Weather and the Modern Mariner part 4

by Mark Michaelsen

SUPERCELLS, TORNADOES and WATERSPOUTS

Photo courtesy of: www.earth.li/~kami

These represent three of my four favorite subjects when discussing weather. Only hurricanes are more fascinating to me than these amazing weather phenomenon. Hurricanes generally contain all three although the lifecycle and elevation of the Supercells is generally quite short when they are a part of a Hurricane.   So what is a SUPERCELL Thunderstorm?  By definition it is a convective storm that possesses a deep, persistent mesocyclone. Okay...so what is a Mesocyclone? (From Wikipedia) A mesocyclone is an area of vertically oriented atmospheric rotation (usually but not always cyclonic) that is most often associated with a localized low pressure region within a severe thunderstorm. The phenomenon is normally relatively localized in nature lying between the synoptic scale (hundreds of kilometers) and small scale (hundreds of meters).

Mammatus Clouds generated by a SuperCell Storm Photo Dan Bush

SUPERCELLS develop some of the most fascinating and awe inspiring moments I have ever had in my interactions with nature. The colors, smells and then out right fury when one of these huge storms cuts loose has to be seen in person to be appreciated. Like an explosion from a bomb the clouds formations often build at a rate that does not require time lapse photography to appreciate.   The SUPERCELL is beautiful yet as deadly as storms can get. Hail the size of Softballs kills cattle on a yearly basis. Here is a lovely chunk of ice that will ruin your car and could kill you if you are caught out in a field. There is nothing that smells quite like a corn field that has just been decimated by a hail storm. The smell of crushed recently vegetation is one you'll never forget.  

Now on to the really good stuff...TORNADOES!  

While oddly fascinating the resulting damage is often emotionally devastating for the home owner exiting the storm cellar...|

Tornadoes are what got me interested in meteorology in the first place. Growing up in the piedmont of North Carolina in my younger years we were under the threat of a Tornado on a not infrequent basis. Tornado watches would be posted by NWS several times a season. The state averages 16 of them per year and we were lucky enough to be close but not hit by a few of them. As you have probably heard before, the sound is unmistakable and emulates a freight train going through the forest with tree trunks snapping like match sticks in the stronger storms.   Tornado 101:   Most tornadoes are born from SUPERCELL thunderstorms. Most tornadoes form and exist in the right rear flank of a SUPERCELL. Tornadoes are measured by the damage they cause and are labeled F0 through F5 on the Fujita scale. F5 can have winds to 318 mph.( See table below) Tornadoes can scrape the pavement off of a concrete or asphalt highway. If you are caught in a Tornado you will like have debris in the vortex embedded in your body or skin. Tiny pieces of sand can be excruciating when they hit you at 250+ miles per hour not to mention a brick or a car caught up in the whirling winds.  

• Excellent overview of Tornado facts
• A more lengthy discussion on Tornado life cycle click this link

Tornado Videos I recommend:  

• Here is a nice up close clip at a soccer game- This is a dust devil and not a tornado
• Real tornadoes up close and personal
• Collection of numerous funnels
• This one will give you a better sense of the size and power of a large tornado
• Multiple vortex Tornado
• Birth of a Tornado

Water born tornadoes or "Waterspouts":    

Lake sailors have to worry about the awesome power of the tornado as the vortex's often transit into lakes across the central US but ocean mariners too, even in the open sea must keep an eye out for these towers of spinning water that can wreak havoc on a boat under sail and shred it's sails to ribbons. The Volvo Ocean Race sailors had a quite large and powerful Waterspout in close proximity to them down in Australia in the Sydney Hobart race of 2002 when the crew of Assa Abloy snapped this image of a waterspout just off their port bow-   Photo Assa Abloy crew   There are two general types of waterspouts:   Water spouts can start as tornadoes over land. If they move over a body of water, they are classified as tornadic. This type of waterspout can be fairly destructive.

The second type of waterspout is formed over water initially due to warm temperatures in the lower atmosphere along with high humidity. Fair weather waterspouts are generally not as dangerous and are more common than tornadic waterspouts. However, boaters and people who live near larger bodies of water should take waterspout warnings and watches very seriously.

I apologize for this article being a bit choppy. It has been hectic around the Michaelsen household the past few weeks getting ready for the holidays.... This article may leave you asking more questions than giving you real answers so please feel free to e-mail me at: DryArmour@aol.com with those questions.

Next time on Weather and the Modern Mariner- HURRICANES & TYPHOONS 

Happy holidays to you all...be safe and stay aboard.

12/21/06