That doesn't mean it will blow tropical storm force winds for six hours or 12 hours. It could be one minute or three, but it means if you have awnings that can't withstand tropical force winds, you should take them down.
It's a very rare tropical cyclone making landfall in the Iberian Peninsula.
Once Irene hits the icy waters of the North Atlantic in about 48 hours, any remaining tropical characteristics should quickly disappear.