meeting reviews

Summary of the 14th Conference on Severe Local , 29 October-1 November 1985, Indianapolis, Indiana

John T. Snow1

Conference Chairman

1. Introduction ferent from the distribution of producing strong straight-line . The distribution for the -pro- The Fourteenth Conference on Severe Local Storms was ducing storms was also different from that of -pro- held in conjunction with the Sixth Conference on Hydrome- ducing storms. The results provide the forecaster with useful teorology. The conference was organized by the AMS Com- background information concerning the possibilities of dif- mittee on Severe Local Storms,2 working through a Program ferent types of events, and pose some intriguing questions for Committee.3 The conference format consisted of 12 sessions dynamicists. with oral presentations (83 papers), two of which were held Benjamin and Lanicci described their efforts to model the jointly with the Sixth Conference on Hydrometeorology, and evolution of the background environment in two specific two poster sessions (32 presentations). Details of the confer- cases: SESAME (Severe Environmental Storms and Meso- ence program and titles of all papers presented are to be scale Experiment) I (10-11 April 1979) and SESAME IV (8-9 found in the June 1985 issue of the BULLETIN. May 1979), focusing on the effects of soil moisture and topog- raphy on the movement of the dryline. The role of these two parameters in modulating the behavior of the dryline was clearly shown in their results, as was the impact of dry air 2. Session summaries flowing northward out of the central Mexican plateau. Hales and Kelly discussed the impact of the warning-veri- The following summaries were prepared from material pro- fication program of the National Service (NWS) on vided by those who chaired the individual sessions, and from the statistics for damaging straight-line winds and large hail. notes taken by the Program Chairman. The summaries re- Their analysis indicates the verification data base has some flect only those papers actually presented. Sessions 9 and 10 shortcomings, reflecting both a bias due to population dis- were conducted as joint sessions with the Sixth Conference tribution and differing verification procedures between fore- on Hydrometeorology and are not summarized here. cast offices. They recommend a rethinking of the verification process. a. Session 1: Dynamic Climatology of Severe Local Storms Barker and Banta identified preferred regions for thunder- Colquhoun and Shepherd reported on the use of a simple storm formation over the central Rocky Moun- model and proximity soundings to estimate tains using geosynchronous-satellite imagery. They found the mass flux through more than 150 tornado-producing that the regime on a given day determines which ridge thunderstorms. It was found that there appeared to be a good lines will act as source regions. Orographic lifting, leeside correlation between mass flux and observed tornado inten- convergence, channeling effects, and wake effects could all sity; this was incorporated into a logic sheet to aid in the fore- be identified as playing roles in activating the formation of casting of severe thunderstorms. storms. In a study of the climatology of nontornadic severe thun- Tecson and Fujita reported on their continued analysis of derstorms over a 29-year period, Schaefer et al. found that the DAPPL (Damage Area Per Path Length) tornado data the distribution of large hail-producing storms was quite dif- set, here focusing on providing probability of occurrence of maximum wind speeds. The peak with a 10~4 probability of occurrence was 65 m • s"1 in central Oklahoma; with a 10"7 probability, the peak values were 137 m • s-1 in Ok- 1 Department of Geosciences, Purdue University, West Lafayette, lahoma and 138 m*s_1 in northern Alabama. IN 47907. 2 AMS Committee on Severe Local Storms: Ralph A. Petersen (Chairman), Ronald L. Alberty, Howard B. Bluestein, Donald W. Burgess, Dennis W. Feltgren, Dennis H. McCarthy, Frederick P. b. Session 2: Remote-Sensing Techniques I (F. R. Robertson Ostby, Jr., Richard Rotunno, John T. ,and M. Steven Tracton. T A. Seliga) 3 Program Committee: John T. Snow (Chairman), Henry E. Fuel- berg, Gerald M. Heymsfield, Robert H. Johns, Dennis H. McCarthy, Papers in this session concentrated on two areas of research: Ralph A. Petersen, W. David Rust, and Robert E. Schlesinger. the use of satellite data to define convective environments, 1144 Vol. 67, No. 9, September 1986

