Floods: When water attacks

After two years of severe flooding in the U.S., including this spring's Red River and Mississippi River floods, MNN takes a closer look at how these disasters occur -- and what you can do to stay safe.

By

Russell McLendon

Fri, May 06 2011 at 12:02 PM

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Related Topics:

Weather & Climate, Natural Disasters

FLOOD PRESSURE: Trees are reflected in Mississippi River floodwaters near Cairo, Ill., on May 4, 2011. (Photo: ZUMA Press)

People have been settling near rivers for millennia, relying on them for transportation, energy, food and, most importantly, water. But despite the many perks of waterfront property, this prime real estate is also haunted by a hidden danger: floods. And thanks to growing human populations and wilder weather from global warming, the threat of flooding is forecast to rise in many parts of the world for decades to come.

 

Floods aren't a new problem, of course. Even the first human fishing camps likely suffered when rivers flooded. But the stakes grew higher as populations swelled, and when early farmers found rich soil along river banks — leading to permanent settlements in floodplains — the stage was set for future disasters. Manmade dams have since reduced death tolls from floods, but economic losses continue to surge as cities expand near water.

 

Global warming is expected to worsen this trend, since warmer temperatures make more water evaporate, pumping more moisture into the atmosphere. Still, floods can't be directly tied to climate change, points out Mike Halpert of the U.S. Climate Prediction Center.

 

Too many factors are involved, Halpert explains, including local geography, ground cover, long-term precipitation and climate trends like El Niño, La Niña or the Arctic Oscillation. Theannual floods that strike the Red River in North Dakota and Minnesota, for example, are spurred by spring rains as well as months of winter snow. "When you put 4 feet of snow on the ground and then you get warm temperatures, or you get a nice warm rain on top of it, that's a prime setup for flooding," Halpert says. Elsewhere, the record-breaking 2011 Mississippi River floods have come after an unusually snowy winter was followed by intense spring storms, trends that many blame on the Arctic Oscillation as well as a southerly jet stream, and even La Niña.

 

Yet with U.S. weather forecast to become more extreme and erratic — and U.S. watersheds growing more crowded and paved — Americans will likely face events like the 2011 Red River and Mississippi River floods long into the future. And while floods are famously difficult to forecast, people's precautions and reactions can still mean the difference between life and death. Below is a look at how floods work, why they might be getting worse and what you can do to stay safe.

 

There will be flood 

Floods are the most common natural disaster in the U.S., capable of striking almost any river, creek, lake or coast nationwide. They kill about 140 Americans each year and are often more destructive than the storms that caused them — water flowing at 10 mph exerts the same pressure on a structure as 270 mph wind gusts, according to the Federal Emergency Management Agency. Across the country, floods destroy some $6 billion worth of property every year.

 

Overflowing rivers are behind most U.S. floods, but anything from tsunamis and hurricanes to broken dams and urban runoff can cause one. A single flood may fit multiple categories, but floods are generally classified as one of the following:

 

• Flash floods: Most deaths and damage from floods are due to flash flooding — "a rapid and extreme flow of high water into a normally dry area, or a rapid rise in a stream or creek above a predetermined flood level," according to the National Weather Service. Flash floods develop suddenly, often in just a few minutes, and while they occur in all 50 states, they're most common in hilly areas with steep valleys, or along small waterways in urban environments. Their speed, depth and element of surprise make flash floods highly dangerous, causing major damage while allowing little time to prepare or evacuate. Heavy rains are the top cause of flash floods, but urban runoff, "ice jams," dam failures and other factors may also be involved.

 

• Slow river floods: Rising waters may spur flash floods in steep, narrow river basins, but in flatter, wider ones, flooding tends to be slow, shallow and long-lasting. Flat floodplains can remain inundated for days or even weeks, but these floods are at least usually easier to predict than flash floods. Spring snowmelt regularly swells northern rivers, and when big blocks of unmelted ice are floating downstream, they can become lodged under bridges or in narrow passages, creating an "ice jam" that sets off a flash flood on top of the slower, pre-existing flood.

 

• Coastal floods: Storms and earthquakes are the two leading causes of ocean floods. Hurricanes push walls of sea water ashore when they hit land, creating a saline flash flood known as a "storm surge." Storm surges are often responsible for the majority of deaths from tropical cyclones, as was the case in New Orleans after Hurricane Katrina in 2005. Despite hurricanes' strength, though, deep-sea earthquakes are capable of displacing even larger amounts of water, forming long-range waves called "tsunamis." Tsunamis can push floodwaters many miles inland, as seen after the 2004 Sumatran quake and the magnitude-9.0 temblor that hit Japan in March 2011.

 

• Ground failures: Some floods attack from below, as the water table rises to the surface and washes away chunks of topsoil. This can cause a variety of ground failures, including "subsidence," or sinking soil, and "liquefaction," a process in which water-soaked sediment loses strength and acts like a liquid. Scientists also differentiate between "mudfloods" — a liquid flood that carries up to 50 percent solid sediment loads — and "mudflows" — solid landslides where the downward flow is viscous enough to support large boulders within a wave of smaller particles. Mudfloods and mudflows are most common in California and other Western states, since they tend to occur on hillsides burned bare by wildfire.

