THE FLASH FLOOD ALERT
This instrument provides a rain rate alarm, intended for use
where there is danger of local flooding or downstream flash
flooding. Flash flooding can result when heavy rainfall occurs
at higher elevation, and water rushes toward low-lying areas.
The rain rate alarm warns that heavy rainfall has occurred,
which could result in impending local flood conditions, or flash
flooding within your vicinity (or possibly downstream, outside
of your vicinity). Bear in mind that your success in predicting
flash flooding depends upon many factors, in addition to rain
rate: terrain, elevation, drainage, etc.
Before setting the flash flood alert, be sure to select rainfall
units according to the type of rain gauge you are using.
The rain rate alarm is set in inches-of-rain or mm-of-rain per
hour. An alarm will sound of a specified minimum amount of
rain (called the threshold) falls at a rate equal to or greater
than the rain-rate setting. The default threshold value is 0.5
in, or 12.7 mm.
EXAMPLE: If you set an alarm for a rain rate of 2 inches per
hour, the alarm will sound if 0.5 inches of rain (the default
threshold value) falls within 15 minutes, which equals an
hourly rate of 2 inches per hour.
To adjust the Flash Flood Alert rain rate:
1. Press and release
.
2. Press
. The rain, clock, and alarm symbols will
appear in the display, and the present rain rate alarm setting
will be displayed.
3. Press and hold
or
until a value is shown and
begins to change. The rain rate can be adjusted from 0.1
in/hr to 10 in/hr in 0.1-in increments, or from 2.5 mm/hr to
254.0 mm/hr in increments of 2.5 mm/hr.
4. Press
or
repeatedly until the desired rain rate
setting is shown.
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