Cyclone vs Hurricane

Cyclones are stormy atmospheric systems that have the potential of causing destruction. They are caused due to instability in atmospheric conditions. According to the region and severity of stormy conditions, these storms may be referred to as typhoons or hurricanes.

Hurricanes are a type of tropical cyclones that also have the potential of causing massive destruction due to their high winds, rain and floods.

Cyclone	Hurricane
About:	A cyclone is an atmospheric system characterized by the rapid inward circulation of air masses about a low-pressure center, usually accompanied by stormy often destructive weather. Storms that begin in the Southern Pacific are called cyclones.	Tropical cyclones in the North Atlantic Ocean, the NE Pacific Ocean east of the Internat'l Date Line, or the South Pacific Ocean east of 160E with sustained winds of (or those that exceed) 74 mph are hurricanes.
Rotation:	Clockwise in the southern hemisphere and counterclockwise in the northern hemisphere.	Clockwise in the southern hemisphere and counterclockwise in the northern hemisphere
Intensity:	Commonly quite strong. The scale for measuring cyclones is called the Beaufort Scale and Saffir-Simpson scale and may vary in different countries.Winds may approach 300kph and cause widespead damage.	Hurricanes are classified into five categories according to the Saffir-Simpson Hurricane Wind Scale. The wind speed and intensity of damage increases as from category 1 to category 5.
Most affected areas:	Pacific Ocean	Caribbean Sea
Location:	Southern Pacific Ocean, Indian Ocean	North Atlantic Ocean, the Northeast Pacific Ocean east of the International Date Line, or the South Pacific Ocean east of 160E. Hurricanes are found near the tropical zone, over warm waters in the Atlantic and Pacific ocean.
Frequency:	10-14 per year	10-15 per year
Occurrence:	warm areas	Usually warm areas

Lightning strikes to Chicago's skyscrapers: Sears, Hancock & Trump

Lightning strikes to Chicago's skyscrapers: Sears, Hancock & Trump

CHICAGO, IL - For the past 4 years, I have been working on an ongoing project to document upward lightning strikes to Chicago's skyscrapers. Lightning routinely strikes the Sears Tower, the John Hancock building and now the Trump Tower during most storms that pass over the city. So far I have made seven separate expeditions to the city to attempt capturing imagery and video. While upward lightning is common and occurs many times per year, it is very difficult to know ahead of time when a storm capable of these type of discharges will pass over the city. Out of the 7 trips to Chicago, I have captured upward strikes to the buildings on only three of them. I plan to continue this project indefinitely (or until I obtain satisfatory results).

A note about the June 23, 2010 event: A prolific upward lightning event occured in Chicago on the evening of June 23, 2010 and made international headlines. I unfortunately missed this event due to incorrectly forecasting the placement of the thunderstorms by evening. This event was typical of Chicago upward lightning. Despite rumors to the contrary, it is very common for upward discharges to initiate on more than one tall object simultaneously (see the FAQ below). In this case, several of the discharges hit all three major skyscrapers at the same time (Sears, Trump and Hancock). The photos and videos in the news were all authentic and unedited. You can read more about upward lightning in my online article on the subject.

Thunderstorms

Air Mass Thunderstorm

The air mass thunderstorm is common in Florida. As with all thunderstorms, it contains thunder and therefore has lightning. The air mass thunderstorm lasts approximately one hour and has a very distinctive life cycle.
Cumulus Stage: Rising air, or updraft, cools and forms the cloud. The rising air is occurring in an environment that is favorable for convection. Lifting mechanism include solar heating or convergence from a sea breeze. It is not raining during this stage of the thunderstorm.
Mature Stage: As the cloud continues to grow, precipitation particles form and fall from the cloud. The precipitation falls into the updraft. The falling particles drag air down with them. This sinking air is referred to as downdrafts. Entrainment into the downdraft results in some evaporation of the precipitation, which causes a cooling which makes the air more dense, thus increasing the downdraft. Rain begins to reach the surface. Hail may also make it to the surface, but they are not very large.
Dissipating Stage: When the downdrafts encompass the storm, the updrafts are shut off and the storm begins to die. The intensity of the rain decreases.
Prior to the development of a thunderstorm, the air near the surface is often warm and moist. With the downdrafts come cool air and the temperature at the surface drops. After the storm passes, the temperature may begin to rise again.

