Imagine if weather maps were barred from public view? It happened during World War II

An Associated Press story "Weather Maps Discontinued" as it appeared in the Seattle Post-Intelligencer on Dec. 17, 1941 (Photo courtesy, Seattle Post-Intelligencer via Seattle Public Library)

With all the attention recently to the "bomb cyclone" and the tremendous role social media played in getting the word out and disseminating not only forecasts and warnings but detailed charts of expected conditions, could you imagine what would happen if weather maps were barred from public view?

It actually happened in the days after the Pearl Harbor attack in 1941.

Granted, in those days long before the internet, or even widespread television coverage, the main way to see weather maps and data were in the newspaper, and even then, they were pretty rudimentary. That's because weather information itself was fairly limited.

These were in the days before computer forecast models and satellite imagery, so weather forecasters relied greatly on information gleaned from ground observations, weather balloons, pilot reports and ship reports, says Ted Buehner with the National Weather Service office in Seattle.

"Forecasters used combination of plotted and analyzed surface charts, and upper air charts (mainly plotted (weather balloons) and (pilot reports)) to glean trends together with forecaster experience," Buehner said. But back then, that was only good for about a two day forecast, with perhaps a general outlook for a third day, Buehner said.

Here's a sampling of some of the weather information available in the Seattle Post-Intelligencer on Dec. 5, 1941 -- two days before the Pearl Harbor attack.

The National Weather Bureau (the predecessor to the National Weather Service) also offered a daily weather map via subscription to those who needed weather information, like this one from that same date:

But everything changed on that fateful day on Dec. 7 when World War II was brought to America. Among the many concerns in the wake of the bombings was a potential attack on the West Coast.

To that matter, the U.S. Government ordered an end to all publications of daily weather charts and a strict limitation to what weather information would be disseminated publicly, for fear of giving crucial weather information to the enemy.

A story from the Associated Press, published in the Dec. 17, 1941 edition of the Seattle P-I, tells the public what's going on. (Click here to enlarge)

"The weather bureau today discontinued weather maps, long range forecasts, most wind, fog and cloud data, and some rain and other crop information which might be useful to enemies," the AP wrote. "F.W. Reichelderfer, chief of the weather bureau, said that generally the only weather information to be given out publicly would be limited to temperature extremes expected in a twenty-six hour period."

Reichelderfer said the weather bureau would try to warn the public of "serious weather conditions such as cold waves, hurricanes, floods, heavy snows and severe storms."

The AP story noted public weather forecasts will no longer give the directions of the winds or air pressures -- critical data in the age before satellites to deduce where storm systems may or may not be lurking in the Pacific Ocean or expected cloud conditions in the area. However, they noted an exception during fruit growing areas that warnings would be given when strong winds were expected.

Also of note, they would discontinue the "storm signal lights" along marinas and coastal shores (I guess so any enemy ships offshore couldn't get clued in on any approaching storms) but would use the flag system instead. This would be to denote small craft advisories, gale warnings and storm warnings -- a system still in use today. In addition to the triangular and square flags, some areas used lights as well, but no more!

What about forest fire danger? Warnings would be restricted "exclusively to agencies responsible for protecting forests."

Of concern to the Pacific Northwest, river and flood bulletins would no longer include rainfalls of less than one tenth of an inch. And in a blow to ski resorts, weekend forecasts for winter sports were abolished but some temperature and snow reports would be "available for sports purposes." Monthly weather summaries were issued a week late -- and crop bulletins would be altered, the AP reported.

Indeed, farther up the page the weather section now just had some major U.S. city temperature readings and the weather forecast simply noted it would be "slightly cooler" over the next two days with two predicted low temperatures at the Downtown Federal Building and Boeing Field (Sea-Tac Airport? Not around yet...) and a high the next day predicted of 52 degrees.

The Daily Weather Bureau Map also noted the new restrictions:

"Owing to the value of weather reports and forecasts to the enemy, the Weather Bureau, at the request of military authorities, has curtailed the publication of current weather data," Reichelderfer wrote. He mentioned the required seven day waiting period for the maps and even then, the maps would only be available for record keeping, instruction or other purposes to a "list of those who would make written application to the Chief of the U.S. Weather Bureau. The applications should state in detail the proposed use of the map." ("Hi, I'd like to be on the list. I don't need it for today, but it'll come in really handy in 76 years.")

Reichelderfer also noted his office would "resume regular service in whole or in part when such resumption may be accomplished without detriment to the national defense."

That would encompass nearly two years. The weather maps issued by the weather bureau would note for several months: "NOTE: This map was not released until 7 days after the above date."

It wasn't until Nov. 1, 1943 that the maps resumed their regular daily dissemination.

Special Thanks to Steve and Carl at the Seattle Public Library for helping track down the newspapers, to Dustin Guy at the National Weather Service for the blog idea, and to Ted Buehner who gave me one last interview for the blog before he retired after a long, successful 40-year career at the Seattle National Weather Service office. Happy retirement, Ted!

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