Was Air France flight brought down by turbulence or hail?

Was Air France flight 447 brought down by a 100 m.p.h. updraft?

Or were its two jet engines snuffed out by hail or heavy rains?

In the absence of a black box, the leading theory now is that the Airbus 330-200 was brought down by a 300-mile-wide band of tropical thunderstorms that it could fly neither around nor over.

Brazil's defense minister confirmed Tuesday afternoon that military planes found a three-mile path of wreckage in the Atlantic, hundreds of miles from Fernando de Noronha, a Brazilian archipelago.

Professional pilots and meteorologists are digging through the available data – flight routes, satellite images, aircraft specifications, and weather reports – and spinning out several likely causes.

One of the most detailed and cogent pieces of analysis of Flight 447’s last minutes – winning the praise of pilots around the world – is a blog by Tim Vasquez.

Mr. Vasquez is a former US Air Force meteorologist. He now consults and publishes weather forecasting texts and software.

Vasquez plots the likely flight path of Air France 447 and overlays it on satellite imagery and weather reports in the area at the time:

It appears AF447 crossed through three key thunderstorm clusters: a small one around 0151Z, a new rapidly growing one at about 0159Z, and finally a large multicell convective system (MCS) around 0205-0216Z. Temperature trends suggested that the entire system was at peak intensity …

Air France says that it received an automated message from Flight 447 reporting electrical faults and loss of pressurization. Vasquez says that message was sent just as the jet was nearing the final edge of the storm cells, but after being battered by turbulent updrafts as high as 100 mph for about 12 minutes (or 75 miles).

Several pilots, in comments on his site, agree that turbulence was probably a factor.

AccuWeather.com, a private forecasting firm, issued a statement Tuesday, offering a similar theory based on its own data:

The plane appears to have flown into or near a large cluster thunderstorms that were in the development stages northeast of Fernando De Noronha, which is located off Brazil's northern coast, and along the Intertropical Convergence Zone (ITCZ), the belt of low pressure that surrounds the Earth at the equator.

Based on weather information from Fernando De Noronha, the updrafts associated with the thunderstorms may have reached up to 100 m.p.h. Such an updraft would lead to severe turbulence for any aircraft. In addition, the storms were towering up to 50,000 feet and would have been producing lightning.

At its last check-in time, the Air France aircraft was flying at 35,000 feet. A check of the Airbus 330-200 specifications shows that the aircraft has a ceiling of 41,000 feet.

It couldn’t fly above a thunderstorm with a 50,000-ft. top. It would have been using its onboard radar to try to pick a path through the storm cells.

Vasquez also makes note of another possible cause: The jet engines were shutdown by rain or hail.

A dual engine flameout due to precipitation or ice ingestion is a noteworthy possibility as has been discussed on other sites

(specific to the A330 type too). The precipitable water content in any tropical weather system can run very high.

Vazquez says that lightning may also have been a factor. And Accuweather raises the same point:

Tropical thunderstorms and the lightning patterns generated by them are different from storms that typically occur over the United States. Studies have shown that the top region of tropical thunderstorms is highly charged and more conducive to lightning, which indicates that an airplane flying near the top of a tropical thunderstorm could be more susceptible to a lightning strike. Tropical thunderstorms are also notorious for producing frequent cloud-to-cloud, as well as cloud-to-air lightning.

But commercial pilots and aviation safety experts say that such jets are designed to take lightning strikes without significant damage. Still, the fact that this was a fly-by-wire aircraft (where the control surfaces are moved by electrically signaled controls, rather than cables, chains, and pulleys) raises doubts among some pilots.

Most pilots, in the absence of more information, are leaning toward turbulence or engine flameout as the most likely causes of AF447’s demise.

But there is at least one faction within the meterological community that disagrees with the theory that the Air France jet was brought down by a storm.

The World Meteorological Organisation (WMO) says that two Lufthansa jets – heading from South America to Europe – flew through the same area where the thunderstorms were reported, about half an hour before the AF447.

The two aircraft collected wind and temperature information during their flight as part of a WMO program.

On Monday, a source with access to the data transmitted to WMO told Reuters in Paris that the two jets passed through turbulence before and after the plane without incident….

More than 5,000 aircraft collect data under WMO's Aircraft Meteorological Data Relay Programme (AMDAR). The two Lufthansa jets participated in the system, but not the Air France flight, according to the Geneva-based United Nations agency.

But Herbert Puempel, chief of the WMO's aeronautical meteorology division, also told Reuters that thunderstorms tend to be very localized. If one plane reports turbulence, another one passing through the same area even shortly afterward is unlikely to experience it.