Just watching satellite loops, I realized August 1999 is a perfect example of a hyperactive season that blew up in perhaps the perfect 'flick of the switch' fashion that we're possibly expecting this year.
August 15 saw a dead basin with nothing but dry air in the MDR and hardly even any clouds; only tropical wave of note in the western Caribbean having struggled across the Atlantic without development
August 22 one week later saw category four Hurricane Bret develop in the western Gulf from the Caribbean wave, and the MDR suddenly became very favorable with Hurricane Cindy present just off frame to the east (temporarily a tropical storm, eventually reaching category four) and a strong tropical wave NE of the Lesser Antilles
August 27 sees Hurricane Cindy recurving, newly christened Hurricane Dennis developed from the Antilles wave headed for the East Coast, and Tropical Storm Emily fully developed from a wave east of the Antilles
Looks like early August 1999 was quieter than this August, at least we have tropical waves maintaining at least a little convection. When dry air finally starts to settle later in the month (still seems likely) things could get pretty nasty pretty fast... August 1999 wound up with two category fours, a category two, and an additional tropical storm after being literally completely dead the first half
