"Invest" is short for Area of Investigation, usually an area of low pressure. They are numbered in order from 90 to 99, and then it goes back to 90 again. An invest is something the hurricane center is keeping an eye on, essentially, for tropical development. Next comes a depression followed by a storm. This one won't get beyond the invest stage, due to coming ashore before it can really get going. Sometimes when the tropics are really cooking one or more stages get skipped, and we might go directly from an innocent looking blob of showers to a full-fledged storm.
I think Atlantic invests usually have an "L" as in 90L, because the same strange numbering system is used in all the oceans, with a letter to identify the ocean.