“This one is very challenging,” says
Dave. “You take a big system that’s moving through four
states in the night and you have to coordinate the ground systems
and the aircraft in the right locations— man, it’s going
to be tough.” BAMEX, or the Bow Echo and MCV (Mesoscale Convective
Vortex) Experiment, is the most ambitious attempt yet mounted
to peer into giant clusters of thunderstorms, called mesoscale
convective systems, that batter the eastern two-thirds of the
country. The storms typically form by evening, rage through the
night, and die the next morning. Some regenerate the following
night or even the next. They can dump as much rain as a landfalling
hurricane and plaster huge areas with hurricane-force winds.
Morris Weisman and Chris Davis flank a bow
echo.
Chris Davis and Morris Weisman of the Mesoscale
and Microscale Meteorology Division are overseeing the experiment,
which will run from 20 May to 6 July. Collaborating institutions
include NOAA’s National Severe Storms Laboratory, the Naval
Research Laboratory, and over a dozen universities. ATD and the
Joint Office for Science Support (JOSS) will be handling much
of the logistics.
“Ultimately, what we’re trying to do
is get enough knowledge so these storms can be predicted,”
Morris says.
The stakes are high for protecting lives and property.
Chris talks about a storm that formed in South Dakota in July
1977, dumped torrents of rain as it moved east, and ultimately
caused a devastating flood in Johnstown, Pennsylvania, that killed
78 people.
And just three years ago, a storm barreled through
Kansas City, packing winds that were clocked at 74 mph (119 kmph),
ripping off roofs, downing trees, and cutting electric power to
about 100,000 homes and businesses. Such storms can be terrifying,
especially late at night—the most likely time for the Midwest
to get summertime thunderstorms.
“I saw water coming through the ceiling,”
13-year-old Reginald Smith told the Kansas City Star. “The
water started getting heavier, so I panicked and started packing
my clothes and put the rest of my stuff in my closet.” His
family fled to safety in the darkness when the roof of their townhouse
blew off.
The
alarming bow
While lines of storms are informally called squall
lines, some of them are classified by meteorologists as “bow
echoes.” The name comes about because strong upper-level
winds that descend through the core of rain-cooled air cause the
leading edge of the system to bow outward. The characteristic
radar echo that results can serve as a good indicator of potential
severe weather.
Bow echoes are dangerous because the outflowing
winds of their rapidly moving thunderstorms produce gusts that
can approach 100 mph (161 kmph)—and they can also spin off
tornadoes. Such tornadoes can be difficult to predict because
often there are no clear precursors, such as a storm-scale rotation
at upper levels, that can signal potential tornado formation.
While a typical tornadic thunderstorm might span
20 kilometers (12 miles), the agglomerations to be studied in
BAMEX can stretch more than 140 kilometers (87 miles) in width
and carve paths that span several states.
For years Morris and his colleagues, have simulated
various modes of thunderstorm growth and decay in computer models,
while Chris Davis and his colleagues have studied and simulated
mesoscale convective vortices. Davis and NCAR colleague Stanley
Trier were the first to reproduce the vortices in a cloud- resolving
computer model. They found that when a vortex outlives its parent
thunderstorms, it can help trigger more storms the following day—making
it a potentially useful forecast tool.
The scientists decided to move from modeling to
fieldwork because, as Morris puts it, “We came to realize
that we’d gone about as far as we could with the idealized
simulations. We needed to get good data.” They joined forces
with Roger Wakimoto (University of California, Los Angeles) and
Dave Jorgenson (National Severe Storms Laboratory), who had extensive
experience making aircraft observations of convective systems—and
BAMEX was born.
The BAMEX study area extends from the central plains
to the Ohio Valley, an expanse that should keep the odometers
of both aircraft and ground vehicles churning. On the ground,
researchers will line up three vehicles on a north-south axis,
with two ATD sounding units flanking the University of Alabama
in Huntsville’s Mobile Integrated Profiling System (an atmospheric
research system that includes Doppler radar, lidar, and other
instruments). In addition, a mobile weather station will double
as scout car, seeking out clearings large enough for the balloon
launchers and profilers to operate safely.
Three aircraft will probe the storms, including
P-3s from NOAA and the Naval Research Laboratory with onboard
Doppler radars. A chartered Learjet will deploy NCAR dropsondes,
key to analyzing the convective vortices. All three planes will
be based at MidAmerica Airport, a little-used facility located
about 25 miles east of St. Louis. BAMEX will virtually have the
place to itself, which simplifies the aircraft operations enormously.
“At least on paper, it’s probably the ideal setup for
this kind of experiment,” Morris says.
A
daunting task
Still, the logistics are formidable. To begin with,
researchers are confined to areas that are built up enough to
have good networks of paved roads, but not so densely populated
as to have regular traffic jams and obstructions such as power
lines that could snarl weather balloons. Much of the Midwest is
made to order but, as Morris points out, “the farther west
you go, you just run out of road.”
A second challenge is the sheer size of the region.
Traveling as a unit between deployments, the ground crews will
zigzag from one storm to the next, working without a home base
for the entire seven-week project.
And then there’s the matter of the timing
of the storms. Most bow echoes blow through at night, meaning
crews will often work past midnight.
“It’s going to be unique in that we’ll
be all over the place and never know where we’ll be the next
night,” says ATD’s Ned Chamberlain, who is overseeing
the balloon launches. “We’ll be driving hundreds of
miles in a day. We’ll head out about 10, and then at noon
we’ll get a further definition of the forecast area. Early
to mid afternoon is when they [the scientists in Mid America Airport]
do a final sighting of the system. Then we’ll set up and
start working. We’ll start making balloon launches at 4 p.m.,
and we may be out there until 2 in the morning.” The goal
is to work no more than 42 hours during each three-day period,
and then take the fourth day off, Ned explains.
At ATD, dozens of staffers are working on the project.
Brigitte Baeuerle is the division’s BAMEX project manager,
and she is working with Mike Daniels, Allen Schanot, Peggy Taylor,
and Melinda Tignor on project logistics. Terry Hock is overseeing
dropsonde operations; Mike Spowart is taking care of outfitting
the Naval Research Laboratory P-3; and Eric Loew, Kurt Zrubek,
and a team of technicians are assisting with aircraft operations.
JOSS will help oversee the airport-based operations
center. The office also created the online BAMEX catalog, which
has a substantial real-time component. “It’s a living,
breathing thing on the Web,” says JOSS’s James Moore.
The catalog will ingest vast amounts of data from the BAMEX fleet
as well as the standard National Weather Service observing network.
If the storm season comes through, this $4 million
experiment—funded primarily by NSF—may compile as many
as 15 case studies. With any luck, that will include two or three
detailed cases. It’s about time, says Morris. The last major
study of mesoscale convective systems was in 1985, when the emphasis
was on fixed sensors. This time, the behemoths are being chased
instead of watched.
•Bob Henson and David Hosansky
Also
in this issue:
The
long riders: How some staffers cope with epic commutes
Study
finds lower atmosphere warming
An
information divide
Building
bridges for Latina students
Short
takes
Delphi
Question: Publications on the Web