 

• Lake floods: Most lakes experience fluctuating water levels, but they usually don't "flood" the way rivers do because lakes typically have outlet streams or rivers to help them drain. But not all lakes have such outlets, and these "closed-basin lakes" are prone to potentially catastrophic floods if their water level rises too high. Glacial lakes — which were carved and filled by glaciers, and make up most lakes in North America — are also at risk of drainage problems, and can undergo dramatic, long-term fluctuations in depth.

 

Opening the floodgates 

While rain and snow cause most floods, they're also pawns of broader climatic trends that shape daily weather. Linking specific weather events to these trends is never easy, but climatologists can at least trace the origins of some recent U.S. flood problems to unusually heavy precipitation during preceding months.

 

The winter of 2010-'11 saw record snowfall in much of the U.S., for example, which was largely blamed on the Arctic Oscillation pushing Canadian weather south. That helped feed another big Red River flood the following spring, and when a low-slung jet stream later began producing frequent thunderstorms across the Midwest, it contributed to historic flooding on the Mississippi and other major rivers. A similar phenomenon also occurred between 2009 and 2010, when El Niño-driven rains were initially welcomed, helping end long droughts from California to South Carolina. 

 

Within a few months, however, much of metro Atlanta was underwater (pictured). That region's drought had faded, and by September '09 El Niño was already drenching the U.S., sending storm after storm east across the country. October '09 was thewettest month nationwide in 115 years of record keeping, and when winter arrived, all that rain began falling as snow instead. El Niño reached its peak in December, helping fuel one of the snowiest winters in recorded history — 63 percent of the U.S. had a white Christmas in 2009, and by February, the entire Northern Hemisphere's snow cover was more than 1 million square miles above average.

 

The effects were so extreme, in fact, that climatologists soon realized El Niño wasn't working alone. Its accomplice turned out to be the strongest negative phase of the Arctic Oscillation ever recorded, a phenomenon that essentially shoves cold Arctic air south into mid-latitude regions, while pulling their warmer air up north. That helped create unseasonably cold temperatures across the U.S. and Europe, which in turn transformed El Niño's barrage of rainstorms into blizzards. When that snow later melted, it released a huge amount of moisture all at once — and many soils were still too waterlogged in 2010 to handle it.

 

"Snow always melts; it just depends how much is on the ground," Halpert says. "[2010] was unusual in that both December and February had all-time record low values for Arctic Oscillation, and the seasonal value was also a record." While that was odd, though, nearly the same thing happened in 2011: A negative Arctic Oscillation fueled heavy winter snow, followed by frequent spring storms, which proved too much for many rivers to contain. In March, U.S. officials warned that half the country faced spring-flooding risks, including the Red and Mississippi river basins.

 

Two recent studies have since linked intensifying U.S. winters to climate change, while two others even specifically related rising temperatures to rising floodwaters. Scientists typically discourage such specific attributions, but climate change could potentially affect flooding in several ways, depending on the region and type of flood in question. Most experts agree melting glaciers and warm, swollen seawater are raising sea levels, which may eventually flood low-lying coastal cities. NASA and other science agencies also predict weather patterns will swing more violently, possibly causing drought/flood cycles even more extreme than the ones seen recently in the U.S. And if climate change does create stronger storms as expected, many U.S. rivers could be in for unprecedented floods — suggesting that even if record flooding in 2010 and 2011 isn't a reflection of global warming, it may still be a preview.

 

Flood safety 

The main rule for staying safe during a flood is to never willingly go near the water, whether on foot or in a car. Just six inches of moving water can knock people off their feet, so FEMA warns against walking through flowing floodwaters, and points out that since even apparently dry land could be subject to ground failure in a flood, it's not a bad idea to use a pole or stick to test the soil before stepping on it. The best place to be is high ground, but if you're in a building when floods arrive, go to the roof or the highest floor, but be careful not to get trapped in an attic or other confined space by rising water.

 

More than half of all deaths in floods happen when vehicles are swept away, usually in flash floods. Many of the drivers are overtaken before they can react, but people also frequently overestimate their ability to drive through flowing water, often with tragic results. NOAA's "Turn Around, Don't Drown" campaign is aimed at reducing these preventable deaths by raising awareness of how dangerous road flooding can be.

 

Electrocution is another dangerous side effect of flooding, one more reason to stay away from the water. Avoid and report any downed power lines and electrical wires, and consider turning off your home's electricity and checking around for gas leaks.

 

Infection and disease can be major problems during a flood as well as long afterward. While water levels are still high, an array of contaminants can be mixed in with the flood, ranging from untreated sewage to toxic chemicals. But even after the threat of water-borne bacteria and synthetic pollutants wanes, respiratory risks arise from black mold and other fungi that flourish in water-damaged wood and fabrics. Anything that got wet from flooding should either be thoroughly cleaned or thrown away.

