UCAR > Communications > Staff Notes > April 1998

April 1998

COMET's convective training takes the weather service by storm

A few of the key players on COMET's convective team: (clockwise from top left) Pat Parrish, Greg Byrd, Morris Weisman, and Wendy Abshire. (Photo by Carlye Calvin.)

On the Web

COMET's "meted" site is open to all users with .edu domains.

The COMET home page.

News of other COMET developments can be found in the spring issue of the UCAR Quarterly.

A pack of tornado-bearing thunderstorms raced across central Florida under cover of darkness the night of February 22-23. In its wake, 42 people were dead. Tragic as it was, the high death toll wasn't for lack of official warning. The National Weather Service (NWS) in Melbourne, Florida, was on top of the situation, issuing warnings from 13 to 43 minutes in advance.

UCAR and NCAR played a role in the Melbourne office's preparation for the storms. Last fall, forecasters at Melbourne went through two CD-ROM courses, Anticipating Convective Storm Structure and Evolution and A Convective Storm Matrix: Buoyancy/Shear Dependencies. Both modules were prepared by UCAR's Cooperative Program for Operational Meteorology, Education and Training (COMET) with the assistance of content expert Morris Weisman (MMM). The modules combine storm theory, observations, and computer models to help students peg storm types in advance based on a given day's blend of ingredients--in particular, buoyancy (instability fueled by warm, moist surface air) and shear (winds that strengthen and/or veer with height).

With the COMET modules and other NWS training under their belts, the Melbourne forecasters spotted the potential for Plains-style supercell storms well in advance. A special statement alerted the public to the severe potential 36 hours before the deadly outbreak. "The pattern was a classic severe-weather set-up, just like you see in the modules and the textbooks," says Melbourne forecaster Tony Cristaldi, who worked a 19-hour shift through the storms. He calls the COMET modules "an excellent extension of the training we receive at [NOAA's] WSR-88D school." (The WSR-88D is the weather service's Doppler radar, installed across the nation over the past decade.)

The COMET Program is in the midst of a multiyear effort to get the nation's forecasters trained to the teeth in how to anticipate thunderstorm hazards. The emphasis was first on single storms: supercells, multicells, and the like. Now the focus is broadening to mesoscale convective systems (MCSs), clusters of storms that have their own hazardous qualities. This spring, MCSs are the focus of several symposia, COMET's first Web-based modules, and a new form of teletraining.

A good idea in theory

Convection (showers and thunderstorms) has been part of COMET's training from the start. One of the first two modules, issued on laser disc in 1992, featured ATD scientist Jim Wilson explaining how fine-scale wind boundaries visible on Doppler radar can trigger storms. That module relied on radar imagery combined with Jim's video narrative.

It was another matter for COMET to translate the ideas being generated on the other side of the Foothills Lab. Since the 1980s, MMM's Mesoscale Dynamics Group--including Morris, Chris Davis, Joe Klemp, Rich Rotunno, and Bill Skamarock--has forged a body of theory on storm behavior based on the interplay between buoyancy and shear. First came the group's explanation of how supercells, the longest-lived and most severe of thunderstorms, develop. More recently came a series of papers on the life cycle of MCSs--in particular, bow echoes (see sidebar).

Morris saw a special opportunity through the COMET Program to convey his group's work in a three-dimensional, animated format. "Who needs another textbook? We're trying to take a step beyond that to a new level of education."

Beginning in 1995, about a quarter of Morris's time was devoted to the COMET Program. He teamed up with meteorologist Wendy Abshire, instructional designer Pat Parrish, animator Steve Deyo, graphic artist Heidi Lindenlaub, multimedia programmer Carl Whitehurst, and other COMET staff to develop Anticipating Convective Storm Structure and Evolution. Also working with the COMET team were Ed Szoke (NOAA Forecast Systems Laboratory) and Steve Keighton (NWS-Blacksburg, Virginia). The project grew so large that A Convective Storm Matrix was spun off as its own module. It allows users to apply the knowledge from the first module by plugging in one of 54 combinations of buoyancy and shear and seeing what kinds of storms develop.

