Mammatus Clouds • Dave Jones, UW-Space Science and Engineering Center
Those types of cloud are called mammatus. They often extend from the bottom of the anvil cloud of a thunderstorm, also called a cumulonimbus cloud, and indicate an intense storm is nearby. This was the case on Tuesday. Mammatus clouds may have a very ominous appearance; however, they are usually seen after the worst weather has passed. When they occur near sunset, they provide a beautiful sky.
Mammatus occur frequently in the Midwest during summer. We do not fully understand why they form, but there are a few hypotheses for their occurrence. Unlike most clouds, which form in rising air, mammatus are associated with sinking air in the upper parts of a thunderstorm. We also know that to form, there must be rapid changes in temperature, moisture and wind between the bottom of the anvil and the cloud-free air below. This rapid change in wind is a hazard to aviation, so pilots avoid mammatus and thunderstorms in general.
The widely accepted cloud classification system used today is based on a scheme introduced by Luke Howard in 1803. This naming convention uses Latin roots to describe the appearance of different cloud types. The Latin ‘mamma’ means udder or breast, and refers to the clouds’ characteristic udder-shaped protuberances.
Check out this video to see the storm from the rooftop cameras atop the AOSS Building.
Rock ’n’ roll is older, although not by much.
On May 6, 1955, a revolution that continues to this day began with little fanfare: the first daily weather forecasts made by a computer were issued. This was the result of nearly a year of collaborative effort between the United States Weather Bureau, the Air Force and the Navy in what was called the Joint Numerical Weather Prediction Unit, or JNWPU.
Formed in July 1954, the JNWPU was charged with applying emerging computer technology to the production of weather forecasts. The numerical forecasts issued during its first couple of years were not nearly as good as the forecasts being prepared manually with just pencil, paper and theory by experienced meteorologists at the Weather Bureau. Many academic meteorologists thought it was folly to pursue numerical weather prediction, and they were not afraid to express their opinions on the matter. But by 1958 the forecasts began to show steady improvement in skill.
Fueled by improved understanding of the atmosphere, better observations (many of which are supplied by satellites that did not exist in any form in 1955), and incredible increases in computer power, the science of numerical weather prediction has developed into an enterprise that now informs or supports a large part of the U.S. economy.
From the seven-day advance warning of Hurricane Sandy to our December blizzard this past year when schools were canceled before a single snowflake fell, we are indeed living in revolutionary times.
We should be proud of the fact that substantial contributions to that revolution have been made at UW-Madison for more than 60 years.
We are not sure we can, but we have always wanted to do so! In the past, people rang bells or fired cannons to prevent lightning or cause rain — producing sound and fury but nothing in the way of success.
The scientific era of weather modification took hold in the 1940s and ’50s with the advent of cloud-seeding experiments. In cloud seeding, airplanes drop particles of dry ice or silver iodide into clouds with temperatures below freezing. These particles are very effective in generating ice particles, with the hope of increasing the amount of rainfall or snowfall.
However, progress in cloud seeding has been slow as the processes are poorly understood. Not only that, these experiments aren’t reproducible in the sense that we can never really know if a seeded cloud would not have precipitated on its own, without assistance.
Farmers have long sought a way to suppress hail. One hailstorm can destroy a year’s crops in a few minutes. Cloud seeding during the early stages of cumulonimbus development is thought to encourage a reduction in hail damage by keeping hailstone sizes small, but again, the results have been mixed.
Another active area of weather modification has been fog dispersal. Fog can shut down an airport for hours, causing delays with negative economic impact. Like clouds, fog can be seeded with materials that cause the water droplets in fog to turn into ice, which then precipitates out, dispersing the fog. While a practice at many airports worldwide, it is impractical to apply over large regions.
Humans have changed the atmosphere in many ways. These changes usually come about as unintended byproducts of modern civilization. So far, humans have been more effective at modifying weather and climate by mistake than by design.
If you’ve had any lingering suspicion that 2013 has gotten off to an amazingly wet start, that suspicion can now be confirmed. As of April 24, both Madison and Milwaukee have recorded the wettest start to a calendar year ever.
Milwaukee recorded 15.19 inches of liquid-equivalent precipitation, just outpacing the prior record of 15.08 inches set in 1976. Madison recorded 13.45 inches of liquid equivalent through April 24, breaking the former record of 13.30 inches set in 1973.
It does appear that the faucet will be turned down at least for the next week or so, though occasional showery days still seem to be in the near future.
What is causing the persistent snowy/rainy pattern that we have endured these past couple of months? The answer to such questions regarding the behavior of the atmosphere is not often easy to uncover, and a lot of effort must be spent after the fact looking for explanations.
One of the most satisfying aspects of studying atmospheric science is that interesting questions come up all the time. It is easy to remain motivated to keep thinking.
Pursuing such questions invariably leads to new insights about a variety of other weather phenomena that were not originally part of the research project.
When you hear people talk about the importance of “basic research,” this is what they mean: that by pursuing question A, a curious mind will stumble upon answer B and that answer may lead to the development of brand new insights about nature. Study of this wet beginning to 2013 will almost surely yield unintended new insights as well.
An incredible late winter/early spring of colder-than-normal temperatures and above-normal precipitation continued unabated last week.
Through April 17, Madison had recorded 12.95 inches of liquid equivalent precipitation for the calendar year. That means that 2013 has gotten off to the third wettest start in Madison history. Milwaukee has received 13.15 inches of liquid equivalent this year, also making it the third wettest start to a year.
Both cities trail only 1876 and 1974 in the record books.
As far as temperature goes, Madison is running 4 degrees below normal for April. This is in the wake of a February and March that were 2 degrees and
7.4 degrees colder than normal. A similar set of circumstances has affected Milwaukee where February was 1.8 degrees below normal and March was 5 degrees below the average.
The bottom line is, we are well overdue for the arrival of warmth.
Even Major League Baseball has suffered from the incessant rain, posting an unusually large number of rained-out games in April (13 so far) in an era when the rainout is less likely because of domed stadiums.
The good news is the medium-range forecasts issued by the National Center for Environmental Prediction suggest warmth is coming. It appears that by the end of this week we will finally be looking at bona fide warm spring days.