The number of hours into the future. 00 is considered the initial time with each successive row being 6 hours later. Therefore, the 0 to 24 hour time scale needs to be adjusted for every time zone. It is quite simple once one gets the hang of it. More info on the Web .
Wind direction is given as the direction the wind is coming from along a compass direction.
That means .01 inches of liquid-equivalent precipitation is forecast between the 42 nd and 49 th forecast hour. The column is cumulative meaning that the total precipitation for the 48 period is the sum of all forecast times. This number is used to estimate thunderstorm and severe weather potential. 534 equates to 534 Dm thickness. These are mean relative humidity values in percent for that time period.