It wasn't until the 1950's that the very first forecast models were developed for predicting the path of a hurricane.
Prior to that time, there was really no warning at all.
In fact, unless a storm was witnessed by a passing ship, airplane, or happened to sweep over an island, there was no way to know a storm was brewing.
In the 1940's and 50's, aircraft reconnaissance and very basic computer technology were used to learn about storms.
Of course, these beginning forecast models were not always reliable and scientists are always working to create more precise methods for predicting the path of a big storm.