When your app tells you it's going to snow, but it isn't

Oct. 30, 2017 morning forecast from KING 5 Meteorologist Rich Marriott.

If viewing in the app, click here to see images

No, it’s not going to snow in the lowlands this weekend. But, some weather apps on your phone may be thinking differently.

What’s going on?

A lot of these apps are not made by humans, but by a computer using something called ensemble forecasting. Here’s an example from a viewer posting on the KING 5 Facebook page.

Pablo shared this -- looking at Saturday -- commenting “hmmm."

See the snowflake? This app was saying it was going to snow basically at sea level. It certainly wouldn’t be the earliest we’ve seen lowland snow, but there are problems using weather apps to predict extended forecasts.

Let’s talk about what ensemble forecasting is. Here’s an example of a hurricane spaghetti plot -- a type of ensemble forecasting.

Ensemble forecasting has to do with numerical modeling, tweaking some initial details, then letting the model run out. You can see ensemble forecasting gives us a range of scenarios which helps us forecast a range of possibilities. But sometimes there are outliers, like in that automated phone app. While a couple of outlier models were predicting lowland snow, most are showing it’s just going to be too warm.

Here’s what we are expecting: It will be getting colder and wetter later this week. And the snow level maybe getting down to 1,500 feet by the weekend, but only light amounts above that level are expected. A big upper level low with the coldest air of the season, so far, is to blame.

And that same phone app Monday morning? It wasn't showing any snow or any rain for Saturday. Just a reminder to take your computer generated weather apps with a grain of salt.

© 2017 KING-TV


JOIN THE CONVERSATION

To find out more about Facebook commenting please read the
Conversation Guidelines and FAQs

Leave a Comment