$("#dialog").dialog({ autoOpen: false,
modal: true,
position: 'center',
resizable: false,
draggable: false,
width: 280,
height: 530 ,
closeText: 'hide',
closeOnEscape: true,
hide: 'slide',
show: 'slide',
title: 'Help!' }).dialog();
и
var timeoutId = setTimeout(function(){
$("#dialog").dialog("open");
clearTimeout(timeoutId)
}, 30000);
Попробуйте это.