Severe Thunderstorm

In the air mass thunderstorm the precipitation falls into the updraft, cutting off the storm's moisture supply and eventually kills itself. The air mass thunderstorm only lasts about an hour which is not enough time to produce severe weather. In the Severe thunderstorm the updrafts and downdrafts are separate from one another, This allows the storm to last longer and severe weather may develop. To separate the updraft from the downdraft requires wind shear.
Winds speed increase with altitude case to updraft to tilt. Because it tilts, when precipitation falls, it does not fall into the updraft, thus allowing a continuous source of moist warm air to fuel the storm. In addition to the winds increasing with altitude, the wind direction also changes. Enormous severe storms that develop and have a tilted updraft are calledsupercell thunderstorms.
Below are some animations of the updraft and downdrafts in a supercell thunderstorm. As you view these animations keep track of the following features: The overshooting top, the cirrus anvil, the updrafts (yellow lines) and a downdraft (green lines).

TORNADO BASICS

TORNADO BASICS

What is a tornado?

A tornado is a narrow, violently rotating column of air that extends from the base of a thunderstorm to the ground. Because wind is invisible, it is hard to see a tornado unless it forms a condensation funnel made up of water droplets, dust and debris. Tornadoes are the most violent of all atmospheric storms.

Where do tornadoes occur?

Tornadoes occur in many parts of the world, including Australia, Europe, Africa, Asia, and South America. Even New Zealand reports about 20 tornadoes each year. Two of the highest concentrations of tornadoes outside the U.S. are Argentina and Bangladesh.

How many tornadoes occur in the U.S. each year?

About 1,200 tornadoes hit the U.S. yearly. Since official tornado records only date back to 1950, we do not know the actual average number of tornadoes that occur each year. Plus, tornado spotting and reporting methods have changed a lot over the last several decades.

Where is tornado alley?

Tornado Alley is a nickname invented by the media for a broad area of relatively high tornado occurrence in the central U. S. Various Tornado Alley maps look different because tornado occurrence can be measured many ways: by all tornadoes, tornado county-segments, strong and violent tornadoes only, and databases with different time periods. Please remember, violent or killer tornadoes do happen outside “Tornado Alley” every year.

When are tornadoes most likely?

Tornado season usually refers to the time of year the U.S. sees the most tornadoes. The peak “tornado season” for the Southern Plains is during May into early June. On the Gulf coast, it is earlier during the spring. In the northern plains and upper Midwest, tornado season is in June or July. But, remember, tornadoes can happen at any time of year. Tornadoes can also happen at any time of day or night, but most tornadoes occur between 4–9 p.m.

What is the difference between a Tornado WATCH and a Tornado WARNING?

A Tornado WATCH is issued by the NOAA Storm Prediction Center meteorologists who watch the weather 24/7 across the entire U.S. for weather conditions that are favorable for tornadoes. A watch can cover parts of a state or several states. Watch and prepare for severe weather and stay tuned to NOAA Weather Radio to know when warnings are issued.

A Tornado WARNING is issued by your local NOAA National Weather Service Forecast Office meteorologists who watch the weather 24/7 over a designated area. This means a tornado has been reported by spotters or indicated by radar and there is a serious threat to life and property to those in the path of the tornado. ACT now to find safe shelter! A warning can cover parts of counties or several counties in the path of danger.

Watch this Youtube video for a great explanation!

How is tornado strength rated?

The most common and practical way to determine the strength of a tornado is to look at the damage it caused. From the damage, we can estimate the wind speeds. An “Enhanced Fujita Scale” was implemented by the National Weather Service in 2007 to rate tornadoes in a more consistent and accurate manner. The EF-Scale takes into account more variables than the original Fujita Scale (F-Scale) when assigning a wind speed rating to a tornado, incorporating 28 damage indicators such as building type, structures and trees. For each damage indicator, there are 8 degrees of damage ranging from the beginning of visible damage to complete destruction of the damage indicator. The original F scale did not take these details into account. The original F Scale historical data base will not change. An F5 tornado rated years ago is still an F5, but the wind speed associated with the tornado may have been somewhat less than previously estimated. A correlation between the original F Scale and the EF Scale has been developed. This makes it possible to express ratings in terms of one scale to the other, preserving the historical database.

