Natural variation: Warm North Atlantic Sea encourages extreme winters in U.S. and Europe

The ultimate cold temperature observed across Europe and also the new england of america in recent winters might be partially lower to natural, lengthy-term versions in ocean surface temps, according to a different study released today.

Scientists in the College of California Irvine have proven that the phenomenon referred to as Atlantic Multidecadal Oscillation (AMO) -- an all natural pattern of variation in North Atlantic ocean surface temps that switches between an optimistic and negative phase every 60-70 years -- can impact an atmospheric circulation pattern, referred to as North Atlantic Oscillation (NAO), that influences the temperature and precipitation within the Northern Hemisphere in the winter months.

Once the AMO is within its positive phase and also the ocean surface temps are warmer, the research has proven the primary effect in the winter months would be to promote the negative phase from the NAO which results in "obstructing" episodes within the North Atlantic sector, permitting cold temperature systems to exist within the eastern US and Europe.

The outcomes happen to be released today, Wednesday 2 April, in IOP Publishing's journal Environment Research Letters.

To reach their results, the scientists combined findings in the past century with climate simulations from the atmospheric reaction to the AMO.

Based on their findings, ocean surface temps within the Atlantic can depend on 1.5 ?C warmer within the Gulf Stream region throughout the positive phase from the AMO in comparison towards the negative, cooler phase. The weather simulations claim that these anomalies in ocean surface temps can enjoy a predominant role in marketing the modification within the NAO.

Lead authors from the study Yannick Peings and Gudrun Magnusdottir stated: "Our results indicate the primary aftereffect of the positive AMO in the winter months would be to promote the appearance of the negative phase from the NAO. An adverse NAO in the winter months usually goes hands-in-hands with cold temperature within the eastern US and north-the european union.Inch

The findings also suggest that it requires around 10-fifteen years prior to the positive phase of AMO has any important effect around the NAO. The reason behind this lag is unknown however, a reason may be that AMO phases make time to develop fully.

Because the AMO has been around an optimistic phase because the early the nineteen nineties, it might have led towards the extreme winters that both US and Europe have observed recently.

The scientists warn, however, the future evolution from the AMO remains uncertain, with lots of factors potentially affecting the way it interacts with atmospheric circulation designs, for example Arctic ocean ice loss, alterations in photo voltaic radiation, volcanic eruptions and levels of green house gases within the atmosphere.

The AMO also shows strong variability in one year to another additionally towards the changes seen every 60 - 70 years, which causes it to be hard to attribute specific extreme winters towards the AMO's effects.

Reacting towards the extreme weather that held the eastern coast of america this winter, Yannick Peings ongoing: "Unlike the 2012/2013 winter, this winter had rather low values from the AMO index and also the pattern of ocean surface temperature anomalies wasn't in conjuction with the typical positive AMO pattern. Furthermore, the NAO was mostly positive having a relatively mild winter over Europe."

"It is therefore unlikely the positive AMO performed a determining role around the new england of america, although further jobs are essential to answer this. This kind of event is in conjuction with the large internal variability from the atmosphere, along with other exterior forcings might have performed a job.

"Our future studies will turn to compare the function from the AMO in comparison to Arctic ocean ice anomalies, which are also proven to affect atmospheric circulation designs and promote cooler, more extreme winters."

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North Atlantic atmospheric oscillation affects quality of cava

The standard of cava is dependent on technical factors for example fermentation, aging and bottling processes, which often remain stable for a long time. Scientists from Malaga College (The country) have found that shake within the North Atlantic -that affects European climate- also impact the characteristics of the sparkling wine. Time by which there's existence of the Azores anticyclone, there's a stop by the standard of cava.

The scientists Raimundo Real and Jos? Carlos B?ez, in the College of Malaga, have analysed the potential results of its northern border Atlantic oscillation, known in scientific literature as NAO, on the standard of The spanish language cava inside a study released within the Worldwide Journal of Biometeorology.

