By Wally Pyrah ONCE again, the weather in Hong Kong is likely to play an important role in determining winners at Happy Valley when racing gets underway with a nine-race programme starting at 11.40am today. Rain has been lashing down in biblical proportions since the start of the week, and with intermittent thunder and lightning bringing the city at varying times to a standstill, this doesn’t augur well for the city’s flagship event, FWD Champions Day at Sha Tin on Sunday. The forecast of rain is set to continue at regular intervals throughout the week, and sure to be a cause of concern to som…