How do tornadoes form?

The truth is that we don't fully understand. The most destructive and deadly tornadoes occur from supercells, which are rotating thunderstorms with a well-defined radar circulation called a mesocyclone. (Supercells can also produce damaging hail, severe non-tornadic winds, unusually frequent lightning, and flash floods.) Tornado formation is believed to be dictated mainly by things which happen on the storm scale, in and around the mesocyclone. Recent theories and results from the VORTEX2 program suggest that once a mesocyclone is underway, tornado development is related to the temperature differences across the edge of downdraft air wrapping around the mesocyclone. Mathematical modeling studies of tornado formation also indicate that it can happen without such temperature patterns; and in fact, very little temperature variation was observed near some of the most destructive tornadoes in history on 3 May 1999. We still have lots of work to do.

What do storm spotters look for when trying to identify a tornado or a dangerous storm?

Inflow bands are ragged bands of low cumulus clouds extending from the main storm tower usually to the southeast or south. The presence of inflow bands suggests that the storm is gathering low-level air from several miles away. If the inflow bands have a spiraling nature to them, it suggests the presence of rotation.

The beaver's tail is a smooth, flat cloud band extending from the eastern edge of the rain-free base to the east or northeast. It usually skirts around the southern edge of the precipitation area. It also suggests the presence of rotation.

A wall cloud is an isolated cloud lowering attached to the rain-free base of the thunderstorm. The wall cloud is usually to the rear of the visible precipitation area.

A wall cloud that may produce a tornado usually exists for 10–20 minutes before a tornado appears. A wall cloud may also persistently rotate (often visibly), have strong surface winds flowing into it, and may have rapid vertical motion indicated by small cloud elements quickly rising into the rain-free base.

As the storm intensifies, the updraft draws in low-level air from several miles around. Some low-level air is pulled into the updraft from the rain area. This rain-cooled air is very humid; the moisture in the rain-cooled air quickly condenses below the rain-free base to form the wall cloud.

The rear flank downdraft (RFD) is a downward rush of air on the back side of the storm that descends along with the tornado. The RFD looks like a “clear slot” or “bright slot” just to the rear (southwest) of the wall cloud. It can also look like curtains of rain wrapping around the cloud base circulation. The RFD causes gusty surface winds that occasionally have embedded downbursts. The rear flank downdraft is the motion in the storm that causes the hook echo feature on radar.

A condensation funnel is made up of water droplets and extends downward from the base of the thunderstorm. If it is In contact with the ground it is a tornado; otherwise it is a funnel cloud. Dust and debris beneath the condensation funnel confirm a tornado's presence.

How Winter Storms Form

How Winter Storms Form

In North America, winter storms, like other storms at other times of the year, require just the right dynamics for a specific weather type to form.

Some of the ingredients include the proper positioning of the jet stream in the middle latitude regions of the United States. The proximity of a relatively warm air mass accompanied by plenty of moisture flowing up from the south is important.

A sufficient amount of cold polar air flowing down from the north is also needed, cold enough to drop temperatures so that frozen or freezing precipitation will fall.

The intensity of a storm depends upon several items, such as the strength and positioning of the jet stream and associated upper air disturbances, the related strength of the horizontal temperature gradients, and the availability of moisture.

The major moisture sources for winter storms in the United States are the North Atlantic Ocean, the Pacific Ocean, and the Gulf of Mexico.

If cold temperatures are in place and a significant amount of moisture is pumped into a storm system from any of these sources, the result could be a major winter storm.

Winter Storm Development
Winter storms have various components, including low pressure centers, warm fronts, and cold fronts. In the continental United States, winter storms are common from November through April, and sometimes as early as October or as late as May.

The winter dip in the jet stream allows polar air to surge south. This cold, dry air brings with it temperatures cold enough for snow, sleet, or freezing rain to develop.