 

For more flood advice, see FEMA's floodsmart.gov page, which has safety tips as well as information on the National Flood Insurance Program. 

http://www.mnn.com/earth-matters/translating-uncle-sam/stories/floods-when-water-attacks

Flaking out: How snow forms

How snow forms

The trick to starting a snowstorm is "atmospheric lift," which basically refers to anything that causes warm, moist air to rise from Earth's surface into the sky, where it forms a cloud. This often occurs when two air masses collide — forcing the warmer air on top of the colder "dome" — but it can also happen when warm air simply slides up the side of a mountain. In another common process, known as "lake-effect snow," a mass of cold, dry air moves over a lake, creating temperature instability that pushes the lake's warm water vapor upward.  

 

No matter what lifts it, rising water vapor eventually cools so much it converts back to a liquid. The resulting water droplets can create clouds, but first they need something to condense onto, much like dew condenses onto grass or water condenses on the outside of a glass. The atmosphere may seem like a sparse and lonely place, but it's not empty: Long-range winds carry all kinds ofmicroscopic debris up there, mainly in the form of dust, dirt and salt. These floating tidbits circulate all around the sky, even crossing continents and oceans, and they give cloud droplets something to cling onto (see illustration at right). When you catch a snowflake on your tongue, you could be eating a speck of sand from the Sahara, soil from the steppes of central Asia, or even soot from your own car's tailpipe.

 

Storm clouds tend to billow upward as they develop, gradually towering into colder and colder regions of the sky. Most clouds are still made of liquid water droplets, even during frigid winters, but they will eventually start sporadically freezing once they drop below about 14 degrees Fahrenheit. Individual cloud droplets solidify one by one into ice particles, which may then attract other water vapor and droplets toward their surface. This leads to tiny but fast-growing "snow crystals," which suddenly fall downward once they become heavy enough.

 

Snow crystals grow into their famously diverse shapes depending on the cloud's temperature and humidity (see the chart below for details). They collect more and more ice particles as they drop through the cloud, and often clump together as the crystalline drizzle evolves into a snowstorm. By the time these falling crystals exit the cloud's base, they've usually grown into the intricate, latticed starbursts we call "snowflakes."

 

 

If the air is below freezing all the way down to the surface, these flakes keep their distinctive patterns and accumulate on the ground as snow. They often go through various other transformations during their descent, however, giving rise to some other, less popular forms of precipitation. Snowflakes that melt while falling become rain, but sometimes they refreeze before they land, in which case they're called "sleet." If they don't refreeze until after they land, however, they're known as "freezing rain" — a deceptively dangerous weather event that looks like normal rain but coats roads and sidewalks with a slick, icy sheen.

 

 

Snow in America

An average of 105 snowstorms hit the United States each year, typically producing snow for two to five days while spanning several states. Almost every part of the country has seen at least mild flurries at some point in modern history — even much of South Florida — but snow falls so irregularly and unevenly that the National Oceanic and Atmospheric Administration doesn't bother keeping official snowfall records at the state level. It does track cities' totals, however, and records from its National Climatic Data Center suggest New York state is home to some of the snowiest cities in the country: Syracuse averages 115 inches annually, followed by Buffalo (93 inches), Rochester (92 inches) and Binghamton (84 inches).

 

 

Of course, there are also less populated areas that receive far more snow than that. Mount Washington, N.H., averages 260 inches, for example, while Thompson Pass, Alaska, leads the nation with its yearly average of 551 inches. Thompson Pass also set several national records for extreme short-term snowfall during a major storm in late 1955 — 120 inches fell in two days, 147 in three days, 163 in four days, and 175 in five days — and set the six- and seven-day records with another blizzard two years earlier. (See the map above for nationwide total-snowfall averages.)

 

Snow problem

On top of temperature-related threats like frostbite andhypothermia, snowstorms can wreak havoc with human society by stranding commuters, closing airports, blocking movement of supplies, and disrupting emergency and medical services. Large buildups of snow can also topple trees, snap power lines and cause roofs to collapse, sometimes isolating people, pets and farm animals for days on end. The huge blizzard of 1993 is a prime example — it shut down all interstate highways north of Atlanta, paralyzed cities across the Eastern Seaboard and caused more than $6 billion in damage — but recent winter weather has also been ferocious. Following two major snowstorms in early December 2009 that dumped more than a foot of snow on many states, another storm from Dec. 22-25, 2009, was blamed for at least 20 deaths nationwide, widespread road closures and flight cancellations, and even some two dozen tornadoes in Texas and nearby Southern states. The wild winter weather continued into 2010, from Washington, D.C.'s "Snowmageddon" to the violent storms and flooding that hit California in December. It wasn't just the U.S., either: Much of Europe was crippled throughout December 2010 when unusually heavy snow shut down London's Heathrow airport. And according to a recent study, increasing snowfall in Europe is at least partly (and paradoxically) linked to global warming, since the loss of Arctic sea ice lets more cold air flow southward.

