SERP Tool

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SERP Tool

• Tim Barker, Boise

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The serp tool will take point data and convert it
into a grid
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Creating an image like this
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In some ways, serp is like many other objective
analysis schemes
It is distance weighted
But in other ways it is not
It matches all control points exactly It has no
radius of influence
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Distance weighted and matches all points
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The result
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No radius of influence gives behavior that is
sometimes not what you first might expect.
What should result look like?
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Should it be a bulls-eye?
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Since there is only one piece of information, it
controls the entire adjustment field
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This can be a good feature. What if several
points need the same adjustment...
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Should there be many bulls-eyes?
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The information is the same at all points, so it
is spread out as far as it can
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Two different point values gives a gradient
of information
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Fitting the points via serpentine curves
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Prior versions of serp accentuated the gradient
As the points get closer the gradient used to
get extrapolated and accentuated
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Prior versions of serp accentuated the gradient
As the points get closer the gradient used to
get extrapolated and accentuated
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Prior versions of serp accentuated the gradient
As the points get closer the gradient used to
get extrapolated and accentuated
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Prior versions of serp accentuated the gradient
As the points get closer the gradient used to
get extrapolated and accentuated
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Zoomed in view of the gradient
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Newest version of serp just "draws up to" the data
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Serp still has a clustering problem
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Points with essentially the same information in
the same area are "weighted" more than they should
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Serp can include "topographic effects" so the
resulting changes are not so smooth and entirely
based on distance
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Zoomed into a particularly difficult area
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Without any topographic influence, only
distance matters
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But we can say that "100 feet" in elevation
change is equivalent to "1 gridpoint of
distance", and now we get
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But be careful! Serp will let you think only
about points and make all the changes elsewhere
for you.
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But be careful! Serp will let you think only
about points and make all the changes elsewhere
for you.
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Just set the final values you want...
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This looks fine - matches what you want at all
the points you specified - so what is wrong with
that?
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But be careful! The temptation is strong to just
think about the final values at a few points -
and "let the computer figure out the rest". You
might feel a little better if you specify the
"changes" rather than the "actual values"
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And when you get the changes you want...
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The results are the same. Are you sure the
changes match your reasoning behind them?
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The changes serp made look like this
Is this really what you wanted?
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Run serp on a blank "change grid", get a start on
a complex pattern of changes, then modify the
changes using other tools
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The result looks nearly the same - but you have
used your meteorological knowledge well - rather
than letting a simple algorithm spatially
distribute the changes
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Sometimes you dont have any idea about how
to spatially distribute the changes. Say you
have some statistical procedure that gives you
values at certain points. Go ahead and use serp
- but use it as a starting point. Most commonly
- you could plug in MOS values into
serp. MatchMOS decodes MOS bulletins for you -
and runs serp with those values. This can be a
great starting point for further edits (best if
you have a nice spatial distribution of MOS
points)
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The SmartInit gives us a MaxT grid with a lot
of spatial structure
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Copy that SmartInit field into your MaxT grid and
then run MatchMOS
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You get the best of both worlds... SmartInit
to give you physically-based spatial
structure MatchMOS to "spread out" the
statistical corrections in a reasonable way -
but not in the SAME way every day MatchMOS
works on T, Td, MaxT, MinT, Wind and PoP
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Ideally, MatchMOS could be run as part of
the SmartInit step - so that you could see, for
example, the Eta MaxT field adjusted for the MET
MOS, the AVN MaxT field adjusted for the MAV MOS,
etc. You could then compare all the MOS
adjusted fields, and use the best one as the
starting point for further edits (or you could
just copy them into your forecast and admit that
you can add no value...) Unfortunately, there
are some routines in SmartScript that are not
available in SmartInit so we can't quite do this
yet.
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However, you can add a bunch of parms to
your forecast database (MaxTMET,
MaxTMAV, MaxTMEX, MaxTFWC, etc.) and run a tool
called MatchMOSAll - which, for all times and
parameters (T, Td, MaxT, MinT, Wind, PoP), copies
in the appropriate model SmartInit field and
runs serp to match to all the MOS values. You
can even set up a trigger or cron that will
run this tool (via runProcedure) when the last
MOS bulletin for a particular model comes in...,
so that you will automatically have these fields
available to you. At least you will be able to
next week...
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But Don't Forget... Concentrate on the "changes"
you are making. Why you are making them Where
you are making them How big they should be The
American People are paying for meteorologists to
do this job!