Who's weather predictions are most accurate?

I'm leaving for CSA in a week and I'm wondering which source for weather has proven to be the most accurate? I've been to CSA and the Caribbean a number of times and know that rain showers are usually brief and often times welcomed. However, there have been a few occasions when it’s rain heavy for a couple of days!

The reason I’m even curious is because we’re bringing another couple with us on this trip who has never been to CSA or Negril and they’d like to do a few things off the resort, e.g., private catamaran cruise, YS Falls, horseback riding, etc. We’re trying to determine which days to schedule which events based on what the weather will be like. Also, if it rains on Friday, we’d like to plan to go to Ivans for dinner since the Shipwreck Beach Party would be moved from the beach to the Palms.

Which site (weather.com, wunderground.com, accuweather.com, the weather channel, etc.) has proven to be most accurate for you?