Following W3C's Alternative Text Decision Tree, as the image text and content description may exceede 120 characters then this exceedes the capacity of a usable alternative text attribute.
<figure> element and it's native
<figcaption> child element group the image and it's content description semantically.
A caution is that WCAG directs that when a figure is removed from a document, the document's meaning is not degraded. Clearly that conflicts with the intention of this image type and its accessible content. There are alternatives including DIV and SPAN soup, or the
<section> and, or
<article> landmarks. In this use case, the semantic connection between the
<figure> and its
<figcaption> is strong and reliable when conveyed in a browser when CSS and, or JS are not available. It is the strategy of choice.
<figure> <img src="../img/dieux-by-pat-godfrey-deadline.png" alt="Cartoon Strip" > <figcaption> <p>[Assistant] The Director wants your plan for the information architecture. <br> [Our Designer] Says nothing. <br> [Assistant] I'll tell him you are at lunch.</p> </figcaption> </figure>