It seems to me the merged product, particularly the 0-2km, highlights nearly every updraft whereas the AzShear seems to do a good job discriminating, and highlights the cell most likely to have strong rotation. In this case the couplet shows up in the western side of the AzShear display and is associated with an embedded rotating updraft, while the AzShear does not highlight the cells further southeast which show weaker rotation. However, the merged product (bottom right) shows bullseyes on all these cells which would make it difficult to triage which storms need attention.

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