How unusual was our dry and warm October weather?

Posted on November 4, 2024 by WeatherGuys Editor
The National Weather Service in La Crosse says there have been precipitation deficits of 1 to 8 inches in Door County, with the greatest deficits of 4 to 8 inches south of Interstate 90. That has resulted in the dry and drought conditions for Wisconsin, Minnesota and Iowa. (Image credit: NWS-La Crosse)

Meteorologists often compare current temperature and precipitation measurements to “normal” values to interpret unusual weather. The weather data observed over the 30-year period between 1991 and 2020 are used to define “normal” or “average” weather. These normals are recalculated every 10 years. The normals are determined on annual, seasonal, monthly, daily and even hourly timescales. The maximum and minimum values also are tracked for each day of the year.

The weather that southern Wisconsin has experienced this October has been different from our normal October weather. Throughout most of October, we experienced very dry conditions. Prior to the storms that occurred on Oct. 30 and 31, the total precipitation across most of the state was less than 50% of the normal precipitation. This lack of precipitation throughout the month was alleviated during the final two days. Many areas in Dane County received over 3 inches of rain on Oct. 30 and 31.

Record warm temperatures were recorded in Madison on October 29: The high was 82 degrees Fahrenheit, tying the record high temperature for that day set in 1937 and making it only the second time we have hit 80 degrees or higher that late in the year. Also, the low temperature of 65 degrees that day set a record warm minimum temperature, breaking the old record of 63 degrees set in 1946. The National Weather Service at Green Bay also set high temperature marks: 82 degrees on Oct. 29 and 80 degrees on October 30 were new records.

The record temperatures were supported by strong winds from the south and southwest moving warm air northward. The lack of precipitation throughout most of the month has contributed to low soil moisture. These dry conditions also support warmer air temperatures.

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: Uncategorized

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What is a meteorological bomb?

Posted on October 28, 2024 by WeatherGuys Editor

Storm systems that form in middle or high latitudes, in regions of large temperature contrast are called extratropical cyclones. This contrasts with tropical cyclones, such as hurricanes, which form in regions or relatively uniform temperatures.

A mid-level water vapor image from GOES-West, that is, Band 9 at 6.95 micrometers.  The yellow and blue enhancements are regions where water vapor is constrained to the middle part of the troposphere; the white and green parts are where moisture is present at the top of the troposphere. (Image credit: CIMSS) 

Extratropical cyclones are surface low-pressure systems where the air at the surface flows counterclockwise in the northern hemisphere and clockwise in the southern hemisphere. The winds around these centers of low-pressure spiral inward at the surface, forcing rising motions.  The rising air can result in clouds and precipitation. The process of extratropical cyclone development and intensification is referred to as cyclogenesis. In North America there are favorable regions for cyclogenesis, including the eastern slopes of mountain ranges, the Atlantic Ocean off the Carolina Coast, and the Gulf of Mexico. The jet stream also influences cyclogenesis.

The polar jet stream is a zone of faster moving air in the upper troposphere. Its meandering pattern has regions of convergence and divergence. The position of the jet stream influences cyclogenesis. To maintain a low pressure at the surface, the rising air associated with the surface convergence, must transported away at the top of the developing storm. The upper air divergence associated with a jet stream maintains the low pressure at the surface, by removing air from the column, reducing its weight and causing the pressure to fall at the surface.

During cyclogenesis the surface pressure in the storm is decreasing. How fast the surface pressure decreases is an indication of how the storm is developing.

A ‘meteorological bomb’ is an unofficial term for very rapid, or explosive, cyclogenesis. It is defined as when the central pressure of a developing extratropical cyclone falls 24 millibars in 24 hours.

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: Phenomena, Severe Weather

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Science-based policy is shrinking ozone hole

Posted on October 21, 2024 by WeatherGuys Editor

The Southern Hemispheric ozone hole usually begins to develop in mid- to late August, as the hemisphere emerges from its winter, and peaks in mid-October.

The Antarctic ozone hole — the total area where ozone amounts are below 220 Dobson units — on September 21, 2023, the day of its largest extent for the year. The annual maximum extent of the ozone hole in 2023 (light purple bar, measured in millions of square kilometers) compared to all years in the satellite record (dark bars). NOAA Climate.gov image based on NOAA (map) and NASA (graph) satellite data. (Image credit: NOAA)

This year it first appeared closer to the end of August and by mid-September was 18.48 million square kilometers in size, smaller than in recent years, including both 2022 and 2023. Though this year’s slow start does not necessarily reflect a recovery of the ozone layer, it does support the notion that expert guidance has made a positive contribution to this vexing problem.