 

Heavy snowfall can pose serious threats to homes and businesses, but it's especially dangerous for drivers. About 70 percent of all injuries caused by ice and snow are from vehicle accidents, according to NOAA, with a quarter of them happening to people who were caught out in a storm. But the danger doesn't end when the storm does, since melting snow often leads to black ice, slippery road surfaces and even springtime floods, such as the ice jams and heavy snowmelt that frequently cause flooding along the Red River between North Dakota and Minnesota.

http://www.mnn.com/earth-matters/translating-uncle-sam/stories/flaking-out-how-snow-forms

9 scary images of shelf clouds

Shelf esteem

Thunderstorms and politicians are a lot alike: Both drift with the wind, both are full of hot air and both shy away from high pressure. And, fair or not, many people judge both by their faces.

 

While politicians grin for votes, though, storms glower over their constituents. Some even grow strange "shelf clouds" along their leading edges, like the one pictured here over Enschede, Netherlands. These cloudy countenances stretch out ahead of a storm, sometimes foreshadowing danger and sometimes just grandstanding.

Little Chute, Wis.

As a storm cell swept across eastern Wisconsin on June 13, 2004, it was led by a haunting shelf cloud, seen here over the town of Little Chute.

 

The storm made for some stunning images from Greenville to Green Bay, but luckily it was less severe than the photos suggest. "Although its appearance is threatening, and almost always precedes gusty winds, the [shelf] cloud is not necessarily a precursor to severe weather," the National Weather Service explains. Still, shelf clouds can generate dangerous straight-line winds, including the rare "derecho" and "gustnado," and shouldn't be taken lightly.

Yucatán, Mexico

July is often a stormy month for Mexico's Yucatán Peninsula, and this picturesque shelf cloud on July 15, 2005, was just a precursor to a far more dangerous storm three days later.

 

After nearly an inch of rain on July 15, the eastern Yucatán got double that on July 18, whenHurricane Emily made landfall as a Category 4 storm. Emily left a path of destruction from Grenada to Mexico, and remains the strongest Atlantic [skipwords]hurricane[/skipwords] ever recorded in July.

Saskatchewan, Canada

Shelf clouds don't only glow blue, or from within. This one shone red, for example, as it was struck by the rising sun over the prairies of Saskatchewan, Canada, in August 2001.

http://www.mnn.com/earth-matters/climate-weather/photos/9-scary-images-of-shelf-clouds/saskatchewan-canada

Weatherization: Energy efficiency hits home

 

Drafty doors, floors, walls and windows are slowly letting air out of the U.S. economy, as consumers pay rising prices to wrangle warmth that freely escapes and invades their homes. This HVAC crisis has been simmering for decades, but as Congress now struggles to cut U.S. energy costs, carbon emissions and unemployment all at once, the fight against outdoor climate change is increasingly focusing on indoor climate control.

 

President Obama made that clear earlier this month when he proposed his $6 billion Home Star program, aka "cash for caulkers," the latest in a string of federal efforts to both shrink the country's carbon footprint and revive its economy. Following last summer's $3 billion "cash for clunkers" and the $300 million "cash for appliances," Home Star would offer consumers cash rebates from $1,000 up to $8,000 for making certain energy-saving home renovations. The recession may have crushed the construction industry and stalled efforts to curb climate change, but supporters say Home Star could give both a boost — and without touching political pitfalls like coal mining or cap-and-trade.

 

"Cap-and-trade is kind of like health care, in that you have lots of people with diametrically opposed viewpoints," says Larry Zarker, CEO of the nonprofit Building Performance Institute and a member of the Home Star Coalition. "But if you look at energy efficiency itself, there are very strong Republican and Democratic arguments for doing this. There's very strong support across the political spectrum, and I think there's a strong likelihood it will pass."

 

But if Congress does pass Home Star — it was the subject of a Senate committee hearinglast week, and the House is working on its own version — what would happen? What are the chances the $6 billion investment would actually create jobs and save money? The proposal is likely to change as it winds around Capitol Hill, but here's a quick look at its basic ideas: 

 

What is weatherization?

Nearly a quarter of all energy used in the United States is used in people's homes, and about half of that is dedicated to heating and cooling. It already takes a lot of energy to keep houses cool during an Arizona summer, for example, or warm during a Minnesota winter, but much of that energy is also wasted as warm air enters or escapes through hidden air leaks. "Weatherization" is the process of sealing cracks and insulating walls and windows to stop air and heat from getting through.

 

Home energy audits and large-scale overhauls — which require skilled workers, therefore creating jobs — could qualify a project for the Home Star program's more lucrative Gold Starrebates, but there is still cash to be had for DIY caulkers, too. A variety of simple efficiency upgrades would not only qualify for Silver Star rebates, but also for already-existing tax credits. The trick is often locating the leaks in the first place — much harder to do with air than with water.

 

How does air escape?

The simplest way to trace air leaks is to close all windows and doors in the house, then light a candle or incense stick and walk from room to room. If the stream of smoke is blown toward or away from any windows, door frames or walls, there's probably some air getting through. According to the U.S. Department of Energy, the most common sources of leaking air are floors, walls and ceilings, which account for nearly a third of all leaks, followed by air ducts (15 percent), fireplaces (14 percent), plumbing penetrations (13 percent), doors (11 percent) and windows (10 percent). Fans, vents and electrical outlets make up the other 6 percent.

