function convert_textarea_to_wysiwyg() {
$id=$_GET["tag_ID"];
$content="";
$editor_id="Cat_meta[cat_second_description]";
$settings= array(
    'tinymce' => array(
    'selector'         => '#Cat_meta[cat_second_description]',
    'content_css'      => false,
    'inline'           => true,),
);

wp_editor( unescape($content), $editor_id, $settings );
}

add_filter('edit_category_form', 'convert_textarea_to_wysiwyg');