It's always hard to judge from a photograph - they tend to make the sea look flatter than it feels in real life. The sea itself looks very flat compared to the heel of the boat, and there are few white horses, possibly there's land to windward? The sea itself looks like a strong 4. The heel of the boat to sail area suggests more of a solid 6.
How high are the waves there? They don't look very high to me, unless I'm grossly misjudging the size of the boat. I'd vote for Sea State Slight to Moderate.
Don't know the tide/wind situation. Is it over a shallow bottom? Some round bilged or keel boats are more tender (Sonata, Folkboat). Could be rounding up into a wind shift, that always seems to give a bit more lean. Sails may be set a bit full, giving more heeling moment. Difficult.
TW 35 on the sail. Is that a Twister?
This is one of these posts where we old-time forum-within-a-forum lurkers can patronizingly pat you on the head and say "No sonny, this is Parahandy's Trade Wind...."
I reckon the winds gusting. The level of heel indicates about a 5 but looking at the reefed main, It looks a bit baggy which would create a more pronounced level of heel so I will go for F4 gusting 5 in an estuary or funnelled channel.
Interestingly, I thought that as well .. but considered the genoa to be the main culprit being cut akin to Bet Lynch's nightie (or Robbie Colrane's trousers (for the benefit of the ladies here)), do you think the auld scrote needs new sails perchance?