 

How can it be stopped?

A home's "heat flow," or the natural movement of heat from warmer to cooler spaces, is the basic problem that weatherization services aim to solve. During summer, solar heat flows in from outside, either directly through openings or by heating up walls and radiating through. In the winter, warm air doesn't have to flow outside to be wasted — it often just seeps into unheated attics or crawlspaces, or its warmth moves indirectly through walls and windows, radiating out on the other side. Of course, leaky doorways and windows are still always prime places for heat to escape, too (see the two photos below, which use infrared imaging to show where the house loses heat.) 

 

 

The leading weapon against heat flow is thermal insulation, which can take many different forms, each assigned an "R value" based on how well it stops heat. Since walls, floors and ceilings are usually a house's main heat transmitters, they're often in greatest need of insulation, but attics, air ducts, basements, crawlspaces and any other unheated areas may also contribute to heat loss. "Blanket insulation" is the most common and widely available type, and while it's typically made of fiberglass or plastic fibers, it also comes in eco-friendly materials like cotton or sheep's wool. Other insulation types include concrete blocks, spray foam, reflective materials and straw bales. 

 

It often takes an energy audit to know what needs renovating, but weatherization can involve anything from caulking and weather stripping to installing new windows and doors to closing a fireplace damper and tightening an electrical-outlet cover. While such upgrades are widely seen as wise, they can introduce a potential health risk: radon gas. The naturally occurring, radioactive gas seeps up from soil and can be trapped inside houses, especially when windows and doors are kept closed for winter. But in a truly weatherized house, radon can't penetrate the foundation in the first place — one benefit of doing a whole-home energy audit rather than piecemeal projects.

 

What is 'cash for caulkers'?

Formally known as Home Star, the proposal was named after the DOE's and EPA's popular Energy Star program. The idea is similar to "cash for clunkers" and "cash for appliances": Give consumers immediate cash rebates that encourage energy-efficiency. While "clunkers" paid people to trade in their gas guzzlers for fuel sippers, Home Star would pay them for making energy-saving renovations to their homes, supporting both the retailers that sell the materials and the contractors who install them. That's especially appealing to the construction industry, which is still reeling from the housing crash.

 

"You hear about us being in a recession, but the construction industry is in a depression right now," says Matt Golden, a co-creator of the Home Star proposal and president ofRecurve, a San Francisco-based contracting company. The U.S. construction industry'sunemployment rate rose to 27 percent in February — meaning one in four American construction workers is out of work — and in the insulation industry specifically, it's closer to 40 percent.

 

Home Star would create 168,000 jobs, according to the American Council for an Energy-Efficient Economy, a weatherization advocacy group, although Golden calls that "a very conservative number." The Home Star Coalition also predicts the program could retrofit 3.3 million homes in two years — saving homeowners $9.4 billion over the next decade, and cutting carbon emissions by as much as 615,000 cars, or four 300-megawatt power plants. According to the White House, consumers could expect to save $200-$500 annually in energy costs, while "improving the comfort and value of their homes." And to ensure they meet those standards, Home Star would require contractors to be certified, and quality inspectors would conduct field audits of finished renovations.

 

In its current form, Home Star allows for rebates ranging from $1,000 as high as $8,000, depending on the scale of each renovation project, which it divides into two categories — Silver Star and Gold Star.

 

Silver Star: Many simple renovations would be eligible for 50 percent rebates up to $1,500 with the Silver Star track, including insulation, duct sealing, water heaters, HVAC units, windows, roofing and doors. Under Silver Star, consumers could choose a combination of upgrades for a maximum rebate of $3,000 per home, with only the most energy-efficient categories of products covered. The Home Star Coalition says 2.9 million homes would take part in these rebates.

 

Gold Star: More comprehensive projects could pursue the Gold Star track, in which whole-home energy audits and retrofits would be eligible for a $3,000 rebate if they're designed to achieve energy savings of 20 percent or more. Consumers could also get an extra $1,000 for every additional 5 percent boost in their home's energy efficiency, up to a total of $8,000 per household. Gold Star would build on existing whole-home retrofit programs like the EPA's Home Performance with Energy Star, and about 500,000 homeowners are expected to participate.

 

While Home Star's proposed $6 billion investment is big news, the federal government has supported weatherization for decades. The DOE's Weatherization Assistance Programhas retrofitted some 6.4 million low-income homes since it began in 1976, helping those residents save 30.5 million British thermal units (Btu) of energy annually, according to government data. And in 2009, the federal stimulus package invested an extra $4.73 billion in the weatherization program, up from $450 million the previous year.

 

Yet even with an existing system in place, the stimulus-funded weatherization has been slow to pan out, according to a report published by the DOE's inspector general last month. In fact, only 8 percent of the money had been distributed as of Feb. 16 — a full year after the stimulus bill was signed into law. These delays are mainly due to local furloughs and hiring freezes, the report found, but while it praises the government's "proactive steps" to spend stimulus funds, it does call the lack of progress so far "alarming." Six states hadn't completed any of their planned projects by Feb. 16, and only two — Delaware and Mississippi — had finished more than 25 percent.

