How to look at the sky and predict the weather

Jerry Wyckoff

Growing up, Toby Carlson would watch the sky outside his Northampton home and create weather forecasts for his family. "Most of the time I was right," he says. Now Carlson is a retired meteorology professor at Penn State and coauthor of a new book, "An Observer's Guide to Clouds and Weather: A Northeastern Primer on Prediction," that promises to teach interested readers the same prognosticating skills he honed long ago.

Carlson remarks that meteorologists today rely heavily on computer models, which allow them to make reasonably accurate weather predictions nearly two weeks out. They spend a lot less time learning how to read the atmospheric conditions right in front of them. "This is stuff that fascinated me when I was a kid and very few people seem to pay attention to that anymore," Carlson says.

In the book, Carlson discusses the atmospheric forces that create weather events. The third chapter features a series of cloud photographs from the late photographer Jerry Wyckoff, with descriptions of the weather that those cloud formations portend. One key to reading clouds, Carlson notes, is to pay attention to how they evolve over the course of a day. You might notice, for example, cirrus clouds gradually thickening from the west, which indicates an approaching storm. With knowledge like that, Carlson boasts in the introduction to his book, "It should be possible for the keen observer to outperform computer model forecasts for short periods" — as far as 36 hours into the future.

Here are several other cloud formations commonly seen in the Northeast, with descriptions of their meteorological significance that Carlson provided by e-mail.

Altocumulus layer clouds, which are a harbinger of storm. They signal the approach of a low pressure center and rain or snow if they continue to thicken from the west.Jerry Wyckoff

Cumulus clouds swelling to a thunderstorm. Unlike layer clouds, these clouds signify an unstable atmosphere that allows air to rise vertically through considerable depths of the atmosphere very quickly. This produces short but heavy showers, sometimes with lightning and thunder with hail, strong wind gusts, and occasionally, a tornado.Jerry Wyckoff

Stratocumulus clouds. These are layer clouds, but they’re distinguishable from storm clouds by the clear spaces between them (unlike the top image, where the altocumulus clouds have upper-level layer clouds above them).Jerry Wyckoff

Kevin Hartnett is a writer in South Carolina. He can be reached at [e-mail].