Don't Trust Weather Apps

Look at the sky, not your phone screen!

On August 28, 2019, I used Accuweather on my cell phone and saw the following:

This report basically saying “100% humidity, rain is imminent” continued for several days. However, August is during the dry season in Indonesia, often with no rain at all for the entire month. When I looked at the sky instead of my phone screen, I saw this:

I mentioned the discrepancy to a Dutch neighbor, who told me TV weather reports in his country repeatedly err by showing rain icons in Indonesia during the dry season.

The explanation seems to be: someone programmed a reading of 100% humidity (common in Indonesia early in the morning all year long) to mean clouds or rainfall, based on a little knowledge that rain occurs when humidity = 100%.

In fact, other conditions might cause rain not to occur, such as supersaturation:

https://glossary.ametsoc.org/wiki/Supersaturation

The satirist Jonathan Swift published his book Gulliver’s Travels in 1726. The third of its four parts describes the flying island of Laputa, whose citizens are absorbed in abstract thought to such a degree that one of their eyes is always “turned inward” while their minds are “taken up with intense speculation.” I highly recommend (re)reading this classic, which seems timely as its 300th anniversary approaches.