[wxqc] High Frequency Updates verses Noise (or when the seagull, butterfly, and flea have their day)

[Dave Helms]

Hey Sam,

You got me thinking about the importance, or lack of importance, of high 
frequency observations. Chaos theory explains how it is possible for 
small differences in the initial conditions to cause large differences 
in future predictions. The atmospheric physicist Edward Lorenz 
discovered this by making what he thought were statistically 
insignificant approximations in his numerical weather models which he 
observed caused disproportionately large changes to the forecast output.

Its true that most wiggles on your time series will never influence 
future weather events in any tangible way. However, there are several 
cases that show how gravity waves, detectable by small pressure changes, 
can travel hundreds of miles to trigger thunderstorm formation.

More from Edward Lorenz and Johnathan Swift on the importance of small 
differences in initial conditions -

In a paper in 1963 given to the New York Academy of Sciences, Lorenz 
remarked: /
One meteorologist remarked that if the theory were correct, one flap of 
a seagull's wings would be enough to alter the course of the weather 
forever./

At the December 1972 meeting of the American Association for the 
Advancement of Science in Washington, D.C., the sea gull had evolved 
into the more poetic butterfly - the title of his talk was:
/Predictability: Does the Flap of a Butterfly’s Wings in Brazil set off 
a Tornado in Texas?/

In an 1733 quatrain by Jonathan Swift:
"So, naturalists observe, a flea will bite its dog most readily. The 
dog, surprised, will bite its master, who changes course with actions 
rasher."

One more plug for the magic of 5 minute updates... It is always better 
to have time synchronized data updates. ASOS is currently delivering 
only hourly updates, but there is interest from both the government and 
private sector in collecting ASOS data every minute (AWOS stations 
typically send updates every 20 minutes). However, every other major 
observing system in NOAA updates every 5 minutes including GOES Rapid 
Scan, NexRad storm mode, and the NOAA Profiler Network.


Sorry about my fixation on this issue as I'm making a mountain out of a 
mole hill, me thinks :),

Dave
CW0351

***********************************************************
More on butterflies, power outages, and ensemble model prediction:
http://www.uh.edu/engines/epi652.htm
http://www.sfgate.com/cgi-bin/article.cgi?file=/c/a/2003/08/15/MN191082.DTL
http://www.windows.ucar.edu/physical_science/physics/thermal/Butterfly.html
http://www.its.caltech.edu/~mcc/chaos_new/Lorenz.html
http://www.kporterfield.com/writes/Creative_Writes_13.html
http://boinc-doc.net/boinc-wiki/index.php?title=Why_doesn't_the_exact_same_model_work_out_the_same%3F 


An Ensemble Forecasting Primer: 
http://ams.allenpress.com/amsonline/?request=get-document&doi=10.1175%2F1520-0434(1997)012%3C0809:AEFP%3E2.0.CO%3B2 

To describe the flow of information from small to large scales, the 
authors offer an inversion of the 1733 quatrain by Jonathan Swift that 
inspired Richardson2 
<http://ams.allenpress.com/amsonline/?request=get-document&doi=10.1175%2F1520-0434%281997%29012%3C0809:AEFP%3E2.0.CO%3B2#n2> 
: