The title of the thread is coined a triangle breakout and not just simply breakout. The specificity itself suggest a particular pattern is being considered. I did not set the premise but I am questioning the accuracy of the premise. Secondly, I have said that triangles are unique in its attributes in terms of post breakout measured moves. It is a different conversation on whether clearer identification will result in an improved outcome.
I am still open to you or the OP that will point to some authoritative work that fits the definition of a triangle pattern as evident before us.
I didn't want to go down this road, as the chart shows a tradable ascending triangle and that's good enough. I think the search for authorities who can better and better fit or define a pattern is just a search for spurious accuracy and reliability and I don't see it as improving the bottom line which is what's most important.
However as you ask, Bulkowski in Encyclopedia of Chart Patterns has this to say -
Identification Characteristics of Ascending Triangles
"Triangle shape
Two price trendlines, the top one horizontal and the bottom one sloping up, form a triangle pattern. The two lines join at the triangle apex.
Horizontal top line
Prices rise up to and fall away from a horizontal resistance line at least twice (two minor highs). Prices need not touch the trendline but should come reasonably close (say, within'/s). The line need not be completely horizontal but usually is.
Up-sloping bottom trendline
Prices decline to and rise away from an up-sloping trendline. Prices need not touch the trendline but should come close (within '4). At least two trendline touches (minor lows) are required.
Crossing pattern
Prices should cross the chart pattern several times; they should not leave a vast amount of white space in the center of the triangle.
Volume
Volume is heavier at the start of the formation than near the end. Volume is usually low just before the breakout.
Premature breakouts
Somewhat prone to premature breakouts, both up and down. Volume on a false breakout is also heavy, just as the genuine breakout.
Upside breakout -
Volume is heavy (but need not be) and continues to be heavy for several days.
Price action after breakout -
Once prices pierce the horizontal resistance line confirming a breakout, prices move up and away from
the formation. Throwbacks to the formation top are common. If prices continue to climb rapidly, volume will probably remain high. For downside breakouts, volume is high at first and usually tapers off unless the price decline is rapid, in which case volume will probably remain high."
Please be aware this isn't my preferred definition, its probably not the best definition, its just that you demanded an authority and I'm happy to quote this one.