http://cimss.ssec.wisc.edu/tropic/real-time/wavetrak/sal-atl.html

Here is all the information concerning the sal.The SAL factor is an important one in my estimation because it causes systems to weaken after they develop into depressions,tropical Storms or hurricanes.Last year for example TD#6 which formed east of the lesser antilles was forecasted by the models to be a hurricane in the eastern caribbean sea but weakened to an open wave and never came back to redevelop because the SAL factor came into play with dry air entraining the low level circulation.There are many other examples of storms and hurricanes that haved hitted a big wall of dry air.