Cone of uncertainty in cyclones
As the name suggests it is a region of uncertainty.
There are many uncertainties when modeling and predicting weather systems.
When meteorologists model the path of a cyclone/typhoon/hurricane they never know for certain where a cyclone will actually end up. At any point along its path a local variation may cause it speed up, slow down, rotate at a slightly different rate or slightly change its path, left or right.
Meteorologists run several models for such cyclone systems on computers. Each uses either a different algorithm and/or different weather parameters. The results of all the models are then used to determine a region where the cyclone is likely to be in with a given time frame.
The greatest certainty is closest to the cyclone. The further away the projected path is from a cyclone the greater is the uncertainty. This results in a larger spread of possible locations where the cyclone could eventually be. When drawn on a map this region looks like a cone.