Whenever the Governor, Controller, and Director of Finance determine that the General Fund revenues for any fiscal year commencing on or after July 1, 1947, are below the amount estimated in the budget submitted by the Governor to the Legislature for the fiscal year, they may jointly authorize the transfer from the Revenue Deficiency Reserve Fund to the General Fund of an amount equal to the difference between the actual revenues received for the General Fund and the amount which it was estimated would be received.