T&T: Forecast Errors (was: Weather Routing Services)

[Kevin Redden]

> -----Original Message-----
> .................... If you
> believe that any weather predictions extending out more than 48 hours
> are anything more than a fairy tale, then you are taking more of a
> gamble than I would consider safe, if it involves any sort of serious
> storm. 

Mike's weather observations in his last post were spot on. Many boaters
sometimes put blind faith is what some shore side weather wizard reads off
his computer screen instead of believing the trend to be seen right outside
the pilot house.

Of great importance to the mariner when looking at weather forecasts of over
24 hours is the old 1-2-3 rule (see:
www.prh.noaa.gov/cphc/HAW/marine_safety.php).

The 1-2-3 rule, while primarily designed for use in dealing with Atlantic
hurricanes, is a good rule of thumb when trying to decide on the accuracy of
multi-day forecasts for any cyclonic storm. The rule basically gives a
distance error range for each day into the future of the forecast:

    1-100 mile error radius for 24hr forecast 
    2-200 mile error radius for 48hr forecast 
    3-300 mile error radius for 72hr forecast

In other words, the track of a storm that is forecast 72 hours into the
future could be as much as 300 miles off!

The web page referenced above has some very interesting information for
anyone who has to deal with a hurricane forecast and make decisions on it
while at sea.

Kevin Redden