2011 Hurricane Update for August

August 11, 2011

With Tropical Storm Don fizzling before making landfall in parched south Texas, it’s important to remember that its only been two months since the start of the 2011 Hurricane Season. Since June 1, there has been 4 named storms — that leaves 8 to 10 storms yet to come (according to predictions) with the majority forming up in September. While the season normally ends on December 1, there have been some off-season hurricanes. As of 2011, there have been 60 off-season storms in the Atlantic Hurricane Database, which began in 1851. Recent examples are Tropical Storm Olga in December, 2007 and Tropical Depression One in May, 2009.

This year is forecast to be active and it is probably a good idea not to let your guard down on December 1.

There is good news, however. The La Nina pattern that had reduced wind shear patterns in the Caribbean and Atlantic and enabled storm formation has dissipated. Also, NASA satellites captured photos of massive dust plumes coming off the west coast of Africa. Meteostat 9 tracked a massive dust plume off the western coast of Africa from the Sahara April 6. Another massive plume was found on June 24, 2011. Several days later, on July 15, NASA’s Terra satellite captured a plume in the western portion of Tassili n’Ajjerm mountains of Algeria. What’s so great about dust storms in the Sahara? Simple: it helps to prevent or weaken hurricanes.

The area in the atmosphere located over the Atlantic Ocean off the northwest Coast of Africa and is known as the Sahara Air Layer. Sahara desert dust is reddish-brown and very fine. When a windstorm blows across the Sahara, it picks up this dust very easily. Because the wind is hot and dry it has a low density. When the dust storm arrives at the coast, heavier, denser sea air forces this desert air to climb over it. That can be as high as 18,000 feet. Dust from the Sahara has been found deposited in the Caribbean, South America, and North America. In 2000, nearly 8 million tons of Sahara desert dust was deposited in Puerto Rico.

When present, the Sahara Air Layer (SAL) causes two things. The fine dust carried high over the moist air locally reflects sunlight away from the Earth and cools the ocean surface. Lower temperatures, even if they are only between 2 and 5 degrees, robs energy from potential storm systems. The SAL also increases wind shearing. That is, when the hot dry air collides with the cool moist air over the ocean it cause turbulence as the two air masses push past each other. Low pressure storm rotation has a harder time forming in these “circumstances.”http://tropic.ssec.wisc.edu/misc/sal/info.html

One recent example has been Invest 91L, a tropical wave that formed between July 27 and 29 off the coast of West Africa and traveled east towards the Leeward and Windward Antilles. As it crossed the Atlantic, it was buffeted by theSAL wind shear of 30 to 40 knots to its north. For the next several days it battled the shearing, looking for a while that it would not develop into a tropical storm. On August 1, however, it organized enough to become Tropical Storm Emilywith maximum winds at 40 mph, gusting to 50 mph. Its storm track took it towards Florida. before ultimately dissipating. As of August 2, the dry air, wrapped around the storm’s northwestern edge. Coupled with the on going wind shear, prevented further intensification over the life of the storm.

Had the SAL not been present, doubtless it would be a full-fledged hurricane by the time it reached the Leeward Islands and caused millions of dollars of damage. While the SAL is difficult to forecast, this year so far has been active. Whether the dust settles by September at the height of the hurricane season, though, remains to be seen.

All the same, stay on your guard. Just because experts have predicted that there will be 12 to 14 storms doesn’t mean that the Atlantic Ocean will run out on December 1. Since 1854, 55 tropical storms and hurricanes have passed within 65 miles of Houston alone, 5 of which were Category 5 hurricanes. Don’t fool yourself. It’s happened before, it will happen again. The important thing is to be prepared when a major tropical storm hits. If you and your family don’t have a plan then make one.

Stay tuned to the Bounce Energy Hurricane Prep Center for the latest hurricane information. Check out the Bounce Energy Hurricane Tracking Chart for Emergency contact numbers for your local utility company. There’s also emergency/routine numbers for your local authorities. Get resources and tips for creating your family’s disaster plan, what to do if you decide to evacuate, how to secure your home, caring for your pets, and other information what to do before, during, and after the storm.

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