 

Ultimately, the stimulus weatherization effort may have been slowed down by the very system that was supposed to speed it along, the report concludes: "The results of our review confirmed that as straightforward as the program may have seemed, and despite the best efforts of the [Energy] Department, any program with so many moving parts was extraordinarily difficult to synchronize."

 

Under Home Star, however, the federal government would work more directly with retailers and contractors, reimbursing them for the rebates they give their customers. That's why supporters argue it can begin creating jobs quickly, potentially having a more immediate impact than the stimulus money has, although it may still not take off quickly as "cash for clunkers" or "cash for appliances." While those programs offered rebates for pre-made products, many of the Home Star rebates would be for complex services — services that take time to complete, and that require workers to be trained before performing them.

 

Although training time might hurt some Home Star projects' shovel-readiness, advocates say it also creates steadier, better-paying jobs in the long run. And combined with weatherization's ability to cut energy bills as well as carbon emissions, many say Home Star's job-creation potential gives it a shot at bipartisan support in Congress. "From the left and from the right, the rationale is actually consistent," says BPI's Larry Zarker. "What we should be doing is working on our existing housing stock." There are 128 million housing units across the United States, according to the U.S. Census Bureau, which collectively use 10 quadrillion Btu of energy annually, costing their occupants more than $200 billion a year.

 

Despite his optimism about Home Star, Zarker admits the delays in weatherization projects so far have been discouraging. "I was just in Wyoming doing a talk, and they have 250,000 housing units," he says. "So if they're going to do this in 10 years, they need to do roughly 25,000 units a year, and if they're doing it in 100 years, they need to do 2,500 a year.

 

"But in Wyoming right now, they're on a 10,000-year plan," he says. "And that's pretty common across the country."

http://www.mnn.com/earth-matters/translating-uncle-sam/stories/weatherization-energy-efficiency-hits-home

What causes hurricanes?

 

Hurricanes are more than just thunderstorms on steroids — they're angry mobs of thunderstorms on steroids, built from many smaller squalls that team up in the tropics each summer. These meteorological mosh pits are impulsive and violent, but there's a method to their madness: They help control Earth's climate by hauling heat around the planet, moving it out of the tropics and toward the poles.

 

Lately, though, their workload has been spiraling out of control, with global sea-surface temperatures increasingly reaching record highs. The U.S. National Climatic Data Center reported in mid-July that 2010 is on track to surpass the two warmest years on record, 1998 and 2005, and that June 2010 was the warmest June since 1880. And although hurricanes are just mindless masses of water and wind, the overworked cyclones seem to be taking out more and more of their aggression on human civilization, including one of their favorite targets: the United States.

 

Hurricane formation is a collision of global influences, and any tropical storm is unpredictable even once it's full-grown, forcing forecasters to issue only a "cone of uncertainty" about its upcoming path. But tropical storms in general become much more consistent over time, haunting the same parts of the world year after year. And while weather-tracking technology reduced many of those regions' death tolls in the 20th century, property damagekept soaring along with coastal population densities. Combined with the gradual loss of coastal wetlands that once buffered against cyclones, this means the average hurricane today is far more destructive than 100 years ago. Add in the expected effects of global warming, and the outlook is even worse.

 

The United States isn't the only or even the most cyclone-prone country on Earth, but a string of big ones recently through the populous, energy-rich Gulf Coast — plus the fear of future hits on East Coast hubs like Miami, New York or D.C. — has drawn widespread attention to the country's risks. The Gulf oil spill has also added another wrinkle to the 2010 Atlantic hurricane season, which is already forecast to be one of the worst in years due to record-high ocean temperatures and the emergence of La Niña.

 

Even with vast improvements in hurricane forecasting and preparedness over the past century, recent cyclones such as Hurricane Katrina in 2005 and Typhoon Morakot in 2009 have been tragic reminders of how devastating an expected storm can still be, and how much vigilance is needed to truly be ready for one. Since understanding and appreciating Mother Nature is often a key step toward surviving her, MNN offers the following look at how hurricanes form, when they form, where they go, why they're dangerous, how they're affected by climate change, and what you can do to be safe.

 

How do hurricanes form? 

Hurricanes are huge heat engines that run on warm water, capable of producing roughly 200 times the entire world's electrical generating capacity with rain and cloud formation alone. Their power source is the sun, which heats up tropical sea water all spring to have the engines building and revving themselves by early summer.

 

Up-and-coming cyclones are categorized by their wind speeds and their degree of organization, giving forecasters a way to classify the threats they pose. Tropical cyclone formation is generally divided into the following four steps:

• Tropical disturbance: a loosely organized system of tropical or subtropical storming that maintains itself for at least 24 hours. Even the largest hurricane was once a humble disturbance.
• Tropical depression: a tropical disturbance that has tightened into a cyclone and developed a closed loop of circulation. Tropical depressions have a maximum sustained wind speed of 38 mph.
• Tropical storm: a tropical depression with more concentrated storming near its center and with outer rainfall forming distinct bands. Tropical storms have maximum sustained wind speeds between 39 and 73 mph.
• Hurricane/typhoon: a tropical storm that has come of age, with tight, powerful cloud rotation and maximum sustained wind speeds of 74 mph or higher. Known as "hurricanes" in the Atlantic and "typhoons" in the Pacific, major tropical cyclones are further classified by strength, from a Category 1 to a Category 5.

