Theoretical maximums?

One photograph to explain this post:

I took this pic of the inverter at about 1pm today. Outside, the bright autumnal sunshine is slowly warming the cold air. The sun is only about halfway up in the sky, but that's the highest it's going to get today.

Check out the input power (Pin) reading on the inverter - 2140W.  I had to look at it a few times myself to let it sink in.  

The theoretical maximum of our array is 240W per panel x 8 panels. That's 1920W (1.92kW).

This puzzled me on two counts:

1. It's approaching the middle of October - I thought that as the sun got lower in the sky, the radiant energy falling on the panels decreased, meaning that the output power of the panels dropped as you approach the winter solstice.
2. Irrespective of the time of year, how can the array be kicking out more kW than its theoretical maximum?

 I've decided not to call it a theoretical maximum anymore, since it obviously isn't. I shall call it the nominal maximum. After a moderate bit of googling, I have two ideas that I think explain this anomaly. 

1. All solar panel nominal maximum ratings are calculated from their measured W per square meter rating (W/m2), multiplied by their surface area in meters.  My solar panels have a measured rating of 190W/m2, and are 1.6m x 0.8m in size. Multiply them together, and you get 240W output. But... for the sake of standardised comparison, all panels have their W/m2 rating measured with a level of 1000W/m2 of radiant energy shining on the panel.  Apparently, the maximum energy from the sun measured at the surface of the earth is 1367W/m2. http://www.powerfromthesun.net/Book/chapter02/chapter02.html 
   So it is entirely plausible, depending on atmospheric conditions, that more than 1000W/m2 could be landing on the panel, in which case it would be generating more than its nominal maximum.
2. The thermal coefficient.  http://www.solar-facts-and-advice.com/solar-panel-temperature.html
   All solar panels have a thermal coefficient, which means that as the panel itself get hotter, they get less good at turning sunlight into electricity. All panels have their output measured at a temperature of 25 degrees celsius, and as the temperature of the panel goes below or above that, the panel's conversion efficiency goes up and down. The cold air and windy weather will have the effect of cooling down the panel, making it more efficient.

I think a combination of these two factors explain why I'm getting 220W more out of my array than it says it can generate.

A surprise. A very pleasant one, to be sure, but a surprise nonetheless.