Story by Joe Ebner

Photos courtesy of the National Oceanic and Atmospheric Administration (NOAA) and Joe Ebner

These churning vortexes of water and air are fascinating and fun to watch IF you’re lucky enough to spot one from the beach.

It's a calm mid-summer morning.  You're among friends and family taking a leisurely stroll along the beach.  Already, as the glowing sun peeks over the horizon, the air is warm and heavy.  To your delight there is a cool onshore breeze.

Ahead, you notice a group of people focused on something off shore that has caught their eye.  You look out over the ocean waves toward the horizon and clearly see what caught their attention.  You stop, dead in your tracks, staring out over the sea in total amazement and wonder.

There—seemingly stationary—out over the open water of the Atlantic, churns what appears to be a dark vortex extending from beneath the base of a string of cauliflower-like clouds.  The long, thin, conical tail stretches from the bottom of a cloud and dips in a gentle arch all the way to the surface of the sea.  It is clearly visible against the light blue sky to everyone on the beach that morning.

As you continue to stand and watch, totally mesmerized by the site, it seems to slowly lighten, becoming nearly transparent.  Within minutes, it vanishes into thin air right before your eyes.  Afterwards, no traces of what you have just witnessed remain.  There is no wind, no angry storm clouds, and no thunder, only Carolina-blue skies and a spattering of white, puffy clouds.

You've just witnessed one of coastal Carolina's most fascinating weather phenomenon— a waterspout.

Two Flavors of Waterspouts

While the Florida Keys remain the world's waterspout capital, North Carolina sees its fair share of waterspouts.  As a matter of fact, the first mention of waterspouts in the New World came from British ships off the North Carolina coast in 1586 and 1590 where sailors reported "great spouts" just offshore.

There are actually two varieties of waterspouts and each develops under different weather conditions.

Tornadic waterspouts, the most dangerous, generally begin as true tornadoes over land in association with a severe thunderstorm.  They then move out over the water to become waterspouts.  Tornadic waterspouts can be extremely large and powerful just as their land-based counterparts.  Because these are true tornadoes, they are capable of considerable destruction. Tornadic waterspouts possess the same characteristics as a land-based tornado and are accompanied by high winds, dangerous lightning, and hail.  Since tornadic waterspouts are, in all instances, true tornadoes over water, they are not a common occurrence.

Fair weather waterspouts, on the other hand, are cousins to tornadic waterspouts and form only over open water.  Unlike true tornadoes, which spawn from powerful thunderstorms known as supercells, fair weather spouts develop at the surface of the water and grow skyward. Warm water temperatures and high humidity in the lowest several thousand feet of the atmosphere make ideal conditions for waterspout development.  They are usually small, relatively brief, and less dangerous.

Waterspout Forecasting

"Most of our waterspouts occur during the early morning hours of the summer months," explains Tim Armstrong, a waterspout expert for the National Weather Service office in Wilmington.

At night, the landmass cools off more than the ocean and this creates a temperature discontinuity across the shoreline known as a landbreeze front.  At around sunrise, we'll see this effect as a line of tall cumulus clouds—those billowy, cauliflower-shaped clouds so common in the summer months.  "As the updrafts rising into these clouds begins to rotate along the landbreeze front, waterspouts form," says Armstrong.

According to Armstrong, high-risk days for waterspout formation are identified by several weather conditions.  A warm tropical airmass must be present to support the development of clouds and showers.  Waterspouts also require days with very weak wind shear.  Wind shear is a change of wind speed or direction at different levels of the atmosphere.  Waterspouts can be torn apart before they even have a chance to strengthen if the surrounding winds are not light and all from the same direction.

"We also look for fairly rapid decrease in temperatures between the water surface and temperatures at 10,000 feet up.  This ensures the atmosphere is unstable enough to support the updrafts where waterspouts develop," says Armstrong.  "It's safe to say that waterspouts can develop anywhere from the beaches to hundreds of miles offshore."

Reporting Waterspouts

Since fair weather waterspouts are so small and last perhaps only a few moments, they can’t be detected by even the most advanced Doppler weather radar.  Meteorologists like Armstrong depend on mariners and citizens to report waterspout sightings so they can better forecast their development and warn mariners by issuing a Special Marine Warning.

Armstrong says that it's all a matter of scale.  Fair weather waterspouts are at best only a few hundred feet wide.  Tornadoes involve the entire thunderstorm cell and Doppler radar easily detects the rotation of entire cells due to their much larger size.

According to Armstrong, most waterspout reports originate from mariners operating within a few miles of the shore calling the Wilmington National Weather Service (NWS) office on their cell phones.  "This is the quickest way to get the information into the hands of forecasters who then can warn other mariners through the issuance of a Special Marine Warning."  Mariners can also contact the Coast Guard via VHF radio who then pass the report on to the NWS.  Many waterspout reports also come in from aircraft pilots.

"Reports vary from year to year, but on average we get about twelve to eighteen waterspout reports annually," says Armstrong.  "We suspect we only hear of a small number of all the waterspouts that actually occur."

Real-time reports are ideal since they allow forecasters to warn other mariners, but even reports days later are helpful since they allow forecasters to better categorize the conditions when waterspouts develop.

"Since we suspect many waterspouts go unreported, mariners can help by reporting any waterspout activity they encounter," says Armstrong.

Tomorrow morning when you step out onto the beach and notice those large, billowy cumulus clouds hanging over the ocean, take a closer look under those clouds for waterspouts. Although they aren't an everyday occurrence, they can be an impressive sight for those lucky enough to spot them.

Waterspout Safety

Before venturing out to sea, listen for special marine warnings about waterspout sightings that are broadcast on National Oceanic and Atmospheric Administration (NOAA) Weather Radio.

Watch the sky for certain types of clouds.  In the summer, with light winds, look for a possible waterspout underneath a line of cumulus clouds with dark, flat bases.  Anytime of the year, a thunderstorm or line of thunderstorms, can produce very intense waterspouts.

If a waterspout is sighted, immediately head at a ninety-degree angle from the apparent motion of the waterspout.

Never try to navigate through a waterspout.  Although waterspouts are usually weaker than tornadoes, they can still produce significant damage to you and your boat.

Source: The National Weather Service

 

Assist Your Fellow Mariners
Report waterspout sightings to the National Weather Service office in Wilmington, N.C by calling 910-762-4289.

Include details of the time and location of your sighting.

JOE EBNER is a weather hobbyist who owns and operates a local weather information web site serving the greater Topsail Island region.  He collects local weather information from his own on-site weather instruments and publishes his data on the Web at www.topsailweather.com.  The site also provides current radar and satellite images, marine weather, tide data, and weather forecasts along with several weather tools for visitors, residents, and business owners around the island.  TopsailWeather.com is updated every 15 minutes.