The Weather Guys

What is a gale wind?

Posted on November 13, 2023 by WeatherGuys Editor

A gale is a strong, sustained wind with wind speeds between 39 mph and 54 mph. The word is typically used as a descriptor for maritime weather.

The National Weather Service issues gale warnings when winds of this strength are expected for maritime settings. Gale warnings allow mariners to take precautionary actions to ensure their safety or to seek safe shelter. A gale warning flag is solid red and in the shape of an isosceles triangle. The equivalent warning for land is a wind advisory. The next level of warning for maritime winds that NWS issues is a storm warning for winds of 55-72 mph at sea.

Gale winds are common in November on the Great Lakes. Last week saw the anniversaries of some strong November gales in the Great Lakes region. The most famous of these include the White Hurricane (Nov. 7-10, 1913), the Armistice Day Blizzard (Nov. 11, 1940), the Edmund Fitzgerald storm (Nov. 9-10, 1975), and the Nov. 10-11, 1998, storm.

The 1913 storm sank 19 ships and killed more than 250 people. Most of the damage occurred in Lake Huron.

The Armistice Day Blizzard dropped 16.7 inches of snow in Minneapolis/St. Paul. The cyclone intensified rapidly and was accompanied by a very intense surface cold front that quickly dropped the temperatures as much as 50 degrees in parts of the Midwest. This rapid drop in temperature caught many people by surprise, and more than 150 people perished.

The Edmund Fitzgerald storm achieved grisly fame through its association with the sinking of the ore freighter and the loss of its 29 crew members.

Gale winds that sunk the SS Edmund Fitzgerald.
Credit: NOAA

That storm also was accompanied by extremely strong winds and rapid intensification over the mid-continent.

That event was memorialized by Gordon Lightfoot’s ballad “The Wreck of the Edmund Fitzgerald.”

The November 10-11 storm from 1998 saw a six-hour period during which its minimum sea-level pressure dropped 15 millibars.

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: Meteorology, Severe Weather

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What role did Wisconsin play in establishing the National Weather Service?

Posted on November 6, 2023 by WeatherGuys Editor

Portrait of Increase Lapham (Photo credit: Wisconsin Historical Society archives)

Wednesday was the 153rd anniversary of the first day of operation of what has become the National Weather Service. On Nov. 1, 1870, the first organized set of observations around the country were taken under the auspices of the Army Signal Service.

On Feb. 9 of that same year, President Ulysses S. Grant, fresh from his own experiences during the Civil War, enthusiastically signed the service into existence. Its purpose was “to provide for taking meteorological observations at the military stations in the interior of the continent and at other points in the States and Territories … and for giving notice on the northern (Great) Lakes and on the seacoast by magnetic telegraph and marine signals, of the approach and force of storms.”

Within a week of its first day of operation, the first official weather forecast from a United States government agency was made by Professor Increase Lapham, through the Chicago office. It was a successful forecast of strong winds and significant waves on the Great Lakes, and its issuance may well have saved lives and property, exactly as intended.

Lapham, of course, was perhaps the most famous professor during the early years of the University of Wisconsin-Madison. It was he, in fact, who petitioned U.S. Rep. Halbert Paine, of Milwaukee, himself a Civil War veteran, in the immediate post-war era regarding establishment of a national weather service.

Thus, Wisconsin, and in particular UW-Madison, played a prominent role in the establishment of our National Weather Service.

Category: Uncategorized

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Are hurricanes intensifying more quickly?

Posted on October 31, 2023 by WeatherGuys Editor

Hurricane intensities are classified using the Saffir–Simpson scale, which 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 one minute of sustained winds between 111 mph and 130 mph. The one-minute sustained winds in a Category 5 hurricane are greater than 155 mph.

Forecasting hurricane intensity is a difficult task, and forecasting how rapidly they might intensify is particularly difficult. Rapid intensification is when a tropical cyclone strengthens dramatically in a short period of time. The National Hurricane Center (NHC) defines rapid intensification as an increase in the maximum sustained winds of a tropical cyclone by at least 35 mph in a 24-hour period.

Intensification of a hurricane requires the right environmental conditions. One is water temperature. If water in the ocean beneath the hurricane is warm enough, it releases large amounts of energy as it evaporates, creating a dip in air pressure that generates powerful winds.

