National Weather Service

This map shows the track of a tornado on May 3, 1999, in green; and the track of Monday's tornado in red. The similarity of the paths is coincidental, but the larger patterns of storm activity in "Tornado Alley" are due in part to the region's geography.

Do tornadoes follow well-worn tracks? Where do the deadliest twisters hit? Will climate change make such storms worse? Monday's devastating tornado in Oklahoma raises some questions for which scientists have ready answers, and others that could puzzle them for years to come:

Was this tornado a repeat of a famous twister in 1999?

For a time, Monday's storm followed a track that was similar to the path of a tornado with the fastest wind speed ever recorded, 318 mph (512 kilometers per hour), which occurred on May 3, 1999. That twister was one of 74 tornadoes that touched down in Oklahoma and Kansas in less than 21 hours, according to the National Severe Storms Laboratory. The 1999 outbreak of severe weather caused 46 deaths and nearly $1.5 billion in property damage.

The tracks weren't all that similar, however: Monday's tornado took a more southerly route as it moved east. And there's nothing unique about the area's geography to make it a magnet for super-powerful twisters, according to Bob Henson, a tornado expert with the National Center for Atmospheric Research in Boulder, Colo.

"If there were geographic features, that would tend to cause multiple tornadoes every few years," the meteorologist and writer told NBC News. "Well, why has this been happening only since 1999?"

The similarity in the tracks of these devastating storms is "a good example for how weather events can be clustered in ways that are striking yet ultimately coincidental," Henson said.

A classic example of this phenomenon, he noted, is Codell, Kan., which was hit by tornadoes on the same day — May 20 — in 1916, 1917, and 1918. The third tornado killed 10 people and destroyed a part of the community. "That's a good illustration of how sometimes things like this can just happen in clusters," he said.

NOAA SPC

The purple streaks on this map from the National Oceanic and Atmospheric Administration's Storm Prediction Center stand for tornado tracks from 1950 to 2011. The dark blotches indicate population densities.

But isn't Tornado Alley more prone to deadly twisters?

On a wider scale, the geography of America's midsection makes it more prone to tornadoes than any other region on Earth. That's because the Rocky Mountains tend to impede the eastward flow of moist air, while the Great Plains allow frigid Arctic air to stream southward from Canada and meet up with warm, humid air from the Gulf of Mexico. It's the collision of that warm and cold air that breeds powerful twisters.

"Tornado Alley" generally refers to the region centered in Texas, Oklahoma, Kansas and points north, where tornadoes are most frequent — but multiple studies indicate that the deadliest twisters occur to the east, in a region that's come to be known as "Dixie Alley." The reasons for that have to do with geography and demographics as well as meteorology in the southeastern United States: Storms tend to move faster, and they're more likely to strike at night. There are more trees and other obstructions to raise havoc. Population densities are generally higher, and the region has many manufactured homes that lack basements in which to take shelter.

The United States has the highest incidence of tornadoes, with an average of more than 1,000 every year, according to the National Climatic Data Center. But other regions of the world have twisters as well. Canada is No. 2 with about 100 per year, followed by northern Europe, western Asia, Bangladesh, Japan, Australia, New Zealand, China, South Africa and Argentina. Britain has more tornadoes than any other country, relative to its land area. "Fortunately, most UK tornadoes are relatively weak," the data center says.

Why do these tornadoes seem to be hitting all of a sudden?

After a relatively quiet start to the tornado season, tornadoes have been erupting from Texas to Minnesota over the past week. A cold front advancing to the east appears to be to blame. That pocket of cold air has run into warm air from the Gulf, causing the warm air to rise and spawning powerful thunderstorms. "It's kind of like the perfect setup," Jeff Weber, a scientist with the University Corporation for Atmospheric Research, told LiveScience.

The earlier calm was due to the fact that jet stream had been dipping farther south than usual for this time of year. That kept the Gulf's warm, moist air from advancing into Tornado Alley. Now that warm air is pushing northward, and the cold front has moved on to Minnesota and Wisconsin. As a result, the storm system that created Monday's big tornado should soon weaken, Weber said.

Will climate change make tornadoes worse? More frequent?

"The short answer is, we have no idea," Michael Wehner, a climate researcher at the Lawrence Berkeley National Laboratory, told NBC News. For years, Wehner has been studying the climate models for extreme weather, and he's a lead author for the next report from the Intergovernmental Panel on Climate Change as well as the federal government's latest national assessment on climate change.

One problem is that the observational record for tornadoes has not been uniform over time. "It has a bias to it, because more people are living where tornadoes occur, and more people are out looking for them," Wehner said. That contributes to the perception that tornadoes are happening more frequently than they used to.

The other big problem is that current climate models don't have the resolution that's needed to simulate the localized, violent activity of a tornado. Currently, global models are built up from atmospheric interactions on a scale of 100 kilometers (62 miles). Improvements in computer power could soon bring that down to a scale of 25 kilometers (16 miles). That should make it possible for scientists to simulate the weather phenomena that give rise to tornadoes, but not the tornadoes themselves, Wehner said.

On a larger scale, extreme weather events are expected to become more frequent in a warmer world, Wehner said. "The metric that I like to look at is the daily amount of rain for a storm that happens once every 20 years," he said. "That storm, in a much warmer world, would happen more frequently." For example, if the world follows a "business-as-usual" scenario, he projects that the average temperature would rise 11 degrees Fahrenheit (6 degrees Celsius) by the end of the century, and that a once-in-20-years rainstorm would come around every five to 10 years on average.

