Wind Gust Calculation
History
The Coastal weather stations were delivered with a default peak gust filter
setting of 4 seconds for an averaging window. Over the years of operation,
numerous people have reported that the NCAR weather stations were producing
low peak gust readings. The problem is that most weather stations report
peak gusts on a 1 second time frame and the 4 second average is almost
always going to be a lower number. In an effort to better align our readings
with most other weather stations, the peak gust average has been reduced
to 1 sample. This change is effective Feb 3, 1999, 18:00 local time.
Here is what the Coastal Climate weather station manual says:
Maximum Wind Speed
Maximum winds (gusts) are determined during each individual averaging period.
Gust information is important for risk studies of damage to constructions
and buildings.
The duration of the gust is an important consideration and is often related
to the intended application.
Some applications require information about extreme values of the shortest
gusts (1 second duration), while in other cases, the damaging gusts are those
that engulf the entire structure (5-10 seconds duration).
Fortunately, with little error, there is a technique for relating extreme
gust measurements taken for one duration to extreme gusts of other durations
(1).
The gust duration D in the Weatherpak can be factory set to values between
1 and 5 seconds.
In the Coastal Environmental Systems wind algorithm, a D-second running
average of the speed measurements is applied to the data as it is collected.
At the time of each measurement the average of the circular buffer is computed
and compared against the maximum value up to that time.
When the current "gust" measurement exceeds the stored maximum, the maximum
value is updated.
(1)Beljaars, A.C.M. (1987) The Influence of Sampling and Filtering on Wind Gusts.
Journal of Atmospheric and Oceanic Technology, 6, 613-626