TS Chantal first Atlantic named storm of 2013 ...

[STexan]

And it seems like they must have tweaked some models or something is causing more confidence in predicting storm paths this year because I don't recall seeing such a narrow cone going 3, 4, 5 days out ... we'll see.

 

[MClarkson]

Atlantic seasons start with the letter A, so this is the third named storm. The forecast track has the same uncertainty based on deviation in miles as previous years. This storm looks narrower because of its rapid forward speed, so the angle deviation is lower.

 

[STexan]

You're right. I meant to add in it was the first storm to develop well out in the Atlantic that had potential for more then significant rainfall if it makes landfall somewhere.

 

[Mark Ellinwood]

And it seems like they must have tweaked some models or something is causing more confidence in predicting storm paths this year because I don't recall seeing such a narrow cone going 3, 4, 5 days out ... we'll see.

They did narrow the done this year compared to last year... Here's their PDF of forecast changes to 2013, which includes the new radii: http://www.nhc.noaa.gov/news/20130405_pa_2013productChanges.pdf

Forecast cone radii 2012 vs. 2013:

 

[Patrick Marsh]

The cone is based on the climatological errors at those forecast hours. Thus, as the forecasts improve, the cone shrinks.

 

[Patrick Marsh]

I also wonder if the 72HR, 2013 Atlantic Basin radii is a typo...

For all other Atlantic Basin forecast hours, the change in radius is 3NM. At the 72HR forecast, it's decreased by 13NM...

HMMM.....

 

[Mark Ellinwood]

I also wonder if the 72HR, 2013 Atlantic Basin radii is a typo...

For all other Atlantic Basin forecast hours, the change in radius is 3NM. At the 72HR forecast, it's decreased by 13NM...

HMMM.....

Yeah I thought that was a bit strange, too, but kind of dismissed it using similar thinking as your previous post that each period is assessed independently.