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June-July 2007
Strong winds damage hangar
roof at Jeffco
Microburst one possible explanation
The roof materials landed about 200
yards (183 meters) north of the hangar. (Photos courtesy
John Pereira.) |
On Monday, June 11, exceptionally strong winds blew off
a 5,000-square-foot section of the roof of NCAR’s aircraft
hangar at Jeffco. The incident occurred at 3:26 p.m. and
lasted only 20 seconds. The roof materials landed in the
parking lot of Redstone College, about 200 yards (183 meters)
north of the hangar. The wind also blew open several of the
hangar’s doors, which weigh about 17,000 pounds, and
blew two off their tracks.
Nobody was hurt, and no property in the area other than the
roof was damaged. Security video cameras caught the incident
on tape from several vantage points. The videos show strong
south winds bending nearby trees, with a section of the roof
flying off the hangar’s southeast corner just above
a single open door.
“There was a big booming sound, and all the loose materials
in the hangar started blowing around and the doors were moving
without anyone touching them,” says Al Schanot (EOL),
who was in the hangar at the time.
“I was running to try to close the door,” adds
Brent Kidd, who was also in the hangar at the time, “but
there was a loud boom and I looked up and a section of the
roof was gone.”
A 5,000-square-foot section of
the hangar’s roof was blown off by strong
winds |
According to John Pereira, director of Physical Plant Services,
the hangar roof is designed to International Building Code
standards to withstand steady winds up to 100 miles per hour,
and three-second gusts up to 120 mph. These are higher standards
than the required construction codes for the area, he says.
A dry microburst is one likely explanation for the incident,
as a weak storm cell passed near Jeffco at the time. “It
was possibly a microburst, but closer examination of radar
data would be required to be certain,” says Jim Wilson
(RAL). “It’s really hard to determine without
a series of radar images and precise mapping of locations
and times.”
A dry microburst is a small, intense downdraft generated
by precipitation falling into very dry air during which the
rain nearly completely evaporates before reaching the ground.
Microbursts can produce extremely strong winds that curl
outward as the cold air of the microburst moves away from
the point of impact with the ground. The wind gusts, which
may approach 120 miles per hour, can be very dangerous for
aircraft taking off or landing and are estimated to have
caused up to 20 major airline crashes.
The possibility of a microburst damaging the hangar presents
an ironic twist, since research on microbursts spearheaded
by NCAR in the 1980s led to the development of radar-based
microburst warning systems in place at airports around the
country today. Since then, no further aircraft crashes have
been attributed to this phenomenon in locations where microburst
detection radars are in place.
In this issue...
Christmas
in August
Nuts
about science
NCAR
welcomes new researchers
SOARS
protégés in the thick of another summer
Just
before Sunrise....
Strong
winds damage hangar roof at Jeffco
Short
Takes
Bill
Randel to lead ESSL/ACD
Just One Look
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