In Stanza II of Ode to the West Wind, Percy Bysshe Shelley use a metaphor to compare the West Wind to a funeral song (dirge) played to the waning year of 1819; Shelley writes in the autumn of 1819.
Shelley furthers the metaphoric comparison by calling the night on which he writes his lyric ode (ode is a form of lyric poetry) the "closing night" as though it were the closing movement of the funeral dirge.
He goes on to build the imagery of this metaphor, the scope of which is continually increasing, by saying that the metaphorical "closing night" (closing movement of the dirge) will be a metaphorical dome (high vaulted ceiling) to a sepulcher (tomb, grave, place of burial) that is vaulted (curved architecturally) and architecturally supported by the symbolic force of the West Wind held in the collected waters of Earth.
Shelly refers to the fact that the warm Mediterranean west wind evaporates the waters and precipitates torrential rain storms in the autumn. It is these collected waters that first support the vaulted dome and then storm down as signifiers of mourning in the form of "Black rain, and fire [lightning], and hail...."
In summary, Shelley calls the "closing night" the last movement of a funeral song (dirge); a vaulted dome; a ceiling for a tomb; a vaulted dome supported the rains of mourning. If my count is correct (I confess to being dizzy with all Shelly's twists), that's a metaphor within a metaphor within a metaphor.
In the poem 'Ode to the West Wind' by Percy Bysshe Shelley, the poet likens the closing night to a grave. He uses the more mysterious creepy term 'sepulchre.' This is also a religious term, conjuring images from the Bible and New Testament where Christ's body is entombed after the crucifixion. Ancient graves were often placed in secure, dry places like caves in hills or holes in rocks. Special graves were often added to in later years and if the body was that of a high status individual, then decorations, worship accoutrements and a roof were sometimes added - as in the case of the 'vaulted' roof in this poem. In this case Shelley likens the 'vapours' (clouds) to a huge domed roof for the sunset. Wind, in classical times, it was credited with more mystery than just the weather - it represented soul and imagination.