Otis, a storm that struck the southern coast of Mexico, was initially forecast to be a weak tropical storm (one-minute maximum sustained winds between 39 and 73 mph) at peak intensity. Instead, Otis underwent rapid intensification, reaching peak winds of 165 mph when it made landfall near Acapulco, Mexico, at 1:25 a.m. Wednesday. Otis strengthened from a tropical storm to a Category 5 hurricane in only 12 hours. This rapid intensification occurred over a patch of ocean with sea surface temperatures approaching 88 degrees. It came ashore as the strongest storm on record to hit Mexico’s Pacific coast.

Hurricane Otis prior to landfall. Click for an animation. Credit: CIMSS

While forecasts of intensification have improved, challenges remain. A recent paper in Nature found that rapidly intensifying storms that are within 240 miles of coastlines are now significantly more common than they were 40 years ago.

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: Meteorology, Phenomena, Tropical

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What is the status of sea ice this year?

Posted on October 23, 2023 by WeatherGuys Editor

The surface waters of our polar oceans freeze seasonally, forming a layer of sea ice that varies in thickness from centimeters to meters. The era of polar orbiting satellites has enabled the monitoring of sea ice distribution for more than four decades.

Seasons are reversed between the Northern and Southern hemispheres, so the sea ice maximum and minimum occur at different times of the year. Generally speaking, around mid-September the extent of the sea ice at the south pole is reaching a maximum, while in the Arctic it is approaching a minimum in September as our Northern Hemisphere summer comes to an end.

Arctic sea ice extent for September 19 2023, was 4.23 million square kilometers (1.63 million square miles). The orange line shows the 1981 to 2010 average extent for that day. (Image Credit: National Snow and Ice Data Center)

This year, the sea ice amount around Antarctica has fallen to a record low. Satellite observations indicate the sea ice extent around Antarctica peaked on Sept. 10. At that time, sea ice covered 6.55 million square miles, which is the lowest winter maximum since satellite records began in 1979. That’s about 386,000 square miles less ice than the previous winter low, set in 1986. The extent of the summer’s Antarctic sea ice also hit a record low in February, breaking the previous mark, set in 2022.

Arctic sea ice reached its minimum extent for this year on Sept. 19, covering 1.63 million square miles. This 2023 minimum extent is the sixth-lowest in the nearly 45-year satellite record. For reference, the combined surface area of the Great Lakes is 94,250 square miles.

The satellite data show a trend in sea ice extent over the Arctic that is decreasing annually at a rate of 4%, plus or minus 1%, per decade. The reduction of Arctic sea ice is rapid, as the northern polar region is warming four times faster than the global average. Over the Southern Hemisphere, satellite data shows no significant trend in sea ice extent. The climate change associated with global warming contributes to melt glaciers in Antarctica, which impacts sea ice extent around the continent.

Category: History, Seasons

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Is there a typical season for waterspouts?

Posted on October 16, 2023 by WeatherGuys Editor

A waterspout is a whirlwind that forms beneath a cumulus cloud over water. Before you see the waterspout, you may see a funnel-like cloud hanging from the cloud base. The Florida Keys, Gulf of Mexico, and Chesapeake Bay are common regions for waterspouts.

The Great Lakes also have waterspouts, though seasonally. August and September are the most common months for Great Lakes waterspouts to develop, with the full season considered to run from the end of July into October.

*Life cycle of fair weather waterspouts (Image credit: NOAA/NWS Sullivan)*

There are two types of waterspouts: fair weather waterspouts and tornadic waterspouts associated with severe thunderstorms. The fair weather variety of waterspout is more common than the tornadic and is the most common over the Great Lakes. A fair-weather waterspout is a whirlwind that forms beneath a cumulus cloud and over water and is generally not associated with thunderstorms. A fair weather waterspout develops on the surface of the water and moves upward.

Lake Michigan Waterspout offshore Racine, Wisconsin. Credit: Phil Moeller

Fair weather waterspouts form when cold air moves across warm water. They form when a large temperature difference between the warm water and the overriding cold air exists. Fair weather waterspouts develop in light wind conditions, so they tend to stay in one place or move slowly. They typically have weak circulations and winds, although the bigger spouts can produce wind gusts that can exceed 50 mph and can flip a small boat or damage a dock if they come ashore. Fortunately, these types of waterspouts move relatively slowly and are most often visible from a great distance over the flat expanse of lake waters, so there is ample time to get out of their way.

The International Centre for Waterspout Research is an international organization that monitors and studies waterspouts from all over the globe.