Warm tropical air filled with moisture from the Gulf of Mexico often continues to flow up from the south during the winter months. When this warm, moist air mass from the south meets the cold, dry air mass from the north, winter storms can result.

Low Pressure Systems 

The term low pressure is used to indicate an area of air pressure that is lower than other areas of pressure around it. Air always moves from areas of high pressure to areas of low pressure.

Winds would blow in a straight line if not for the coriolis force, in which the earth's rotation causes winds to turn as they move away from high pressure areas into areas of low pressure. In the Northern Hemisphere, these winds circulate counterclockwise around areas of low pressure, or cyclones.

As the low develops, the warmer air from the south begins to flow northward on the eastern side of the low. At the same time, colder air from the north flows southward around the low's west side.

Areas of low pressure that produce winter storms often form along a developing or pre-existing frontal boundary. When conditions throughout the troposphere (the lowest layer of the atmosphere) are right, an intense winter storm can form.

Wintertime Warm Fronts
A warm front does not have to wedge and push its way into a colder air mass. Warm air is both lighter and less dense than cold air. Because it is lighter, warm air merely lifts over the cold air it encounters.

The leading edge of a warm air mass encountering a retreating cold air mass is a warm front. As a warm front approaches, the clouds become thicker and lower in the sky. These clouds produce a variety of precipitation types.

Wintertime Cold Fronts
The leading edge of an advancing cold air mass that displaces warm air in its path is called a cold front. Because cold air is heavier and more dense than warm air, an advancing cold front must wedge its way under a warm air mass, then lift and push it out of the way.

Gusty winds and a sharp drop in temperature often accompany and follow cold fronts in winter.

 

Lake Effect Snow

Lake Effect Snow 

Lake effect snows occur when a mass of sufficiently cold air moves over a body of warmer water, creating an unstable temperature profile in the atmosphere.

As a result, clouds build over the lake and eventually develop into snow showers and squalls as they move downwind. The intensity of lake effect snow is increased when higher elevations downwind of the lake force the cold, snow-producing air to rise even further.

The most likely setting for this localized type of snowfall is when very cold Arctic Air rushes over warmer water on the heels of a passing cold front, as often happens in the Great Lakes region during winter.

Winds accompanying Arctic air masses generally blow from a west or northwest direction, causing lake effect snow to fall on the east or southeast sides of the lakes.

Whether an area gets a large amount of snow from lake effect is dependent on the direction of the winds, the duration they blow from a particular direction, and the magnitude of the temperature difference between the water and air.

Since cold air can hold very little moisture and the low level of the atmosphere is quite unstable, clouds form very rapidly, condensation occurs and snow begins to fall. Lake effect snow is lighter than snow that forms from frontal stratus or nimbostratus

Areas of relatively high elevation downwind of the Great Lakes generally receive heavier amounts of lake effect snow than do other locations in this region.

For example, residents of the Tug Hill Plateau in New York State east of Lake Ontario can spend the winter months digging out of anywhere from 200 to 300 inches of snow. Likewise, the mountains of West Virginia can receive over 200 inches of snow in a winter, helped by the lake effect.

The only other lake that produces significant lake effect snow in the United States is the Great Salt Lake in Utah.

Cape Cod Bay in Massachusetts and Chesapeake Bay in Maryland and Virginia, on occasion, produce what is called bay effect snow. Bay effect snow forms in the same manner as lake effect snow, only over the ocean.

Ask Tom why: How often has Chicago's barometric pressure dropped below 29.00 inches?

 

Dear Tom

About a year ago, Chicago was hit by a severe storm with record low pressure. How often has Chicago's barometric pressure dropped below 29.00 inches? —Martin Jarebek, Chicago

  Dear Martin,

The Oct. 26, 2010, storm battered Chicago and the Midwest with high winds, severe thunderstorms and some tornadoes. Chicago's official barometric pressure dropped to 29.00 inches, an October record. Chicago climatologist Frank Wachowski noted that barometer readings below 29.00 inches are rare here, occurring in only 18 storms dating back to 1871. March and December have each logged five storms with pressures less than 29.00 inches, followed by January with four and February and April with two each. The city's last low pressure encounter was on Dec. 9, 2009, when the barometric pressure dropped to 28.92 inches. Chicago's all-time lowest pressure was 28.70 inches on March 12, 1923.

