Posted at 8:52 AM on June 2, 2009
by Paul Huttner
Graphic shows how a microburst can cause jetliners to crash near the ground. A microburst caused Delta Flight 191 to crash in Dallas in 1985, killing 135 people.
Early speculation is that weather MAY have played a role in the Air France crash over the Atlantic Monday. The fact is, we just don't know yet. Reports indicate the airliner did encounter strong to severe thunderstorms in a band called the Inter Tropical Convergence Zone, or ITCZ.
Weather is fingered as the cause in about 12% of all air crashes. Lightning has caused many incidents. Improvements in aircraft design have made today's jet liners mostly safe from lightning strikes. A University of Florida study indicates about one jetliner a year is struck by lightning over U.S. skies. Usually the lightning strike passes right around the aluminum skin of the aircraft in a process called the Faraday Effect. It's the same reason you are generally safe in your car if it is struck by lightning. We do no yet know if the Air France jetliner was struck by lightning.
It is interesting to note that only 6% of all airliner crashes occur at cruising altitude even though cruising occupies 57% of total flight time.
Most weather related air crashes probably occur closer to ground level, where icing and downbursts are more common.
Extreme turbulence has also factored in aircraft incidents. In 1997 extreme turbulence killed on person on a flight from Japan to Hawaii.
Downbursts and microbursts have causes several crashes over the years. Microbursts are violent downdrafts of turbulent wind from severe thunderstorms. The Delta 191 microburst crash in Dallas helped spur NOAA to assemble the network of NEXRAD Doppler radars we use to detect severe local storms today.
Icing is also a danger in winter months in colder climates, and is cited as a possible factor in the crash of Continental flight 3407 in February near Buffalo, New York.
It is impossible to know yet what caused Air France flight 447 to go down in the tropical Atlantic. What we do know is that even though aviation has adapted to fly in all kinds of weather, weather still has the power to bring down an aircraft when conditions are right.
Thankfully advances in aircraft design and construction, and advances in weather forecasting and warning technology have made flying on of the safest ways to travel.
Posted at 2:29 PM on June 2, 2009
by Paul Huttner
Temperatures in northern Minnesota will plunge into the 30's by Wednesday morning.
Welcome to meteorological summer in Minnesota.
A cool dry Canadian air mass will allow temperatures to drop to near and below freezing overnight in much of northern Minnesota. There may even be some patchy frost as far south as St. Cloud and Hinckley.
Even the metro will feel the chill after dark tonight. The overnight low temperature at Twin Cities Airport may dip to near 45 degrees by morning. Some of the outer suburbs could see readings a slow as 40 degrees.
While the early morning chill is noticeable for early June, it is not likely to be record setting. The record low for the Twin Cities Wednesday is 34 degrees set in 1945. Up north, frost is common until mid-June in many areas.
The air mass over Minnesota is also very dry. Dew points are in the 30's today. The air over Minnesota today is as dry as the Arizona. The dew point in Phoenix is 34 degrees at noon today. Dry air heats and cools easily. That is one reason we are seeing big temperature swings from day to night as the powerful June sun heats the air quickly during the daylight hours.
The cool start to June is likely to persist into the coming weekend. Thursday looks like the warmest day this week.
Our dry weather pattern looks persistent as well. There is some chance of rain this weekend, but so far it does not look very impressive. The longer range weather crystal ball shows some chance of a wetter pattern developing around mid-month. That too, is too far out to bet the farm on. We need the rain badly. Today's crop report shows short to very short topsoil conditions over much of central Minnesota centered on the Twin Cities.
So we'll have to enjoy the pleasantly cool days and chilly nights for most of this week. It could be worse, that's for sure.