What a difference a year makes. After the record-breaking 2005 Atlantic hurricane season, the 2006 season is now below normal.
As of yesterday (20 August) three tropical storms will have formed in the Atlantic in an “average” year, which is the same number that have formed this year so far. Because of multi-year averaging, that means that today (August 21) slightly more than three storms would have formed, making this year (statistically speaking) just below normal.
In the hurricane category, this year is decidedly below normal, with no hurricanes so far, while by this date 1.5 hurricanes have formed in the average of years 1944 though 2005.
Reason for the Season?: Cooler Sea Surface Temperatures
Part of the reason for the slow season is that tropical western Atlantic sea surface temperatures (SSTs) are running about normal, if not slightly below normal (see graphic below, which shows SST departures from normal).
In contrast, at the same time last year SSTs in the same region were running well above normal.
The cooler SSTs in the Atlantic are not an isolated anomaly. In a research paper being published next month in Geophysical Research Letters, scientists will show that between 2003 and 2005, globally averaged temperatures in the upper ocean cooled rather dramatically, effectively erasing 20% of the warming that occurred over the previous 48 years.
The slow hurricane season and the cooling sea surface temperatures might be somewhat surprising to the public. Media reports over the last year have suggested that, since global warming will only get worse, and last year’s hurricane activity was supposedly due to global warming, this season might well be as bad as last season. But it appears that Mother Nature might have other plans.
The Rest of the Hurricane Season
With only 3 named storms compared to 9 on this date last year, it is nearly impossible at this late date to have a season anywhere near as busy as last season, which totaled 27 by the end of the year. The most recent prediction from the National Weather Service (see first graphic, above) is for there to be 12 to 15 named storms by December — only half of last year’s total. It now looks like that prediction might be too generous.
While it is still possible for this hurricane season to end up above normal in activity and reach that forecast, each day that passes without so much as a tropical ‘depression’ makes that target less and less likely.