Sunday rains were record-setting in Md., but didn't match Isaac

Rains across Baltimore and on the Eastern Shore on Sunday were record-setting and the heaviest of the year, but they didn't end up matching Tropical Storm Isaac's moisture, according to observations.

At BWI Marshall Airport, 3.36 inches of rain fell Sunday. That far surpassed the previous precipitation record for Baltimore on Aug. 26, which was 1.73 inches in 1974. It also surpassed normal rainfall for all of August, 3.29 inches.


It was also more rain than had been measured at BWI in a single month since December, when 4.5 inches of rain fell. Every month since then has had below-normal rainfall, but August will be the first of 2012 to finish above normal.

So far this month, 5.79 inches of rain have fallen at BWI, 2.99 inches more than normal.


Despite the extreme nature of the rainfall and the widespread flash flooding and road closures it caused, it was not as much as the 6, 10 or even 15 inches some forecasters have estimated based on radar.

Rain gauges measured more than 2 inches across much of Anne Arundel and Baltimore counties, with 2.62 inches near Gambrills, 2.5 inches in Pasadena and 2.26 inches in Reisterstown, according to CoCoRaHS, a network of amateur weather spotters.

Trained weather spotters reported to the National Weather Service rainfall totals of about 3.5 inches across much of western Baltimore and Baltimore County.

The heaviest rain fell where it was most needed -- on the Eastern Shore. CoCoRaHS spotters in the Easton area reported totals as high as 7.37 and 6.66 inches, with 6.1 inches down the road in St. Michael's. Most of the Eastern Shore is under a severe drought, according to the U.S. Drought Monitor, but this could help ameliorate those conditions.

That's compared with measurements of 10.56 inches, 9.14 inches and 8.14 inches in parts of Palm Beach County and more than 6 inches in Broward County in southeastern Florida.

What did your rain gauge show?

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