Hurricane Sandy dumped 11bn gallons of raw sewage in eastern US waterways

Hurricane Sandy dumped about 11bn gallons of raw and untreated sewage into waterways from Washington DC to Connecticut, the science journalism group Climate Central said on Tuesday. That's or enough human waste to cover New York's Central Park in 41ft of sewage, or fill 17,000 Olympic-sized swimming pools, scientists told a conference call with reporters.

The group, which drew on data from the Environmental Protection Agency, state protection agencies and water treatment plants, said most of the outflow during the storm, which hit the eastern US in October last year, was caused by storm surges, which overwhelmed sewage treatment plants. But power shutdowns – and heavy rain in Washington DC – also played a part. A third of the sewage was untreated.

The scientists said the report exposed yet another risk factor to America's crumbling infrastructure, due to climate change.

New York City authorities have been working for years to reinforce the city's subway system, which is vulnerable to flooding, and to shore up power stations, which are located along the coast. The scientists said that in the wake of Sandy, when storm surges raised waters more than 9ft above the high tide mark, it was time to look at waste-treatment plants.

"Our sewage infrastructure isn't built to withstand such surges and we are putting our property, safety and lives at risk if we don't adequately plan for these challenges," said Alyson Kenward, a senior scientist and research manager for Climate Central, adding that almost all of the sewage had ended up in New Jersey and New York. It was unclear, however, what the effects were on human health.

The estimated cost of repairs to New York and New Jersey's sewage treatment plants could reach $4.7bn. "In the long run, sea-level rise is going to force us to rework our infrastructure physically if we are going to keep it intact," she said.

Floods create a muddy Middle East

Torrential downpours have caused flash-flooding across parts of the Middle East. The worst of the rain began to develop across the southern half of the Arabian Peninsula three days ago.

Qatar remains on the northern edge of a line of heavy showers which stretch from central parts of Saudi Arabia, through the UAE and right across Oman. This unsettled weather has tended to edge northwards then and south, spreading the rain across a greater area for a time, but essentially it is stuck over the same area. 

At times there has also been heavy rain affecting Yemen leading to the flooding shown in some these pictures. Rainfall totals have been in the range of 30 to 50mm over a 24 hour period. 

The heaviest rain reported is 51mm at Qalhat, which lies 170km to the southeast of Muscat. This unusually wet weather is expected to remain across the region for much of this week with signs of drier weather finally returning by Friday.
http://www.aljazeera.com/weather/2013/04/201342810447251587.html

Severe storms cause Mississippi mayhem

A state of emergency has been declared across much of the Midwest in the USA after heavy rain caused widespread flooding.  At least three people are known to have died as rivers, streams and creeks overflowed. No less than six states have been affected. On Sunday, more than 45 rivers or streams were in major flood in parts of Missouri, Iowa, Illinois, Wisconsin, Indiana and Michigan. The floods have reached record levels in parts of Illinois and Michigan. The rain was heavy enough in Chicago to rip open a sinkhole large enough to swallow three cars. One driver required hospital treatment. Burlington, Iowa saw the Mississippi River reach its fourth highest level since records began after severe weather brought hail storms and 175mm of rain to the region. A number of people were trapped in their cars and there were mudslides with dozens of roads and bridges damaged or blocked. In Indiana, the high waters threatened several towns, forcing hundreds of people to evacuate their homes. The Wabash River in Tippecanoe County reached its highest level since 1958. The flooding is set to linger for some time yet and the river levels in parts of southern Illinois and Missouri may not crest until later this week. Worse still we do expect further rain across much of the Midwest throughout much of Monday night and Tuesday. We could see a further 25 to 30mm of rain affecting parts of Wisconsin into Missouri. At the same time we could also see a further 15cm of new snow over the Black Hills of South Dakota. Concerns are further heightened by the heavy snow already lying across northern parts of the Midwest as a result of the long protracted winter. We are likely to see subsequent flooding from this when the thaw sets in over the coming weeks and makes its way into tributaries of the Missouri and Mississippi rivers.

http://www.aljazeera.com/weather/2013/04/201342294436422738.html

Welcome rain for drought-hit New Zealan

Heavy rain has put an end to New Zealand’s most widespread drought in 30 years. Farmers here welcomed the downpours over the weekend, but despite the rain, much of New Zealand expects to keep a drought declaration in place until September.

