 All major forecasting agencies predicted an above @-@ average season . All reduced their seasonal predictions in early August , but even the revised predictions were too high . The lack of activity was primarily caused by an unexpected significant weakening of the Atlantic Ocean thermohaline circulation between winter and spring . This resulted in continuation of the spring weather pattern over the Atlantic Ocean , with strong vertical wind shear , mid @-@ level moisture , and atmospheric stability , which suppressed tropical cyclogenesis . 
