3 ms·
Often I can't even say for sure if the forecast is wrong or not. For example, what is a 10% chance of rain at 10? That could mean 10% chance that rain will occ
by tropo 8y ago
Often I can't even say for sure if the forecast is wrong or not.
For example, what is a 10% chance of rain at 10? That could mean 10% chance that rain will occur at some point from 10 to 11, 10% chance that it will be raining at a randomly selected point between 10 and 11, or 10% chance that it will continuously rain from 10 to 11. Also, it could be any of those three, except from 9:30 to 10:30. Also, it could be a 10% chance of raining at exactly 10.
So right there, I see 7 possible interpretations.
Add in a map, and we can apply those to an area. It may be a 10% chance of raining at some place within this region, but any one place gets a smaller chance. It may be a 10% chance everywhere in the region, but a 99% chance that some part of the region gets rain.
- labster 8y agoWhat it really means in terms of exact timing is that an AWOS (weather station) will record measurable precip between the 1000 report and the 1100 report. Sometimes percent means forecast confidence, sometimes it means that they can't predict what area will get hit with rain. Like synoptic conditions will say "this region will definitely get a few thunderstorms", but when you drop down to mesoscale then you can't tell which city will actually get the rain. In longer-term forecasts, 10% usually means "I have no idea what's going to happen, so I guess precip is possible then." At mid range, like 3-5 days, it usually means "we haven't nailed down the timing of this thing yet". If you actually want to know what the logic is, go read the forecast discussions.