The visual advantage

To call the COMET modules graphics-intensive is an understatement. Steve and Heidi have generated more than 10,000 stills and animations for 18 modules to date. "As computers have matured, we've really been pushing the envelope in visualizations," says Wendy. "It took the [recent] increases in computer power to handle MCSs. We couldn't have done this five years ago."

Often the COMET classroom serves as a womb for embryonic material before it makes its way into a module. Subject experts deliver lectures as part of regular NWS courses, then use the feedback to write a draft script reviewed by COMET staff. (Morris went the extra mile, says Pat: "He reorganized and redelivered his lectures just for us to videotape. Not all our modules begin this way, but it's a model we like to use.")

Next comes the real fun: the long, iterative process of putting pictures and schematics on paper and developing multimedia interactions that bring the user into the material. Morris sees the process as "an incredible amount of doing and rethinking, looking at the holes in what was presented. . . . Trying to come up with useful presentations can take a long time. Pat's insights on education and his ability to understand and translate the scientific concepts were really critical in bringing the whole process together."

And it did come together. Once the two modules went out last spring, Morris notes, "forecasters could see the basis of the scientific studies of the past ten years. Reading the literature is one thing, but seeing the simulations and the animations of theoretical concepts really brings it home." For instance, the idea of an updraft tilting a horizontal vortex tube into vertical sections takes on new clarity. "In Joe Klemp's review paper, you see one illustration that shows the end state. In the module, you can see the whole tilting process animated from beginning to end."

What to do for the Web?

Before the pixels were dry on the first two convective modules, the COMET team went to work on MCSs. This time they set out to show not just how a single storm grows and dies, but how groups of storms interact with each other and behave as a unit. There was another wrinkle, too. For the first time, COMET wanted to place a complete module on the Web--a medium that thrives on low-resolution graphics but chokes on multimegabyte animations.

To adapt to the Web's graphic limits, the MCS team worked in stages. A module on squall lines and bow echoes debuted on the Web in November; a follow-up, on physical processes within MCSs, will be on line in April. The data-heavy case studies will appear in June on CD-ROM as part three of a complete MCS package. The entire Web site will be compiled on CD-ROM soon afterward with several enhancements, including a more complete set of MCS simulations. For the MCS modules and lectures, Morris teamed with fellow MCS expert Ron Przybylinski (NWS-St. Louis). "We want to bring the theorists and the forecasters together," says Morris.

Even with the limitations of the Web, the on-line MCS modules feature a wealth of color imagery: downdrafts and updrafts, vortices forming at the ends of squall lines, supercells evolving into bow echoes, lines evolving into circular masses. You don't need a technical background to admire the beauty of the animations and learn some basic concepts. However, the module developers expect serious users to have an upper-division undergraduate or beginning graduate background. Says Morris, "You have to know what the basic equations are."

The MCS modules are part of a new "meted" (meteorology education and training) Web site created by the NWS and COMET for on-line instruction. The area is open to any .edu domain, which alludes to a primary audience: the university community.

Many professors, including Kerry Emanuel (Massachusetts Institute of Technology) and Richard Johnson (Colorado State University), have already used COMET modules in their teaching. Morris did the same last fall when he taught at the University of Washington on sabbatical. The modules have also been used overseas--for example, at the European Centre for Medium-Range Weather Forecasts. "People love the modules," says Morris. With the storm matrix, "it's like they have 54 case studies to go through."

A meeting in four states

On a mild Boulder evening this past February, about 30 NWS science and operations officers--the chief scientists and trainers at each forecast office--took part in a first for COMET. The group was in town for a week-long symposium on MCSs. On this night, in the COMET classroom, they shared audio and graphic connections with three other NWS sites to discuss the devastating Jarrell, Texas, tornado of last May.

COMET's first foray into "audiographics" came off without a hitch. Audiographics is akin to teleconferencing, but the visual component is limited to graphics rather than full video. "It's basically a PowerPoint-type presentation that's preloaded at the various sites," says Greg Byrd, manager of the COMET classroom. People at each site--in Silver Spring, Maryland; Norman, Oklahoma; Fort Worth, Texas; and Boulder--could present images, mark them up on the screen for all sites to see, and exchange questions and answers for all to hear. "I think a lot of the participants got to see the power of what could be done," says Greg.

