The numbered sections of "Ode to the West Wind" do follow some sonnet conventions.   The sonnet rose to popularity during the Renaissance, and Percy Shelley wrote hundreds of years later, so he would be familiar with the form.

• First, the sonnet form demands fourteen lines.  Each section of "Ode to the West Wind" contains fourteen lines. 
• Next, Elizabethan sonnets are generally structured as three quatrains followed by a couplet.  The poem follows this convention as well. 
• Rhyming in sonnets may vary.  A traditional Elizabethan sonnet utilized the rhyme scheme ABABCDCDEFEFGG, or close variances, with seven rhymes.  The Petrarchian sonnet utilized only five rhymes with ABABBCBCCDCDEE or similar variances.  Shelley's ode rhymes ABABCBCDCDEDEEk, with some accounting for imperfect rhyme.  This use of rhyme tends toward the Petrarchian sonnet.
• The content of a sonnet typically presents either a problem/solution scenario or presents three views of a situation.  Both types of sonnets resolve the problem or the views in the final couplet.  Ode, as a sonnet sequence rather than a single sonnet, does present varying views of the west wind in the three quatrains leading to the couplet.  However, the couplet does not serve to resolve anything but simply to pose additional questions or topics about the wind.

Shelley's ode does follow both sonnet forms closely while mingling the two styles with his own.