What type of figurative language does Lord Capulet use to describe Juliet’s grieving?

Capulet compares Juliet’s grief over Tybalt's death to a storm.

Figurative language is language that is used descriptively, not literally.  Shakespeare uses figurative language often, because in a play you only have the words of the actors to tell a story and for characterization.  Figurative language helps create a more vivid world for the audience.

When Romeo kills Tybalt, this is a terrible tragedy for the Capulet family.  It is particularly horrific for Juliet.  She loves both Tybalt and Romeo.  She does not know what to do, and she knows that Romeo is not a bad person.  Her family has no idea that she is not just grieving for Tybalt, but for Romeo too.

Juliet’s parents want her to marry Paris, a nobleman her father has chosen.  They have no idea that she is married already to Romeo.  Romeo has been banished for fighting with Tybalt.  The Capulets agree to let Paris talk to Juliet later, when she is not so upset. 

PARIS

These times of woe afford no time to woo.
Madam, good night: commend me to your daughter.

LADY CAPULET

I will, and know her mind early to-morrow;
To-night she is mew'd up to her heaviness. (Act 3, Scene 4) 

Lady Capulet uses figurative language here, using the metaphor that Juliet is “mew'd up to her heaviness” over Tybalt’s death.  In other words, she is so upset that she has shut herself up in her grief and needs to be left alone. 

Lord Capulet also uses figurative language to describe Juliet’s grief, comparing it to a storm.

When the sun sets, the air doth drizzle dew;
But for the sunset of my brother's son
It rains downright.
How now! a conduit, girl? what, still in tears?
Evermore showering? (Act 3, Scene 5)

A storm is an appropriate metaphor for grief, because you cry and cry when you are sad.  In this comparison, Juliet is crying so much that she is causing a storm.  Capulet wants her to stop crying so that she can move on with her life and marry Paris.

They have no idea how bad things will get.  We have to remember that the entire Capulet family is grieving and not thinking too clearly right now.  It helps to explain why Lord Capulet went from saying that Juliet was too young to agreeing to let Paris marrying her.  Juliet is hurting in ways her family can’t imagine, but they are hurting too.