On the Last Day, a trumpet and clouds. Why?

The Apostle Paul, in I Thessalonians 4, announces that the Lord shall descend from heaven with a shout, and a trumpet sound, and the elect shall be caught up to meet him in the clouds. The shout and  the trumpet signify the Gospel by which he has been gathering his elect through the ages; the cloud signifies  the presence of God, and our union with him in everlasting bliss and glory.  Sermon for Vespers.