Unauthenticated | Downloaded 09/23/21 10:03 AM UTC Bulletin American Meteorological Society 1145 and the study of convective storm structure as revealed by veal the existence of regular wave-like features about 1 km Doppler radar. wide near the surface gust front in a thunderstorm outflow. Weaver et al. used VAS (VISSR [visible infrared spin scan Dual- and multiple-Doppler analyses have increased our radiometer] atmospheric sounder) satellite soundings to knowledge of the air motions within storms and, with recent augment surface observations in defining the thermody- mathematical retrieval techniques, have been used to reveal namic structure of the lower troposphere in convectively ac- the pressure and temperature perturbation fields as well. tive environments. Delineation of different air masses was Roux described the recovered three-dimensional wind field accomplished via buoyant energy calculations. The absorp- and perturbation thermodynamic fields for a tropical squall tion of radiant energy by water vapor in regions of clear air line. From these the vertical fluxes and lateral exchange rates was found to be of particular importance. In a related study, of heat and along- and across-the-line momentum were de- Hillger et al. used single field-of-view soundings to study spa- termined as a function of height to estimate the influence of tial variations in low-level precipitable water. Soundings the squall line on its environment. Schmidt and cotton ana- based on the 35-km TOVS (TIROS [Television and Infrared lyzed the dual-Doppler wind field and evolving reflectivity Observational Satellite] Operational Vertical Sounder) data features of a bow-shaped cell within a squall line to reveal the were able to depict mesoscale variability without the aid of possible source of the surface outflow air. surface observations in the retrieval process. Belunik et al. Airborne Doppler , a newer sensing tool still in its used three-minute rapid-scan GOES (Geostationary Opera- testing phase, is now demonstrating its ability to accurately tional Environmental Satellite) data to retrieve vertical wind measure winds in the subcloud region. Papers by Emmitt and shear during two cases from the Cooperative Convection by McCaul and Bluestein described the use of NASA's (Na- Experiment (CCOPE). -height assign- tional Aeronautics and Space Administration) airborne ment was done by correcting infrared (IR) cloud tempera- Doppler-lidar system to examine the subcloud outflow re- tures for partially filled fields-of-view and consideration of gion of thunderstorms, revealing the vortices and divergent cloud shadows. It was noted that mesoscale convective com- flow patterns occurring near the outflow boundaries. Storm- plex (MCC)-like systems are not restricted to environments top data gathered via satellite IR imagery and high-altitude with weak vertical wind shear. Funk and Fuelberg used VAS airborne lidar and radiometer systems also provide impor- soundings to calculate vertical motions by three techniques; tant severe-weather information. The utility of lidar returns results from the quasi-geostrophic w-equations were judged in indicating the height and density structure of storm tops superior to estimates obtained from both the and was illustrated by Sinhirne et al. Smith and Partacz discussed the adiabatic thermodynamic equations. a possible relationship between cloud-top warming based on Using a case study of a severe storm, Brown demonstrated satellite IR data and the subsidence of high-speed tropo- that a thunderstorm can act as a barrier to the environmental spheric air initiating surface that lead to mesocy- winds and so contribute to the generation of cyclonic and anti- clone and subsequent tornado formation. cyclonic motion at the right and left flanks, respectively. Storm movement toward the right was found to result from successive initiation of new updrafts as opposed to propaga- d. Session 4: Analysis and Display of Data (Poster Session ) tion due to rotation. Johnson performed multiple-Doppler (E. M. Agee) analyses of a storm to evaluate the effects of including sur- This session displayed a diversity of approaches to incorpo- face data as a lower-boundary condition. Inclusion rating new data sources and burgeoning new technologies of such data resulted in a significant directional shift of the into the forecasting arena. Because the new data sets and horizontal wind vector, with the effects being concentrated in technological capabilities are unfamiliar to most forecasters, the lowest one kilometer. Parsons et al. combined Doppler- the majority of papers in this session were exploratory. derived three-dimensional wind fields with the Klemp-Wil- Papers by Lin et al., Maier and Hiscox, McNulty et al., helmson numerical cloud model to study microbursts. They Wade et al., and Pratte et al. were concerned with prospective found that negative buoyancy resulting from evaporation operational data sets (including -occurrence maps, below cloud base may be the primary driving mechanism for Doppler radar, automated surface observations, and satellite microbursts. sounding retrievals). These papers concentrated on explor- ing the forecasting potential of new observing systems. c. Session 3: Remote-Sensing Techniques II(R. W. Walkoand In