So this is what a 10% chance of precipitation looks like

[PotomacCyclist]

Nice. Thanks, Weather.com.

I wasn’t riding, but I was out swimming, in an outdoor pool. The lifeguards had to close the pool early because storm clouds rolled in and we could hear thunder overhead.

Topic

[KelOnWheels]

Yeah, Capital Weather Gang just apologized. Weird little summer blow-up they weren’t expecting.

[eminva]

Sometimes it is good to work on the late shift.

Liz

[PotomacCyclist]

I can understand if they aren’t sure. But what I don’t get is why they don’t say that there is a 50% or 60% chance of precipitation. I checked the hourly forecast 10 minutes before I went out. They said 10% chance. Oops.

[MV Clyde]

I’m watching the Nats game. Rain delay…. Clear everywhere except over DC. Weird.

[vvill]

It still rains 1 of out 10 times when there’s a 10% chance.

[KelOnWheels]

60 percent of the time, it works every time.

[creadinger]

Looks like you got the 10% chance. What’s so hard to understand about that?! So did we. The storm that doused part of Arlington, DC southern PG county wasn’t even 4 sq miles. In a forecast area that spans ~200×200 miles that’s way less than 10% of the area. I’d say they nailed it.

[PotomacCyclist]

But the forecast I checked was for my specific zip code, not the entire DC area.

[PotomacCyclist]

If this was a rare miss, then I wouldn’t complain so much. But there have been other days where the hourly forecast is for a 0% chance of rain for the rest of the day and night. Then a rain shower comes through. I still check those forecasts because there’s no alternative. But I wish they would at least build in some leeway in case they think there’s a decent chance of rain. Helps a little with scheduling.

[MV Clyde]

90% of weather forecasting is 1/2 mental.

[MCL1981]

It is a not an exact science. It’s a forecast. Not a rule. Especially in the summer time when convective activity can pop up and develop with very little notice. Also, they do not update the forecast every 5 minutes to account for what changed 5 minutes ago. If there was a 10% chance of rain and you got wet, sucks for you. You made the 1 out of 10 chance.

[creadinger]

@PotomacCyclist 29032 wrote:

But there have been other days where the hourly forecast is for a 0% chance of rain for the rest of the day and night. Then a rain shower comes through.

“other days”? That is not very scientific. Since meteorology is based in science and math using extremely complex models run on supercomputers, to make any meaningful statements about accuracy you’re going to need little bit more than an anecdote.

@PotomacCyclist 29032 wrote:

I still check those forecasts because there’s no alternative. But I wish they would at least build in some leeway in case they think there’s a decent chance of rain. Helps a little with scheduling.

There are other forecast alternatives, but you’re right, 100% accurate forecasts do not exist. If you’d like to devote the next few decades of your life to making that happen and providing the alternative to future PotomacCyclists then please do because the field could use a few new ground breakers to really push the science of forecasting forward. I can say that in the past 10-20 years, forecasts have gotten tremendously better and more accurate. The 5-7 day forecast today is as accurate as the 1-3 day forecast was 20 years ago. I can point you to some scientific articles about that if you want.

Anyway, I’m just giving you a hard time because I have degrees in the field and I’m a little sensitive when people complain about busted forecasts. My go to response while I was in college was – “You try to predict the future.” Seems appropriate.

[vvill]

@creadinger 29040 wrote:

100% accurate forecasts do not exist. If you’d like to devote the next few decades of your life to making that happen and providing the alternative to future

According to Back to the Future Part II we should only have to wait until 2015!

[creadinger]

@vvill 29041 wrote:

According to Back to the Future Part II we should only have to wait until 2015!

And wouldn’t life be extremely boring if we knew exactly what the weather would be all the time? Sheesh. That’s part of the fun of summer storms, winter blizzards and hurricane season. PS – Florida residents should take notice for 1 week from now.

[jordash]

Just like news sources or your savings portfolio, diversify. Check a couple websites or applications. I use Wunderground (great website and phone application) & Apple’s/Yahoo’s weather application. Always check the radar because that’s the most up to date. Look at the sky and hope that it doesn’t open up and start spraying water in your face like it has twice in the last few days. That said, I kind of like riding in the rain aside from low visibility in front of cars.

[Author]

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