# How to calculate hourly rainfall projections?

If the National Weather Service website shows increasing probability of precipitation (POP) over a 6 hour period (e.g. 10% rising gradually to 60%), what is the POP in this time interval if the confidence percentage is unknown?

• Homework help question? May 15 '17 at 8:32

The Probability Of Precipitation or POP is the exceedance probability over a given area for a given duration. The exceedance amount is generally taken as 0.25 mm, but may be any specified value. Again, the time $t$ must be specified, and is usually 3, 6, 12 or 24 hours.