The precipitation rates that you see in the tdump file associated with the trajectories comes from the meteorological model you are using to calculate the trajectories. Assuming you are using the EDAS data, the rates you see are computed by subtracting the rain amount in the current grid cell of the trajectory endpoint at the current time from the rainfall
amount in the current grid cell for the previous time (3 hours earlier) and dividing by time (3 hours in the EDAS). Keep in mind that this precipitation is not the observed precipitation and that we only save every other grid point
of the EDAS (prior to May 2004 the 80km EDAS was created by removing every other grid point from the 40km EDAS dataset without interpolation. The 40 km EDAS became available in January 2004 and does not have any data removed).
Glenn Rolph
NOAA ARL