Figure 1: Locations of 38 rainfall stations which make up the Western Sahel precipitation index as well as the 24 Gulf of Guinea precipitation stations. August to November rainfall within the Gulf of Guinea region shows a predictive signal for Western Sahel rainfall and hurricane activity during the following season. June-July rainfall in the Western Sahel region provides a strong predictive signal for the following August through October hurricane activity (see Landsea [2]).

Figure 2: Bar graph of the early season rainfall anomaly index which includes the previous year August-November rainfall from the Gulf of Guinea (weighted 0.30) and June-July Western Sahel rainfall (weighted 0.70). Rainfall is expressed as standardized deviations from the 42-year average (from Landsea [2]).,

Figure 3: Plot of Julian day versus intense hurricane activity (nine-day running mean) using data for 1886 through 1989. Note that nearly all intense hurricane activity occurs between 1 August and 1 November.

Figure 4: Illustration of the two basic US coastal regions which are observed to have different hurricane destruction responses to varying amounts of seasonal West African precipitation. The approximate separation point is the Apalachee Bay of Florida (from Landsea [4]).
 

Figure 5: Conceptual rendering of the difference in composite intense hurricane (Saffir - Simpson category 3-4-5 cyclones) storm tracks during three years of higher West Africa rainfall amounts (top diagram) in contrast to a similar period of lower rainfall amounts (bottom diagram). Note the lack of track difference along the US Gulf Coast but the quite substantial difference in the western Atlantic and along the US East Coast.