That doesn't necessarily mean tornadoes would be more frequent, however. In fact, the current projection calls for wetter spring weather in the northern U.S., and drier weather in the Southwest — with Tornado Alley right in the middle. "There's some evidence that there might not be a change" in the character of a tornado season, Wehner observed.

Wehner may sound a bit apologetic about the lack of clear answers in the short term, but in the long term, he's optimistic. "The reason I'm optimistic that we can get somewhere on this is that supercomputing technology is driving this very hard," he said. "We're just getting into the sweet spot for these kinds of issues, with the largest mainframes that money can buy."

More about tornado science:

• Why tornadoes seem as if they're on the rise
• Flash interactive: What causes tornadoes?
• Full coverage of the Oklahoma tornadoes

Alan Boyle is NBCNews.com's science editor. Connect with him by "liking" the NBC News Science Facebook page, following @b0yle on Twitter and adding him to your Google+ circles.

John Roach is a contributing writer for NBC News. To learn more about him, visit his website. 

This story was originally published on Mon May 20, 2013 8:20 PM EDT

Hurricane Sandy is posing a monster challenge for weather forecasters and emergency agencies, due to an amazing combination of meteorological factors, but what's just as amazing is how well they've been able to predict what seemed to be an unpredictable disaster.

"It looks like we've been fairly consistent on this, even five days out," Chris Landsea, science and operations officer at the National Hurricane Center in Miami, told me today. "I think when all is said and done, on the track forecast, we're going to be quite accurate."

Sandy's path, which took a left turn from the Atlantic to slam head-on into the heavily populated Northeast, is just one of the unusual aspects of this storm. "The size of this system, the late-season nature, and the track — all these are fairly unique characteristics," Landsea said. To look for precedents, you have to go back to infamous hurricanes such as Agnes in 1972, Hazel in 1954, even the great storms of 1944, 1938, 1815 and 1804. But today, the region is so much more populous and developed that the impact is certain to be far greater.

Here are five factors that have turned Sandy into a superstorm:

Northerly track: Atlantic tropical storms most commonly tear through the Caribbean and the Gulf of Mexico, and lose energy as they pass over the U.S mainland. This storm, however, crept along the Eastern Seaboard, where waters that were warmer than usual for this time of year kept the storm alive. As the storm moved northward, it morphed into a hybrid storm, drawing additional strength from the differential between the storm's warm air and cold northern air from the jet stream.

"There's a transformation that this system is undergoing," Landsea explained. "This is actually evolving into a winter storm, and later, a nor'easter." One result of this evolution is that the storm system has widened to more than 800 miles in diameter, stretching from the Carolinas to Maine and Canada.

NASA / NOAA

NOAA's GOES-13 weather satellite shows the storm system associated with Hurricane Sandy covering the northeastern United States even before landfall on Monday.

The left turn: Hurricanes that get so far north could drift off into the cold Atlantic to die — but they can also be pushed into the mainland, as Hurricane Irene was last year. Irene followed a path that was roughly parallel to the coastline, but Sandy took a hard left turn that put it on a course for a direct, perpendicular strike on the coast. That's because a cold front on the mainland is drawing the storm westward, while the current state of a weather pattern known as the North Atlantic Oscillation is blocking the storm from heading eastward. 

Storm surge: Sandy's top sustained winds of 85 miles per hour typically wouldn't rate as a superstorm, but its effects will be magnified, Landsea said. "Even though it's not a 'major' hurricane by any means ... there is substantial threat because of the storm surge and because of the rainfall. There's going to be flooding. Both of those factors are going to be killers," he said. The storm surge is projected to range from 6 to 11 feet. One of the big reasons for such a high surge is that the waters off the coast of New York and New Jersey are so shallow: As the surge from the deeper ocean nears the coastline, all that water piles up to create a higher wave.

Full moon: Another reason for the huge storm surge is the fact that the moon is hitting its full phase just as Sandy is making landfall. The celestial lineup of the sun, moon and Earth contributes to higher-than-normal high tides. 

Winter storm: Sandy is such a late-season storm that it's running into winter weather in the northeastern United States, which is adding an extra dimension to the misery. "I have not been around long enough to see a hurricane forecast with a snow advisory in it," Craig Fugate, administrator of the Federal Emergency Management Agency, told NBC's TODAY. The storm could trigger up to 3 feet of snow in the Appalachians, the National Weather Service reported. The Weather Channel's Tom Niziol said that "an amazing combination of factors" have come together to make Sandy a threat due to the snow as well as the rain.

Landsea and other forecasters may marvel at the factors behind what some have called a "perfect storm" or "Frankenstorm," and there'll surely be lots of lessons learned for future weather modeling. But that's not what's uppermost on their mind right now. "What's really important are the impacts," Landsea said.

To keep on top of the storm, and to keep safe, keep an eye on NBC News' hurricane coverage:

• Sandy swamps coastal towns, cuts power to 700,000
• Live updates on Hurricane Sandy
• Your images of Hurricane Sandy

Update for 3:10 p.m. ET Oct. 30: The storm surge was clearly one of the biggest impacts of Hurricane Sandy, and for good reason: The National Hurricane Service reported that in some cases, the surge exceeded its own maximum prediction of 11 feet. At New York's Battery Park, for example, the surge measured 13.7 feet — and it was devastating. On another note, I've corrected the spelling of Landsea's apt last name since this item was originally published.

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with Cosmic Log as well as NBCNews.com's other stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.