This skylight has a lot of condensation forming on the underside of the interior pane of glass. Because it's in a bathroom, the high level of humidity in the air (from showering), causes an excessive amount of condensation to form, during cold weather. The colder the  winter temperatures outside, and the higher the humidity level inside, the more condensation will form. IN Fact, the condensation was so much that it would occasionally drip down onto the drywall below and it has caused the paint to bubble.
This is an example of a skylight drainage system working properly. This Velux curb mounted glass skylight’s condensation drainage system is allowing any condensation that forms on the inside of the glass, to drain properly to the exterior. In cold weather, this continuous slow drainage of condensation, forms like an icicle.
Theres so much condensation on the inside of this skylight that you can clearly see if from outside. Eventually , all this condensation drips down into the gutters, drains down to the low end of the skylight, and is discharged to the outside.
