Stories tagged extreme weather

Apr
21
2012

Tornadoes form in regions of the atmosphere that have abundant warm and moist air near the surface with drier air above, a change in wind speed and direction with height, and weather systems such as fronts that force air upward. The United States provides these three ingredients in abundance, so it is not surprising that the majority of the world’s reported tornadoes occur in the USA. Within the United States, tornadoes can occur in nearly every state and in every month of the year. Wisconsin has experienced tornadoes in every month except February. It is generally accepted that tornado season begins in the springtime— and that is now.

Tornado season is based on when the ingredients for severe weather come together in a particular place. Because a change in wind with height is closely related to the presence of a jet stream, tornado season moves north and south during the year with a jet stream. Tornado season peaks in March and April in the Southeast but not until July in the upper Midwest and Northeast. The deep South has a secondary peak in tornado occurrence in November.
Month of maximum tornado threat: The geographic distribution of the month of maximum tornado threat for the continental United States.
Month of maximum tornado threat: The geographic distribution of the month of maximum tornado threat for the continental United States.Courtesy Ackerman & Knox: Meteorology: Understanding the Atmosphere

Tornadoes can also happen at any time of day or night. However, they thrive on solar heating and in some cases the ability of warm, moist air at the surface to penetrate the capping inversion. Therefore, the most likely times for tornadoes are late afternoon or early evening. More than half of all U.S. tornadoes occur during the hours of 3:00 PM to 7:00 PM local time.

Have I got a visual snack for you! But first, let's review:

Weather is not the same as climate. Weather is the actual day-to-day temperature, precipitation, wind, etc. Climate is the average long-term pattern of temperature, precipitation, wind, etc.

Got it? No? If you need more of an explanation (and who doesn't), check out this past Buzz post.

Great job! Now enjoy these amazing photos of extreme weather.

Did you check out the photos I shared with you above?

Get to it!

I'm waiting...

Alright. Moving on:

While Lane Turner's introduction to the photos makes it clear that a single extreme weather event is not evidence of climate change, she states (without citation) that

"a trend of weather intensity, and oddity, grows."

Beautiful Disaster: Cologne, Germany.  August 22, 2010
Beautiful Disaster: Cologne, Germany. August 22, 2010Courtesy meironke

Turner's continues by asking whether weather is becoming more extreme and, if it is, whether these increasing extreme weather events are evidence of climate change.

Say that 10 times fast... and then post your own answer to Turner's question below.

Jul
30
2010

A new record hail stone fell on 23 July 2010 near Vivian SD!

It is 8-inch in diameter hail stone and weighs 1.9375 pounds.

The old record heaviest U.S. hailstone was a 1.67-pound found near Coffeyville, KS on Sep. 3, 1970. The old record for the largest diameter hailstone was 7 inches found in Aurora, NE on June 22, 2003. This Aurora, NE hailstone still holds the U.S. record for circumference: 18.75 inches. The Vivian, SD hailstone circumference was only 18.5".

Here is a photo of the stone

Hail is precipitation in the form of large balls or lumps of ice. Hailstones begin as small ice particles that grow primarily by accretion. The production of large hail requires a strong updraft that is tilted and an abundant supply of supercooled water. Because strong updrafts are required to generate large hailstones, it is not surprising to observe that hail is not randomly distributed in a thunderstorm; instead it occurs in regions near the strong updraft. Supercell thunderstorms, in which the strongest updrafts are created with help from the mesocyclone, often produce the largest hail.
Eventually, though, the weight of the hailstone overcomes the strength of the updraft, and it falls to earth. The curtain of hailstones that falls below the cloud base is called the hailshaft. These regions are often said to appear green to observers on the ground, although recent research suggests that heavy rain as well as hail can create this optical phenomenon. As the storm moves, it generates a hailswath, a section of ground covered with hail.

Hailstorms can severely damage crops, automobiles, and roofs. Sometimes the swath can be so big you can see it on the ground from a satellite