What is a landspout?

Posted on July 1, 2025 by WeatherGuys Editor
Landspouts can occur in cumuliform clouds without the parent cloud rotating. Typically, these occur along weather boundary where air converges under weak vertical rotation. The convergence of air at the boundary forces it up forming a cloud and this updraft stretch the rotation increasing its spin. (Photo credit: NOAA/NWS)

According to the American Meteorology Society’s glossary, a landspout is a colloquial name for a small tornado whose vorticity (a vector that measures local rotation in a fluid flow) originates in the boundary layer and has a parent cloud in its growth stage. Landspouts occur when colliding winds at the surface begin to make a vortex and then a developing thunderstorm passes overhead. The updrafts from that thunderstorm draw the rotating vortex upward and give it a tornado-like appearance. While relatively weak compared to traditional tornadoes, landspouts can be strong enough to cause damage and warrant caution.

The term “landspout” was coined by atmospheric scientists in the 1980s to describe a type of vortex associated with thunderstorms that do not possess a strong mid-level mesocyclone. A mesocyclone is a cyclonically rotating vortex, around 2–10 km in diameter, in a convective storm.  Strong tornadoes form in mesocyclones.

Landspouts are generally short lived, usually lasting less than 15 minutes, and have a short track. They can occur under rapidly developing cumuliform clouds and along a surface boundary, or at a point where two boundaries collide. As the rotation occurs at low levels in the atmosphere, the resulting vortex does not extend very far up into the cloud. Landspouts form from a ground circulation that is sucked up into a storm, while tornadoes form from a rotating supercell thunderstorm. Tornadoes form in thunderstorms and reach down to the ground. They can tap energy sources, such as the jet stream, that are far more powerful than those energy sources at the ground.

Tornadoes form when winds at the cloud-level begin to spin and the cloud rotation can be detected using Doppler radar. Landspouts form at the ground and are often below the radar beam and therefore go undetected.

Steve Ackerman and Jonathan Martin, professors in the UW-Madison department of atmospheric and oceanic sciences, are guests on WHA radio (970 AM) at noon the last Monday of each month. Send them your questions at stevea@ssec.wisc.edu or jemarti1@wisc.edu.

Category: Meteorology, Phenomena, Severe Weather

Comments Off on What is a landspout?

Has the EPA rolled back regulations on greenhouse gas emissions?

Posted on June 25, 2025 by WeatherGuys Editor

On June 11, Environmental Protection Agency Administrator Lee Zeldin proposed repealing all “greenhouse gas” (their quotes, not ours) emission standards for the power sector under Section 111 of the Clean Air Act.

This proposal is based upon the false assertion that “emissions from fossil fuel-fired power plants do not contribute significantly to dangerous air pollution.” This assertion flies in the face of centuries of evolving understanding of the influence that carbon dioxide, the primary by-product of such combustion, has on the radiation balance of Earth’s atmosphere.

CO2 is one of several so-called greenhouse gases, all of which share the characteristic that they do not absorb visible radiation (the kind we can see and the predominant type of radiation emitted by the sun) but do absorb infra-red radiation (the kind emitted by the cooler surface of Earth, its oceans, and its inhabitants).

Over the last two centuries, industrialization has greatly increased the fraction of CO2 in our atmosphere and so has increased the planet’s temperature in what is known as global warming. There is absolutely no scientific dissent regarding the fact that an increased CO2 concentration in the atmosphere will have a warming effect — a conclusion that has been understood since the late 19th century.

Thus, the administration is willfully ignoring a robust scientific consensus on an issue that will continue to negatively impact our world and the world inherited by our children and grandchildren. Surely, they can’t believe that asserting a rule that irresponsibly ignores a festering problem will, by some miracle, simply eliminate the problem. You don’t have to be a scientist to be certain that that is not how nature works.

Steve Ackerman and Jonathan Martin, professors in the UW-Madison department of atmospheric and oceanic sciences, are guests on WHA radio (970 AM) at noon the last Monday of each month. Send them your questions at stevea@ssec.wisc.edu or jemarti1@wisc.edu.

Category: Climate, Meteorology

Comments Off on Has the EPA rolled back regulations on greenhouse gas emissions?

Does North America have a hurricane season?

Posted on June 17, 2025 by WeatherGuys Editor

Recently FEMA Director David Richardson claimed he was unaware that there is a hurricane season in the United States.  There most certainly is such a season. The Atlantic hurricane season climatologically runs from June 1 through November 30, with the most active part of the season being mid-August through mid-October. Hurricanes are tropical storms over the Atlantic Basin (Atlantic Ocean, Caribbean Sea, and Gulf of Mexico). Based on a 30-year climate period from 1991 to 2020, the average Atlantic hurricane season has 14 named storms, 7 hurricanes, and 3 major hurricanes. A developing tropical cyclone is given a name when it reaches sustained winds of 39 mph and it becomes a hurricane at 74 mph.

A summary infographic showing hurricane season probability and numbers of named storms predicted, according to NOAA’s 2025 Atlantic Hurricane Season Outlook. The official start of the Atlantic hurricane season is June 1 and runs through November 30.  (Image credit: NOAA NWS)

Hurricanes can occur outside this season but these are the months with favorable conditions for formation of the storms. One such condition is the ocean temperature exceeding 79.7F, which is common in the Atlantic Basin between June and November. Hurricanes have difficulty forming off the U.S. west coast due to cold water, cold currents, and unfavorable winds. 

