Extreme Cold Can Grip Texas

Q: When did the worst period of cold weather occur in Texas?

A:  The record was more than 100 years ago, says Texas A&M University’s John Nielsen-Gammon, who also serves as the state climatologist. “On Feb. 12, 1899, both Texas and Oklahoma had its coldest weather ever,” he reports. “On that day, all of Oklahoma was below minus-10 degrees, while one-half of Texas was below zero. Galveston Bay had areas of ice in it. Most cold waves in Texas aren’t that bad because the cold air tends to move east quickly, but on this particular day the air mass was so cold and large that there was little that Mother Nature could do to prevent it.”

Texas' coldest recorded weather occured in 1899

Q: What about other cold periods?

A: In December 1895, Amarillo had a cold spell in which the city spent 261 consecutive hours below freezing. In January 1930, the temperature reached only 13 degrees in Galveston while farther north, Oklahoma set its all-time cold record of minus 27 degrees in the town of Watts, Nielsen-Gammon adds. “In the more modern era, on Jan. 4, 1959, Spearman in north Texas had a high temperature of zero. On Jan. 9-12 of 1962, the temperature dropped to minus-14 degrees in the Panhandle and 10 degrees in the lower Rio Grande Valley, which saw 65 consecutive hours below freezing. And in the last days of January 1951, Houston was below freezing for a record 132 consecutive hours.”

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Weather Whys is a service of the Department of Atmospheric Sciences at Texas A&M University.

Jet Stream – River of Air Controls Weather

The jet stream is a huge river of air that controls weather all over Earth.

Q. You often hear about the jet stream. What is it?

A.  The jet stream is one of the most influential forces of weather that is known, says John Nielsen-Gammon of the Texas A&M Department of Atmospheric Sciences. “The jet stream is a river of air that flows high above the earth, usually between 20,000 to 40,000 feet, and its true extent was not discovered until World War II when pilots made frequent trips across the vast Pacific Ocean,” he explains. “The core of the jet stream is a fast-moving wind current that blows west to east around the earth, and it can range from speeds of 90 to more than 250 miles per hour. Winds in the jet stream are stronger during the winter months because that is when the temperature contrasts between the equator and the North Pole are greater – the greater the surface temperature, the bigger the contrast.”

Q: How does the jet stream affect the weather where I live?

A:  The strength of the jet stream enables it to push weather systems from one area to another, thereby greatly affecting the weather where you live, making some places stormy and giving others extended periods of fair weather, Nielsen-Gammon says. Because the jet stream winds are greatly affected by mountains and oceans, their movement is not always a uniform west to east direction. “They often contain arcs or dips, creating what meteorologists call troughs and ridges. Since the jet stream usually separates warmer air to its south, extended spells of warm or cold weather can be caused by jet stream patterns, too. There is still a lot of research being done on the jet stream, but we do know that it may stretch for thousands of miles around the world, but it is only a few hundred miles wide and usually no more than three miles thick,” he adds.

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Weather Whys is a service of Texas A&M University’s Department of Atmospheric Sciences.

Whither The Weather? For Answers, Turn To ‘Weather Whys’

A tornado touches down on a Texas roadside.

Ever wonder why the sky turns green before a hail storm, why there are sometimes rings around the moon, if rainmaking efforts really work or who made the first barometer?

These are some of the more than 100 topics posed to Texas A&M’s top weather experts and answered each week in a column called Weather Whys. The free nuggets of weather wisdom have been issued to various media outlets as a weekly service of the Department of Atmospheric Sciences for more than 10 years, and they showcase faculty expertise in a particular area.

Texas A&M’s Division of Marketing and Communications, in conjunction with the College of Geosciences, writes and distributes the weekly column, which uses a Q and A format on a particular topic. Various faculty members serve as sources and provide concise answers per the requests of receiving media, who are known for their get-to-the-point-in-a-hurry in today’s fast-paced communications environment.

Photos are also used to illustrate the weather topic of the week

“We have some world-class faculty in our various departments,” says Kate Miller, dean of the College of Geosciences. “They are always eager to answer a question if they can, and they provide us with excellent sources for Weather Whys material. This is a great way for the college to expand its community outreach efforts.

