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How an iPhone app is revolutionising the way we get the weather

Dark sky iphone appHollis Johnson/Business InsiderThe Dark Sky app for iPhone.

Adam Grossman remembers getting trapped by a “torrential downpour” while on vacation with his wife a few years ago.

He opened The Weather Channel app on his iPhone to see that there was a 40% chance of rain in the area.

It was the last straw. He decided to make his own weather app. It would prioritise the immediate forecast for the next hour. Above all, it had to be accurate.

“I just got sick of getting stuck in the rain too many times,” he tells Business Insider.

Enter Dark Sky.

SchematicDark Sky

Grossman’s three-year-old weather app for the iPhone may have a great design, richly detailed radar maps, and the smarts to notify you right before it’s going to rain, but the most important thing it gets right is accuracy.

And with the help of Dark Sky users, Grossman is building a mobile-first weather service.

Since getting successfully funded as a Kickstarter project in November of 2011, Dark Sky has been beloved by App Store users and curators. It has an average rating of four stars, consistently sits near the top of the paid charts, and is listed under Apple’s “Essentials” list, an app hall of fame of sorts for the best of the best.

It’s also excellent on the Apple Watch, which can’t be said for most third-party apps.

While Dark Sky started as a way to just see the next hour’s forecast, it’s evolved over the years to offer much more.

The main screen focuses on the current conditions, including whether it’s going to precipitate and how long until the sky clears up again. There’s also a visual forecast for the next 24 hours. Swipe to find a week-long forecast, a custom radar view of the entire globe, and settings for the app’s impressive notifications.

FullSizeRender 5Business Insider

Notifications are where Dark Sky really sells its $US3.99 price point. A friendly push will tell you when it’s about to rain. It’s a feature that could be the difference between arriving to work drenched or with an umbrella in hand.

Grossman, who lives in upstate New York and works on Dark Sky development full time with co-founder Jay LaPorte, has no background in meteorology. Both men studied physics and computer science in school, skills they have applied to building a successful weather app and the infrastructure that powers it.

When meteorologists make long term forecasts, their predictions are generally based on simulating shifts in the atmosphere. To do so, they need access to radar data, which the US government makes commercially available for free.

There’s also the Global Forecast System, a supercomputer owned by the U.S. that puts out global forecasts up to 16 days in advance.

The magic happens when Dark Sky’s brain, called Forecast, aggregates these sources and others to make the most accurate predictions possible. It’s all based on computer algorithms by Grossman and LaPorte that crunch the raw data.

“If you look at a radar loop for a while you can see that a storm is headed this direction and it’s generally swirling counterclockwise in this way,” explains Grossman. “Basically, what we’re doing is using computer vision to look at the radar images and extrapolate into the future.”

“It does what your brain does when you look at the image and can tell how things are changing, expect it can be a lot more precise than a human brain. We’re basically doing what your brain does on a large scale.”

The end result is an app that, based on your iPhone’s GPS coordinates, can tell you that it’s going to start raining lightly in 6 minutes and stop 20 minutes later.

Becoming the world’s first modern weather provider

Dark Sky radarPlay GIFDark Sky

Last week, Dark Sky was updated with several big improvements, one of them being crowd-sourced weather reporting.

It’s a long-term effort that Grossman thinks will be a “game changer” for fixing the main inconsistencies with the way weather reporting works today.

The U.S. has about 150 ground stations that report current conditions, but they can tend to be physically spread apart. Radar helps fill in the gaps by showing what’s going on in the atmosphere, but sometimes rain doesn’t actually make it to the ground. It can get blown off course or evaporate. Sometimes radar doesn’t detect it at all.

“It’s hard to know what’s actually happening on the ground”

“It’s hard to know what’s actually happening on the ground,”says Grossman, referring to a term in the industry called “ground truth.” Now that Dark Sky has hundreds of thousands of users, he sees it as the perfect time to start crowd sourcing.

“The meteorological field is definitely a little conservative in what techniques they’re willing to use,” he says. “And we don’t have that problem with not being meteorologists ourselves.”

There are two ways Dark Sky users can submit weather reports. One way is to manually do it through the app, like when it’s actually overcast around you instead of sunny. The second way happens in the background automatically, and it’s quite ingenious.

Dark Sky can tap into the iPhone 6’s barometer, a little sensor that tells a whole lot about the state of the atmosphere above you, and in turn, provides helpful meteorological data to Dark Sky’s servers.

Primarily used for determining altitude, a barometer measures the weight of the atmosphere around you going all the way up into space. It provides reliable data because pressure is typically the same indoors and outdoors. So an iPhone sitting in an office would give just as helpful of a reading as one out on the street.

Where things really start to get interesting is when you have a high density of barometers in one area, like thousands of Dark Sky users in a city.

Grossman sees pressure data submissions as “more of a long term endeavour,” since not everyone has a barometer-equipped iPhone yet. Only the iPhone 6 and 6 Plus have the sensor. But eventually he hopes to use pressure data to build out Dark Sky’s hyper-specific forecasts beyond the next hour and make better future predictions.

Since the app update was released last week, he’s already seeing hundreds of manual weather reports and around a quarter million pressure submissions per day.

All of this data makes Dark Sky’s brain, Forecast, smarter. Other companies licence Forecast to get its weather reports, like the search engine DuckDuckGo and numerous other weather apps.

An obvious comparison to Dark Sky’s crowdsourcing approach is Waze, the mapping app that got popular from its user-submitted traffic reports. Waze users can submit data like car accidents, traffic cop locations, and lower gas prices to the system to help out other Waze users. Google bought Waze in 2013 for a reported $US1.1 billion and has started integrating crowdsourced Waze data into Google Maps.

Predicting the future

Dark Sky only works in the United States, United Kingdom, and Puerto Rico right now, so there’s definitely room to expand its reach.

The $US3.99 price is another barrier to entry when there’s countless free weather apps in the App Store, but Grossman says his app has been profitable since day one. Besides the $US38,000 that was raised from the original Kickstarter campaign, he’s never taken outside funding.

At the end of last year, Danny Hillis’s Applied Invention become a partner in Dark Sky, but Grossman and LaPorte still retain majority ownership of the app and Forecast. Grossman describes the relationship with Applied Invention as “still in the early stages,” but seems excited about what it could mean for the future.

Applied Invention describes itself as a “multidisciplinary innovation company” that works on everything from database software to futuristic biotechnology.

According to Applied Invention co-founder Dan Abrutyn, his company came across Dark Sky when it was looking for a hyper-accurate local weather source. He tells Business Insider that the partnership is as “an opportunity to develop a new way of weather forecasting that could dramatically improve on standard forecast models.”

So what’s next for Dark Sky? Grossman says he may experiment with lowering the price and offering in-app purchases down the road, but he doesn’t have a specific timeline in mind. For now, he’s focusing on improving the accuracy of his forecasts and building out Forecast. If things keep going well, his iPhone app could change the way weather reporting is done.

And he’ll never get stuck outside in the rain again.

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