Electric Thunderstorms

Electric storms are frightening. On inland waters, they can arrive very quickly,  especially on a hot sultry day. Electric storms are frequently accompanied by high and very erratic winds. Huge wind bullets, which are sudden wind gusts, can come seemingly out of nowhere.

Such storms are produced from fast-rising damp air which cools as it rises. The phenomenon of lightning is pretty interesting and knowledge of it gives you some grounding (ha ha) in its cause and effect which is a 4 step process:

1. Charge Separation in Storm Clouds:

Lightning is a result of the buildup and discharge of electrical energy within a storm cloud. Inside a thundercloud, collisions between ice particles and water droplets cause a separation of charges. Typically, positive charges accumulate at the top of the cloud, while negative charges gather at the bottom.

2. Electrical Discharge:

When the difference in charge between the cloud and the ground (or between different regions within a cloud) becomes large enough, the insulating properties of the air break down, allowing an electrical discharge to occur. This discharge is the lightning strike.

3. Flow of Electrons:

Lightning is the movement of electrons between two points of opposite charge. For cloud-to-ground lightning, the negative charges at the bottom of the cloud are attracted to the positive charges on the ground. As the lightning channel forms, electrons flow rapidly along this path, releasing energy in the form of light, heat, and sound. The sound of thunder is the shock wave produced after air is explosively heated during a lightning bolt.

4. Lightning Stroke Process:

The process typically starts with a stepped leader—a faint, negatively charged channel that descends from the cloud. When this leader gets close to the ground, it attracts a stream of positive charge rising up to meet it, forming a complete path. Once connected, a large current of electrons rushes downward, resulting in the bright flash of lightning, known as the return stroke.

Static Electricity Generated

While you should always be prepared for a storm, when you observe a heavy cloud formation rising rapidly with huge white clouds called “thunderheads,” – technically “cumulonimbus” – it is time to make further preparations. Get to a safe harbor if time permits. If not, prepare for a storm: close hatches, keep away from metal objects if possible, put on life jackets, and turn off electronic gear. Crew safety is paramount.

During a thunderstorm, while a lightning strike to your boat is possible, what is definitely going to happen is that you will be hit hard by extremely high winds called a squall and intense cool rain.

A squall forms beneath a thunderstorm due to a combination of intense atmospheric dynamics and rapid changes in wind speed and direction. The phenomenon of this is also important to understand as a boater and is defined also in a 4-step process:

1. Downdrafts from Thunderstorms:

• Thunderstorm Structure: A thunderstorm consists of an updraft, where warm, moist air rises, and a downdraft, where cooler air descends. The downdraft forms as rain-cooled air accelerates downward due to its higher density compared to the surrounding air.
• Creation of a Gust Front: As the downdraft reaches the ground, it spreads out, creating a gust front. This boundary between the cool, descending air and the warmer air at the surface is often associated with sharp changes in wind speed and direction.

2. Rapid Changes in Wind Speed and Direction:

• Wind Shear: A squall is characterized by sudden and intense wind changes. Beneath a thunderstorm, the gust front produced by the downdraft can create significant wind shear—a rapid change in wind speed and direction over a short distance. This wind shear is what defines a squall.
• Cold Pool Formation: As the downdraft hits the ground and spreads out, it can form a cold pool of dense air at the surface. The leading edge of this cold pool can further enhance the gust front, making the winds stronger and more sudden.

3. Atmospheric Instability and Mixing:

• Instability: Thunderstorms often occur in unstable atmospheric conditions where there is a lot of buoyant energy – the measurement of this is called CAPE (Convective Available Potential Energy). This instability can enhance the strength of downdrafts, contributing to the formation of stronger gust fronts and squalls.
• Air Mixing: The intense mixing of air from different levels of the atmosphere caused by the thunderstorm can lead to abrupt changes in local wind patterns, increasing the likelihood of squalls forming.

4. Precipitation and Evaporation Effects:

• Evaporation Cooling: As precipitation falls through the dry air below the storm, it can evaporate, cooling the air further. This cooled air becomes denser and sinks faster, intensifying the downdraft.
• Enhanced Wind Gusts: The accelerated downdraft can lead to more powerful and erratic wind gusts as it spreads out upon reaching the surface, contributing to squall formation.

If a violent thunderstorm is approaching

1. turn on engines (take sails, bimini shade or soft tops, “boat tarps” in, if applicable),
2. (reduce apparent wind velocity on your boat by running, or setting a course downwind,
3. verify vesel is secured for sea (gear on deck, gear below decks, hatches and vents),
4. ensure crewmembers on deck are wearing harnesses and lifejackets. Use safety tethers and rig jacklines. Ensure crewmembers are clipped in prior to coming on deck.
5. Seek safety from a “lee” shore, or go to a safe harbor.

Watch the destructive force on this boat – fortunately in a harbor with no one on board.

View this awesome microburst video which shows a thunderstorm producing deadly winds.

Weather Microburst