The NAO is really a microclimate index that reflects the atmospheric pressure distinction between the Azores and Iceland, so the existence of an anticyclone within the Azores is positive which is negative if you will find regions of low pressure for the reason that same area. This pressure difference that oscillates with time, has an effect around the climate conditions within the Iberian Peninsula.

"We discovered there is an association between your NAO and the standard of cava between 1970 and 2008. The presence of positive NAO values throughout the several weeks of March to August, once the grape is developing and ageing, reduced the capability of acquiring high quality cava," Raimundo Real told SINC.

Its Northern Border Atlantic oscillation plays a significant role in weather fluctuations within the hemisphere. The phenomenon affects the weather in Europe and also the Iberian Peninsula. It relates to temperature and rain versions in cava creating regions, which affects the physiological processes throughout the grape's duration of maturity.

"The probability of acquiring a high quality cava is greater once the average worth of the NAO is negative. This will make the typical temperature within the cava region drop and the standard enhances," the expert described.

Inter-annual versions in the standard of cava are determined based on the different aromas and the quantity of sugar within the grape. These characteristics from the plant consequently, in a single section of production, rely on climate conditions, for example cloud cover, temperature and rain fall that the guarana plant is exposed, particularly throughout the grape period (March to September).

Predicting time of top-quality cava

The weather within the Atlantic Sea, the med basin and also the surrounding continents shows considerable weather variability.

"Throughout 1 / 2 of time we analysed, the NAO values are intermediate and don't clearly affect the standard from the cava, however in another half, the tend to be more extreme and result in clearly favorable or unfavorable conditions for acquiring top-quality," states Real.

The data for 2012 pointed towards an 80% probability of acquiring a high-quality cava, although this odds are around 45% for 2013, always based on the model acquired. The model properly predicted the 80% for that clearly favorable years for acquiring top-quality cava and also the 70% probability of the clearly unfavorable years.

The NAO value between March and August could be calculated in the wine the harvest, while the standard from the cava are only able to be valued 2 yrs later. "This will be significant for having the ability to predict many years of top-quality cava production, too for going through the potential side effects and versions of global warming on the standard" he came to the conclusion.

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Sandy retired from list of Atlantic Basin tropical cyclone names

April 11, 2013

This NOAA GOES-13 satellite image taken on October 29, 2012 shows the storm as it is centered off of Maryland and Virginia. 

Download here. (Credit: NOAA.)

Sandy has been retired from the official list of Atlantic Basin tropical cyclone names by the World Meteorological Organization’s hurricane committee because of the extreme impacts it caused from Jamaica and Cuba to the Mid-Atlantic United States in October 2012.
Storm names are reused every six years for both the Atlantic and eastern North Pacific basins. If a storm is so deadly or costly that the future use of the name would be insensitive or confusing, the WMO hurricane committee, which includes personnel from NOAA’s National Hurricane Center, may retire the name. Sandy is the 77th name to be retired from the Atlantic list since 1954. The name will be replaced with “Sara” beginning in 2018.
Sandy was a classic late-season hurricane in the southwestern Caribbean Sea. The cyclone made landfall as a category 1 hurricane (on the Saffir-Simpson Hurricane Wind Scale) in Jamaica, and as a 115 mph category 3 hurricane in eastern Cuba.  Hurricane Sandy merged with a frontal system hours before making landfall as a post-tropical cyclone near Brigantine, N.J., and its size and strength caused catastrophic damage all along the mid-Atlantic shoreline.

Because of its tremendous size, Sandy drove a catastrophic storm surge into the New Jersey and New York coastlines. Preliminary U.S. damage estimates are near $50 billion, making Sandy the second-costliest cyclone since Katrina to hit the United States. There were at least 147 direct deaths recorded across the Atlantic basin due to Sandy, with 72 of these fatalities occurring in the mid-Atlantic and northeastern United States. Sandy caused the greatest number of U.S. direct fatalities related to a tropical cyclone outside of the southern states since Hurricane Agnes in 1972.

