useful


Equatorial Massive for Storm
June 4, 2009, 9:50 am
Filed under: world news

Air France Flight 447 vanished in a zone of ferocious weather over the Atlantic Ocean known as the birthplace of some of the world’s strongest storms — just as the plane was encountering a 400-mile-long maze of lightning, hail, driving rain and fierce 100-mph updrafts.
So why didn’t the pilot simply turn around, avoid the storms or divert to another airstrip, standard procedure for avoiding severe weather anywhere in the world? After all, no pilot willingly flies directly into a large thunderstorm.
The plane’s crew may have tried to navigate through the storms using onboard radar, threading through holes in the weather, but then found themselves trapped, unable to get around or over the clouds that towered up to 50,000 feet, experts said.
Joe Mazzone, a retired Delta Air Lines pilot who flew for 23 years, said captains often will look to their radar at night to weave through thunderstorms, which appear as red blotches, but that in such a volatile region, storms can converge suddenly around you, leaving a pilot nowhere to go but through it.
“You’re penetrating where you think you’ve got a hole, and you get in there, and you basically now see that it’s red all around you, so you’re committed now,” Mazzone said.
At that point, he said, even if the plane were to turn around, it would have to go back through the same weather, presenting a dicey situation both ahead and behind.
And no pilot, Mazzone said, is going to try to simply keep on schedule despite dangerous weather, at the potential expense of passengers’ lives.
“Their egos don’t get over on safety,” he said. “They’re gonna die with everyone else.”
A Brazilian Air Force spokesman has said the plane’s debris field in the ocean may suggest the pilot did indeed try to return, because parts of the plane were found just outside the flight’s path, near where the last signal was emitted before it disappeared.
Searchers were finding debris smack in the middle of a region known to scientists as the Intertropical Convergence Zone, a nearly continuous band of colliding weather systems near the equator.
It’s where winds from the northern and southern hemispheres clash, spawning violent thunderstorms that can tower up to 60,000 feet, far higher than any commercial airliner could fly over.
Weather reports from the time indicate massive thunderstorms were developing in the area over a 400-mile-long route directly along the flight’s path on Sunday night.
The jet was carrying 228 people from Rio de Janeiro to Paris when it crashed into the sea between Brazil and Africa near the equator.
Basically, this zone, which experts refer to as the ITCZ, is a stormy weather band that wraps some 25,000 miles around the world, generally hugging the equator. Like an ocean current, it’s fluid in its movements as the seasons change, deviating several degrees north and south.
The zone’s shape is more like a slithering snake than a pencil-straight line, and can sometimes be several hundred miles wide.
While the region can be quiet and calm, it is also “the birthplace of our strongest storms on Earth,” said Henry Margusity, a senior meteorologist for AccuWeather.com.
In the tropics, the intense sun and warm water along the equator heat the air, making it buoyant and sending it upward as the north and south trade winds collide. The convergence of weather from opposite hemispheres fuels the zone’s production of thousands of small storms that can merge to form massive ones, sometimes in continuous bands, like what apparently happened Sunday night.
Brazilian officials said the last electronic message from the plane came in at 10:14 p.m. EDT, indicating loss of air pressure and electrical failure. Accuweather reported that weather data from the region showed towering thunderheads were sending updrafts of up to 100 mph into the jet’s flight path at that time.
Mazzone said if the Air France pilot found himself trapped amid these storms, it could have been catastrophic, with pummeling updrafts sucking the plane up and down, while being battered by huge hail.
“The hail will flame out those engines, just like a bird strike,” he said.
Still, a plane crash caused solely by a storm in this volatile weather zone is rare, said Larry Burch, deputy director of the Kansas City, Mo.-based Aviation Weather Center, a branch of the National Weather Service that issues daily weather advisories for pilots.
Thousands of flights every year travel across this stormy equatorial region worldwide without incident. Anytime a flight goes from Australia, for instance, to Los Angeles, it crosses into the zone.
“It’s something that’s done every day,” Burch said. “For the most part, a pilot is not going to fly right into a thunderstorm … They know these conditions are always there,” Burch added. “What happened Sunday night, though, I just can’t say.”
Thunderstorms are suspected to have played a role in the crash two years ago of a Kenya Airways flight immediately after takeoff from Cameroon, a West African nation that sits along this active equatorial region. Although the final report on that accident is not complete, some speculate storms lingered a few miles from the runway and that the pilot unwittingly flew into them, possibly encountering massive wind shear. All 114 people aboard died.
“The ITCZ is certainly thought of as a hazard, but it’s not normally thought of as life-threatening,” said Richard Pasch, a senior hurricane specialist at the National Hurricane Center in Miami. “But strong thunderstorms are an aviation hazard, period.”


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