In February 2014 Britain experienced a high volume of rain and major flooding, centred on the South West of England. Weatheraction did not specifically predict this, but a comparison with the actual pattern of weather against his forecasts highlights my main conclusion of Weatheraction.
Corbyn predicted that there would be a number of very low pressure areas attacking the British Isles from the Atlantic and that they would deposit huge volumes of rain over Ireland and Western Scotland. He was correct in this general pressure forecast but the low pressure areas pushed 200-300 miles further east than his central predictions and it was the South West of England, as well as Ireland, that got a soaking. He issued an update stating that the low pressures were coming in more easterly than forecast. It was stated on the initial forecast, however, that there was uncertainty as to how far east the lows would reach.
My principle conclusion of Weatheraction is that the general pattern of weather and of the formation of areas of high and low pressure is forecast to a level that far exceeds chance; however, due to pressure systems being several hundred miles across - almost as big as the British Isles - these general pressure forecasts are not always translated into accurate weather forecasts for specific areas. The pressure forecasts are often only slightly different from the forecasts but this can result in weather that is markedly different from the forecasts.
Somebody wishing to find fault with Weatheraction could draw on inaccuracies such as the mis-forecast location of the February 2014 rain. Somebody wishing to praise Weatheraction could draw on the wider pressure scenario for the month being accurate. Given that Corbyn himself does not claim to be bang-on accurate with precise weather I believe it is unfair to assess his forecasts on that basis. The outline prediction for the month has been pretty accurate so far: waves of low pressure bringing very strong winds and heavy rain in the west of the British Isles, a very mild month overall with almost no snow, and some fine spring-like weather in week 3.
I say again - there is definitely something to the SLAT method that deserves critical recognition from the established meteorological community.
However, there is one element to Weatheraction that has failed twice in two years. I discussed in the July 2013 update that Corbyn had predicted a violent storm and instead the UK received glorious summer weather. Corbyn accepted the error and modified the SLAT method to take into account the formation of "cut-off highs" where a high pressure area gets trapped for days in the same place. Alas for the revised SLAT method, the same thing has happened in March 2014. The forecast was for a violent storm on the 10th-12th of the month due to an "R5" warning (of a high level of activity on the sun). However, as in July 2013, there has been a "cut-off high" over the UK delivering some fine spring-like weather. There is still some way to go for this phenomenon to be incorporated into the SLAT method.
May 2014 edit: in May two cut-off highs were correctly predicted by Weatheraction. This represents a major advance in the SLAT method -well done to Weatheraction!