Please explain the term "flash" measure of sentiment

Hi,
I would like to know what is meant by “flash” measure of sentiment. Is it a snapshot of the way eg. purchasing manager feel about the market? I look forward to your feedback.

The “flash” measure of sentiment among manufacturing purchasing managers fell to 47.1 in August, the worst figure in 77 months and a decline from the index’s final reading of 47.8 in July, according to Caixin Insight and Markit Economics. Any number below 50 indicates a deceleration in the manufacturing sector.