Just a few years after the ozone hole was detected via satellite, the industrialized nations of the world, meeting in Montreal in 1987, adopted what is known as the Montreal Protocol. That international agreement, based upon the consensus scientific understanding of the problem, placed prudent restrictions on the use of chlorofluorocarbons, or CFCs.

The result of this scientifically informed policy-making has been a gradual but systematic healing of the ozone hole. Despite the success of the Montreal Protocol, current estimates are it will require another four decades, if the protocol is followed, before recovery toward pre-ozone hole conditions.

This success should serve as a leading example of the power of scientific analysis and understanding to shape important environmental policy.

The world is facing a slower-burning crisis as a result of human-induced changes to the atmosphere that are, in turn, compelling a change to a warmer climate. There is no lack of scientific consensus of the roots of this problem nor any shortage of science-based prescriptions for seeking its remedy.

The time has long passed for our society to seriously debate, and then begin to take, the bold actions necessary to meet this crisis. Our scientific and industrial infrastructure is more than sufficient to meet this pressing challenge — we have successfully done so before!

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, Phenomena

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Can we control the weather?

Posted on October 14, 2024 by WeatherGuys Editor

We watched in stunned horror the suffering of our fellow citizens across parts of the South in the aftermath of the nearly back-to-back disasters wrought by hurricanes Helene and Milton.

Naturally the question of whether these storms were made more intense and impactful by the ongoing, slow background warming has been considered in discussions of these events.

It is true that the Gulf of Mexico sea surface temperatures in the regions from which these storms came is as many as 4 degrees Fahrenheit warmer than normal this season. It is also true that the ocean heat content, a measure of how much heat is actually available in the ocean, well below the surface, has been increasing during the warming era. Both of these ingredients are potent fuel for tropical storm intensification.

So, from that perspective, it is reasonable to conclude that global warming has at least a plausible physical connection to the development of these monsters.

(Image credit: Environmental Change and Security Program, Woodrow Wilson International Center for Scholars)

One of our major political parties has decided that it is best to ignore this possible connection and to carry on as if nothing of concern were happening. One particular elected public servant, U.S. Rep. Marjorie Taylor Greene, has even suggested that there is a nefarious conspiracy afoot wherein unspecified government officials are controlling the weather. Writing on X on Oct. 3, she proclaimed, “Yes, they can control the weather. It’s ridiculous for anyone to lie and say it can’t be done.”

Any expert, and certainly the two of us, can say with great certainty that it is not possible to control the weather. Even the huge investments in cloud seeding in the 1950s and 1960s, made in hopes of alleviating local drought, were eventually declared inconclusive — certainly not a triumph for weather control.

It might be better if the passion exhibited by Taylor Greene, along with other elected (and unelected) officials in her party, was directed toward continued funding for better understanding of the science underlying the weather and climate rather than asserting outrageous conspiracy theories and threatening to weaken our exceptional National Weather Service.

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, Weather Dangers

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Is it safe to shower or bathe during a thunderstorm?

Posted on October 10, 2024 by WeatherGuys Editor

Taking a shower or bath during a thunderstorm could put you at risk from a lightning strike. When you are indoors during a thunderstorm, the National Weather Service (NWS) recommends that you seek a safe location, away from electrical systems, electronic equipment, and avoid plumbing, including sinks, baths and faucets. Most indoor lightning casualties are due to conduction via lightning. The plumbing systems in many households include metal pipes, which can serve as conduits during lightning strikes. Lightning travels long distances in metal including wires and pipes. Metal does not attract lightning, rather it provides a path for the lightning to follow.  Water is also excellent conductor of electricity.

National Weather Service’s poster for Lightning Awareness Week (Image credit: NOAA/NWS)

The plumbing systems in many households include metal pipes, which can serve as conduits during lightning strikes. Lightning travels long distances in metal including wires and pipes. Metal does not attract lightning, rather it provides a path for the lightning to follow.  Water is also excellent conductor of electricity.

Lightning strikes the United States about 25 million times a year. Lightning kills about 20 people in the United States each year, and hundreds more are severely injured. If caught outdoors, never shelter under an isolated tree. When lightning strikes a tree, or other object, energy travels down the object and outward along the ground surface. This is referred to as the ground current and causes the most lightning deaths and injuries. A lightning bolt that strikes a tree can cause the tree sap to boil and burst shards of the tree outward.

Just because a lightning bolt is a few miles away doesn’t mean that you are safe. Most lightning starts inside a thunderstorm and travels through the cloud. A “bolt from the blue” is a lightning bolt that starts inside a cloud, then travels away from the cloud before going to ground. That bolt can strike the ground at a location that is blue sky above.

When thunderstorms are in your area, no outside place is safe. So, follow the advice “When thunder roars, go indoors.”

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: Severe Weather, Weather Dangers

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