What does the hurricane season look like?

Posted on June 1, 2022 by WeatherGuys Editor

The official Atlantic basin hurricane season runs from June 1 through Nov. 30, with an average of 10 to 15 storms each year.

2022 Atlantic Basin Hurricane Season Infographic. (Credit: NOAA)

The peak of activity in the Atlantic basic runs from mid-August to mid-October. During that subset of the entire season, more than 70% of all storms in the last 100 years have occurred.

The National Oceanic and Atmospheric Administration, or NOAA, predicts that there is a 70% chance that this year’s Atlantic hurricane season will include 14 to 21 named storms, or storms with winds of 39 mph or higher. Of those, NOAA predicts that six to 10 hurricanes will have winds of 74 mph or greater, and three to six major hurricanes will have winds of 111 mph. This could be the seventh year in a row that the hurricane season is more active than usual.

Hurricanes are given people’s names because it is easy to identify one storm from another and the names are easy to remember. When a tropical storm reaches wind speeds of 39 mph, the storm is then called Tropical Storm “Blank,” the blank being whatever name is next on the alphabetical list. A tropical storm is classified as a hurricane when it reaches wind speeds of 74 mph. If the storm turns into a hurricane, it keeps its original name and is referred to as Hurricane “Blank.”

The first storm of the 2022 year will be named Alex, and the next four will be named Bonnie, Colin, Danielle, and Earl, according to the National Hurricane Center.

The Saffir–Simpson scale rates hurricanes on a scale of 1 to 5 based on the damage their winds would cause upon landfall. Major hurricanes are those classified as Category 3 and higher on this scale. Category 3 hurricanes have a one-minute sustained wind between 111 mph and 130 mph. The one-minute sustained winds in a Category 5 hurricane are greater than 155 mph.

Steve Ackerman and Jonathan Martin, professors in the UW-Madison department of atmospheric and oceanic sciences, are guests on WHA radio (970 AM) at 11:45 a.m. the last Monday of each month. Send them your questions at stevea@ssec.wisc.edu or jemarti1@wisc.edu.

Category: Climate, Severe Weather, Tropical

Comments Off on What does the hurricane season look like?

Is 2022 an active tornado season for the U.S?

Posted on May 23, 2022 by WeatherGuys Editor

Tornadoes can occur anytime of the year, so it is too early to answer this question.

Tornado damage in the town of Dunkirk near Stoughton Wisconsin from March 2022.
(Photo credit: State Journal archives)

Tornado season is based on when the ingredients for severe weather come together in a particular region. Because a change in wind with height is closely related to the presence of a jet stream, tornado season moves north and south during the year with a jet stream.

Tornado season peaks in March and April in the Southeast but not until July in the upper Midwest and Northeast. The deep South has a secondary peak in tornado occurrence in November.

Tornadoes happen at any time of day or night. However, they thrive on solar heating and in some cases the ability of warm, moist air at the surface to penetrate a low-level capping inversion. Therefore, the most likely times for tornadoes are late afternoon or early evening. More than half of all U.S. tornadoes occur during the hours of 3 p.m. to 7 p.m. local time.

As of Friday, there have been 573 confirmed tornadoes in the U.S., causing 15 fatalities. The number of tornadoes puts this year at the 75th percentile climatologically.

The ongoing La Niña is predicted to continue through spring and possibly summer. La Niña conditions favor a more active severe thunderstorm and tornado season in the US.

Tornadoes are classified based on the damage the tornado does, which enables us to estimate the wind speed of its rotating winds. All tornadoes are assigned a single number from the Enhanced Fujita scale, abbreviated EF, according to the most intense damage caused by the storm. The weakest tornado is EF0, with winds less than 85 mph. The strongest is EF5, where the winds are greater than 200 mph. As of Friday, there have been no EF5 tornados, 15 EF3 and 2 EF4 tornados.

Steve Ackerman and Jonathan Martin, professors in the UW-Madison department of atmospheric and oceanic sciences, are guests on WHA radio (970 AM) at 11:45 a.m. the last Monday of each month. Send them your questions at stevea@ssec.wisc.edu or jemarti1@wisc.edu.

Category: Climate, Meteorology, Severe Weather

Comments Off on Is 2022 an active tornado season for the U.S?

How does the recent humidity stack up against prior Mays?

Posted on May 16, 2022 by WeatherGuys Editor

The dramatic shift in our weather that took place over the last week will likely be memorable for a number of reasons.

First, on Tuesday Madison reached 90 degrees for the first time this year, the fourth earliest first 90-degree day in Madison’s history.

The all-time earliest was on April 22, 1980, when the temperature reached 94. The other two earlier first 90-degree days were April 28, 1952 (90, followed by 90 on April 30 — making April 1952 the only one in at least the last 80-plus years in Madison with two 90-degree days) and May 5, 1949 (90).

As if that were not enough, we also became the second May ever with four days at or above 90 — the first time was May 26-29, 2018.

