Weather forecasting...?

Question

So, when you read a forecast and it says, for example, 60% chance of rain for the Daytona Beach area, does that mean that 60% of daytona beach will see rain, while 40% of the area will not? Or, does that mean that there is a 60% chance that it will rain, and a 40% chance that it wont rain?

If you could find a source, that would be great!

Answer 1

60% chance.

Weather is all about probability. If the identical weather conditions occured 100 times (impossible of course, but it's easier to understand probability that way), it will rain 60 of those times.

Answer 2

You have asked a question that has been debated by the meteorologists for a long while.  

When I first enter this profession, I was trained to write my forecast with the probability of precipitation (POPs) to represent the chance for my forecast area will get measurable precipitation.  This is especially true when you are expecting stratiform precipitation.  Since this type of precipitation covers a large area with steady rain, if it does develop, it would most likely result in measurable precipitation for my whole forecast area. Then one can zsay that the POPs should represent the chance of that occurring.  

However, if you expect off and on, convective precipitation, where you are dealing with convective cells, then your POPs forecast can be written to represent the total areal coverage of precipitation for all those cells.

I think that was the best solution.  But not everybody agreed.  So a few years later, the forecasters suddenly got a notice that POPs should only mean the chance.

But that did not end the debate among the forecasters and today I still see forecasters using POPs to represent areal coverage.

For more information on forecasting and POPs , please click on the following links.

http://pajk.arh.noaa.gov/info/articles/s...

http://www.stormtrack.org/forum/showthre...

http://www.cimms.ou.edu/~doswell/probabi...

http://www.ametsoc.org/policy/2008enhanc...

http://ie.tamu.edu/people/faculty/Bickel...

http://blog.washingtonpost.com/capitalwe...

Answer 3

60 % chance.. its about probability..

10%-20% >> Slight chance

30%-40% >> Some chance

50% >> Good chance

60%-70% >> Likely

80% or above >> Will have precipitation