Hurricane Update: The Calm Before the Storm?
This year has brought record droughts, killer tornados and devastating flooding, yet our hurricane season has yet to rev up. This may cause some to believe we could be spared substantial tropical activity this year. Don't believe it.
What may seem like a quiet tropical Atlantic region right now, historically speaking, is no indicator of the entire season to come, though there are a few indicators that do bode well for us this year.
Even though hurricane season begins in June, there is, on average, only one named storm every two years in that month. Tropical Storm Arlene spun up in the Bay of Campeche at the very end of June, managing to hit your two-year average. Statistically, July is nearly identical to June, with an average of about one named storm every other year.
It isn't until mid-August when things start to get busy in the Atlantic basin as storms, fueled by light winds, a general decrease in dust blown into the lower atmosphere off the Sahara Desert and warm ocean temperatures.
One sign of hope, despite how early it is in the season, is the third item mentioned above: ocean temperatures (referred to as sea surface temperatures or SSTs). SSTs are a primary contributor to the development and strengthening of tropical storms. Looking at the charts below gives us a very small historical window and provides some reason for optimism.
Atlantic Sea Surface Temperature Map, July 14, 2005
In 2005, the busiest Atlantic hurricane season on record, which included both Katrina and Rita, it is clear that the water in the Atlantic basin on July 14 was already unseasonably warm, with some downright hot pockets in the Caribbean and the Gulf of Mexico. That large blog of red in the Gulf is what turned both Katrina and Rita from small storms into monster hurricanes.
Atlantic Sea Surface Temperature Map, July 14, 2010
Last year, we had a large number of named storms, but none of them made landfall in the U.S., a fortunate and fairly rare occurrence. In the graphic above, however, on July 14 of last year, the water was extraordinarily warm in the Caribbean and many of the storms of last season originated there.
Atlantic Sea Surface Temperature Map, July 14, 2011
This year, our one glimmer of hope resides in this map. The Atlantic as of July 14 is substantially cooler than the two years above. It is still very warm in the Caribbean and the Gulf, but not to the degree we saw in 2010 or 2005, two of the busiest seasons in the last 15 years. While it may not be conclusive proof that our hurricane season will be less busy this year, it at least provides a bit of encouragement in that direction.
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