Chart Scales on Vertical Velocity Chart
Date: Spring 2012
At the above weather link: The 700 mb Vertical Velocity plot is confusing in that the plot key uses the same colors for different values. For example: the key at the bottom uses the color yellow to denote -18, 6, and 30. How do I know what value yellow is on the plot?The same goes for the other colors.
In areas where there is clockwise flow (high pressure) the vertical
should be negative and where the flow is counterclockwise (low pressure) the
vertical velocities should be positive. That's the easy part. Why the color
scheme is repeated for positive vertical velocities in the 12 hour
is a bit hard to fathom (note that this does not happen in the 24, 36, and 48
hour forecast plots). Note also that the forecast vertical
with time, which may be why the repeating of the colors in the
positive is only
needed for the 12 hour plot.
I suspect that the upper color band in the 12 hour plot is not really used,
unless there is one false very high forecast value that is causing
the scale to
be artificially increased.
David R. Cook
Climate Research Section
Environmental Science Division
Argonne National Laboratory
Click here to return to the Weather Archives
Update: June 2012