Missing winds

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
*************************************************************