Weather Wednesday: The weather app on your phone is unreliable

Published 12:00 am Wednesday, August 15, 2018

Have you ever canceled outdoor plans because of the weather app forecast on your phone?

It is very disappointing when the forecast for rain never materializes. We all want to have reliable weather forecasts so we can schedule activities.

Most people have no idea where the app comes from or if it’s even a real forecast. There are more than 8,000 apps for weather.

In many discussions with followers of Rowan County Weather, I’ve found they want to know why my forecast was so different from their app forecast. In some cases, I have even been blamed for their weather app being wrong.

Many of the apps are automated and have a single source of data from just one model. Accurate weather forecasts should be based on large amounts of data and many forecast models. No one model ever does a perfect job.

All my forecasts use data from numerous models, their ensembles, and local knowledge and experience.

Forecasting weather has become a very complex science.

Weather apps can be a great source for current conditions and also give you a general idea of what might happen. It’s a great place to start, but you should always seek professional expertise to make any decisions about your activities.

Let’s make some comparisons between app forecasts and my forecasts. Last weekend, I predicted a 50 percent chance of rain on Friday. A stock weather forecast predicted a 20 percent chance of rain. Rowan County ended up with more than an inch of rainfall in many areas Friday.

On Saturday, I predicted a 40 percent chance of rainfall, and the app predicted a 40 percent chance. The county airport recorded three-fourths of an inch in its gauge. Finally on Sunday, I predicted a 50 percent chance of rain and the app predicted a 10 percent chance. Heavy rain showers moved in on Sunday evening.

I was also contacted by a follower Friday who asked about the weather conditions for 3 to 5 p.m. Sunday. Her weather app was calling for rain chances during this time. She was having a pool party and wanted to know if she should cancel it.

I recommended that she go ahead with her plans for the pool party based on the data I had. The follower was able to have her pool party as planned. Showers and thunderstorms did not move in until the evening hours.

I’m never going to be right about the forecast 100 percent of the time. My goal is to be as credible as possible with few errors. Weather prediction is complex, and we can’t always predict the future.  Sometimes I have to change my forecasts to fit conditions as they develop. An app is updated only every six to 12 hours so it cannot be as accurate.

Apps are just tools that should always be used with caution. If you really have a question about the forecast, send me a message on Facebook and Twitter via the Rowan County Weather pages. Or email me at stevemonday@rowancountyweather.com. I may not be able to answer immediately, but I will get back to you as soon as I can.

Steve Monday is chief forecaster for Rowan County Weather.

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