NATURALIST'S 



NOTEBOOK 



"Basically we make a 

 forecast every day, and we 

 never hear whether or not a 

 waterspout occurred unless 

 someone reports one," 

 Armstrong explains. "[The 

 reports] help us grade and verify 

 our forecast and help improve 

 the service we provide our 

 public." 



The NWS receives reports 

 of 6 to 1 waterspouts on 

 average per year through the 

 Wilmington office. However, "if you look at the 

 entire North Carolina coastline, I'm sure that 

 there are a couple dozen waterspouts forming a 

 year," says Armstrong. 



DISSECTING THE SPOUT 



"On the still summer mornings, when 

 there's nothing going on, when its perfectly 

 peaceful right around sunrise, you may see a 

 waterspout out there spinning — kind of Oz-like," 

 Matheson describes the more benign fair-weather 

 beauties. 



For Matheson, these waterspouts seem 

 "almost miraculous." They usually don't come 

 ashore, but rather, sit over the water for a few 

 minutes, stabilizing the eariy morning atmosphere 

 as the land breeze carries the nighttime drift of 

 cooler air out to the ocean. 



When the cooler air of the land breeze front 

 undercuts the warmer air over the warm summer 

 ocean, the atmosphere becomes unstable 

 because the discontinuity in temperature creates 

 a horizontal spin. These waterspouts become less 

 of a destructive force than an "efficient vertical 

 mixing process," Matheson explains. 



"The spinning process is a more efficient 

 way to transfer mass, to transfer the warm air 

 upward," he adds. 



Tall, puffy cumulus clouds with flat, dark 

 bottoms are formed by updrafts and are signs 

 that air is rising and could spin up a waterspout 

 on the water surface. As the air rises beneath 

 the cloud and above the surface-fed vortex, a 

 connection between sea and sky is made, and a 

 waterspout is formed. 



"The updraft grabs the spin and stretches 

 it out. It's kind of like skaters pulling their arms 



Staff from the RV/Cape Fear 

 spot a waterspout churning 

 on the horizon. 



Ken Blevins/ Wilmington Star News 



in, which causes them to spin faster and faster," 

 Orrock explains. 



Sunnse to noon is the most conducive time 

 for waterspout formation — before the afternoon 

 sea breeze creates enough wind shear to 

 break up fair weather waterspouts. Wnd shear is 

 the tendency for winds to change direction and 

 speed between slightly different altitudes. 



According to Orrock, fair weather systems 

 are fragile, and require low wind shear to form 

 and remain stable. 



Once formed, waterspouts are an impressive 

 sight, as their winds can reach 100 mph and travel 

 at a speed of about 1 knots. The lifespan of a 

 waterspout varies but usually lasts no more than 

 20 minutes. "The bigger, the more impressive it 

 looks, the longer it will last," Orrock says. 



PROMOTING OCEAN SAFETY 



When atmospheric conditions are right, 

 forecasters can predict the risk of waterspouts on 

 any given day. But you don't have to be a trained 

 meteorologist to take safety precautions. 



Safety Tips for Boaters 



Be informed: Know the time of day that 

 waterspouts form, the typical cloud structures 

 and associated weather patterns. 



Be prepared: Check forecasts for storms 

 and threatening weather and always give a float 

 plan to your local marina before leaving safe 

 harbor. 



Be aware of your surrounding: Pay 

 attention to weather inland to avoid surprise 

 thunderstorms. Listen to weather radio alerts and 

 warnings issued for storms brewing inland as well 

 at sea. 



Steer clear: If you do cross paths with 



a waterspout, remain calm. 

 Remember the typical 

 waterspout affects a very small 

 area. "Observe its motion or 

 direction and move away from 

 it in a straight line as fast as you 

 can," Armstrong advises. 



Seek safe harbor: "If 

 you're dealing with a true 

 thunderstorm that is becoming 

 a tornado, that's a whole 

 different story," says Orrock. A 

 large, tomadic thunderstorm 

 could produce lightning and many different 

 waterspouts. 



Coastal communities and visiting 

 beachgoers also should watch the forecasts for 

 waterspout risks. "It's not uncommon forthem to 

 skirt onto the beach," Orrock says. 



While onshore, waterspouts can do the 

 same damage associated with small tornados. 

 However, since waterspouts thrive best over the 

 smooth, frictionless ocean surface, they don't 

 survive long on land. The sand, dunes, trees and 

 buildings found along most beaches usually rip 

 a waterspout's circulation apart within a few 

 seconds. 



Boaters may worry about imploding 

 windows or torn canopies. But according to 

 Purifoy, waterspouts also could be armed with 

 slippery projectiles — raining schools offish. 



"The waterspout could be a mile away, and 

 you'll actually see fish landing and things hitting 

 the water — it's rare, but it does happen." □ 



Visit the National Weather 

 Service (NWS) in Wilmington online. 

 The new waterspout risk forecasts can 

 be viewed at www.erh.noaa.gov/ilm/beach. 



To report a waterspout, 

 immediately call the NWS office, 

 91 0/762-4289, with details on the 

 time and location of the sighting. 



Information and pictures also 

 can be sent to Tim Armstrong at 

 Timothy.Armstrong@noaa.gov. 



20 SPRING 2005 



