Ryan,
Are you running a CRON job for nws-alerts.php every 8 minutes or so (looks like your cache time is 10 minutes)? When I bring up your page, it shows between 4 and 6 seconds to process your nws-alerts zones. If you run a CRON job that updates the cache every 8 minutes, the results will always be in the cache and your page should load 4-6 seconds quicker.
Steve