The birth of a tropical cyclone begins when warm surface water evaporates, rises, cools and falls back down as rain. This creates a thunderstorm, the building block of hurricanes, and it's this thunderstorm activity that releases stored heat from sea water so it can fuel the growing cyclone. The water has to be at least 80 degrees Fahrenheit and 150 feet deep, but it also must be at least 300 miles away from the equator to glean the right amount of spin from the Coriolis effect.

 

Once enough heat is being pumped from the sea into the sky, an outside disturbance is still needed to get everything spinning. One of the more common triggers in the Atlantic is something called an "African easterly wave," produced by temperature differences between the Sahara Desert and the Gulf of Guinea. These waves travel west along a path of warm water known as "Hurricane Alley" (pictured), often stirring up a cyclone along the way. In fact, 60 percent of all Atlantic tropical storms begin with such waves from west Africa, as do 85 percent of the basin's major hurricanes, according to the National Oceanic and Atmospheric Administration.

 

By the time a tropical cyclone evolves into a hurricane, most of the storm has organized into rain bands, which are horizontal cloud strips that vacuum up warm water vapor and send it to the sky, where it cools and condenses into rain (see illustration below). But some cool air is sent inward to the storm's point of lowest atmospheric pressure, where it sinks down and can create a deceptively tranquil, cloud-free zone known as the "eye." The eye is separated from the rain bands spiraling around it by the "eye wall," where the storm's winds are strongest.

 

 

When do hurricanes form? 

Tropical cyclones are typically a summer phenomenon, since they can't exist without lots of warm, sun-baked sea water. The Atlantic hurricane season officially runs from June 1 through Nov. 30, but the region's cyclones don't always follow the rules, sometimes arriving early and sometimes flouting their curfew. The latest date that a tropical storm was ever recorded in the Atlantic is Dec. 30, which has happened twice: Hurricane Alice in 1954 and Hurricane Zeta in 2005. 

 

Since the Pacific Ocean is larger and warmer than the Atlantic, its typhoon season is usually longer and more intense. Some areas are so active that they have no official "seasons," with cyclones sprouting up virtually year-round. Still, most regions see few typhoons in winter, with the vast majority developing between May and December.

 

In both the Atlantic and Pacific basins, cyclone formation shifts into high gear by late summer, hitting its peak around August or September. The Atlantic hurricane season's average peak is Sept. 10, and many of the worst storms in U.S. history have occurred within two weeks of that date.

 

Where do hurricanes go? 

Seven ocean basins around the world host tropical cyclones, six of which are in the Pacific or Indian oceans and only two of which directly affect the United States (see map). One, off the coast of western Mexico, presents little risk to U.S. soil aside from rare clashes with Hawaii. The other fills up much of the North Atlantic, and is responsible for almost all hurricanes that hit the United States. 

 

All seven basins have at least one big risk factor in common: lots of warm sea water to their northwest or southwest, a problem since tropical storms feed on warm water, travel westward and like to curl away from the equator. But geography alone doesn't make a region susceptible; a wide range of other issues like wind currents, water depth and coastal geology also play a role. The U.S. East and Gulf coasts face a high risk because they're an ideal distance away from the equator, and many of their large port cities are sitting ducks for big storm surges. Throw in the annual blast of easterly waves from Africa, and much of the United States' eastern half finds itself trapped in the middle of a busy hurricane highway for six months every year.

 

Why are hurricanes dangerous? 

Hurricane winds can rip off roofs, blow out windows and flatten buildings, and they're notorious for making deadly weapons out of random debris. But the storms also spark an array of other disasters, some of which are even worse than their wind. Coastal storm surges kill more Americans than any other effect from hurricanes, and left an indelible mark on the nation's collective memory by flooding much of New Orleans after Hurricane Katrina. Heavy rain is another killer, especially in hilly parts of Asia and Central America, where rains can spur massive mudslides and sinkholes. And the tail end of a hurricane often generates tornadoes, which feature even stronger winds than the hurricane itself.

 

The deadliest hurricane in U.S. history was an unnamed storm that ambushed Galveston, Texas, on Sept. 8, 1900, killing 8,000 people. But while advances in hurricane forecasting and preparation have reduced U.S. death tolls since then, any given cyclone is now capable of more devastation than in the past. That's mainly due to rising population densities along the world's coasts, especially in developing countries. Yet affluent nations aren't immune from coastal crowding, either: In the United States alone, some 160 million people — more than half the total population — are now crammed into just 673 oceanfront counties, up 46 percent from 1970. Another 7.1 million are expected to join them by 2015, a 5 percent increase in less than five years.

