How do you stay safe from lightning?

Posted on July 3, 2014 by WeatherGuys Editor

There is no place outdoors that is completely safe during a thunderstorm, so the saying goes, “When thunder roars, go indoors!”

The safest thing to do is to get inside a safe building or vehicle. A safe building is one that is covered with a roof, walls and floor, and has plumbing or wiring. Stay away from metal and electrical equipment, including computer, plumbing and faucets. Keep away from windows and doors, and don’t hang out on a porch to watch the lightning storm.

Many lightning injuries and deaths occur on boats that do not have cabins.

So, listen to the weather when boating, and if thunderstorms are forecast, get off the water.

If you cannot get indoors, avoid elevated areas like mountain tops and open fields. Never lie on the ground or seek protection under an isolated tree. Stay away from metal objects like fences, golf carts and farm equipment.

A lightning bolt can travel many miles away from a thunderstorm before striking the ground. These are called “bolts from the blue” because they appear to strike out of the clear blue sky. New instruments to study lightning have measured lightning bolts that seem to come out of the cloud base, striking ground 50 miles from where they originate.

The National Weather Service keeps track of when, where and who gets hit by lightning.

Lightning strikes Wisconsin soil about 300,000 times a year, mostly during spring and summer. On a yearly average, lightning causes about one death in Wisconsin and 62 deaths nationally. Your chances of getting hit by lightning are about one in 1 million.

Category: Severe Weather, Weather Dangers

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When is Wisconsin’s tornado season?

Posted on June 23, 2014 by WeatherGuys Editor

Tornadoes can happen in just about any location and at any time, although the chances of having one in late fall and winter are small.

For example, there have been only six tornadoes in Wisconsin during the month of November, and Wisconsin has never recorded a tornado in February.

On average, there have been 21 tornadoes touch down in Wisconsin in a year, with a record 62 tornadoes in 2005. For the 20-year period between 1991 and 2010, there was an average of nine tornadoes in the month of June.

For a tornado to occur, the right weather ingredients must come together in a particular place.

Severe weather requires warm, moist air near the ground and a change in wind speed and direction, or wind shear, with height above the surface.

Weather systems, such as fronts, are also needed to force air upward. Because vertical wind shear is closely related to the presence of a jet stream, tornado season in the U.S. moves north and south during the year.

In the Southeast, the number of tornadoes peaks in March and April, but not until late June and July in the upper Midwest and Northeast.

These conditions have been absent over Wisconsin until last week when tornadoes struck Platteville, Madison and Verona.

On average, this is a rather late start for tornado season.

In fact, 2014 will go down as the sixth latest start to a tornado season and the latest start to a tornado season since 1995. That year had the latest start with the first tornado occurring on June 28.

In 1995 there were less than 10 tornadoes reported, so we can hope for a low tornado count this year, although it is not assured scientifically.

Category: Meteorology, Severe Weather

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When is the summer solstice?

Posted on June 18, 2014 by WeatherGuys Editor

The summer solstice in the Northern Hemisphere is the day when the sun is farthest north. In 2014, this occurs on June 21 at 5:51 a.m.

As Earth orbits the sun, its axis of rotation is tilted at an angle of 23.5 degrees from its orbital plane. Because Earth’s axis of spin always points in the same direction — toward the North Star — the orientation of Earth’s axis to the sun is always changing as Earth orbits around the sun.

As this orientation changes throughout the year, so does the distribution of sunlight on Earth’s surface at any given latitude. The summer solstice is the day of the year with the most daylight in our hemisphere.

On the Northern Hemisphere’s summer solstice, the northern spin axis is tilted toward the sun and latitudes north of the Arctic Circle (66.5 degrees N) have 24 hours of daylight.

The length of daylight is related to how high the sun gets in the sky. At the summer solstice, the sun reaches its highest point in the sky and so daylight is longest.

Our earliest sunrise, however, occurred Saturday, while our latest sunset occurs about a week later than the summer solstice. So, while the summer solstice has the longest daylight hours, that day does not correspond to the earliest sunrise or the latest sunset. The reason that the earliest sunrise and latest sunset do not occur on the summer solstice is a combined effect of the tilt of Earth’s axis and the elliptical path of Earth around the sun.

Category: Seasons

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Did weather play a role in D-Day?

Posted on June 13, 2014 by WeatherGuys Editor

Friday marked the 70th anniversary of the Allied invasion of Europe and the beginning of the end of Nazi tyranny and murder in World War II. A perfect combination of full moon (for nighttime aerial navigation purposes), low tide (so that German mines in Brittany would be exposed) and light winds were necessary to give the invasion any reasonable chance of success.

Thus, days on which the tides and phase of the moon were optimal were known some weeks in advance. As late May arrived, it became increasingly clear that choosing among those optimal days for invasion would depend crucially upon the weather and the ability to make an accurate forecast of weather conditions.

In 1944 there were no satellites and no weather radar. In addition, there was no such thing as numerical weather prediction by high-speed computers. Thus, a one-day forecast for western Europe, with the Atlantic Ocean stretching endlessly to the west, was informed only by careful analysis of surface observations and a few upper atmospheric observations near Iceland and Greenland.

The Allies had a rather unorganized approach to the forecasting enterprise, employing a British and an American team of forecasters. These two teams used decidedly different techniques to make their forecasts, and the differences came to a head on June 4 when, in the face of very different forecasts, Group Capt. James Martin Stagg, Gen. Dwight D. Eisenhower’s chief meteorologist, advised the general to delay the invasion one day, from June 5 to June 6.

The British forecast team bet that there would be a sufficiently calm period between two of the endless collection of storms that battered western Europe in June 1944 to allow the invasion to proceed on June 6. They turned out to be right.

While riding to the Capitol on his inauguration day in 1961, President John F. Kennedy asked President Eisenhower why the Normandy invasion had been so successful. Eisenhower answered, “Because we had better meteorologists than the Germans.”

Category: Meteorology, Severe Weather, Weather Dangers

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What causes urban flooding?

Posted on June 4, 2014 by WeatherGuys Editor

Urban flooding occurs when water flows into an urban region faster than it can be absorbed into the soil or moved to and stored in a lake or reservoir. It can be caused by flash flooding, coastal flooding, river floods or rapid snow melt.

On Tuesday, the Madison area experienced urban flooding caused by an intense rainfall. On that day, a daily record rainfall of 1.46 inches fell at Dane County Regional Airport, breaking the city’s previous May 27 record of 1.27 inches. The city sewage system and draining canals did not have the necessary capacity to drain away the large amounts of rain that fell in a short period of time.

Flash floods occur suddenly, and the water can flow quickly. Urban flooding is most often an inconvenience, particularly when it occurs during commuting time as Tuesday’s did, but it can also be dangerous.

Never drive your car across a flooded road. The economic cost of urban flooding can also be high, as water damage to homes and buildings can be very expensive to repair.

Urbanization of the United States and other countries is increasing. Common consequences of urban development include the removal of vegetation and an increase in impervious surfaces and drainage networks, all of which increase precipitation runoff into streams and rivers. This may result in more flooding.

Urban planning explores design strategies that include storm water conveyance systems and other methods to prevent flooding. This long-term planning must include forecasts of expected weather. Current research indicates a trend to more intense precipitation, which could result in more urban flooding if it’s not properly planned for.

Category: Climate, Meteorology, Phenomena

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