contrast, the papers by Xiang and Beckman, Green and M. M. Wolfson) Weaver, Adler and Markus, Hasleretal., Moore, Thompson The papers presented in this session were examples of the and Lin, Beasley et al., Jones et al., and Bonter and Kung complexity in thunderstorm structure, evolution, motion, concentrated on new approaches to treating more-familiar and impact on the environment that has been revealed data sets. The focus in most of these papers was clearly on through the use of remote-sensing techniques. Two tech- using computer processing to more fully exploit the informa- niques, Doppler radar and lidar, formed the basis of most tion contained in such data. papers. Donaldson and Desrochers used an estimate of the rota- tional kinetic energy derived from single-Doppler data to 4 At the beginning of the poster sessions, each paper was intro- classify on a scale indicative of the damage duced and its presenter gave a 45-second summary, in some cases caused by the subsequent tornadoes. Fulton and Zrnic used a showing a few key slides or viewgraphs. Posters remained on display vertical cross-section through a Doppler volume scan to re- through the following day.

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Zubric and Riese addressed the application of expert sys- ducing a low-level downdraft, and downdraft-induced pres- tems to the weather-forecasting problem. This automated sure perturbations were discussed. The paper by Tao and approach to decision making has been exploited with varying Simpson was retitled "Role of Ice Microphysics on Dynamic degrees of success in other fields. The application of tech- Structure of Slow-and Fast-Moving Tropical Squall Lines." nique to is controversial and so the pres- It was found that the simulated tropical cloud lines were entation stimulated much discussion, pro and con. aligned along the environmental shear. Their propagation speeds were well predicted by the model. A simple ice-phase parameterization was found to have an impact on the simula- e. Session 5: Modeling I {Storm Scale) (G. M. Heymsfield tions. The authors noted that the cloud-top structure was and R. F. Abbey) poorly simulated in that the anvil extent was not as large as observed. The papers in this session covered a variety of aspects of thunderstorms. The first two papers dealt with the subcloud environment. Anderson et al. described results for a thunder- f. Session 6: Modeling II (The Me so scale) (K. K. Droegemeier) storm outflow obtained using a "quasi-compressible" form of the equations of motion for simulating the subcloud envi- Klemp et al. discussed the dynamics of a squall-line flow ronment. The quasi-compressible approximations have prop- based on numerical simulations. The simulations showed erties of both the fully compressible and the anelastic sys- that as the squall line passes through its life cycle, midlevel air tems, and have computational advantages over these systems. from the downshear edge of the line is entrained by the storm Droegemeier and Wilhelmson described the modeling of complex, leading to the periodic regeneration of cells along Kelvin-Helmholtz Instability (KHI) in a numerical simu- the line. It was noted that when modeled in three dimensions, lated thunderstorm outflow. A two-dimensional model with the lines behave somewhat differently than when modeled in high spatial resolution was used. KHI was successfully simu- two dimensions. lated, whereas it has not been evident in previous outflow Lipps and Hemler compared results from squall-line simu- models. lations using a two-dimensional model with open lateral The next two papers dealt with the dynamics of cloud tops, boundaries, a three-dimensional model with open boundar- particularly in relation to the thermal couplets sometimes ev- ies, and a three-dimensional model with two open and two ident in infrared imagery of the tops. Adler and Mack used a periodic boundaries. The most realistic results were obtained one-dimensional model to infer parcel dynamics in tropo- from the first and third approaches. The downdraft and out- pause-penetrating thunderstorms. The lapse rate just above flow characteristics were shown to be a function of the termi- the tropopause and the cloud-parcel mixing were important nal hydrometeor velocity. in explaining differences in cloud-top temperatures observed Using a mesoscale model, Lakhtakia and Warner pre- in the infrared observations. Three classes of overshooting sented a detailed picture of the role played by the elevated tops were proposed. Schlesinger discussed the effect of strat- mixed layer of warm, very dry air that flows northward off ospheric lapse rate on the results of a three-dimensional the Mexican Plateau. Their study focused on the SESAME thunderstorm model. Some of the results were similar to the IV case, when this layer was a key factor in determining the findings by Adler and Mack. In