The heavy rain set in on Saturday and most of the country has seen heavy and persistent rainfall for the last three days. The city of Tauranga was soaked with over 210mm of rain over the weekend, which caused some flooding.

The drought began in December and gradually extended right across the North Island. Farmers estimate losses approaching two billion New Zealand Dollars (US $1.7B) in export earnings after they were forced to reduce their herds and cut back on milk production. This amounts to around one per cent of the economy.

Global dairy prices have risen over the past six weeks, partly in response to the drought. The rain does provide some relief to dairy farmers who are now busy planting grass seed to try to take advantage of the rain.

The financial effects are likely to be felt for at least another year and government officials have kept in place an official drought designation. This will allow farmers to continue receiving temporary financial assistance.

The rain is now easing and we expect the week ahead to be one of sunshine and showers. The heaviest showers will be along the western side of the country. Drier weather should set in once again as we head towards the weekend.

A 'normal' monsoon

he Indian Meteorological Department announced on Friday that they expect ‘normal’ rainfall in this year’s monsoon.

India is one of the largest producers of rice, sugar, wheat and cotton in the world, and the annual rains, dubbed the ‘economic lifeline’, are essential to the livelihood of millions of people throughout the country.  

If the monsoon brings too much or too little rain, this can lead to ruin for many farmers. 2008 was one of those years with far too much rain. Crops and homes were washed away, and over 2400 people lost their lives. Just one year later, in 2009, there was the opposite problem and rains failed, leading to shrivelled crops and soaring food prices.

The announcement of ‘normal rains’ will be received with great optimism, but also caution; The Indian Meteorological Department has been wrong before. The worst forecast was in 2009, when it predicted an average monsoon, but what followed was the worst monsoon in nearly four decades.

Even with an ‘average’ amount of rain across the country as a whole, it is almost certain that some locations still will receive too much whilst other places will be crying out for more.

The monsoon rains are vitally important to millions of farmers throughout India, and are invariably a cause of great anxiety.

Awesome Aussie weather

In a slow changing of the seasons we have seen winter outstay its welcome in the northern hemisphere. Likewise, summer has been reluctant to leave some areas south of the equator.

Sydney, Australia continues to bathe in summer-like warmth. As of Monday, the temperature here reached 26 Celsius for the fourth day in a row. 

It has now been 45 years since the city has been as warm this late in the year. Indeed, in the past 150 years Sydney has only once seen such heat this late in the season, and that was back in 1968.

This pleasant taste of late summer did make for a lovely Anzac weekend and final weekend of the school holidays. Temperatures look set to stay in the mid-twenties until later in the week, when a typical autumnal weather front will move through the region by Thursday morning.

Rain or showers are expected across parts of New South Wales as the front goes through. Some parts will see their first rainfall so far this April, bringing a close to what is likely to be their driest April in more than a decade.

Away from here, there is some very heavy rain around, and its not too far away. Just to the north of the Coral Sea, we are watching for the possible formation of a late season tropical storm. This could bring flooding to the Coral Sea Islands as it edges away from the Solomon Islands.

Elsewhere, until recently, the South African Weather Service has been issuing warnings for dangerously hot and humid conditions across the country. It has taken some time, but the uncomfortably sticky weather is only just starting to fall away. 

Meanwhile, Brazil is still struggling to cope with the worst drought in 50 years across the northeast of the country. The seasonal rains have arrived in some parts here, but many of the driest areas remain in a state of severe deficit.

The rain in Spain turns to snow on the Plain

While the eastern Mediterranean has been enjoying a taste of summer with temperatures approaching 30 Celsius, further west it has been a very different story.

