How do snow fences work?

How do snow fences work?

How do snow fences work? Photo: flickr via Wikimedia Commons, by John Talbot. Snow fence might not have helped here (Ottawa, Canada). Snow carried by wind can reduce visibility and cover roads. We cannot “switch off” the wind; but we… More »

Do all snowflakes have unique shapes?

Do all snowflakes have unique shapes?

Do all snowflakes have unique shapes? A snowflake from the Bentley Collection Wilson Bentley on YouTube/Weather Channel, and snowflake fun at the Why Files. It is highly unlikely that you’ll find two identical snowflakes. Feel free to try to prove… More »

What is ‘black ice’?

What is ‘black ice’?

What is ‘black ice’? Photo: AdamKR Black ice in Halifax The term ‘black ice’ refers to either a new layer of transparent ice on water, which allows us to see the deep water below, or a layer of clear ice… More »

Watch for steam devils in late November/early December

Watch for steam devils in late November/early December

Watch for steam devils in late November/early December Steam Devils in Wisconsin One of the many advantages of living near large lakes in temperate climates is the steam fog that shrouds them in fall and early winter. Fog is essentially… More »

How does a lake freeze?

How does a lake freeze?

How does a lake freeze? Enlarge Photo: NOAA Ice forming around the shore of Lake Michigan Lakes freeze from the top down. Ice is less dense than water, which is why ice floats. The density of liquid water is determined… More »

How does frost form?

How does frost form?

How does frost form? Heavy frost on Burr Oak tree in Wisconsin Frost on objects is just water vapor in the air that has condensed as ice onto a surface. Frost forms on objects close to the ground, such as… More »

Why does El Nino often lead to a warmer winter in Madison?

Why does El Nino often lead to a warmer winter in Madison?

Why does El Niño often lead to a warmer winter in Madison? Image: NASA Forecasts of a relatively mild winter are being tied to a phenomenon called “El Niño” in the tropical Pacific Ocean. El Niño is so often invoked… More »

Is global warming real?

Is global warming real?

Is global warming real? Image: NASA Over the past two decades, the global average surface temperature has increased noticeably. This observed warming trend indicates a significant global change and is consistent with other observed changes on our planet: There is… More »

How long have satellites been used to study Earth’s weather?

How long have satellites been used to study Earth’s weather?

How long have satellites been used to study Earth’s weather? NASA image of Explorer VII satellite, 1964 The first successful meteorological experiment conducted from a satellite was launched on Explorer VII on October 13, 1959, just over 50 years ago.… More »

What is the jet stream?

What is the jet stream?

What is the jet stream? Photo: NOAA The jet stream is a narrow current of strong wind that blows through the upper regions of the troposphere, about seven miles above ground. The jet stream generally moves from west to east,… More »

Numerical Weather Forecasting is younger than rock ‘n roll!!

Numerical Weather Forecasting is younger than rock 'n roll!!

Before 1960, the idea that a reasonably accurate two-day weather forecast could be made routinely was a pipe dream – now it’s a routine reality. In fact, it was not until just after World War I that a theory concerning the structure, life cycle and precipitation distribution associated with mid-latitude cyclones, the weather systems that bring snow and rain to Madison, was first proposed by a group of Norwegian scientists, led by Vilhelm Bjerknes, an ambitious but professionally frustrated physicist. More »

How accurate are weather forecasts?

How accurate are weather forecasts?

How accurate are weather forecasts? Image: NOAA In general, weather forecasts are getting better, due to improvements in computer models, observations and our understanding of atmospheric. Accuracy depends on the purpose of the forecast and how far out it extends.… More »

Is there a relationship between sun spots and climate?

Is there a relationship between sun spots and climate?

Is there a relationship between sun spots and climate? 12th century sunspot drawing, from NASA. Since the invention of the telescope in the 1600s, observers have recorded variations in the numbers of dark spots – “sunspots” – on the Sun’s… More »

What are heating degree-days?

What are heating degree-days?

What do heating degree-days tell us? Each degree that the mean temperature is below 65 degrees F is one heating degree-day. So if today’s average temperature is 55 degrees F, the day accounts for 10 heating degree-days. Engineers determined that… More »