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Explorers discover northernmost Atlantic seeps, deep-sea canyon diversity, off U.S. Northeast

August 2, 2013

Alongside the diverse coral community in Hydrographer Canyon, ROV Deep Discoverer observed a glass sponge containing cephalopod eggs. If you look closely you can see what looks to be a recent hatchling! (Cephalopods include squids, cuttlefishes and octopuses.)

High resolution (Credit: NOAA Okeanos Explorer Program/2013 Northeast U.S. Canyons Expedition)

Ocean explorers in July on NOAA Ship Okeanos Explorer discovered a wide diversity of seafloor features and communities of life in the largely unexplored deep-sea canyons off the northeast U.S. coast. Now through August 16, as the expedition continues, the public can join the mission as “citizen scientists,” at oceanexplorer.noaa.gov/okeanos, to see live seafloor video and listen as scientists discuss their observations in real time. During the expedition’s July leg, there were nearly 60,000 visits to the live streaming video.

Canyons represent some of the most striking features of the continental slope off the U.S. East Coast and may also be among the most productive areas in the deep sea. Organic matter and nutrient-rich sediments are often concentrated in these areas and strong currents flow through the steep and rugged terrain of the canyons, exposing hard substrates. With an increase in food availability and a variety of different habitat types across varying depths, submarine canyons may contain higher biodiversity and biomass than the adjacent continental slope, and are likely places to observe deep-sea corals, sponges, and other deep-sea marine organisms.

Close-up of methane hydrate observed at a depth of 1,055 meters, near where bubble plumes were detected in previous sonar data. Pressure and cold temperatures create methane hydrate where molecules of natural gas are trapped in an ice-like cage of water molecules. Methane hydrates, a hydrate patch and chemosynthetic communities were seen during this dive, but no active seepage was observed. Seeps were investigated at other locations.

High resolution (Credit: NOAA Okeanos Explorer Program/2013 Northeast U.S. Canyons Expedition)

During the July leg of the expedition, the ship’s multibeam sonar detected bubbles rising from the seafloor in several locations about 90 nautical miles southeast of Nantucket, Mass. These water-column plumes were traced to seafloor seeps where explorers observed chemosynthetic communities of life supported by chemicals rather than by sunlight. These are the northernmost seeps detected to date on the U.S. Atlantic margin.

The discoveries are expected to help fisheries and other ocean resource managers make better-informed decisions about how to manage, use and protect the ocean and its resources. Scientists believe the need to learn more about these relatively undisturbed canyon ecosystems is becoming more urgent, particularly as the potential for fishing, marine mining, and hydrocarbon exploration extends into the deep sea.

“We found these little-explored canyons are highly dynamic,” said Tim Shank, a deep-sea biologist from Woods Hole Oceanographic Institution, who participated from ashore. “With each dive of the ROVs (remotely operated vehicles that are undersea robots with cameras), we documented vertical walls with jagged rock failures, collapsed features, and extensive debris fields. Each canyon also appeared to host different biological communities — even different depths within the same canyon would reveal different types of coral and sponge ecosystems.

“As we explored different sides and depth zones of these canyons, we discovered a broad physical and biological diversity,” said Shank. “One canyon would host great animal diversity but low animal abundance and the next canyon would reveal just the opposite. As with any new deep-sea region we explore, we observed many suspected new species and remarkable range extensions of known species. All these observations will be highly informative to design and implement ocean conservation and management strategies in the near future.”

ROV Deep Discoverer investigates the geomorphology of Block Canyon.

High resolution (Credit: NOAA Okeanos Explorer Program/2013 Northeast U.S. Canyons Expedition)

Explorers also observed several instances of new coral life establishing itself, hundreds of skate and cat shark eggs on the seafloor and attached to deep-sea corals, and numerous octopus and squid guarding clutches of eggs. Initial impressions revealed these canyons are hot spots for biodiversity, hosting more than 25 species of corals, and hundreds of associated animals.

Andrea Quattrini, a Ph.D. student from Temple University in Philadelphia, said the expedition provided an immense opportunity for the ocean science and management communities to educate and train the next generation of explorers and deep-sea scientists.

