Hugh, I dont agree with you, the dopplergram's pic (1st pic) is showing how strong are the magnetic fields produced by the bigest sunspot of AR11899, this sunspot always have had a strong magnetic field and homogeneous, but now is appearing with a weak polarity in its center.
Do you believe too that we're seeing some artifact created by the computer over the dopplegram? Also, the HMI Magnetogram's pic (B&W) is showing a little point in its center with changed polarity (2nd pic).
Then, I believe that this sunspot is decaying from its inner to outside.


IMAGE ( [link to imageshack.us] )


IMAGE ( [link to imageshack.us] )