Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Midwest Thunderstorm Study Points toward Better Forecasts

28.09.2004


A set of newly documented small-scale circulations embedded in thunderstorm squall lines not only spew destructive straight-line winds, but may spawn up to 20% of all U.S. tornadoes. And the remnant circulations from large thunderstorm clusters can survive for days, triggering new storm cells. Over warm oceans, similar remnant circulations provide seed for hurricane development. Scientists expect these and other findings to help improve forecasts of damaging winds and heavy rain.


This Doppler radar image collected by the National Weather Service on the evening of June 11, 2001, shows a strong bow echo moving southeast across Wisconsin. (Image courtesy National Oceanic and Atmospheric Administration)


This menacing cloud was part of a mesoscale convective system studied in a previous Montana field project. Such systems, dominated by strong, outflowing winds and heavy rain, were the focus of the Bow Echo and MCV Experiment.



The new results emerge from three-dimensional portraits of thunderstorms collected across the storm-tossed Midwest in a field study coordinated by the National Center for Atmospheric Research (NCAR) in 2003. A summary will be presented on October 5 in Hyannis, Massachusetts at the American Meteorological Society’s 22nd Conference on Severe Local Storms.

Based just east of St. Louis, the Bow Echo and MCV Experiment (BAMEX) employed aircraft and ground-based storm chasers to document a wide range of storm types that prowled the Midwest from May to July 2003. Over a dozen colleges and universities joined NCAR and the National Oceanic and Atmospheric Administration (NOAA) for BAMEX. Key funding for the $4 million study was provided by the National Science Foundation, NCAR’s primary sponsor.


Among the most noteworthy results:

Size doesn’t equal strength when it comes to bow echoes, the arc-shaped squall lines that produce intense straight-line winds and spawn dozens of tornadoes each year. “The greatest damage was typically observed not in the most extensive bow echoes, but in smaller ones spanning 60 miles or less,” says NCAR scientist Christopher Davis, co-science director of BAMEX. Within these small bows, even smaller circulations appear to focus most of the storm’s destructive power and the highest risk for tornadoes.

Mesoscale convective vortices (MCVs)—areas of low pressure similar in strength and size to weak tropical depressions—extend through a deep layer of the atmosphere. These MCVs, which can trigger multiday rounds of intense thunderstorms, tend to destabilize the atmosphere as they pull warm, moist surface air northward.

Harbingers of high wind

Up to now, forecasters haven’t been able to tell in advance just when an intense thunderstorm might morph into a destructive bow echo. The process appears to hinge on small-scale factors that everyday weather observations can’t trace and radar operators can’t easily spot.

BAMEX captured this near-storm environment in detail with Doppler radars aboard P-3 aircraft from NOAA and the Naval Research Laboratory. Ground crews launched more than 200 radiosondes (weather balloons), while a Lear Jet dropped more than 400 parachute-based dropsondes.

The result is a set of three-dimensional portraits that will help scientists unravel the processes driving the high winds and heavy rains of bow echoes. For instance, about two hours after damaging winds struck eastern Nebraska on the night of June 9, 2003, BAMEX aircraft showed winds of over 90 miles an hour howling less than a mile and a half above ground level, even as the surface winds had decreased.

“With the data from BAMEX, we’ll be studying several indicators that might provide advance notice of when severe surface winds might develop,” says Davis. These include local enhancement of thunderstorm cells within a line, bands of convergent wind at the surface that feed into a thunderstorm complex at right angles, and other characteristic wind signatures detected aloft by Doppler radar. Forecasters from the National Weather Service (NWS) joined NCAR and university collaborators in gaining a better awareness and understanding of bow echoes through BAMEX, Davis says.

When one storm complex leads to another

Whether over land or sea, thunderstorm complexes can generate broad areas of low pressure, from about 30 to 200 miles in width, that survive after the storms die off. Once formed, one of these mesoscale convective vortices (MCVs) can merge with a cold front, grow to become a larger center of low pressure, and/or generate new thunderstorms for one or more days. It may even become the seed of a tropical or subtropical cyclone if it passes over warm ocean water.

“There’s remarkable continuity in the spectrum of cyclones as you go from midlatitudes to the tropics,” says Davis. “I’m confident that there are some real similarities among these cyclones, especially in the early stages of development.”

A sharper picture of future storms

The Weather Research and Forecasting computer model, soon to enter regular use at the NWS, showed surprising skill at high resolution in projecting storm types 24 to 36 hours in advance during the 2003 BAMEX field campaign, according to NCAR’s Morris Weisman, one of the project’s lead scientists. The special simulations were performed again this summer at NCAR and made available to NWS forecasters on line. At its finest resolution of about 2.5 miles, the model can help forecasters determine whether to expect squall lines, isolated supercells, or other types of storms.

“The output was used daily by forecasters across most of the central United States,” says Weisman. “They’ve told us this new information is really valuable to their outlooks.”

Anatta | EurekAlert!
Further information:
http://www.ucar.edu

More articles from Earth Sciences:

nachricht Water - as the underlying driver of the Earth’s carbon cycle
17.01.2017 | Max-Planck-Institut für Biogeochemie

nachricht Modeling magma to find copper
13.01.2017 | Université de Genève

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

Im Focus: How to inflate a hardened concrete shell with a weight of 80 t

At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).

Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

Nothing will happen without batteries making it happen!

05.01.2017 | Event News

 
Latest News

Explaining how 2-D materials break at the atomic level

18.01.2017 | Materials Sciences

Data analysis optimizes cyber-physical systems in telecommunications and building automation

18.01.2017 | Information Technology

Reducing household waste with less energy

18.01.2017 | Ecology, The Environment and Conservation

VideoLinks
B2B-VideoLinks
More VideoLinks >>>