An area of low pressure, that had its origins over North Africa, has moved across the Mediterranean Sea, into the Iberian Peninsula.  

It has brought thick cloud and heavy rain. Combined with cold air from the Alps which has been drawn in from the northeast, temperatures have been dragged down to well below the late April average.

The whole of the peninsula has been affected. Holidaymakers hoping to escape chilly weather in more northern parts of Europe will have been disappointed to find the Algarve of Portugal and the Spanish Costas all experiencing overcast, wet weather with temperatures lower than in their home countries.

In the nation’s capital, Madrid, where temperatures can be expected to reach 20C in late April, the mercury reached just 8C on Sunday after an overnight minimum of 2C, the lowest since 2001.

Even as far north as Barcelona, temperatures have been as much as six to seven degrees below average.

In some areas temperatures were low enough to produce significant snowfall, with the Asturias region in the north being particularly badly affected. A snow depth of 18cm was reported at the ski resort of Navacerrada, in the Sistema Central mountains, northwest of Madrid.

During Monday, 26 provinces were subject to bad weather alerts. Snowploughs were deployed to keep motorways open and the emergency services warned against all unnecessary travel.

It is expected that the precipitation will die out over the next day or two and temperatures will return to normal, and it could turn out to be a warm weekend in southern areas.

Satellites show summer 2012 sea ice covering the Arctic Ocean shrunk to a record low

During the winter, frozen sea ice covers most of the Arctic Ocean. Every summer, a portion of that ice melts away. Government scientists who keep track of those losses during the warmer months now report this summer has been one for the record books.

On August 26, Arctic sea ice cover fell to 4.1 million square kilometers (about 1.6 million square miles). That’s the smallest ice cover ever observed since scientists started using satellite data in 1979 to measure the yearly melt, note researchers at the National Snow and Ice Data Center (NSIDC) in Boulder, Colo.

“The ice cover is now just so thin and weak in the springtime that large parts of it can’t survive the melt season,” Mark Serreze told Science News. He is an environmental scientist and director of the NSIDC. Melt season in the Arctic typically runs from March through September.

Arctic sea ice plays an important role in Earth’s climate. Unlike glaciers and icebergs, which form from freshwater, sea ice forms when seawater freezes. Usually covered with snow, this ice cools the area around the north pole. The bright-white surface of sea ice reflects sunlight back into space like a giant mirror. During summer, when the ice melts, the ocean’s dark waters become exposed. The result: Less light gets reflected. Seawater heats up as it now absorbs this incoming energy, warming the near-surface temperature of the Arctic Ocean even more.

Satellite data show that Arctic sea ice has hit a new low. The white area shows the extent of Arctic sea ice as of September 3. The orange line shows how much sea ice usually covers the ocean around this time of year.
Credit: National Snow and Ice Data Center

This year’s sea ice probably hasn’t reached its lowest point yet. Every year, scientists watch for the Arctic sea ice minimum, which is the day when that ice cover shrinks to its lowest. This usually happens during September, and this year’s minimum will definitely be the lowest on record.

The ice cover is not only getting smaller in area, but what remains is also getting thinner. The Arctic’s sea ice used to be 3 to 4 meters thick (about 10-13 feet). Now most of it is about half that thick.

“It’s almost like parts of the Arctic have become a giant slushee at this time of year,” says Walt Meier, a sea ice expert at NSIDC. As the ice thins, it also weakens. That may allow it to break up easier when a big storm hits. “The Arctic is becoming like a fighter with a glass jaw,” he told Science News.

As autumn hits, the water will start to refreeze. This year, there will be less sea ice to start with than in years past. So there could be even less sea ice next spring when the annual melt begins again.

“It sets us up for another world of hurt next year,” Serreze told Science News.

Satellites, coral reefs, ancient Roman fishponds and sinking cities help us understand how humans are changing sea level

Visit the beach on a hot afternoon and you may not realize it, but someone — or rather something — is watching from above. If you stand in the right place, the silent watcher’s invisible spotlight will pass right over you, like the spotlight of a police helicopter flitting overhead.

