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(Sorry about the fuzzy picture.) The morning notch is caused by the neighbor's roof, because the sun rises so far to the south that the dormer never shades the panels. By 11am the neighbor's pine trees (close to his house) are providing significant shade. In the afternoon the shade from the close pine trees is mostly gone, but then the distant pine trees (near the neighbor's garage) are providing some shade.

• The red lines in this image show the actual energy generated during a cloudless day near the winter solstice.
• The dashed yellow lines (from left to right) indicate 10am (when the shadow of the neighbor's roof left the panels) and noon (when the sun was due south).
• The black curve represents my theoretical estimate of the energy that could have been generated under ideal, unshaded conditions.

Summary:

Condition	Energy	Percent of Theoretical
Theoretical	15.4 kWh	100%
Actual	11.4 kWh	74.0%
Dormer Shading (morn + eve)	0.0 kWh	0.0%
Roof Shading (morning)	1.1 kWh	7.3%
Pine Tree Shading (11am-4pm)	2.9 kWh	18.8%