Saturday, December 30, 2006

My Neighbor Gives Great Advice About the Local Weather Forcast

Here is some great info about the weather from a neighbor:

The U.S. Weather Bureau for the metro Denver area is
located in Boulder, and has more people working the
forecasts than anyone else. Go to:

The buttons give a variety of information. The official
forecast is gotten by pushing "Zone Forecast" (then
use your browers "Find" function to search for "Ned").
This forecast is updated several times a day, but most
significantly around 4 a.m. and 4 p.m. (only in
unusual circumstances, like today, is it updated
more frequently).

The "Short term forecast" is updated every 3 hours
or so and is more immediate. Look for the part that
includes Nederland. During calm periods, nothing
is posted here.

During periods of potentially bad weather situations,
click on the "Warnings and Advisories" button. During
threatening situations, this is updated every 6 hours
or so. An alternative is the "Special Weather" button,
which is often changed during morning hours more
frequently than the "Warnings...".

For those who really want to understand what to
believe about the official forecasts, the really
special button is "Forecast Discussion". While
this discussion (be sure to go to the Denver
discussion, rather than Grand Junction, Pueblo,
or Goodland) is filled with abbreviations and
technical jargon, the forecasters let their hair
down and tell you about their confidence (or lack
thereof) of the forecasts. Anyone can get the gist
of what's in their minds, behind the official
forecasts, despite the jargon.

For example: last week's storm was confidently
predicted 48 hours in advance, and the "Discussion"
indicated confidence that the storm would happen in
the way it actually did. This storm, that seems
to be ending in our area, had great uncertainty
for the last 5 days. If you read the
"Discussion", it was clear that this meteorological
situation was unprecedented, involved inherently
unpredictable aspects, and the official forecasts
were extremely uncertain. For us, added to the
general uncertainty, is the fact (apparent from
the Discussions) that we have been on the western
fringes of the storm. If it had moved (and, still,
if it might move) a hundred miles to the west, we
could get a lot more snow. But if it moves a
hundred miles to the east in Kansas/Oklahoma,
then we're finished with the snow.

No matter how much you might like Mike Nelson's
personality, he is mainly just giving a "popular"
account of this official forecast. Some media
outlets subscribe to other services (like Accuweather)
which, I believe, are less reliable. For the March
2003 7-foot storm, United Airlines relied on
Accuweather, which predicted snow flurries for
Denver, and flew all its planes into DIA to be
stranded. I relied on the Weather Bureau, which
predicted a possible "storm-of-the-century" in its
forecast "Discussion" 36 hours before the first
flake fell, so I loaded up with supplies. Somne
media simply aren't savvy. KUNC radio, for
example, hasn't figured out when the new forecasts
are issued. So KUNC reported around 5 o'clock
that we would get another foot of snow tonight,m
relying on the official forecast written before
dawn and not realizing that the usual afternoon
forecast (available between 3 and 4 pm) had
downgraded the snow forecast.

I hope this is helpful. Although I am a professional
astronomer, I actually have a Master's Degree
in meteorology and have long been interested in
the there is a bit of professional
backing to my recommendations.

For the next few days, however, we're happily
stranded by all the snow in our driveway.

Happy New Year!

Clark (& Y) Chapman