“Their ability to interact with thirty to forty scientists with different areas of expertise, and the free exchange of ideas and discussion, further advanced the exploration and findings by defining new questions and outlining exciting avenues for future research,” she said.

Teachers may take advantage of an Expedition Educational Module at http://go.usa.gov/jn2h. The site provides products tied to the expedition including standards-based lesson plans and ocean-career connections.

Brendan Roark, a geographer from Texas A&M University who participated in the expedition from the ship, believes corals in the area may live as long as 4,000 years. “Deep-sea corals provide a new archive that can help us reconstruct past ocean and climate conditions,” he said. “They grow in a shrub-like fashion and most importantly, they deposit annual growth rings much like trees do. Because of their extremely long life spans, they may develop high resolution records of oceanographic and climate variability.”

An international team of more than 40 scientists and students – partners from multiple federal agencies and academic institutions – located mostly on shore, participated in the expedition’s first leg, receiving data and live video from the ship via telepresence-technology, using satellite and Internet pathways. The science team included several scientists at sea and others in Washington D.C., 12 U.S. states and two nations.

Scientists on the expedition’s July leg mapped 7,209 square kilometers of seafloor as they explored areas between 560 meters (1,837 feet) and 2,135 meters (7,005 feet) deep, in and between Block, Alvin, Atlantis, Veatch and Hydrographer canyons. The second leg is exploring Welker, Oceanographer, Lydonia, Nygren and Heezen canyons as well as Mytilus Seamount, one of the easternmost seamounts along the submerged northeast New England Seamount Chain within the U.S. Exclusive Economic Zone. Very little information exists for these areas. Scientists on both expedition legs are obtaining valuable data using the latest technologies including state-of-the-art multibeam sonar and NOAA’s new 6,000-meter ROV, Deep Discoverer, coupled with the Seirios camera sled and lighting platform.

NOAA Fisheries’ Deep-Sea Coral Research and Technology Program and the Northeast Regional planning team contributed scientific and financial support to this expedition. The program provides scientific information needed by NOAA and regional management councils to conserve and manage the nation’s deep-sea coral ecosystems.

NOAA’s Ocean Exploration Program is the only federal program dedicated to systematic exploration of the planet’s largely unknown ocean. NOAA Ship Okeanos Explorer is operated, managed and maintained by NOAA’s Office of Marine and Aviation Operations which includes commissioned officers of the NOAA Corps and civilian wage mariners. NOAA’s Office of Ocean Exploration and Research operates, manages and maintains the cutting-edge ocean exploration systems on the vessel and ashore.

NOAA’s mission is to understand and predict changes in the Earth's environment, from the depths of the ocean to the surface of the sun, and to conserve and manage our coastal and marine resources. Join us on Facebook, Twitter and our other social media channels.

Close up view of a stalked crinoid’s (sea lily) mouth and arms. At least two species of crinoids were noted during a dive at Block Canyon, including stalked crinoids.

High resolution (Credit: NOAA Okeanos Explorer Program/2013 Northeast U.S. Canyons Expedition)

Corals, including cup corals and bubblegum corals reside on the hard substrate near the edge of a mussel bed.

High resolution (Credit: NOAA Okeanos Explorer Program/2013 Northeast U.S. Canyons Expedition)

NOAA Ship Okeanos Explorer, “America’s Ship for Ocean Exploration,” is the only federally funded U.S. ship assigned to systematically explore our largely unknown ocean for the purpose of discovery and the advancement of knowledge. Telepresence, using real-time broadband satellite communications, connects the ship and its discoveries live with audiences ashore.

High resolution (Credit: NOAA Okeanos Explorer Program/2013 Northeast U.S. Canyons Expedition)

During NOAA Ship Okeanos Explorer’s mid-expedition port visit to New York City, Dave Lovalvo answers questions for visiting Sea Cadets, about NOAA’s new ROV (remotely operated vehicle) Deep Discoverer, behind Lovalvo. The ROV weighs 9,200 pounds in air, and can dive as deep as 6,000 meters (nearly 20,000 feet). Sea Cadets are with the youth program of the Navy League of the United States.

