Not Texas, but 28.5 inches of rain once fell in just 3 hours … in Pa.
A record for a tropical storm might have been set in Texas, but the raining champ for three-hour and 12-hour rainfall was set in the wilds of Pennsylvania 75 years ago.
The Harvey-related rains along the Gulf Coast that have persisted for days might well be unprecedented, but prodigious rainfall amounts are hardly unprecedented.
For certain, higher amounts have fallen in mountainous areas unobserved by humans or rain gauges, but the 24-hour record as determined by National Climate Extremes Committee is 43 inches, in Alvin, Texas, on July 25, 1979.
The record for a three-hour period, 28.5 inches, was set far closer to home, in Smethport in the wilds of Pennsylvania near the Allegheny Forest and the New York border in July 1942; Smethport also holds the record for 12 hours, 34.3.
It so happened that a thunderstorm complex pounded the area, which is elevated about 2,000 feet, according to Kyle A. Imhoff, the Pennsylvania state climatologist.
In the Northeast elevation is the sine qua non for such a deluge; rain condenses from rising air, and mountain slopes give air a lift.
And while it might seem improbable that a rain gauge was available in such a remote area to verify the amount, actually, it wasn't.
The storm evidently had such profound effects that the U.S. Weather Bureau was moved to investigate, Imhoff said. Bureau officials were able to calculate the amounts from "bucket reports" – rain captured in jars and assorted other vessels by local residents.
After analysis, they affirmed that the totals were valid.
As for the preliminary report of 51.88 inches at Cedar Pass, Texas, which would be a record for a tropical storm, the National Centers for Environmental Information likely will review the measurement, along with the National Weather Service, says NCEI's Brady Phillips.
Even it turns out to be a little off, indisputably that was an incredible amount of rain.