Public Information Statement
Issued by NWS Sterling, VA

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NOUS41 KLWX 311619 CCA
PNSLWX
MDZ505-506-312030-

Public Information Statement
National Weather Service Baltimore MD/Washington DC
1216 PM EDT Sun Jul 31 2016

...Historic heavy rainfall Saturday in Ellicott City...

Extremely heavy rain fell Saturday evening in Ellicott City,
Maryland. Thanks to rain gauge data from Ellicott City, which is
provided by Howard County to the National Weather Service, we have
detailed information on how quickly the heavy rain fell.

The following table lists the rain that was recorded by this
gauge. Note that the gauge reports in increments of 0.04 inch:

DURATION    AMOUNT   TIMEFRAME
----------------------------------------
1 minute  ..0.20 from 7:51pm-7:52pm
5 minutes ..0.80 from 7:50pm-7:55pm
10 minutes..1.44 from 7:50pm-8:00pm
15 minutes..2.04 from 7:46pm-8:01pm
20 minutes..2.48 from 7:44pm-8:04pm
30 minutes..3.16 from 7:36pm-8:06pm
60 minutes..4.56 from 7:30pm-8:30pm
90 minutes..5.52 from 7:00pm-8:30pm
2 hours.....5.92 from 6:45pm-8:45pm

The storm total at Ellicott City was recorded as 6.50 inches.

The nearest point precipitation frequency estimates in NOAA Atlas
14 come from Woodstock, which is approximately five miles away.
Based on this data, the precipitation amounts with duration 10
minutes to 2 hours statistically have a less than one tenth of
one percent (less than 0.1 percent) chance of occurring in any
given year.

This data is preliminary and is subject to correction.

$$

JE


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