Wednesday, September 12, 2012

Debby - When Forecasts are not Accurate

Possible paths for Debby (from The Original Weather Blog)
After I posted "How Accurate are Weather Forecasts?" I encountered Tropical Storm Debby this past June  as it formed  in the Gulf of Mexico.  We didn't experience much besides some rain and 25 kts or so of wind. 

The interesting thing about Debby was the  large error in the forecast which seems to contradict my post in which I linked to the post  Extraordinary Skill for Extended Weather Forecasts  from Cliff Mass Weather Blog

This was an early  forecast from the NWS:

(from The Original Weather Blog)

This is a latter  forecast which is much closer to the actual track.

(from The Original Weather Blog)

In fact forecasters were well aware of the uncertainty in the forecast, here is a chart showing what the various models were showing:
(from The Original Weather Blog)

 The question is; how does the mariner at sea know when forecasters are not confident in the forecast?

 If access to the internet available mariners can dig down deeper by reading the discussion of the forecast which is available on weather web sites including the NWS.

Without internet access it's a little more difficult. The key is to use more then one source when available, in addition to national weather service forecasts  I use a weather routing service if I am going to be in the vicinity of heavy weather. The operations department also sends additional weather if  I request it.  A couple of times I've had my wife email me weather info.

Don't bet too heavy using a single source. As before, with the weather forecast, trust, but verify.


A good discussion of Debby at The Original Weather Blog here
Tropical Storm Debby Forms in the Gulf... Now What?

1 comment:

Anonymous said...

I would believe your wife.