addition, there was evidence location and intensity of convection. The success of their of a "U" shape in the cloud-top temperature field, reminis- modeling effort was attributed to well-established initial cent of that seen in some satellite observations. conditions, and to the inclusion of detailed surface con- Krueger and Wakimoto described the use of a two-dimen- ditions (which controlled the differential heating rates). sional model to estimate the maximum wind speeds and the Wilhelmson and Klemp described results obtained from a space and time scales associated with dry microbursts. This simulation of the Oklahoma squall line of 19 May 1977 using model included simple microphysical and turbulence formu- both two- and three-dimensional numerical cloud models. lations and had coarser horizontal-grid resolution than the Improvements over previous work on the same case included outflow simulations given earlier in the session. increased horizontal resolution. They reported good general Weisman and Bluestein discussed the dynamics of numeri- agreement between the two models and with corresponding cally simulated low-precipitation (LP) storms in an effort to observational studies, with the most notable discrepancy see differences between LP and storms. The general being in the average velocities generated in the two models. characteristics of LP storms could be simulated by setting The formation of a subsynoptic low at the intersection of a rainfall speeds to zero, i.e., particles were carried by the air cold front and a dry line was investigated by McGinley and motions without falling out of the cloud. The authors pro- Ray using a regional-scale numerical model. Their results posed several possible microphysical causes such as large show that the formation of this feature is strongly influenced number of small drops in the cloud to explain their simula- by surface heating, and that as the feature intensifies the ver- tions. tical wind profile of the local environment is modified to The last two papers used three-dimensional cloud models favor the development of intense deep convection. with the ice phase. Downdraft initiation within precipitating Das discussed the application of a two-dimensional axi- convective was investigated by Knupp and Cotton. A symmetric model to updraft-downdraft interaction in rotat- three-dimensional cloud model was run for cases ranging ing thunderstorms. He argued that the results were in agree- from low shear, low instability to high shear, high instability. ment with the conceptual model by Lemon and Doswell, The downdraft developed at mid levels on the downshear including the location of a tornado-like circulation at the up- flank in the wake region. The role of the precipitation in pro- draft-downdraft interface.

Unauthenticated | Downloaded 09/23/21 10:03 AM UTC Bulletin American Meteorological Society 1147 g. Session 7: Scale Interactions (H. E. Fuelberg and will bring. An important emphasis of the session was the R. E. Schlesinger) need for adequate training of the operational workforce in order to insure the success of the NEXRAD program. The seven papers presented in this session addressed inter- actions between severe storms and their environment. The i. Session 11: Tornadoes, Downbursts, and Related Wind first four papers involved observational case studies, while Phenomena (J. Simpson and W. D. Rust) the last three presented theoretical models. Koch and Golus described a case study of interactions be- Rostek and Snow described laboratory experiments on tor- tween gravity waves and bands of convective precipitation nado-like vortices over rough and smooth surfaces. Their re- during the CCOPE in which shear instability just below an sults show the expected increased loss of angular momentum upper-level jet streak was considered a probable mechanism in the surface boundary layer over a rough surface. Conse- for wave organization. quently, vortices over rough surfaces are generally weaker Maddox emphasized that the low-level jet within the cen- than those over smooth surfaces, all other factors being tral United States may evolve differently in each of several equal. specific air-mass types. He hypothesized that this evolution is Using Doppler-radar data, Peterson was able to identify as a factor in nocturnal thunderstorm occurrences. a source of cloud rotation the eddies shed at the end of a large Burge and Curran stressed that storm environments are mountain ridge line. The details of the flow in the vortices mesoscale rather than synoptic scale, even during wide- were nicely resolved in the analysis. spread outbreaks. This mesoscale variability The behavior of a microburst was examined by War- can be sufficiently important to modulate the convective anauskas using dual-Doppler data. This showed a vortex storm type (e.g., supercell, multicell, etc.). propagation speed of 4 m*s_1 with