In May, in preparation for hurricane season, the National Oceanic and Atmospheric Administration (NOAA) uses their state-of-the-art hurricane forecast model to predict if the coming season will be at, above, or below the average number of storms. This year, NOAA’s National Weather Service (NWS) predicts a 60% chance of an above-normal hurricane season, with a 30% chance of a near-normal activity in the Atlantic Basin.

Hurricanes pose life-threatening risks to coastal and inland communities, with water hazards historically the most destructive and lethal. It is therefore important to track, monitor, and be prepared for these storms. Weather satellites provide crucial observations of hurricanes. Working closely with NOAA, university scientists develop techniques to convert large amounts of satellite data into practical information and guidance for weather forecasters. Their tools track storms, identify the strongest winds, and detect storm intensification.

Steve Ackerman and Jonathan Martin, professors in the UW-Madison department of atmospheric and oceanic sciences, are guests on WHA radio (970 AM) at noon the last Monday of each month. Send them your questions at stevea@ssec.wisc.edu or jemarti1@wisc.edu.

Category: Seasons, Tropical

Comments Off on Does North America have a hurricane season?

Did weather forecasting play a role in D-Day?

Posted on June 9, 2025 by WeatherGuys Editor

Last Friday was the 81st anniversary of the Allied invasion of Europe that began with the landings on the beaches at Normandy.  The combined land, air, and sea assault of June 6, 1944 remains the largest such event in history.  The success of the invasion was extraordinarily dependent of weather conditions.  More than three months before the invasion, a combined British and American forecasting team began rigorous forecast exercises designed to iron out the physical and logistical kinks of such a coordinated effort.  As June drew near, the nature of this collaboration was still problematic as the two groups employed vastly different methods in fashioning the requisite 3-5 days forecasts – at the time, absolutely primitive in the underlying science as compared to what is possible at such ranges today.  The British were attempting to make such forecasts based upon the understanding of atmospheric dynamics that had grown substantially during the war.  The Americans were employing a method based on a statistically- based search through old weather data for historical analogues that could be used to guide the forecast.

To maintain secrecy, a large portion of the Allied fleet was squirreled far away in northern Scotland.  Consequently, 5 days of lead time was required to mobilize these forces.  Thus, General Eisenhower needed to know by May 31 whether the first week of June, the prospective target for the invasion, would provide favorable weather.  The forecasters foresaw a break in that year’s unusually stormy late spring and suggested June 5 would work.  As the day approached, the team realized that a one-day postponement would offer better conditions prompting Eisenhower to make the fateful decision to invade on June 6, under barely acceptable conditions.  Had the Allies delayed, the combination of lunar cycle, tides and weather almost certainly would have postponed the invasion for more than a month likely costing the effort the tremendous advantage of secrecy. 

Steve Ackerman and Jonathan Martin, professors in the UW-Madison department of atmospheric and oceanic sciences, are guests on WHA radio (970 AM) at noon the last Monday of each month. Send them your questions at stevea@ssec.wisc.edu or jemarti1@wisc.edu.

Category: History, Meteorology, Severe Weather

Comments Off on Did weather forecasting play a role in D-Day?

Is there scientific consensus on global warming?

Posted on June 2, 2025 by WeatherGuys Editor
Yearly surface temperature from 1880–2024 compared to the 20th-century average (1901-2000). Blue bars indicate cooler-than-average years; red bars show warmer-than-average years. NOAA Climate.gov graph, based on data from the National Centers for Environmental Information. (Image credit: https://www.climate.gov/news-features/understanding-climate/climate-change-global-temperature )

Global warming refers to the recent rise in Earth’s average temperature caused by human activities that emit higher levels of greenhouse gases like carbon dioxide and methane. Scientists understand the physics and chemistry of how these gases warm the atmosphere.

The global average temperature has increased about 1.7°F since 1970. During this same period, temperatures have risen around 2.5°F in the contiguous United States and 4.2°F in Alaska. The 10-year period 2014–2023 was the warmest decade on record.  Such warming has, of course, altered average weather conditions, including temperature, precipitation, humidity, wind patterns, atmospheric pressure, and ocean temperatures and so global warming is nearly synonymous with climate change. Although it is difficult to directly attribute specific weather events to global warming/climate change, data analysis indicates that global warming is linked to more extreme weather events such as droughts and floods. There has also been an increase in days with temperatures above 90°F and heat waves.  Heat waves, defined as periods of unusually hot weather lasting two or more days, have become more frequent in major cities across the United States, rising from an average of two heat waves per year in the 1960s to over six per year in the 2020s.

The Intergovernmental Panel on Climate Change’s (IPCC) Sixth Assessment Report (their synthesis report was published in March 2023), represents the work of hundreds of leading experts in climate science. That report states, “It is unequivocal that human influence has warmed the atmosphere, ocean and land. Widespread and rapid changes in the atmosphere, ocean, cryosphere, and biosphere have occurred.” 

Steve Ackerman and Jonathan Martin, professors in the UW-Madison department of atmospheric and oceanic sciences, are guests on WHA radio (970 AM) at noon the last Monday of each month. Send them your questions at stevea@ssec.wisc.edu or jemarti1@wisc.edu.

Category: Climate, History

Comments Off on Is there scientific consensus on global warming?