High resolution (Credit: NOAA Okeanos Explorer Program/2013 Northeast U.S. Canyons Expedition)

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Atlantic hurricane season on track to be above-normal

August 8, 2013

Image of Tropical Storm Dorian on July 24, 2013, from NOAA's GOES East satellite.

High resolution (Credit: NOAA)

NOAA issued its updated Atlantic hurricane season outlook today saying the season is shaping up to be above normal with the possibility that it could be very active. The season has already produced four named storms, with the peak of the season – mid-August through October – yet to come.
“Our confidence for an above-normal season is still high because the predicted atmospheric and oceanic conditions that are favorable for storm development have materialized,” said Gerry Bell, Ph.D., lead seasonal hurricane forecaster at NOAA’s Climate Prediction Center, a division of the National Weather Service. “Also, two of the four named storms to-date formed in the deep tropical Atlantic, which historically is an indicator of an active season.”
The conditions in place now are similar to those that have produced many active Atlantic hurricane seasons since 1995, and include above-average Atlantic sea surface temperatures and a stronger rainy season in West Africa, which produces wind patterns that help turn storm systems there into tropical storms and hurricanes.
The updated outlook calls for a 70 percent chance of an above-normal season. Across the Atlantic Basin for the entire season – June 1 to November 30 – NOAA’s updated seasonal outlook (which includes the activity to date of tropical storms Andrea, Barry, Chantal, and Dorian) projects a 70 percent chance for each of the following ranges:

13 to 19 named storms (top winds of 39 mph or higher), including 6 to 9 hurricanes (top winds of 74 mph or higher), of which3 to 5 could be major hurricanes (Category 3, 4 or 5; winds of at least 111 mph)

These ranges are above the 30-year seasonal averages of 12 named storms, six hurricanes and three major hurricanes.

The updated outlook is similar to the pre-season outlook issued in May, but with a reduced expectation for extreme levels of activity. Motivating this change is a decreased likelihood that La Niña will develop and bring its reduced wind shear that further strengthens the hurricane season. Other factors are the lack of hurricanes through July, more variability in the wind patterns across the tropical Atlantic Ocean and slightly lower hurricane season model predictions. In May, the outlook called for 13-20 named storms, 7-11 hurricanes and 3-6 major hurricanes.

“The peak of the hurricane season is almost upon us and it’s important to remain prepared for hurricanes through November," said Joe Nimmich, FEMA Associate Administrator for Response and Recovery. "Make sure to review your family emergency plan, check that your emergency kit is stocked and consider insurance options. Learn more about how you can prepare for hurricanes at www.ready.gov/hurricanes.”

NOAA’s mission is to understand and predict changes in the Earth's environment, from the depths of the ocean to the surface of the sun, and to conserve and manage our coastal and marine resources. Join us on Facebook, Twitter and our other social media channels.

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Miriam downgraded in Pacific; Nadine spins in Atlantic

(AP) MIAMI (AP) -- Forecasters say Miriam is rapidly weakening and has been downgraded from a hurricane to a tropical storm well off Mexico's Baja California peninsula.

The National Hurricane Center in Miami said Miriam had top sustained winds of 70 mph at 5 a.m. EDT Wednesday, down sharply from a day earlier. The storm was centered about 430 miles west-southwest of the southern tip of the Baja peninsula.

Miriam is moving northwest at 6 mph. No coastal watches or warnings are in effect and more weakening is expected.

In the open Atlantic, Tropical Storm Nadine remains far from land. It is about 530 miles south-southwest of the Azores islands with top sustained winds of about 45 mph. Nadine has been spinning in the Atlantic for more than two weeks.

Copyright 2012 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.For more information about reprints & permissions, visit our FAQ's. To report corrections and clarifications, contact Standards Editor Brent Jones. For publication consideration in the newspaper, send comments to letters@usatoday.com. Include name, phone number, city and state for verification. To view our corrections, go to corrections.usatoday.com.

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Miriam downgraded in Pacific; Nadine spins in Atlantic

(AP) MIAMI (AP) -- Forecasters say Miriam is rapidly weakening and has been downgraded from a hurricane to a tropical storm well off Mexico's Baja California peninsula.

