Ticker for January 29, 2002

                
MESONET TICKER ... MESONET TICKER ... MESONET TICKER ... MESONET TICKER ...
January 29, 2002   January 29, 2002   January 29, 2002   January 29, 2002


We Didn't See This Use Coming

Quick: what's the Mesonet's best freezing rain detector?  The Ticker
would like to nominate the wind monitor.  That's right, the propvane
that sits atop each Mesonet station serves an unexpected purpose
during many freezing rain events.

As anybody in the electric utility or timber industry can tell you,
freezing rain often accumulates on elevated items (e.g, tree limbs,
power lines) before accumulating on the ground.  This also holds true
for propvanes mounted ten meters (about 33 feet) above ground.

When ice begins to accumulate, the prop part of the propvane is
restricted, resulting in much lower wind speed observations.  Often,
the prop is completely encrusted and a wind speed of zero is observed.
A similar effect sometimes befalls the vane part of the propvane,
resulting in a "stuck" wind direction.

So, while it's a pain for the Mesonet's QA Manager, and causes
a temporary lapse in otherwise high-quality wind data, consider
a frozen wind monitor one of your early indicators of freezing rain!