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Beyond ‘Siri, what’s the weather?’: The pocket guide to forecasting from your phone.

A severe thunderstorm moved past Washington on Aug. 21. (Kevin Ambrose)
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With the power to predict short-term weather on the device in your pocket, it’s helpful to know what your best options are for weather apps. They’re not all created equal, and many users have only a cursory understanding of what maps these apps are referring to.

Here’s a quick guide to some of the most popular national weather apps and how to interpret their data.

Weather Bug, powered by Maryland’s Earth Networks, stands out for its lightning- and storm-tracking features, as well as its simulations of future radar simulations.

They have a live “spark radar map” that shows all the lightning strikes in your area during the past 30 minutes. The most helpful tools are the storm tracker and the future radar. The storm tracker will combine the lightning strike map, past radar and the warning maps to show the areas most likely to be affected by storms. The future radar will show the current trajectory of the storms.

While there is no guarantee that the storms won’t shift direction, this is the best guess at the moment of where the storms are headed.

MyRadar, made by the weather software firm Acme AtronOmatic, shines when it comes to its radar display. With access to an entire world view and excellent local resolution, this is the best bet when it comes to a free app for locating pop-up storms or large bands of precipitation. While there is no future radar option, the ability to find pop-up storms that don’t always show up on other radars because of small-scale resolution makes this the go-to option when looking for precipitation in your area.

MyRadar also offers notifications with precipitation-arrival-time information based on your location.

Meet the ClimaCell weather app. Alerting you when it’s about to rain, down to the minute, all around the world.

Windy, an app from Windy Weather World, is useful for looking at wind speed and direction and wind predictions.

While this app is generally more useful for sailors, wind surfers or pilots, wind direction can be indicative of changing weather and critical to staying informed about potentially dangerous conditions, such as during Santa Ana wind events in California or nor’easters in the Mid-Atlantic and Northeast. Windy provides both a forecast and a “real time” map. Featuring a compass design, the breakdown of wind directions, prevailing directions and strength make quite the visual tools. This is helpful when looking for storm systems or what weather might be on its way with a new air mass.

Weather Underground, from the Weather Company, an IBM subsidiary, is most useful for providing daily forecasts.

Again, this app features a radar display, but there are better options for that. Weather Underground is best used for looking at the hourly forecasts for the day and getting a handle on what to expect generally. For the geekier among you, Wunderground also features access to scientific discussions from the National Weather Service at the bottom of its forecast pages for extra technical details.

Wunderground also provides detailed extended forecasts, along with the option to view the NWS’s forecasts or to rely on the app’s forecasts created from a customized blend of computer models.

Depending on personal preference or brand loyalty, other forecasting and storm tracking options can be used from the Weather Channel, AccuWeather or NOAA Weather Radar. Each has a slightly different layout, but the underlying science remains the same, as does how to read the maps.

When you really need the best forecast, which app should you trust?

Interpreting the data

While the apps give you the ability to view the various elements of storms, you also need to know how to read the various maps — to see where the precipitation is moving and with what intensity it’s falling.

During winter, apps that depict precipitation types are especially useful for tracking the rain, snow and ice line.

The key to reading radar is the reflectivity. Radars send out pulses, and the strength and characteristics of the returning echo indicate the intensity of the precipitation. Much like yelling “echo” into a canyon, the stronger the response, the stronger the source of the bounce.

The bounce is represented by a color bar (usually at the bottom of the map). Light green indicates light precipitation; dark green is moderate; yellows are heavy rain (or sometimes sleet); and reds and magentas are torrential downpours.

Snowflakes reflect back to the radars differently than raindrops and are depicted using a different scale. This is typically presented as a gradient from light blue to dark blue (light to heavy snow), with mixed precipitation as a pale pink and rain remaining green.

As the season shifts toward winter, bands of snow are highly dependent on surface temperatures, leaving a bit of a guessing game as to where the rain/snow line will draw itself. This is where the areas of pink will start to break up the blues and greens on the radar. Depending on the temperature of the atmosphere and the ground, precipitation can shift between liquid and frozen, resulting in sleet (ice as it falls) or freezing rain (freezes on contact with the surface). This is harder to predict using radar alone, as it requires temperature information for various layers of the atmosphere.

A more desktop-friendly option for “straight from the source” forecasting is the National Weather Service website. As a government agency within NOAA, the NWS provides official active alerts, forecast maps, radar and satellite data.

While the customization of weather apps is certainly appealing, they are no substitute for official government-issued weather watches or warnings.

Flake news: Please disregard snow total forecasts on your weather apps

Referring to reliable sources that provide up-to-date warnings or watches and decision support, such as the NWS, the Capital Weather Gang or the Weather Channel, helps provide important details, such as a storm’s likely duration and evolution, the major impacts to expect, communication of uncertainty and suggestions for how to ride out the storm.

John Bravender, warning coordination meteorologist from the Honolulu NWS office, said, “A lot of interpretation can go into looking at radar and satellite, and it’s important to look at input from a recognized provider such as the NWS or your local media.”

Note: All apps mentioned in this article are available free in the Apple App store and on Google Play. Many have accompanying websites. All websites specifically mentioned can be accessed free.

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