It's LH - apparently there was some bad weather in FRA yesterday, though that did not stop the flight from FRA - BKK departing on time (though the MAN-FRA flight was delayed by 2 hours). When does weather become extraordinary? Can it be "extraordinary" such that it delays one flight but not another?
Quite easily I'm afraid. Bad weather tends to reduce flow rates at the larger airports, so they have to cancel or delay some services, and the shorter flights are the ones that get it. See the Dashboard thread on Fog Disruption as background. There have been some successes in the German courts challenging the use of weather, and it remains the case that even if extraordinary circumstances do apply, airlines still need to do take all reasonable measures to get the passenger back on track. However in the absence of legal processes - with uncertain outcomes - I very much doubt Lufthansa will pay up compensation if this was the cause.