WxWorx or Anywhere Wx

"Jonathan Goodish" wrote:

In particular, since the NEXRAD provided is base reflectivity, ...

Not exactly true. Here's what WxWorx has to say about it (with minor
paraphrasing):
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WxWorx develops their own version of a composite radar picture using the 124
nm base reflectivity from each radar scan (revolution). They arbitrarily
undertake compositing at a five minute interval, compositing the latest scan
and going back in time so that all previous elevations are included (if
there are 14 "cuts" conducted by the radar and it is currently on "cut 4",
we include the latest cut, 4, then all others). The composited image from
each radar is then mosaic-ed for the whole U.S. image."

Each elevation scan or revolution produces a product called base
reflectivity. On a 5 minute schedule, WxWorx uses the most recent scan and
the previous 13 revolutions to build the composite reflectivity image. The
timing is arbitrary which means that the most recent scan may be at some
middle elevation. So when the timer goes off, they just dive in and grab the
last scan that completed and the previous 13. Essentially they have
"considered" all elevations by using this method.

The color of the pixel that gets displayed on your screen depends on many
factors. They look at each elevation over the last 13 revolutions (or 5
minutes) and choose the highest reflectivity value. This could have been
from the latest scan or from the oldest scan. You just don't know. They do
this for the entire 124 nm radius. There are other factors that I have not
mentioned that may change what you see (such as clutter filtering.

This is different than the composite reflectivity seen from the NWS SSR-88D
display. WxWorx does not try to align itself with the Scan 1 to Scan N
(called a volume coverage pattern) composite reflectivity image. Obviously
this makes good sense since they are trying to be schedule driven, not
product driven. In most cases, they will produce a product that is taken
from two volume coverage patterns. But who cares? Each elevation is
considered and they can provide the most current product.
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They refer to each scan as "base reflectivity", no matter what elevation the
radar is tilted to. The point is that the colors you see in your airplane
represent the highest level of all the different elevations scanned for that
area.

-Mike

In article ,
"Mike Murdock" wrote:
They refer to each scan as "base reflectivity", no matter what elevation the
radar is tilted to. The point is that the colors you see in your airplane
represent the highest level of all the different elevations scanned for that
area.


I'm not sure of the source of your information, since you didn't provide
a direct reference, and it doesn't seem to appear on the WxWorx web
site. Certainly, none of the information that WxWorx provides on their
web site confirms that a composite reflectivity image is provided, and
the information that you provide suggests that the image is a base
reflectivity image with some "educated guessing" involved in order to
attempt to paint a composite-like picture using some base reflectivity
data. However, I'm not a radar expert, so perhaps I'm misinterpreting
something along the way.

I have never put the WxWorx and NWS products side by side to see how
they compare. I would be interested to hear from anyone who has done
such a comparison. WxWorx seems to be somewhat guarded about the
details, or at least I haven't found a good source for the details yet.

I have heard that WxWorx does a pretty good job of painting the heavy
and severe stuff with yellows and reds, but I've personally had some
yellow cells sneak up on me all of a sudden in a sea of green. Seems
that echo tops (which I had turned off at the time) may have shown a
higher-level return before the cells actually painted yellow on the
NEXRAD image.



JKG