possible steering from A damaging mesoscale wind storm in the Netherlands on winds at about 3 km. Comparison of damage path, surface 12 May 1983, accompanied by an apparent tornadic vortex network, and Doppler-radar data depict a microburst event but without visible funnel or parent thunderstorm, was re- during JAWS (Joint Airport Weather Study). A simple lab- ported by Forbes. Imbedded in an intense baroclinic meso- oratory simulation depicts rotor formation and movement, , tracking partly over the ocean, the storm was not essentially as analyzed. forced by boundary-layer heat flux or by orography, but a In an unusual study, Anderson documented the distribu- merger between the cold front and a trailing secondary tion of debris from the Barneveld, Wisconsin, tornado. trough appeared to be an important feature. Large pieces were found to have been transported many tens Using an assumption of steady Beltrami flow, Davies- of miles. The distribution of debris over such an enormous Jones presented a new model for the dynamic pressure per- area is not easily explained. There appear to be a number of turbations around an isolated axisymmetric updraft in a veer- implications regarding storm circulation. ing environmental wind profile. In contrast to earlier dynamic Bluestein described a "landspout" that was observed in a pressure models, pressure deficits (excesses) were placed in "broken squall line." The National Severe Storms Labora- the quadrant of maximum (minimum) wind speed. tory (NSSL) radars did not detect a in the rap- Carrier and Fendell raised the question of whether some idly growing parent line of cumuli. Little shear appeared in a observable quantity far removed from a tornadic vortex, and proximity sounding composited from surrounding rawin- thereby accessible to remote sensing, might provide a dis- sonde observations. The author suggested the possibility of criminant to indicate whether a vortex can evolve from a one- shear arising locally from intersecting outflows. The land- to a two-cell circulation. spout was located just on the sunny side of a cirrus boundary, A two-dimensional linearized nonhydrostatic model was the importance of which in temperature contrast and shear used by Sun to simulate mesoscale convection along the alteration was mentioned in the discussion. Great Plains dryline. Squall-line formation was found to re- Fujita and Stiegler documented the tornado tracks, dam- quire sufficient surface-layer moisture for a low lifting con- age patterns, and pressure drops associated with the storms densation level. Under suitable conditions, the model pro- of the 28 March 1985 Carolinas tornado outbreak. The pres- duced squall-line evolution in qualitative agreement with ence of a strong mesocyclone was emphasized but due to lack observations. of time, was not related to regional developments. One of the severe tornadoes occurred with a relatively low cloud top. The remaining tornadoes occurred with deep convection as h. Session 8: Operational Techniques (R. H. Johns) shown by very cold brightness temperatures in GOES IR Session 8 focused on current and proposed operational tech- data. niques for the detection of severe local storm events using In a contrasting approach to the same outbreak, Purdom radar. The topics addressed included 1) how to use current reported on combining satellite products with conventional equipment better (through improved techniques and train- data to help understand and eventually forecast the timing ing); 2) how prototype equipment (the Radar Data Processor and locality of severe events within a much larger storm sys- [RADAP II] system and computer algorithms) could pave tem. The satellite products included cloud-track winds, the way to the NEXRAD (Next Generation ) VISSR, and layer-averaged sounding from TO VS. The result- era; and 3) how NEXRAD data might be collected and ana- ing stability analyses led to maps of available buoyant energy lyzed more effectively. Severe-weather-warning statistics which helped identify the relative susceptibility of regions from Oklahoma and Colorado appeared to justify the auto- traversed by the storm system to convective forcing. In the mated, man-machine mix of technologies that NEXRAD talk (not in the preprint volume), smoothed anomaly fields

