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20010225: zero and negative wind speed contours

>From: "Paul L. Sirvatka" <address@hidden>
>Organization: College of DuPage
>Keywords: 200102252359.f1PNxUL00972 McIDAS-X RAOBCON PTCON speed contours


>On this map, why is there a zero speed contour?
>here is actually a NEGATIVE SPEED!!!!

It appears that you have discovered a black hole right in the Texas 

But seriously, I sent your observation to SSEC to alert them that
something must be amiss in the objective analysis routine.

I tried to reproduce your display from 12Z upper air data on 2001/02/25
while pointing at adde.ucar.edu, but I was unable to get a plot that had
zero or negative contours.  This might mean that the problem is in the
decoding of the data.  Which ADDE server were you pointing at when
you created your displays?

>both were done with RAOBCON

RAOBCON runs PTCON, so PTCON is the one producing the bad objective
analysis.  After the objective analysis, GRDDISP is the one that plots
the contours.  The culprit has to be the objective analysis routine in


If this had been over AREA 51 (Nevada), I _might_ have understood :-)


>From address@hidden Mon Feb 26 07:54:32 2001
>To: address@hidden
>Subject: 20010225: RAOBCON producing 0 and negative contours for wind speed


One of my sites just sent me this note about RAOBCON producing contours
for zero and negative wind speeds.  I guess the question of the day
is how a negative wind speed contour can ever be generated?


------- Forwarded Message

On this map, why is there a zero speed contour?


here is actually a NEGATIVE SPEED!!!!


both were done with RAOBCON


* Paul L. Sirvatka          | Office: (630) 942-2118; Lab: (630) 942-2590    *
* Professor of Meteorology  | COD Weather Lab: (630)-858-0032                * 
* College of DuPage         | Address: 425 22nd St.  Glen Ellyn, IL 60137    *

------- End of Forwarded Message

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