Tropical moisture on May 13th tracked by satellites. (Image credit: CIMSS Total Precipitable Water)

Along with such unusually warm temperatures, we also experienced extraordinary humidity with this episode. Along with a high temperature of 91 on Wednesday , the dew point soared to 73 degrees at the airport — and 79 degrees on the roof of our building on campus. Dewpoint is one of several measures of the water vapor content of the air — it measures the temperature to which air must be cooled (at constant pressure) to reach 100% relative humidity. The higher the dewpoint, the greater the water vapor content of the air.

This dramatic moisture surge set the stage for a low temperature of 73 degrees on Thursday — the highest Madison daytime minimum in May since May 29, 1874. At the time of that recording, the official measurement spot for Madison was Bascom Hall. In fact, that observing site was in use on the only other such instances as well — the record 74 degrees on May 28, 1871 (followed by 73 degrees on the 29th and again on the 31st).

The fact that the recent extreme humidity values were recorded more than two weeks before any other such events in Madison history — and as the regional leaf-out began — testifies to the purely tropical nature of the air.

Steve Ackerman and Jonathan Martin, professors in the UW-Madison department of atmospheric and oceanic sciences, are guests on WHA radio (970 AM) at 11:45 a.m. the last Monday of each month. Send them your questions at stevea@ssec.wisc.edu or jemarti1@wisc.edu.

Category: History, Meteorology, Seasons

Comments Off on How does the recent humidity stack up against prior Mays?

Was April colder and gloomier than normal this year?

Posted on May 9, 2022 by WeatherGuys Editor

The recent month of April here in Madison was noteworthy on a number of levels.

First of all, we had snow on seven different days during the month, not quite the record of 13 from April 1950, but substantially above the average of about four days over the last 70-plus years.

Additionally, the month’s average temperature was 2.9 degrees below average — not a result of any particularly bitter days but a seemingly unending succession of cloudy and cool days. It is important to note that this daily average departure from normal of 2.9 degrees was the result of daytime highs being 4.7 degrees colder than normal and overnight lows being only 1.3 degrees below normal.

The cloudiness aspect of the past month’s weather can be directly assessed in comparison to recent Aprils through use of a heliometer, a device that measures the amount of solar radiation incident on the surface in units of watts per square meter.

Courtesy of calculations done by our colleague and department chair, professor Ankur Desai, it turns out that this past April was the “dimmest” April since in the last decade, registering an average of 287.28 watts per square meter (W/m2) during the daytime hours. Its nearest competitor for this unflattering distinction was April 2019, when the monthly daytime average was just 296.62 W/m2. The “brightest” April in the last decade occurred in 2015, when the daily average insolation was 377.82 W/m2.

So, if the past month seemed gloomy to you, you were absolutely correct in that assessment. It appears as though the coming week’s warmth and humidity will make us quickly forget that we had a protracted end to winter this year.

Steve Ackerman and Jonathan Martin, professors in the UW-Madison department of atmospheric and oceanic sciences, are guests on WHA radio (970 AM) at 11:45 a.m. the last Monday of each month. Send them your questions at stevea@ssec.wisc.edu or jemarti1@wisc.edu.

Category: Climate, Meteorology, Seasons

Comments Off on Was April colder and gloomier than normal this year?

Why is May 6 such a special day in weather science history?

Posted on May 2, 2022 by WeatherGuys Editor

Immediately after World War II, it became fashionable to imagine technologies that might allow human beings to control the weather.

In fact, one goal advanced by influential scientists was actually to explode nuclear bombs in the right locations and in the right quantity so as to alter the weather in favorable ways. Such an enterprise would require accurate forecasts of the weather thought possible by using the brand new computer technology to make the millions of requisite calculations.

Modern smartphones deliver weather forecast first generated by computers on May 6, 1955.

The drive to use computer models for weather forecasting was initiated at a secret meeting at the U.S. Weather Bureau headquarters in Washington, D.C., on the rainy morning of Jan. 6, 1946. After a series of successes and setbacks that mostly discouraged the broad meteorological community, the first operational computer-generated forecasts were issued on the afternoon of May 6, 1955.

Thus, in less than 10 years the notion of computer-based forecasts went from dream to reality. In the intervening 67 years, the combination of increased theoretical understanding both of meteorology and computational science, increased observational capacity (a good deal of which stems from satellite data), and sheer hard work on the part of a legion of dedicated scientists has resulted in our current forecasting capability.

The fact that our ubiquitous smart phones give everyone access to quite reasonable forecasts several days in advance is the end result of what might be considered the greatest scientific advance of the second half of the 20th century. So, as you consult your phone for the forecast, remember that one of the first baby steps in the march toward the modern miracle of numerical weather prediction were taken 67 years ago Friday.

Steve Ackerman and Jonathan Martin, professors in the UW-Madison department of atmospheric and oceanic sciences, are guests on WHA radio (970 AM) at 11:45 a.m. the last Monday of each month. Send them your questions at stevea@ssec.wisc.edu or jemarti1@wisc.edu.

Category: History, Meteorology

Comments Off on Why is May 6 such a special day in weather science history?