Well this is what I saw in Doval's thread where he was asking a bunch of question's about stuff like this
"L = g*d*p*w + 30*b + A
L is launch speed seen on the end of game results screen, g is the growth of the move, d is the damage the move deals, p is the percent the target is at after the hit, w is the target's weight (or launch resistance, really), b is the base of the move, and A has something to do with a combination of the angle the move launches at and the character's fall speed acceleration (moves that launch downward have a negative A value).
The A value unfortunately has not been very carefully looked into. It's only applied to moves that send into the tumble, which creates a sort of "hole" in a graph of the launch speed of a move as it moves from a non-tumble percent to a tumble percent. You can find out the launch speed a move tumbles by dividing 1020 by the hitstun multiplier constant (in brawl+, this is .4865, whereas it was .40 in vbrawl). In vbrawl, the tumble line was drawn at 2550, but in brawl+, it is 2097. Most moves tend to have an A of around 100 against mario (when an attack is used against characters with greater fall speed acceleration the A value is larger, and against those with less fall speed acceleration it is smaller). Moves that send straight up or close to it (such as nesss's uthrow, luigi's upB, or jiggs' old rest) have around a 160 or so A value against mario. Admittedly, when I perform calculations to determine a move's launch speed at an arbitrary percent, I take a guess at about what the A value will be based on its angle, so while my calculations may be very close to correct most of the time, they are frequently off by a small amount due to insufficient data, and thus usually require a little fine-tuning after testing."
I also remember in that thread Leafgreen mentioned that the 30 should be 32.2 instead.