Archives
Categories
WeatherGuys Links
Category Archives: Seasons
Was 2024 an interesting weather year for Wisconsin?
Yes, 2024 was a very interesting year. The statewide average temperature was 31.4 degrees Fahrenheit, which is 12.2 degrees warmer than the 1991-2020 normal. December 2023 to February 2024 was our warmest winter since record-keeping began in 1895. The statewide average temperature for the winter was 28.3 degrees, surpassing the previous record by 2 degrees.
Wisconsin’s average temperature during November 2024 was 38.7 degrees, which is 7.1 degrees above the November average temperature. Seventy out of Wisconsin’s 72 counties recorded a November 2024 average temperature much above average. Overall, 2024 is on track to be Wisconsin’s warmest year on record. Continue reading
What is the difference between sleet and freezing rain?
Rain, snow, freezing rain, and sleet all generate hazardous traffic conditions. Freezing rain, and the less intense freezing drizzle, can create the very treacherous road condition referred to as “black ice.” A freezing fog may similarly coat objects in ice while also reducing visibility. Black ice is so named because the affected roadway appears dark, just like wet pavement. Black ice creates nearly zero friction conditions with vehicle tires so that correcting a skid in such conditions can be nearly impossible. Continue reading
Category: Meteorology, Seasons
Comments Off on What is the difference between sleet and freezing rain?
Comments Off on What is the difference between sleet and freezing rain?
Does the warmest autumn on record mean anything about the coming winter?
In the past several years we have occasionally mentioned our tracking of the areal extent of air colder than minus 5 degrees centigrade at about 1 mile above the surface of the Earth. This measurement has proven to be a very valuable addition to the collection of metrics of global warming. We have particularly commented on the wintertime (December, January and February) average of this extent measured over the entire Northern Hemisphere, noting that since 1948 the wintertime average extent has systematically decreased.
We have also been tracking this variable throughout the autumn over all these years and can report that this fall (Sept. through Nov. 30) recorded the smallest average areal extent of this cold air since at least 1948. That means we have just experienced the warmest Northern Hemisphere autumn in at least the past 77 years. Continue reading
How and when do Madison lakes freeze?
The surface of a lake exchanges energy with the air above. Cold air cools the lake surface through energy exchanges with the atmosphere, determined by the weather above. As cool surface water cools, it becomes denser than the warmer water below and so the cooled water sinks. Water from below then rises to the surface where it begins to cool.
What is unique about the H2O water molecule is that as liquid water cools, its density increases until about 39°F (4°C). At that point, the colder water becomes less dense, stays at the surface, and continues to cool. Once the surface water cools to approximately 32°F, the water molecules crystallize into interlocking lattice-like patterns and ice is formed. For a lake surface to freeze, the entire lake needs to be at a temperature of 39°F; only then as the surface cools will the temperature of the liquid water at the surface remain less dense than the water below and thus float and begin to form ice. Shallower lakes usually freeze before deeper lakes since shallower lakes contain less water that needs to be cooled.
Continue reading
Do weather radars detect more than precipitation?
Yes. Radar, an acronym for RAdio Detection And Ranging, consists of a transmitter and a receiver. The transmitter emits radio wave pulses outward in a circular pattern. Objects scatter these radio waves, sending some energy back to the transmitting point where it is detected by the radar’s receiver. The intensity of this received signal indicates the size and density of the suspended objects, such as precipitation. The time it takes for the radio wave to leave the radar and return indicates the distance.
Radar is designed to detect precipitation intensity and type, but it can detect living things as well. Flying insects in huge numbers can reflect enough energy back to a radar site to be detected. As an example, mayflies emerge in summer in enormous numbers around the Mississippi River between Wisconsin and Minnesota and are often detected by the weather radar in La Crosse, WI. Continue reading
