West African Rainfall

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I find it strange that this is not a good predictor anymore. I guess you can't depend on anything staying the same. The difficult part is not even knowing why this is happening. Perhaps its not applicable during the active cycle that we are experiencing. What do you think?
2 Earlier 1 June Statistical Hurricane Forecast Scheme
Our original early June seasonal hurricane forecast scheme was developed in the early 1990s and demonstrated significant hindcast skill for the period of 1950-1991 (Gray et al. 1994). This scheme included measurements of West African rainfall as an important forecast input.

Since the observed shift of Atlantic Ocean SST patterns in 1995 [and the implied increase in the strength of the Atlantic Thermohaline Circulation (THC)], our original 1 June forecast scheme (1994) has consistently underpredicted Atlantic basin hurricane activity. Our earlier 1 June statistical scheme used West African rainfall data as an important predictor. We do not understand why, but the previously observed (1950-1994) strong association between West Africa rainfall and Atlantic hurricanes has not been reliable since 1994. We have lost confidence in the previous 1 June statistical forecast scheme compared to our newly developed one. We have thus decided to discontinue our earliest 1 June forecast scheme.

Over the past couple of years, we have been using an updated statistical scheme that utilized NOAA/NCEP reanalysis data. However, this scheme used mostly data from the previous fall and winter, and therefore we have recently developed a new early June scheme that makes use of mostly spring data.