“Texas A&M has always been known for its service to the state, and this column is one way of informing Texans of weather topics they want need to know about and are interested in.”

Adds John Nielsen-Gammon, who serves as Texas State Climatologist in addition to Regents Professor in the Department of Atmospheric Sciences and  a frequent source used in Weather Whys: “Part of my job as state climatologist is community outreach, and if that means speaking to the media, I will gladly do it.

“I think it’s important that people get the information they need, whether it’s the general public or a major media outlet. Right now, Texas is going through one of its worst times in its history with a severe drought, so there is a real need for accurate information.”

Lightning strikes a Texas field.

Although Weather Whys is aimed primarily at weekly newspapers in Texas — the state has more than 400 — other media outlets have used it.

It has been source material for radio stations such as WOAI in San Antonio, KRLD in Dallas and other large metro areas. National outlets such as National Public Radio have used the column, in addition to numerous Texas daily newspapers, including the Bryan-College Station Eagle, The Huntsville Item, Mexia Daily News, Panhandle Herald, Waxahachie Daily News, New Braunfels Herald-Zeitung, Waco Tribune-Herald and many others.

As for the answers to those questions posed above, all of them will be revealed in upcoming Weather Whys columns — a good reason to stay tuned.

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Media contact: Keith Randall, News & Information Services, at (979) 845-4644

Hurricane Season Ends Nov. 30

Q:   Nov. 30 is the end of hurricane season. Why do some years have many hurricanes and other years seem to have very few?

A:  That’s a question that a lot of people are asking, says John Nielsen-Gammon, professor of atmospheric sciences at Texas A&M University who also serves as State Climatologist. “There were more hurricanes and tropical storms in 2005 than any year in at least 70 years,” he explains. “A lot of fingers are being pointed at global warming for the rise in severe storms. There are a lot of studies being done in this area, and global warming appears to be at least a strong contributing factor. We know that some areas of the oceans are warmer than in years past, and this can contribute to more intense storms.”

Q:  What specific areas of water are warmer?

A: The Atlantic Ocean, Nielsen-Gammon says, is scientifically proven to be warmer than normal. “Large areas of the Atlantic are at least one degree warmer than in years past, and this goes back to 1995,” he points out. “So we have had a decade of warmer water there, and that’s where hurricanes form. The long-range outlook tells us that this warming trend could continue another 5 to 20 years. Since warmer water means stronger storms and hurricanes, it could mean stronger storms in the future. Back in 2005, there were three hurricanes that reached category 5 status — the strongest level — but it remains to be seen if that will happen in the years to come.”

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Weather Whys is a service of the Department of Atmospheric Sciences at Texas A&M University.

Virga Creates Interesting Visual Weather Phenomenon

Q: Sometimes you hear the weather forecaster refer to “virga.” What is it?

A:  Virga is a common weather feature, says John Nielsen-Gammon of Texas A&M University. It refers to rain or snow that forms a wispy streak beneath a cloud and appears not to be reaching the ground. “Most of the virga people see today is usually composed of snow, since snow is so much brighter and easier to see than rain,” Nielsen-Gammon explains. “Even in the warm days of summer, the virga coming from the tall anvil-shaped thunderstorms is most likely snow, forming in the frigid temperatures 5-10 miles above the ground. Virga can also come from the base of a thunderstorm and other types of clouds, and it can be mistaken for a tornado at a distance because of its V-shaped appearance.”

Q:  Is the rain or snow evaporating before it reaches the ground?

A: “That’s just what the ancient Greeks believed and what most modern textbooks say, but it’s just not so a lot of the time,” Nielsen-Gammon adds. “Recent research suggests that what appears to be the bottom of a shaft of precipitation might just be the level where the snow melts and changes to rain. Snow floats, but raindrops fall. It’s sort of like a big traffic jam in the sky. When all of the snow is moving slowly, it’s all bunched together and blocks the sky. But when the snow melts into rain and everything speeds up, there’s suddenly a lot more space between the drops, and the whole shaft of precipitation becomes harder to see.”

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Weather Whys is a service of the Department of Atmospheric Sciences at Texas A&M University.