115012a0_e_Raiders___First_Joint_Action__3
[0] Launching of B-25’s [1] A true wind of at least 7 knots [2] The bombers were not designed for carrier operations. A velocity of 40 knots, or 10 knots in excess of the usual requirement for carrier aircraft was necessary. [3] 
Absolutely essential.
Doolittle Raiders - First Joint Action
3