I did not see any analysis of LGIH 3rd quarter home closings so I did some very light digging.
1,052 closings for the quarter was a small decline from 2nd quarter. LGIH has a short history. In 2014 there was a much larger decline in closings from 2nd to 3rd quarter. In 2015, the 3rd quarter closings were higher than 2Q. Not much data there for seasonal effects. One would think that Q3 would be seasonally strong.

As far as looking to meeting the yearly forecast for closings, they need 976 4Q closings to meet the low end, 1276 for the high end of the range. With communities in Florida and Carolina, there may be a headwind due to the hurricane.

The rate of closings increase is decelerating, but this is a trend and not an every quarter phenomenon. Seems that the closings for the year will likely be at the low end of the forecast range. I added a very small amount today. If Mr. Market disrespects the Q3 or full year results I would be inclined to add a more significant amount if the decline seems based on short term weather problems.