 

To make matters worse, many of those coasts are also much closer to the ocean than they used to be, since dam-building, development and pollution have helped wipe out swaths of coastal marshes that would normally soften a hurricane's blow before it hits land. Without that buffer, storm surges can be more severe, and wind gusts may also be stronger without anything to slow down the storm ahead of landfall.

 

What about global warming? 

Not only are some coastal cities upping the ante as they pack in more people, but humans in general may also be stacking the deck in hurricanes' favor. Scientists now widely agree that rising sea-surface temperatures due to manmade climate change will boost the power of hurricanes, but they remain cloudy on details like when or by how much. A studypublished in Nature Geoscience earlier this year predicts "greenhouse warming will cause the globally averaged intensity of tropical cyclones to shift toward stronger storms," with intensity rising 2 to 11 percent by 2100. Rainfall from hurricanes is also expected to grow by about 20 percent within 70 miles of a storm's center.

 

Global warming may strengthen individual storms, but climate models also suggest it should slash the total number of them. The Nature Geoscience study forecasts a global dip in hurricane frequency of 6 to 34 percent over the next 90 years, and Thomas Knutson, a research scientist at NOAA's Geophysical Fluid Dynamics Laboratory, sums up the issue in a recent report for the GFDL: "Anthropogenic warming over the next century more likely than not will lead to substantial fractional increases in the numbers of very intense hurricanes in some basins, despite a likely decrease (or little change) in the global numbers of tropical storms."

 

As for whether any of this is happening yet, the jury is still out. Atlantic hurricane activity has increased since the 1970s, but there are too many variables to scientifically link any single storm to global warming (although Katrina, pictured, is often seen as a leading candidate). That doesn't mean they aren't related; the situation is just too complex to prove or disprove a connection yet. But as Knutson points out in the GFDL report, it's probably just a matter of time. "It is premature to conclude that human activity — and particularly greenhouse warming — has already had a detectable impact on Atlantic hurricane activity," he writes. "However, human activity may have already caused substantial changes that are either below the 'detection threshhold' or are not properly modeled yet." 

 

What you can do to be safe 

Avoiding the lure of seaside property is the easiest way to stay safe from hurricanes, but there are of course millions of people who can't or won't live anywhere else. For them, as well as anyone who picked the wrong beach for a late-summer vacation, there are still plenty of other ways to prepare yourself before landfall:

• Listen to weather reports if you live near the ocean. Equally important, though, is actually acting on them. Evacuate if you're told to, or if you live in a mobile home, a high-rise building or on a floodplain. If you ride out a storm, stay inside near the center of the house, and don't go near windows or doors.
• Storm shutters are the best option for protecting windows, but in a pinch, you can also just board them up. Use 5/8-inch marine plywood, cut to fit the window's shape, and make sure it's secure. Don't bother taping up your windows, though — not even duct tape can stop a hurricane.
• Strong cyclones are known for ripping off roofs, so if you're expecting a big one, you might want to secure the roof to your house's frame using straps or clips. If you have time, it's also wise to make sure nearby trees are trimmed and healthy, since they provide hurricanes with an arsenal of deadly projectiles.
• Aside from the hurricane itself, you should also prepare for the potential aftermath. Shut off any propane tanks, as well as other utilities if instructed to do so. Turn your refrigerator to its coldest setting and keep its doors closed, because you'll want your food to stay good as long as possible if the power goes out. And ensure a post-hurricane supply of clean water by stockpiling it in jugs, bathtubs, and other large containers before the storm arrives.
• Don't let the hurricane's eye fool you: Make sure the storm is actually over before you go outside. Even when it has passed, still be careful as you survey the damage. Watch out for downed power lines, dangerous debris and falling trees, and don't wade through floodwaters unless it's absolutely necessary.

For more advice, check out the Federal Emergency Management Agency's guide to hurricane preparedness.

  

More information

To learn more about hurricanes, check out the following related stories from MNN, and make sure to watch the video clip embedded below, courtesy of the BBC:

• Are hurricanes linked to global warming?
• Infographic: 2010 Atlantic hurricane season
• 12 NASA photos of hurricanes from space
• Hurricanes in the Gulf oil spill could wreak havoc
• How do El Niño and La Niña affect hurricanes?
• Katrina victims seek to sue greenhouse gas emitters

 

Image credits

Eye of Hurricane Wilma, 2005: NASA Image Science and Analysis Laboratory

Hurricane Bonnie, 1998: NASA Goddard Space Flight Center

Sea-surface temperatures in "Hurricane Alley," 2003: NASA GSFC

Hurricane cross-section: NOAA National Weather Service

Map of tropical cyclone basins: NOAA NWS

Grounded boat after Hurricane Ivan, 2004: ZUMA Press

Surface sea water: NASA Earth Observatory

Hurricane Katrina, 2005: NOAA Environmental Visualization Program

Hurricane evacuation sign: Federal Communications Commission

Fallen tree after Hurricane Frances, 2004: ZUMA Press

Stranded dog in flooded New Orleans, 2005: ZUMA Press

http://www.mnn.com/earth-matters/translating-uncle-sam/stories/what-causes-hurricanes