Explanation of Plots for 2002 Season

Swarm Plots

    The swam plot loops show all the time evolution of the tracks of all 1980 ensemble members in addition to the sub ensemble means and the total ensemble mean. The percentage of ensemble members falling in each 1x1 deg lat/lon box is also displayed. Here's an example:

    The legend for the swarm plots is as follows: the yellow crosshatch indicates the initial storm location, the pink triangle symbol indicates the total ensemble mean forecast, and each black dot indicates an individual ensemble forecast (there are 1980 members in the full ensemble). The percentage of ensemble members falling in each 1x1 degree box (# falling in a given box divided by 1980) x 100% has been computed and graphed as a raster plot. The maximum sustained winds and minimum central pressure at the initial forecast time are displayed for informational purposes only (that information is not used in the kilo-member ensemble). The java loops will take very long to load (~4200 kb) if viewing with a modem.

Cumulative Probability Plots

    The cumulative probability plots show the probability of the storm passing within 75 statute miles of a given location out through 72-hrs and 120-hrs. They are calculated by determining the percentage of ensemble members falling into each 2x2 deg lat/lon grid box (a 2x2 deg lat/lon box has nearly the same area as a 75-mile radius circle, hence the interpretation of the spatial probability as a strike probability product). The contours are smoothed. The outer white line represents the 0% contour -- the ensemble envelope.  For comparison, the NHC strike probability map is included when available. Here's an example of what the kilo-member ensemble cumulative probability map looks like: