I checked the map. The south tip of Florida is about 70 miles south of me. If Irma’s eye goes straight up the center of the peninsula it would take about 3 to 4 hours to reach here. Since the eye would be over land during that time, how much could Irma weaken?
When Katrina passed over south Florida (going west), she strengthened. I don’t think there is a good answer as each storm seems to behave differently over that area.
I have read that because much of South Florida is not “land”, it is warm swampland, that it’s effect on a hurricane is reduced. By how much, I do not have a clue, but I would think that NHC takes it into account.
Not much. Don’t forget this about storm surge. It is not just the ocean which experiences storm surge but the water table as well. All of FL is an aquafer. The hurricane will raise the inland water table substantially -feet, as it passes..
NHC always gives the benefit of the doubt to worst-case, so no one can say “I wasn’t warned”. The usual case with a landfalling storm is that windspeed diminishes rapidly once it’s a few miles in. A landfalling 3 might be a 1 when it gets to your front door. That said, Irma is a very healthy storm, with no high terrain to inhibit it, and lovely warm water close by. Irma may well go down fighting. If your house is up to current code, recently built and in excellent condition, and if your location is high (relatively speaking; this is FL after all) your threat is not wind per se but falling/flying objects. Wind of even 100 mph can be terrifically destructive on trees and large branches, so consider carefully if any are near you. Palm trees do relatively better; pine trees snap like toothpicks. Saturated soil loosens its grip on roots so that an entire tree can be toppled — especially in cases in which the tree’s diseased or termite-infested. Wind-driven branches over your roof can tear off shingles and let water in (so trim them back now). Even a healthy, mature live oak can lose limbs large enough to crush a structure or you. A falling tree can easily take out windows or a roof, crush your car, block a road, etc. And there are always tornadoes to think about. I have evacuated only once (Katrina) and as a matter of principle would resist in most cases, because being on site to mitigate damage can be important if you own nice things that cannot be replaced. Furthermore looters will be looking for your house before government allows you to return. Would I stay in my well-built house with a cat 3 coming ashore 70 miles away? It would depend on trajectory, as I have some trees that worry me. I would want to have bug-out preparations fully in place, including a safe destination close by. Are there neighbors who’d take you in? Are there neighbors you want to help? Do you have family or animals that need you?
It is a hard call, which no one else can make for you. I can only promise that your storm will be different from everybody else’s, and must be evaluated on the unique circumstances as they factor in your life. I’ve done my best to outline points you should be pondering. Good luck.