Many of us are of the opinion numbers, such as the 3 tornados, are important in dreams. This could symbolize 3 events that will alter things in your surroundings or your life. The first two dissolved, but lead to the larger 3rd one. In your dream, you couldn't get shelter from the large tornado. This could mean you will not be able to avoid the event, but will need to face it head on.
On a lighter note, you have 3 boys. My sister has two and I'm sure she would agree they can be very much like tornados, especially around the house:-)
A tornado is something we need to be somewhat prepared for and most definitely pay attention to. This may be a heads up to pay a little more attention to your surroundings, as the busy and distracting Holiday season is upon us.
I'm hoping this helps a little. I've had tornado dreams on a regular basis for years. However, I think mine are different from your dream, in that they occur within a day or two, but I have never been through one myself.