Archive for Thursday, 13 November 2014

What Does the Sahara Desert Have to Do with Hurricanes?

What does the Sahara Desert in Africa have to do with hurricanes in the Atlantic, Gulf of Mexico, and Eastern Pacific Ocean? You might think this sounds a little crazy because hurricanes are very wet and deserts are very dry, but if it weren’t for this huge, hot, dry region in North Africa, we would see far fewer hurricanes in the United States.

The Sahara Desert is massive, covering 10 percent of the continent of Africa. It would be the largest desert on Earth, but based strictly on rainfall amounts, the continent of Antarctica qualifies as a desert and is even larger. Still, rainfall in the Sahara is very infrequent; some areas may not get rain for years and the average total rainfall is less than three inches per year. While not the largest or driest of the deserts, the Sahara has a major influence on weather across the Western Hemisphere.

How a Tropical Storm Starts A-Brewin’

The role the Sahara Desert plays in hurricane development is related to the easterly winds (coming from the east) generated from the differences between the hot, dry desert in north Africa and the cooler, wetter, and forested coastal environment directly south and surrounding the Gulf of Guinea in west Africa. The result is a strong area of high altitude winds commonly called the African Easterly Jet. If these winds were constant, we would also experience fewer hurricanes.

However, the African Easterly Jet is unstable, resulting in undulations in a north-south direction, often forming a corresponding north to south trough, or wave, that moves westward off the West African Coast. When these waves of air have enough moisture, lift, and instability, they readily form clusters of thunderstorms, sometimes becoming correlated with a center of air circulation. When this happens, a tropical cyclone may form as the areas of disturbed weather move westward across the Atlantic.

Throughout most of the year, these waves typically form every two to three days in a region near Cape Verde (due west of Africa), but it is the summer to early fall when conditions can become favorable for tropical cyclone development. Not all hurricanes that form in the Atlantic originate near Cape Verde, but this has been the case for most of the major hurricanes that have impacted the continental United States.

Map of North America with historical tracks of hurricanes in North Atlantic and Northeast Pacific Oceans.

Wave of the Future (Weather)

In fact, just such a tropical wave formed off Cape Verde in mid-August of 1992. Up to that point, there had not been any significant tropical cyclone development in the Atlantic that year. However, the wave did intensify into a hurricane, and on August 24 Andrew came ashore in south Florida as a Category 5 hurricane, becoming one of the most costly and destructive natural disasters in U.S. history … until Sandy. Hurricane Sandy, which eventually struck the U.S. east coast as a post-tropical cyclone, also began as a similar tropical wave that formed off the coast of west Africa in October of 2012.

Some of these “waves” drift all the way to the Pacific Ocean by crossing Mexico and Central America. Many of the Eastern Pacific tropical cyclones originate, at least in part, from tropical waves coming off Cape Verde in Africa. Many of these waves traverse the entire Atlantic Ocean without generating storm development until after crossing Central America and entering the warm Eastern Pacific waters. Then, if the conditions are right, tropical cyclone formation is possible there. Hurricane Iselle, which hit the Big Island of Hawaii on August 8, 2014, was likely part of a wave that formed more than 8,000 miles away off of the West Coast of Africa and an example of the far-reaching influence the Sahara Desert has on our planet’s weather.

While these waves with origins in the Sahara Desert might generate numerous thunderstorms and a pattern with the potential for developing into a tropical cyclone, often the conditions are not quite right. Hurricane Cristobal formed from a classic Cape Verde wave last week and currently is churning Atlantic waters, but is not expected to be a threat to the United States. The formation of these disturbances off the West Coast of Africa will remain a potential source of tropical storms through the end of Atlantic hurricane season in late November. Each wave is investigated by the NOAA National Hurricane Center and you can view these active disturbances on their website.

The Sahara Desert and You

When it comes to hurricanes and hurricane preparedness, it’s interesting to know how a desert half a world away can influence the formation of severe weather on our coasts—and even parts of the Pacific Ocean. And no matter where you live, the old rule of planning for the worst and hoping for the best remains the surest way to stay safe.

Learn more about how we at NOAA’s National Ocean Service are staying prepared for hurricanes [PDF], and how you can create your own hurricane plan [PDF].

What Does the Sahara Desert Have to Do with Hurricanes?.

Posted Thursday, 13 November 2014 by Culebra Snorkeling and Dive Center in Culebra Posts & Reviews

With Lobster Poacher Caught, NOAA Fishes out Illegal Traps from Florida Keys National Marine Sanctuary

July 11, 2014
4 Comments
This is a post by Katie Wagner of the Office of Response and Restoration’s Assessment and Restoration Division.

