Navy Research Lab, Monterey
The explosive winter storm Jolle on Jan. 26. Shortly before this image was captured, Jolle reached a central pressure of 930 millibars, on par with a Category 4 hurricane.
By Larry O'Hanlon
Meteorologists have hit on a possible way to detect one of the worst kinds of storms before they take shape. Explosive cyclones, so called "meteorological bombs," pop into existence in a day or two and can wreak havoc on land as well as at sea. This makes them especially hard to forecast.
Hurricane Sandy was a monster, but not a bomb since it was forecast with extraordinary accuracy a week ahead. A meteorological bomb, on the other hand, develops at a frightening pace -- with the atmospheric pressure dropping a millibar or more per hour for at least 24 hours.
In late January there was a historic meteorological bomb in the North Atlantic, with the pressure dropping a startling 58 millibars in 24 hours. That storm, named Jolle, generated the mammoth waves that enabled surfer Garrett McNamara to break the world record on a 111-foot giant off the coast of Portugal.
"In a more typical storm you might see a pressure drop of one millibar per hour over less than that number of hours," said meteorologist Greg Carbin of the U.S. National Weather Service's Storm Prediction Center. But when conditions conspire to deepen a low pressure area faster and longer, the result is a forecasting challenge and a danger to life and limb.
In the new study published in Geophysical Research Letters, two Australian researchers stepped back from the storms and looked at the large-scale energy budgets, called "Lorenz energetics," of the atmosphere from 1980 to 2011 (32 years). The study focused specifically on the parts of the world most prone to explosive cyclones: the Northwest Pacific, the North Atlantic, the Southwest Pacific and the South Atlantic.
They found a strong energy signature that was "virtually identical for all four geographical regions," wrote the paper's authors, Mitchell Black and Alexandre Pezza of the University of Melbourne.
Even more promising is the fact that the energy signature of these bombs can be seen 48 hours before the actual storm takes shape. That suggests the method might be applied to lengthen forecast times.
"This finding opens a new avenue of exploration of explosive storm behavior based on the large-scale environment," write Black and Pezza.
A new tool for forecasting the bombs would be welcome since, despite significant events like Sandy being handled very well by the weather models, sudden storms can sometimes slip through the cracks, Carbin explained.