How
come that other Bass Lake station's rain totals are so much higher on
wet, windy days? Sometimes the difference is over a half an
inch! That can't be right, can it?
The short answer is a resounding NO! It isn't right!
This all relates to the proper siting/location (improper in this case) of the weather station
sensors during installation to prevent erroneous data caused by the
unwanted influences of nearby surroundings.
A 0.50 in or more difference in 24 hour rainfall totals between two
stations .07 miles apart is highly unlikely to be caused by natural
fluctuations in topological rainfall differences. The more plausible
explanation (if the lower reporting station's data is known to be
accurate and supported by other surrounding stations in the area) is
that the station with the higher total has seen its rainfall data
compromised by structure or obstacle induced "run-off".
In this case, the "other" station's installation location is surrounded
by very tall wind blocking pine trees with the weather station's sensor
array mounted on the roof of a two story structure. During
periods of heavy precipitation accompanied by wind gusts as low as 1-3
mph, the nearby pine trees become saturated with moisture which is then
blown off the trees by the motion of the wind and directly into the
roof mounted rain collection bucket. It would only take a few instances
of this type of contamination to account for errors as high as 1.5
inches per 24 hours.
This is why the NWS and CWOP provide new weather station operators with
a comprehensive sensor siting guide designed to prevent situations such
as the one described above from occurring.
The NWS and CWOP weather station siting guide specifically calls for
the station sensor array to be mounted 5.5 feet above natural ground
cover, in an open space at least 150 feet away from any tall trees,
structures or other obstacles above the height of the rain bucket that
can block wind circulation and/or interfere with accurate rainfall
collection. (D2149 has followed these guidelines to the letter)
This is the primary reason that the NWS did not use the weather data
from this other station on their radio broadcasts or compile archival
weather data reported from it for so many years. It was not until D2149
was made operational in 2009 and its data was found to be up to the
accuracy standards of the NWS that weather data from Bass Lake via D2149 was made
available on the Hanford NOAA weather radio broadcasts and included in
the regional database for Bass Lake Ca. You could say that all of these
problems had a lot to do with our decision to install our station in
the first place. We were tired of not knowing the real numbers and
seeing Bass Lake excluded from all the official modern weather records
for the area.
So... If you want to know what the rainfall total for Bass Lake was
yesterday, you probably don't want to get your data from that "other"
web site. Those who do, are getting highly erroneous rainfall totals.
Especially on days with heavy rain and a lot of wind. ;o)
For the "real" story on any given weather day, D2149 should be your
choice. It isn't the "Official NWS Reporting Station for Bass Lake Ca."
for nothing! ;o)
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Summer High temps... Who do you believe?
Other
privately/commercially owned stations
in this area generally "over-report" their high temps by +5 degrees or
more during the summer months due to improperly sited hardware combined
with inadequate solar shielding of
their weather sensors. A station mounted on a roof or pavement
will compound the over-reporting issue due to radiant heat generated by
the roof or other heat absorbing surface. Our station complies with the
NWS station siting guidelines and is mounted on a mast 5.5 feet off the
ground, above natural soil and groundcover and is also equipped with
the latest
shielding/aspiration technology and thus does not suffer from this
problem.
D2149 is the ONLY FULLY ACCURATE STATION in this area. Any weather
sensor readings reported by D2149 are uploaded directly to the NWS and
documented by that agency as the official historical weather statistics
for Bass Lake Ca.
In short ... This station creates the "historical" weather record for this area.
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Stay tuned to this section in 2011 as we will be posting some additional Q&A content!
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