NOAA’s Restoration Center is leading the project with the help of two contractors, Tetra Tech and Adventure Environmental, Inc. The removal effort is part of a criminal case against a commercial diver who for years used casitas to poach spiny lobsters from sanctuary waters. An organized industry, the illegal use of casitas to catch lobsters in the Florida Keys not only impacts the commercial lobster fishery but also injures seafloor habitat and marine life.Casitas—Spanish for “little houses”—do not resemble traditional spiny lobster traps made of wooden slats and frames. “Casitas look like six-inch-high coffee tables and can be made of various materials,” explains NOAA marine habitat restoration specialist Sean Meehan, who is overseeing the removal effort.

A casita made of panels and cinder blocks on the seafloor.

The legs of the casitas can be made of treated lumber, parking blocks, or cinder blocks. Their roofs often are made of corrugated tin, plastic, quarter-inch steel, cement, dumpster walls, or other panel-like structures.

Poachers place casitas on the seafloor to attract spiny lobsters to a known location, where divers can return to quite the illegal catch.

“Casitas speak to the ecology and behavior of these lobsters,” says Meehan. “Lobsters feed at night and look for places to hide during the day. They are gregarious and like to assemble in groups under these structures.” When the lobsters are grouped under these casitas, divers can poach as many as 1,500 in one day, exceeding the daily catch limit of 250.

In addition to providing an unfair advantage to the few criminal divers using this method, the illegal use of casitas can harm the seafloor environment.

 A Natural Resource Damage Assessment, led by NOAA’s Restoration Center in 2008, concluded that the casitas injured seagrass and hard bottom areas, where marine life such as corals and sponges made their home. The structures can smother corals, sea fans, sponges, and seagrass, as well as the habitat that supports spiny lobster, fish, and other bottom-dwelling creatures.

A spiny lobster in a casita on the seafloor.

Casitas are also considered marine debris and potentially can harm other habitats and organisms. When left on the ocean bottom, casitas can cause damage to a wider area when strong currents and storms move them across the seafloor, scraping across seagrass and smothering marine life.

“We know these casitas, as they are currently being built, move during storm events and also can be moved by divers to new areas,” says Meehan. However, simply removing the casitas will allow the seafloor to recover and support the many marine species in the sanctuary.

There are an estimated 1,500 casitas in Florida Keys National Marine Sanctuary waters, only a portion of which will be removed in the current effort. In this case, a judge ordered the convicted diver to sell two of his residences to cover the cost of removing hundreds of casitas from the sanctuary.

To identify the locations of the casitas, NOAA’s Hydrographic Systems and Technology Program partnered with the Restoration Center and the Florida Keys National Marine Sanctuary. In a coordinated effort, the NOAA team used Autonomous Underwater Vehicles (underwater robots) to conduct side scan sonar surveys, creating a picture of the sanctuary’s seafloor. The team also had help finding casitas from a GPS device confiscated from the convicted fisherman who placed them in the sanctuary.

After the casitas have been located, divers remove them by fastening each part of a casita’s structure to a rope and pulley mechanism or an inflatable lift bag used to float the materials to the surface. Surface crews then haul them out of the water and transport them to shore where they can be recycled or disposed.

For more information about the program behind this restoration effort, visit NOAA’s Damage Assessment, Remediation, and Restoration Program.

Katie Wagner.Katie Wagner is a communications specialist in the Assessment and Restoration Division of NOAA’s Office of Response and Restoration. Her work raises the visibility of NOAA’s effort to protect and restore coastal and marine resources following oil spills, releases of hazardous substances, and vessel groundings.

Opera – Mask – Mares

         

Opera

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An expression of Mares tradition, with its rugged, durable construction, making this a good travel companion for your diving holidays. Symmetrical lenses simplify the option to customize the mask with corrective lenses, which are available in a complete range from -1 to 7 diopters.

Opera – Masks – Mares.

Posted Thursday, 13 November 2014 by Culebra Snorkeling and Dive Center in Culebra Posts & Reviews

Samurai – Masks – Pure Instinct – Mares

Samurai

The Samurai’s qualities have made this mask one of the world’s best sellers, as well as one of the most frequently copied, though never equaled. It offers incredibly small internal volume, a complete lack of dead space, very light weight, and a new hypoallergenic antiglare silicone skirt. The wide field of vision, thanks to the close placement of the lenses to the face, joins comfort and low internal volume to make the Samurai an unbeatable tool for spearfishermen and freedivers who love to dive deep.

Samurai – Masks – Pure Instinct – Mares.

Posted Thursday, 13 November 2014 by Culebra Snorkeling and Dive Center in Culebra Posts & Reviews

X-Vision Mid – Masks – Mares

X-Vision Mid – Masks – Mares.

Blue

X-Vision Mid

The most popular mask in the world

 

 

• State of the art design

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The success of this scuba maskt derives from meticolous computer design and numerous optical tests. The central position of the eyes and the optimally angled windows provides the widest possible viewing angle in every direction. Quick-adjusting ergonomic buckles are positioned directly on the skirt

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