Why is Rossby Wave Front Obscure?

Kelvin Wave Front to the East of SSTA
Clear
Clear Eastward Propagation

Rossby Wave Front to the West of SSTA
Unclear (especially in Low Levels)
Westward Extension is Slow or Absent

Possible Reasons of the "hesitation" of Rossby wave
Dispersion in the Short Wavelength
Superposision with Negative Rossby Wave generated by Negative Rainfall Anomaly