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Missing winds

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  • Subject: Missing winds
  • Date: Thu, 25 Mar 2010 16:34:05 -0600
Hello-
It's my turn to pass something your way. An IDV user noticed the following with ship obs being loaded from an ADDE server: 


New Ticket: Missing winds

I noticed that on some stations (42002) the wind direction is missing in
the raw message, but IDV is coding the wind direction as 0 degrees and
then plotting the wind barb as north. I was wondering if there was a
decoding issue on the server or something with IDV itself. 
KWBC 251900
BBXX
42002 46/// ///10 

Sure enough, the wind direction comes back from the server as 0.
I looked at m0shpdec.for and in there, it seems to set the direction to 0 if it is missing (or it's zero because that is the default value in the array (obs(kdir)): 

      if (ctemp(1:1) .ne. '/')obs(kca) = val0 / 10000
      obs(kdir) = mod(val0,10000) / 100 * 10
      if (obs(kdir) .eq. 990)obs(kdir) = 0
If you plot this in McIDAS-X, you'll see that the winds are north. I'm also assuming that if both the speed and direction are missing, they are set to 0,0 (since there sure are a lot of buoys reporting calm winds): 

There are two ways to fix this:

- fix the decoder to set the values to missing accordingly
- change McPlotWind to check for winds <= 0 for missing, not just < 0
The latter is less preferrable because someone might just store a north wind as 0 instead of 360 and serve it up through ADDE. The former is more correct, since the values are really missing. 

Thanks.

Don
*************************************************************
Don Murray                               UCAR Unidata Program
address@hidden                        P.O. Box 3000
(303) 497-8628                              Boulder, CO 80307
http://www.unidata.ucar.edu/staff/donm
*************************************************************