How can weathermen predict 100% chance of rain?

How can weathermen predict 100% chance of rain - and then change their mind?
Is is just my opinion - or does 100% chance mean there's no way it can't happen?


I looked at the forecast for Wednesday and it said 100% chance of rain on Wednesday. It now says 90%.
My guess is that they will lower it by Tuesday. They usually do.

How do they have credibility when they can claim 100% and then change their mind?

The percentages are based on regional coverage. Data that had indicated 100% coverage of the region can change just prior to arrival and then it's anyone's guess...

I think the main thing is that they were predicting 100% based on the current conditions. When conditions and weather patterns change they adjust.

Yes. The percent isn't actually chance of rain, it's percent of forecast area coverage for the forecast period.

If it rains "somewhere" in their viewing area, they win.

That's a heck of a job. I wish I had it that easy.

Are we seriously discussing the credibility of weather men? Lol

My weather.com app on my Iphone now says "Chance of rain 80%". I don't know how that could be interpreted to mean a percentage of an area.

It was 100% earlier today. Now it is 80%. Funny how they lose their confidence over time.

Think about this a bunch of Bass fisherman discussing the credibility of anyone else. They have are hard time getting the weigh of their fish correct that they have in their hands and they are talking about a weatherman guessing about a weather forecast.

LOL HA LOL

Changing meteorological condition are the reason for rain chance percentages change, predictions are made days in advance
using the most recent available data. We perceive their predictions as WRONG. Many times I prefish using their wind direction data, which on tournament day blows 180 out. I take all weather predictions with a grain, a LARGE grain of salt.

The idiots had a 20% here, well the town next to me had almost 10" of rain last night. All kinds of flooding on rivers where there was no rain predicted.

Consistent, though!

- 10 days out: 100% chance of 10" of rain
- 5 days out: 50% chance of 5" of rain
- 1 day out: 10% chance of 1" of rain
- Today: 5% chance of .15" of rain

Lather. Rinse. Repeat...

You guys don't understand the difficulty in forecasting weather. We understand weather about as well as we understand the human brain. Great on some levels, virtually not at all on others. It's impossible to predict the weather with much more accuracy than we have now until major advances are made in understanding short term weather patterns and behavior. It's not simple by any stretch of the imagination.

Imagine living 100 years ago when you didn't know what the weather was going to do in 15 minutes. And at a time when exposure to the weather could very easily kill you. I'd say we have it pretty damn good with our 10 day forecasts and tornado sirens.

No one is predicting anything anymore. The "weatherman" doesn't have much input if any. Forecasts are based on computer models that analyze weather patterns and simulate what's happening next. They aren't perfect. Sometimes the weather takes an unexpected turn

It actually does mean coverage not actual chance of rain.

it's based on coverage of the broadcast area. Not meaning that you are the only person getting 100% of rain the next ten days.

someone gets it.

If conditions can change and lower the probability then it wasn't really 100% in the first place. If it

meteorology is a complicated science involving sophisticated instruments, precise measurements, radar evaluations and fierce predictions.

They have really been confused with the weather the last few days. Yesterday was maybe a 20% chance late in the afternoon and it rained hard in the morning and in the afternoon. Wind forecasts are something they have yet to figure out good.

Ouija Board.

For a 24 hour forecast, a 50% rain chance for the coverage area means at any given point within the forecast coverage area has a 50/50 chance of having measurable rain precipitation....

A 50% chance of rain at 9PM on an hourly forecast definition varies between providers. Most aps and weather services uses the definition here meaning that there is a 50% chance of measurable rain occurring on a given point in the forecast coverage area within +/- 3 hours of 9PM.

Like a drunk person throwing darts...I predict bullseye...darn...missed...I meant the wall

Maybe Harold Taft had computer models or maybe he was just that good. If the computers are doing it why have meteorologists? Get some pretty girl to read what the computer is spitting out. They are no longer any good at their guesses.

Actually there are dozens of programs and "models" used to formulate a consensus forecast. The experienced weatherman will be able to discern which models provide the most accurate results under various circumstances.

Sure do miss Harold Taft

I give the weathermen a lot of credit. They are very good at predicting days that have a good chance of precipitation.
What I HATE is the fact that they claim 100% and then change their mind. I have so many cancellations because they predict 100% several days ahead of time. They give the illusion that it will be miserable. But the truth is, 100% several days out means it should be a good fishing day. It's a lose lose for a fishing guide. Because the guys who live by the weather app look for the lowest precipitation days. Those end up being the days that I burn up 15 gallons of gas running all over the lake working my butt off and not catching much.

BTW, they changed the forecast for Wednesday from 100% on Sunday to 50% today.

I'd rather them say it's going to rain and it not, than say it's not going to rain and it does.

Getting the weather wrong is one thing-getting the wind forecast wrong is like a rite of passage for weathermen. I've been out on lakes when winds were supposed to be 5-10 and they were 20-30. And I've stayed home on days when its supposed to be windy and theres no wind at all.

There's an 85% chance that 90% of the people will be disappointed with the forecast.

When they say 100% it means the total area will get rain. 50% chance of rain means only 50% of the area will get it. They can't do a forecast for your yard or it would say 0% chance or % 100% chance but never anything beside that. The forecast covers several thousand square miles, and if you look at the accuracy of the forecast over that wide area, they are pretty accurate.

I have heard, add and then double. 5-10 forecast is 15 and double is 30.

My app has a place for text. It says "chance of rain 100%". If they mean 100% of the area, they could say "100% of the area". But what does that really mean if that is the case?

Next time when you listen to the weatherman on the news, listen for the word coverage. They say that word many times rather than saying percent chance of rain. It changes the meaning of the forecast when you hear it that way.

How is 100% coverage of rain different than a 100% chance of rain? If they say everyone and every place in the area will get rain...that is the same thing as saying there is a 100% chance of rain at any given place.

A 100% chance of anything means there is no possibility whatsoever that it won't happen. If there are factors that can change and lower the probability, it was never really 100% to begin with.

There's a 100% chance it's flat pouring outside right now and has been for a while...

I'd like to say this will clear it up, but since you haven't gotten by now it will probably just confuse you more. http://www.srh.noaa.gov/ffc/?n=pop

Raining at the time?

They are wrong 80% of the time but still get paid 100% of the time.

The same way they predict 0% chance of rain. They use all the modern gizmos and gadgets they have to make a prediction. They are never 100% right either way.