That aerial observer zooming over your head is the Jason-2 satellite. It flies 1,340 kilometers (832 miles) high — as far above the ground as New York City is from Chicago. It travels 25,000 kilometers per hour, 27 times as fast as a commercial jet. And it circles Earth a little over 12 times a day.

Two thousand times per second, Jason-2’s spotlight — pointed down at Earth — flashes on for an instant. It isn’t a flash that you could see even if you were looking. The spotlight is throwing off radio waves, which are invisible to the eyes of humans and other animals. Those waves ripple down to Earth and bounce off of its surface, back into space. A computer aboard the satellite times exactly how long those reflected radio waves take to return — usually, about nine-thousandths of a second.

The Jason-2 satellite before it was launched into orbit. Circling Earth at an exact height, the satellite measures sea surface by beaming radio waves down to the planet and timing how long they take to bounce back. Credit: NASA Jet Propulsion Laboratory

By measuring how long the signal takes to bounce back, Jason-2 can measure the distance between itself and Earth’s surface. The satellite was launched into space to measure sea-surface heights. Or, more to the point, Jason-2 is measuring how quickly the planet’s seas are rising.

Scientists these days are worried about sea level. As Earth warms, the surface of the ocean is creeping upward. This creep is happening partly because saltwater expands a tiny bit as it warms. “Warmer water literally is taller,” explains Josh Willis. He’s a climate scientist at the NASA Jet Propulsion Laboratory in Pasadena, Calif.

Sea level also is rising because warm temperatures have prompted glaciers in Antarctica, Greenland and other usually cold places to melt more quickly. Glaciers are essentially rivers of ice, and their melting adds freshwater to the ocean. Antarctica and Greenland are together losing about 350 cubic kilometers of ice per year — enough meltwater to fill up 80,000 Yankee baseball stadiums. Spread over the world’s oceans, that meltwater alone raises sea level about 1 millimeter (1/25^th of an inch) or so each year.

Jason-2 has shown that overall, sea level is currently rising about 2.4 millimeters per year — a little more than the thickness of a quarter.

That may not sound like much — but those quarters stack up year after year. This slow rise is expected to cause flooding in many of the world’s coastal cities in the next 50 to 100 years. Worse yet, the speed of sea level rise is also expected to grow. Seas may eventually rise four to eight times faster than they are today.

The high life

Donald Barber was an astronomer at Norman Lockyer Observatory. Its telescopes sat on a grassy hill surrounded by farmland on the south coast of England. Barber was using the telescopes to measure the light from far-off stars. He captured the starlight in photographs produced on glass plates coated with chemicals, like the film in an old camera. It was only after Barber developed those photographic plates in the summer of 1937 that the first signs of tiny alien invaders emerged.

As Barber developed his photographs, he found they were ruined. Thousands of strange black dots covered the images. Barber looked at the glass plates through a microscope and discovered the culprit: At the center of each black dot was a tiny island of life, a clump of single-celled bacteria too small for the unaided eye to see.

Barber figured out that the germs were drifting down from the sky and into a rooftop tank of water that he drew from to develop his pictures. The bacteria had unusual abilities. Somehow they could grow in the poisonous chemicals on the photographic plates — chemicals that killed most other living things. When Barber sent some of the germs to a government lab, the researchers there told him that they had never seen bacteria like these before.

Evolution of a Frankenstorm

Two nights before Halloween, as kids were putting the finishing touches on their costumes, an immense hurricane called Sandy crashed into New Jersey. It came ashore near Atlantic City. The storm, which had already killed 69 people as it powered through the Caribbean Sea, pummeled nearly one-third of the eastern United States. It caused tens of billions of dollars worth of damage and killed more than 100 additional people.

Heat, Flood or Icy Cold, Extreme Weather Rages Worldwide

WORCESTER, England — Britons may remember 2012 as the year the weather spun off its rails in a chaotic concoction of drought, deluge and flooding, but the unpredictability of it all turns out to have been all too predictable: Around the world, extreme has become the new commonplace.

Frozen in Place and Time

Spring arrived last week in New York, bringing warm days and a bumper crop of daffodils to grassy patches all around the city. In Los Angeles, the weather was — predictably — pleasant.