Unauthenticated | Downloaded 09/23/21 10:03 AM UTC 1148 Vol. 67, No. 9, September 1986 produced from TIROS microwave brightness-temperature detection radar, and a cloud-to-ground (CG) lightning-flash data were used to demonstrate its potential for revealing the location system. The intracloud flash rate increased when role of mid- and upper-level circulations in the storm event cyclonic shear increased and the CG flash rate was greatest as sequences, even in the presence of clouds. the mesocyclone dissipated. The hypothesis was advanced Neither of the last two authors had time to relate portions that the intracloud flash rate increases as updraft velocity in- of the puzzle to regional events, such as coastal secondary- creases during intensification of the mesocyclone, and that low development and flow damming by the Appalachians. the CG rate decreases as a result of the collapse of the weak The relationship of regional events to storm severity has been echo region. revealed by Kaplan's model and regional/mesoscale data Holle et al. reported that in an MCC, most of the CG light- analyses. The importance of relating the interacting scales of ning was coincident with the convective echoes, that is, with motion in severe-event studies was raised by Petersen in the the rapidly growing portions embedded in a larger region of discussion and is underlined by the session cochairs. stratiform precipitation. Mazur et al. presented S-band radar data on a multi-cell thunderstorm showing that during the early, rapid growth of j. Session 12: Thunderstorms and Related Phenomena a cell within the storm, lightning discharges were concen- (Poster Session) (G. S. Forbes and R. M. Wakimoto) trated in a region between the edge of the 50 dBZ reflectivity core and a decaying neighbor cell. This region appears to be The session was largely devoted to examination of the struc- at an altitude at which previous observations have found ture of thunderstorm phenomena via an assortment of plat- negative charge, radio emissions, and lightning radar echoes forms. Microbursts were studied by Wolfson et al. (Memphis- to be concentrated. The peak of lightning activity appeared area surface mesonetwork), Bedard and Caplan (FM-CW to occur when a growing cell and a decaying cell merged. radar and Boulder Atmospheric Observatory tower), and Goodman observed CG lightning activity associated with Hjelmfelt and Roberts (Doppler radar). Knupp and Jor- MCC using a four-station detection and location system. It gensen examined a -producing storm using air- was observed that rates of 2000 flashes per hour (hourly av- borne Doppler radar; Wright examined box echoes with the erages) were sustained for several hours; rates approaching NWS Marseilles, IL Doppler radar; Harris et al. presented a 4000 per hour were observed occasionally. Evolution and technique for gust-front detection and prediction using decay of CG activity with time could be represented by em- Doppler radar; Scott examined a dissipating gust front mov- pirical relationships of exponential form. ing through a surface mesonetwork. Rust and MacGorman described a system of thunder- Bluestein examined wall clouds having an apparent eye- storms that were found to have produced an unusually high like structure. In presentations dealing with interaction of percentage of positive CG flashes. Of the various quantities scales, Anderson examined a spiral echo with a subsynoptic- that were examined for correlation with this activity, only the scale cyclone accompanying the Barneveld, Wisconsin, tor- wind shear across the 850-300 mb layer correlated well with nado and Simpson et al. examined similarities of certain tor- the occurrence of positive flashes. nadoes, , and dust devils. Ziegler et al. reported on the results obtained when mea- Many of the posters contained material relevant to severe- surements of cloud physical and electrical parameters asso- weather forecasting. Weiss dealt with forecasting hurricane- ciated with a mountain thunderstorm were used to initialize a related tornadoes. The nature of mesoscale divergence fields numerical cloud model. The model involved cloud growth was examined by Ulanski and Heymsfield, and by Smith et and kinematics, precipitation growth, collisions between al. The forecasting of MCCs in Iowa and Montana was dis- cloud particles, and noninductive charge transfer and sepa- cussed by Barlow and by Lussky, respectively. Hirt focused ration. The computed rate of charge separation (~10 C • min-1) on severe-thunderstorm forecasting in North Dakota, while was of the same magnitude as that determined for the rate of Moller and Ely discussed the problems of issuing warnings in charge transfer in the accompanying CG activity. This con- situations involving intricate scale interactions without rec- clusion is sensitive to the amount of charge transferred per ognized signatures. particle collision assumed in the model. Marshall et al. described results obtained using instru- k. Session 13: Electrical Phenomena (W. Beasley and mented balloons to carry electric-field meters and rawin- C. R. Church) sondes into the anvil of thunderstorms. The densities of negative charge in the screening layers of these anvils were Meteorologists are becoming aware that an understanding of determined. The existence of very high electric-field strengths electrical phenomena is an integral part of a complete knowl- (~ 105 V • m"1) at large distances (up to 50 km) from main pre- edge of severe storms. Several papers