I would be interesting to know what the humidity level is in the house. For those readers that are just passing by - The condensation is the result of warm, MOIST air condensing-out onto the cold storm door. It doesn't matter how 'thick' the glass is, or even how many layers of glass there are. Depending, you can get condensation to form on almost ANY window or surface.
If condensation was forming on the storm door when the INTERIOR door is closed, then you'd have a warm-air-leak from the house into the 'cavity' between the 2 doors. If you have a humidifier, try dropping it to 35%. If you don't have a dehumidifier, consider getting one. Also, if the door is near a bathroom or a kitchen or on the 'cold' side of the house, the problem is magnified.
My best to ya and hope this helps.
Jay J -Moderator
PS: God Bless America!
You may want to check the sill at the bottom of the Pella door.
You may need to adjust it for a tighter seal.
Jay J. is right about the condensation.