Long-range tropical experts from Colorado State University have downgraded their predictions for the hurricane season, now forecasting that only 9 tropical storms will form, with 4 becoming hurricanes. This is a significant change from the forecast made back in April, which was for 12 tropical storms and 7 hurricanes. Forecasters from NOAA generally agree with this downgrade, making it a below-average hurricane season.

There are two main reasons for the big change. First, hurricanes depend on warm ocean water for fuel, and waters in the Atlantic are running slightly colder-than-average. Second, high-altitude winds over the tropical Atlantic have been slightly faster-than-average, and that tends to blow the top off budding tropical systems.

How did these speedier upper-air winds develop? Most likely, they're related to the developing El Nino in the Pacific. During El Nino, waters over the central and eastern tropical Pacific warm up, creating more thunderstorms than usual there. The rising air in these thunderstorms adds momentum to upper-air winds, which then blow eastward into the Atlantic where they can disrupt the formation of tropical storms and hurricanes.