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Board » General Discussion » Forecast accuracy?

Posted by
76Trombones


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2009-08-03 18:04:56
2013-04-12 13:57:19 - Forecast accuracy?
SOL mostly uses "real-time" winds and forecasts based on the National Oceanic and Atmospheric Administration's (NOAA) models. There have been a few questions in chat about how reliable the forecast is, and if it's reasonable to make long term strategy decisions based on the predicted winds.

There are a few ways to look at this, and "weather forecasters" in general get a bad rap because the average person is most interested in what will happen on *their* commute home or for the bbq on the weekend than the actual weather systems. The forecaster is usually the guy who gets a minute and a half on the morning talk/news show.

We had some unusual weather for the balloon race, and had to switch gears about halfway through. The image below is a composite of the May 11, 1200utc forecast taken from SOL's Wx for the week prior, starting at the top.



It's pretty obvious that the weather predicted on the 4th is quite different from what we ended up with, but certainly the last 4 days are very close. What happened? Is the 7 day forecast wildly inaccurate?

Leading up to this sequence there were three lows in the N Atlantic - one well N, one SW of the finish and a more powerful one following. Each major system is well defined, but how they merge can get messy. In the earliest forecast, the SE low moved onshore - allowing the following one to quickly move NE.

By Friday, you see evidence of a dramatic slowing, but the prediction is still for a merge to the NE. This is where a bunch of us started to worry - if the earlier pattern held, we'd have a fast and safe approach to the finish, but it was looking like we'd have to loop in from the SE. The SE approach was very risky, as any shift back would leave boats stranded. I posted an analysis Friday evening in which the speeds in the NOAA model were called into question. The UK Met model showed the low lingering S of Ireland, and indeed this is what ended up happening.

By Sat, it was obvious that we were in a new pattern - remembering that it was always one of the options... The critical system was pulled down, giving us the Southerly winds eventually needed to finish.



--- Last Edited by 76Trombones at 2013-04-13 00:05:10 ---
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