Read here. Great explanation of the what-and-why of hurricane seasonal activity. In summary, if a weak La Niña (an ENSO phase) develops in the Pacific, and in combination with warmer Atlantic Ocean waters, the number of 2010 hurricanes could be large. Update: here.
"Last year, there were only three hurricanes. The long-term average is 10 tropical storms, six that develop into hurricanes. The season runs from the first of June to the end of November — hurricanes only form over water that is 80 degrees or warmer, as the Atlantic Ocean is usually not warm enough to support hurricanes in June and July. But this year, we’ve already got Alex, so we are off and running. Generally the warmer the water, the greater the chance there will be a stormy season. But there are other important factors.....It is a radically different picture this summer. The water is very warm in the hurricane breeding grounds, and there are signs of a La Nina developing. In fact, the water is at least as warm as 2005, and the developing La Nina will reduce the winds over the Atlantic. These two major factors would seem to indicate that this hurricane season will be another one for the books."
