The Weather Guys

Waves form as the wind’s energy is transferred to the surface of water.

A weak gusty wind can make ripples appear on smooth water. These ripples will dissipate quickly once the wind stops.

The size of a wind-generated wave depends on the following:

• The wind speed. The stronger the winds, the larger the force and, thus, the bigger the wave. The wind must also be constant, not just a wind gust here or there.

• The duration of the winds. The longer the wind blows over the open water, the larger the waves.

• The fetch. This is the distance of open water over which the wind blows. The longer the fetch, the larger the waves.

• The depth of the water also plays a role, as it is difficult to generate large waves in shallow water.

Waves in a deep lake or sea can be taller and last much longer.

Waves in the open ocean have been measured to be larger than 100 feet in height.

Waves in the Great Lakes have reached heights of 35 feet. The storm Sandy generated waves on Lake Michigan of 21.7 feet.

High sustained winds from one direction can push water up at one end of the lake, resulting in a storm surge.

Weather can also cause a seiche on the Great Lakes. In French, the word “seiche” means “to sway back and forth.”

An atmospheric disturbance causes waves to slosh back and forth between shores of the lake basin resulting in huge fluctuations of water levels in a short period of time.

The classic rainbow is a single, brightly colored arc. Red is the outermost color of this arc, and violet is always innermost.

On occasion, you may see two rainbows at once. The lower rainbow is the primary rainbow, and the higher, more faintly colored arc is the secondary rainbow. The color sequence of the secondary rainbow is opposite to the primary; red is on the inside of the arc and violet is on the outside.

To form a rainbow you need large drops of water, the sun at your back and at the correct angle. Raindrops act as prisms, bending and reflecting the sunlight that falls on them; just like a crystal hung in a sunny window.

As light enters water, the path it takes changes. How much the direction changes is a function of the color of the light. You probably noticed that a smooth water surface can act like a mirror and reflect light.

If the light beam entering the raindrop reaches the back of the drop at a certain angle, it undergoes a reflection and heads back toward the sun. Sometimes the light reflects twice off the back of the raindrop; this leads to the secondary rainbow. As the light exits the raindrop and re-enters the air, its path bends an amount that again depends on the color. This bending of the light as it enters and leaves the drop disperses the light of the sun into its spectrum of colors that form the rainbow.

A rainbow is located opposite to the sun; this explains why rainbows are not seen at noon with the sun overhead. There needs to be a clear path from the sun to the rain falling from the cloud. If the sun is overhead and raining, you are probably standing in the rain with the cloud obscuring the sun.