The NWS has installed audiographics equipment at each of its field sites over the past year. Less expensive than full-scale teleconferencing, audiographics has a promising future in the COMET program. At press time, Wendy was preparing to take people at eight test sites on a simultaneous walk through an MCS case study that will call on material from COMET storm modules both old and new. "I'm going to throw them into the fire," she laughs. Adds Greg, "It's our first real venture into COMET-delivered audiographics."

Meanwhile, a few sites around the country have linked with COMET through video teleconferencing. The technology arrived three years ago, but its use has been limited, says Greg, "mainly to bringing in speakers who couldn't travel to Boulder. There were some rough edges, early. But it's improved to become a mature system that we're pretty comfortable with. It's not full-motion video--there's a little bit of herky-jerkiness with the people transmitting, but nothing too distracting."

Use of the COMET classroom for on-site courses peaked at about 34 weeks per year in 1996, dropped to 20 weeks during the NWS budget crisis of 1997, but will climb back up to 26 weeks this year. With new aviation initiatives in the planning stage, it's doubtful the classroom will be gathering dust any time soon. •BH

The vocabulary of storms

Here's a roundup of some important storm types described in the latest MCS modules.

Mesoscale convective system (MCS): The all-encompassing term for groups of thunderstorms that act as a system. An MCS can range across an entire state and might appear as a solid line, a broken line, or a cluster of cells. It can include any of the storm types below.

Multicell: A typical, garden-variety thunderstorm in which new updrafts form along the leading edge of rain-cooled air (the gust front). Individual cells usually last 30 to 60 minutes, while the system as a whole may last for many hours. Multicell storms may produce hail, strong winds, brief tornadoes, and/or flooding.

Supercell: An especially long-lived thunderstorm with a rotating updraft that continually regenerates on the storm's flank (often on the south or right-hand side). Supercells form in regions of strong vertical wind shear. They typically produce large hail and high winds and may also produce violent, long-lived tornadoes. Supercells often feature a hook-like appearance on radar precipitation displays as rain wraps around a tornadic circulation.

Squall line: A linear arrangement of storms, often accompanied by squalls of high wind and heavy rain. Squall lines tend to pass quickly and are less prone to produce tornadoes than are supercells. They can be hundreds of miles long but are typically only 10 or 20 miles wide.

This cross section through a mature squall line shows the formation of new cells on the line's forward flank. There, air is being forced up by a rain-cooled gust front (the short dark line extending up from the lower-right corner). (Illustration copyright COMET® Program.)

Bow echo: The radar signature of a squall line that "bows out" as winds descend behind it and circulations develop on either end. A strongly bowed line may indicate high winds in the middle of the line, where the storms are progressing most quickly. Brief tornadoes may occur on the leading edge of a bow echo. Often the north side of a bow echo becomes dominant over time, gradually evolving into a comma-shaped storm complex.

Derecho: A violent, widespread windstorm caused by a long-lived MCS with a series of bow echoes. Derecho (Deh-RAY-cho) is a Spanish word which can mean "straight ahead." Derechoes produce winds of 60 to 100 mph, downing trees and power lines over paths tens of miles wide and hundreds of miles long.

Mesoscale convective complex (MCC): A particular type of MCS, an MCC is a large, circular, long-lived cluster of showers and thunderstorms identified by satellite. It often emerges out of other storm types during the late-night and early-morning hours. MCCs can cover an entire state with heavy rain; they were implicated in the 1993 Midwest flooding.

This satellite view shows two MCCs--one straddling Oklahoma and Kansas, the other crossing the Mississippi south of St. Louis--just after midnight on 20 May 1979. (Satellite photo courtesy COMET/NOAA/American Meteorological Society.)

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Edited by Bob Henson, bhenson@ucar.edu

Prepared for the Web by Jacque Marshall