How to determine propegation speed of signal peaks?

I have a time series of pressure values at various points along an array. When I plot P vs. X (where X is position along the array) and loop through time I can see various peaks. Some of the peaks seem to propegate down the array at speeds that are higher than the mean speed.

Is anyone familiar with a method that can be done in matlab that would be able to extract the speed of each individual peak and keep values greater than the mean flow and ignore values that are equal or less than the mean flow?

Thanks in advance for any help that you can offer.