Noticed an across the board temperature discrepancy between the Observed Sounding at KJAX and two of the NUCAPS soundings from the afternoon pass of NOAA-20.  Looked at two different NUCAPS soundings which straddled KJAX.  The morning sounding at KJAX (12Z) showed a typical morning, warm tropical but capped sounding.  The two NUCAPS soundings were from six hours later showed a surface change that would be expected but then showed decent cooling from the morning through the entire column.  The image below shows the two NUCAPS soundings, one is in focus (red/green), the second NUCAPS soundings is the drab color and the observed sounding is in blue.  This shows the two NUCAPS soundings to be very similar and follow each other well but are also a few to several degrees cooler than the observed sounding. 

While I would expect some areas of the column to cool with a sea breeze front coming through, but not the entire column.  When I see this type of discrepancy, it makes me not want to trust the NUCAPS sounding in this case as it does not seem to make much sense with the ground truth of the actual measured RAOB.  Of note, when the NUCAPS sounding was taken, the line of sight was free of clouds and the “dots” were green; however, there were thunderstorms to the north and west of KJAX and they had an outflow boundary approaching the area rapidly.  Could this have made a difference?  I don’t know but it is worth noting this did occur.  Also, we also noted the NUCAPS soundings for this area were all cold in comparison to the morning RAOB.  Looking further west to KTLH, the NUCAPS soundings and the observed soundings looked much closer and made a lot more sense.  So, could this be a marine layer influence?  Could this be just a bad batch?  Could this be a bad thermometer and wet bulb sensor on the actual RAOB?  All valid questions that I can’t answer but put here as possibilities that can’t be verified.  

Of note, we also looked at the differences between the KSC 15Z sounding and the afternoon and the afternoon pass of the NOAA-20 NUCAPS soundings.  These two were much closer and seemed to be much closer together.  Also note, the time difference between the two soundings is only 3 hours in comparison to six.  The image below is the KSC sounding comparison.  The sounding in focus is the actual KSC RAOB and the NUCAPS sounding is in the background.

-Strato-Dragon