of CTA has its purpose in that there has to be a way to get people's attention that they need to act on this warning with urgency. It basically says that the consequence of you staying in this storm surge area with 15ft of surge could be your life. Hopefully this would motivate one to take action and leave. Now, should we (NWS) use these CTAs or should the county EM talk about this stuff?
Now the Gal Co OEM talked this thing up, maybe not in the media as much, but they certainly stressed to all the cities that the storm surge will be a life threatening situation. In the end, the EMs end up using the NWS as the buck stops here authority when it comes to the actions that need to be taken in regard to warnings. Even the EMs have a hard time convincing people to take action. So as much as the NWS tries to tell people what to expect, they still ask what they should do. My job as a forecaster has changed from doing straight forecasts to doing the forecasts and interpreting the forecasts so people can understand what to do. There are some people that get the warning and they may seek out a little more information, but by and large they know what to do. Others do not have as much common sense, and need this extra hand holding. That is where the call to action statements come into play. EMs can say all they want about what people should do, but they are not seen as the expert or authority when it comes to weather related warnings. EMs are far more concerned about making sure evacuations are ongoing and preparing for the aftermath. The fact of the matter is that they come to the NWS (in this case our office) and tell us not enough people are evacuating. What can you do? Well, based off the info we have, we can use this CTA. Will that help?
Now, we do not know if the certain death wording caused others to evacuate or not. I don't think anyone can know that for sure. The county did say that later that afternoon and night, more people were evacuating. Perhaps it took them longer to get home from work and make preparations. Maybe it took people longer to get enough information so they know what they need to do. In this regard, I think it helped having the strong language so that it gains attention that the threat is real. It helps put the threat into perspective when some may have trouble thinking what 15 ft of water will do to my house.
In the end, the NWS uses the call to actions to get the attention of people, provide more information on the threat so that the warned people take actions. Some may decide to not take action, and that is their problem. The other issue is that the NWS is seen as the expert and authority when it comes to weather hazards and threats. The NWS has the credibility where as the county EM may not and will likely look to the NWS for information about the threat anyway.