The National Hurricane Center in Miami said Miriam had top sustained winds of 70 mph at 5 a.m. EDT Wednesday, down sharply from a day earlier. The storm was centered about 430 miles west-southwest of the southern tip of the Baja peninsula.

Miriam is moving northwest at 6 mph. No coastal watches or warnings are in effect and more weakening is expected.

In the open Atlantic, Tropical Storm Nadine remains far from land. It is about 530 miles south-southwest of the Azores islands with top sustained winds of about 45 mph. Nadine has been spinning in the Atlantic for more than two weeks.

Copyright 2012 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.For more information about reprints & permissions, visit our FAQ's. To report corrections and clarifications, contact Standards Editor Brent Jones. For publication consideration in the newspaper, send comments to letters@usatoday.com. Include name, phone number, city and state for verification. To view our corrections, go to corrections.usatoday.com.

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Atlantic hurricane season closes with 19 named storms (The Christian Science Monitor)

The curtain has fallen on the 2011 Atlantic hurricane season – one that enters the record books in a four-way tie for the third-largest number of named storms on record.

The others: the 1887, 1995, and 2010 seasons.

Tropical Storm Arlene started things off in late June. By the time Nov. 30 arrived, the roster ended with 19 named storms, ending with Tropical Storm Sean in early November.

Indeed, the season might have topped 19 named storms, but forecasters at the National Hurricane Center in Miami didn't catch a blink-and-you'll-miss-it storm in early September that quickly reached tropical-storm status, only to weaken hours later. It spent its brief life well off the US East Coast.

Forecasters noticed the storm as they performed their usual season's-end review of data on Atlantic-basin activity. The review also led to Tropical Storm Nate's promotion to Hurricane Nate.

Although the number of named storms was well above the long-term average of 11, the number of hurricanes and major hurricanes were only slightly above average, according to the center's post-season analysis.

RECOMMENDED: Five things you can do to keep safe in a hurricane

Still, for much of the US East Coast, it was a season to remember.

In late August, Hurricane Irene moved out of the eastern Caribbean and up along the US East Coast. It made landfall three times as it slid up along the East Coast: at Cape Lookout, N.C., at Little Egg Inlet, N.J., as a hurricane, and finally near Coney Island as a tropical storm.

The storm's winds and heavy rains assaulted a landscape along much of the coast and deep into New England whose trees were laden with leaves and whose roots were clinging to soils already saturated from previous rain storms. Storm-felled trees and limbs left 4 million customers without electricity.

From Maryland and Delaware through Maine, 10 states saw record flooding along rivers and streams from Irene's downpours, according to the US Geological Survey, which monitors stream flows.

"Irene broke the 'hurricane amnesia' that can develop when so much time lapses between land-falling storms," said National Weather Service director Jack Hayes in a statement.

All along its path from the Caribbean northward, Irene inflicted an estimated $10.1 billion in damage; the storm reportedly killed 56 people.

Tropical storm Arlene and tropical storm Lee added a combined 46 fatalities to a season that would reach $11.6 billion in damages throughout the Atlantic, Caribbean, and Gulf of Mexico, and 120 casualties.

The season also showcased the advances forecasters have made in providing local emergency managers with timely warnings. Still, efforts are underway to extend storm-track forecasts another two days beyond the current 5-day outlook while reducing the uncertainties in the forecast.

In addition, researchers have placed a heavy emphasis on understanding the drivers behind rapid changes in storm intensity. Last-minute shifts in strength, up or down, ahead of landfall can have a profound effect on the extent of coastline that needs evacuation.

The efforts are being driven in no small part by analyses showing that between 1900 and 2005, damage from landfalling tropical cyclones in the US doubles every 10 years. Costs are rising as more people move to vulnerable coastal areas, triggering the construction of homes, factories, office buildings, and other assets needed to sustain them.

