Sat Sep 09 2017 05:54 PM


I notice how the storm has been heading "West" for the past 24 hours. However, the lines of Latitude has changed from 22.0N to 23.1 N in the same span. The most egregious was between the 8AM to 11AM advisory this morning. It went from 22.6N / 79.6W to 22.8N / 79.8W. A change of .2 degrees north and west. Wouldn't that indicate a NW movement? The NHC showed a West direction, but I'm not sure why.

NHC does in fact track the eye, but there is consideration given to wobbles and other transitory or short-lived changes, and tends prefer smoothing movement into six hour averages - also what is kept in best track. .

If a NW trend covering 3 hours was to continue as NW when smoothed out over six hours, the verbiage would probably reflect that.

The 24 hour track of Irma from 11AM AST Friday to 11AM AST Saturday (today) per NHC was

08/1500Z 22.0N 75.3W
09/1500Z 22.8N 79.8W

That movement is 0.8 to the N and 4.5 to the W (or generally 'west')

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