Just briefly, here's the difference between operational and ensemble models. The main models used for forecasting are called operational models. An example of the GFS showing southwestern Caribbean tropical development I mentioned during today's outlook is shown below (look for the L surrounded by bright colors).
An ensemble model is a group of models run together but with slightly different parameters. I'll explain this more another day but the idea is to see what the majority of the models predict, in other words is there a trend. This is used to get a better idea if the operational models are correct or just out to lunch. The GEFS is the ensemble version of the GFS. It has 21 separate members. The Euro ensemble, called the EPS, has 51 members. Below is the GEFS output for the same period of time as the GFS model above.
You can see a cluster of red numbers near where the GFS is showing development. These numbers are low pressure systems from some of the 21 members. So in this case I would say that the GEFS is in fairly good agreement with the GFS showing tropical development. As a comparison only a few of the EPS members (not shown) show development for this system so for right now I'd say overall confidence is low.
Both of today's maps are from tropicaltidbits.com.
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