The Monitor's Weekly News Quiz for Nov. 27-Dec. 2, 2011

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Philippe keeps its strength in far Atlantic (AP)

MIAMI – Forecasters say Tropical Storm Philippe is maintaining its strength in the far Atlantic and could become a hurricane, but it's not expected to threaten land.

The storm's center was located Wednesday about 580 miles (930 km) south-southeast of Bermuda and was moving west-northwest at 6 mph (9 kph).

Its maximum sustained winds were 65 mph (100 kph) and Philippe could become a hurricane before moving out to sea. Tropical storm force winds extend outward up to 90 miles (150 km) from the center.

There are no coastal watches or warnings in effect.

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Ophelia expected to strengthen in the Atlantic (AP)

MIAMI – Tropical Storm Ophelia is expected to strengthen into a hurricane as it moves away from the eastern Caribbean island of Dominica.

Ophelia has caused flooding and cut off communities on Dominica. About 1,600 people were stranded on the island and nearly a dozen cars have washed away.

The U.S. National Hurricane Center in Miami said Ophelia is expected to become a hurricane Friday. The storm has maximum sustained winds of 60 mph (97 kph) and is moving northward away from the Leeward Islands. Its forecast to head generally past Bermuda this weekend.

Tropical Storm Philippe is still far from land and moving west-northwest with winds of about 45 mph (72 kph).

In the Pacific, Tropical Storm Hilary has weakened and is expected to become a remnant low by Friday.

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Atlantic Hurricane Season: Words and Phrases to Know (ContributorNetwork)

The Atlantic hurricane season begins on Wednesday and continues through Nov. 30. During this six-month period, conditions in the atmosphere and higher water temperatures in the Atlantic basin are more likely to produce storms ranging from tropical depressions to hurricanes.

What is a tropical disturbance?

A tropical disturbance is an area of moving thunderstorms that continues for at least 24 hours. A tropical disturbance can potentially gain strength over time to become a hurricane.

How does a tropical storm differ from a tropical depression?

The National Hurricane Center in Miami defines a tropical storm as an intense thunderstorm where the maximum sustained wind speed over a one-minute period is 39 mph to 73 mph. A tropical depression is a thunderstorm where the winds reach a maximum sustained speed of 38 mph or less. Both classes of storms form over tropical or subtropical waters from which they draw heat and moisture.

How often does less severe storm gain strength?

In July 2010, a tropical disturbance gained strength and, after being upgraded by the NHC, was renamed Tropical Storm Bonnie. After it crossed South Florida and headed toward the Gulf of Mexico, the NHC clocked Bonnie at 35 mph, downgrading the storm to a tropical depression.

What is a hurricane?

A hurricane is an intense weather system of thunderstorms with a maximum sustained wind speed of 74 mph or higher. In the Northern Hemisphere, the thunderstorms are accompanied by winds that circulate in a counterclockwise motion.

How are hurricanes classified?

The National Oceanic and Atmospheric Administration uses the Saffir-Simpson Hurricane Scale to predict the potential destructive power of a hurricane. Created in 1969 by Herbert Saffir and Bob Simpson, the scale goes from Category 1 (winds of 74 mph to 95 mph) to Category 5 (winds exceeding 155 mph). A Category 5 hurricane has the potential to damage roofs, cause complete building failures and prompt an evacuation of people living within 10 miles of the shoreline.

How often do Category 5 hurricanes occur?

According to NOAA, Hurricane Katrina, one of the strongest hurricanes to impact the United States, was classified Category 3 on the Saffir-Simpson Scale. In the Florida Keys, the Labor Day Hurricane in 1935 was classified as Category 5, with winds reaching a maximum of 200 mph. Hurricane Andrew, another Category 5 hurricane, was clocked at 165 mph when it reached South Florida on Aug. 24, 1992.

What is the long-term forecast for the 2011 Atlantic hurricane season?

For 2011, NOAA is predicting a 65 percent chance of an above-average hurricane season. NOAA cites a two-degree temperature increase in Atlantic Ocean waters as one reason for a more active hurricane season. NOAA also is predicting 12 to 18 named storms and, of that number, 3 to 6 could become major hurricanes (Category 3 or greater).

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