Insights into Current Sea Grant Research 



The Science of Offshore Weather Patterns 



If you could travel 

 30 miles east of Cape 

 Hatteras on a cold 

 January day and then 

 shoot straight up about 

 15,000 feet, you'd see it. 



You'd see warm, 

 moist air rising off the 

 Gulf Stream, like steam 

 rising off a warm 

 highway after a cool 

 summer thunderstorm. 



And if you looked 

 west, toward the 

 Appalachian Mountains, 

 you'd see blue, cold air 

 damming up in front of 

 the mile-high range. 



And, if you waited 

 around long enough, 

 you'd see a phenomenon 

 unique to the Carolina 

 coast: the formation of a 

 major East Coast winter 

 storm. 



This event happens about 13 to 15 

 times every winter in the area over the 

 ocean just east of Cape Hatteras. 



These storms cause considerable 

 headaches. Each year, they are responsible 

 for millions of dollars in agricultural 

 damage. And they are dangerous. In 

 February 1989, the Presidents Day Storm 

 paralyzed the East Coast with snow and 

 ice. In April 1982, several people lost their 

 lives when a Hatteras-formed storm 

 dumped heavy snows in the Mid-Atlantic 

 states. 



Sea Grant researcher Len Pietrafesa, 

 chairman of North Carolina State Univ- 

 ersity's Department of Marine, Earth and 

 Atmospheric Sciences, has teamed up with 

 two other scientists — meteorology and 

 oceanography professor Sethu Raman and 

 graduate student Joe Cione — to study the 



formation of these winter storms. 



Their research should lead to a better 

 understanding of the storms and more 

 reliable methods for correctly predicting 

 when and where they will occur. 



"We've been looking at these storms 

 through satellite images since 1978," 

 Pietrafesa says. "And we discovered that 

 the events that occur off Cape Hatteras are 

 unique in the world." 



Raman agrees. He says a "freezing 

 line" of low pressure air forms off the 

 coasts of Virginia and the Carolinas when 

 the Gulf Stream begins its annual winter 

 migration toward the Outer Banks. 



Northeast winds roll down from the 

 New England states into this low pressure 

 formation, combining with the warm air 

 over the Gulf Stream and the dammed up 

 cold air from the mountains. 



"Nowhere in the world do you get 

 this kind of heat flux," Raman says. 

 Because of this, he says, these storms can 

 sometimes form within the 12-hour span 

 between weather balloon launchings. 



"That's why these storms have been 

 so unpredictable in the past," Pietrafesa 

 says. 



Now, however, with a better under- 

 standing of the upper atmospheric 

 dynamics of such systems, predictions can 

 be more accurate. 



Pietrafesa says the more we know 

 about these storms, the more we'll under- 

 stand other processes that are affected by 

 them — things like flooding, erosion, 

 transport of sediments and fish spawning, 

 the latter of which seems to occur more 

 often just before these storms begin. 



C.R.Edgerton 



COASTWATCH 17 



