For A Change, Forecasters Predict Less Hurricane Activity
April 05, 2012
By Eric Berger, The Houston Chronicle
With optimal conditions across much of the Atlantic, 19 named storms formed in both 2010 and 2011. This year, though, storm development should be hampered by uncharacteristically cool sea surface temperatures and the potential development of El Nino.
For these reasons, in their initial report released Wednesday, seasonal forecasters Bill Gray and Phil Klotzbach predicted that 10 named storms would form, with just four becoming hurricanes and two developing into major hurricanes. Hurricane season begins June 1.
The median number of named storms -- tropical storms and hurricanes -- during Atlantic hurricane seasons since 1980 is 12, including 6.5 hurricanes and 2 major hurricanes.
In some ways, predicting a slightly below-normal season is remarkably bold.
That`s because, since 1995, the region of the Atlantic Ocean where storms form has been warmer as part of an increase in temperatures caused by an upswing in a natural cycle known as the Atlantic Multidecadal Oscillation.
Since then, Gray and Klotzbach have predicted as few as 10 named storms just three times -- in 1995, 1998 and 2001 -- and they`ve never predicted fewer than six hurricanes in a season.
"It`s definitely a risk, but given the current setup in the tropical Atlantic and Pacific, it`s the best we can say," Klotzbach said.
Chris Hebert, a hurricane forecaster with Houston-based ImpactWeather, believes it`s a risk worth taking.
In addition to the cooler sea temperatures and possibility of an El Nino, which increases wind shear that can tear storms apart, Hebert said some forecast models predict higher-than-average air pressures across the Atlantic basin, which includes the Caribbean Sea and the Gulf of Mexico.
Higher pressures would limit storms because they produce sinking air, which inhibits thunderstorm development. High pressures also increase wind shear and bring more cooler water from deep within the ocean to the surface, Hebert said.
"All the signals are there for less named storms than in recent years," he said. "However, less named storms doesn`t translate into no threat."
Longtime Houston residents may remember 1983`s Hurricane Alicia, which was one of only four named storms that year.
Any storms that reach the Gulf of Mexico may find more amenable conditions for development. Due to the warm winter and early spring, in contrast to much of the Atlantic, the Gulf is two to four degrees warmer than normal.
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