in this session pre- cipitation areas was established. sented new insights concerning relationships between electri- cal phenomena and other, more traditionally accepted /. Session 14: Operational Techniques II (J. T. Curran) observables. Much of the progress is the result of the develop- ment of new systems for detecting and observing lightning. It Seablom and Snow described the development of the Purdue was suggested that techniques now available make possible Regional Objective Analysis of the Mesoscale II, a set of nu- both enhanced understanding of storm physics and dy- merical routines designed to produce analyses of surface data namics, and improved short-term forecasts and warnings. that exhibit better hour-by-hour continuity. This is accom- MacGorman et al. discussed observations of two tornado- plished by incorporating data from previous hours into an bearing storms made with a Doppler radar, a lightning- analysis. Bothwell et al. presented an improved objective-

Unauthenticated | Downloaded 09/23/21 10:03 AM UTC Bulletin American Meteorological Society 1149 analysis and data-display system in which surface data oral presentation, for best poster display, and for best talk by changes for any operator-controlled time period are dis- a first-time presenter. Candidates for awards were nomi- played. Derived fields with effective noise reduction provide nated by their respective session chairpersons and by mem- forecasters with improved real-time analysis tools. bers of the Conference Program Committee. The Program Szoke et al. summarized knowledge of low-level bounda- Committee had the difficult choice of selecting the winners. ries in the High Plains as convective initiation mechanisms, The first graphics award was presented to T. T. Fujita at focusing on the difficult-to-observe thermodynamic struc- the 9th Conference on Severe Local Storms in 1975. Since ture of the lowest few kilometers. The use of a mobile sound- Fujita's graphics are consistently unique in their degree of ing system to observe the boundary structure and the role of clarity, organization, and use of color, conference commit- such data in the short-range forecast were discussed. Mc- tees have felt that it would not be fair for him to win at every Carthy presented several case studies demonstrating that the conference; thus, he and members of his group have not been presence of a sharp temperature gradient in the leading edge eligible for consideration for subsequent awards. With time, of a convective cell associate with is a reliable indi- this award has become known as the "Ted Fujita Award for cator of strong, often damaging straight-line winds. Best Graphics." Homan and Petersen presented a simple isentropic poten- The awards for best poster and for best first-time presenta- tial-vorticity model designed to predict short-term changes tion were initiated at the 10th and 11th conferences, respec- in the local static stability and moisture structure. The model tively. The intent of the Best Poster award is to help promote was used to construct sounding profiles around severe-con- that form of presentation, while that of the Best First-Time vective outbreaks. The results indicate the model can be ef- Presenter award is to encourage newcomers to the field, par- fective in isolating areas that have potential for severe- ticularly graduate students. weather development, six to 12 hours ahead of time. An awards ceremony was held immediately following the Dos well et al. presented a fresh look at an old tool: the To- close of the last session. The Best Graphics award, consisting tals Index. His results suggest that closer scrutiny of the of a plaque and a check for $ 100, was given to S. G. Benjamin 700-500 mb lapse-rate patterns can provide better continuity (of PROFS/ERL/NOAA and NCAR) and J. M. Lanicci (of in the evolution of an unstable "air mass" than can be ob- the Air Force Geophysics Lab) for the graphics accompany- tained from severe-weather indices that include low-level ing their presentation titled "Effects on Dryline Behavior sounding parameters. Lanicci showed the importance of the Due to Soil Moisture and Topography: Numerical Results capping inversion or lid in the severe-storm environment. from SESAME I and SESAME IV." The Best Poster Display The integration of lid-identification techniques into conven- award, also consisting of a plaque and a check for $100, was tional analysis schemes can give good indications of severe- given to D. R. Smith, E. M. Agee, and T. E. Klingler (all of weather potential due to lid removal. Miller described the Purdue University) for their poster titled "Severe (and Non- Severe Weather Forecast and Detection System (SWORD). Severe) Weather Development in the Upper Midwest on 27 The system is an operationally oriented analysis, display, and April 1984." The award for best First-Time Presentation, forecast program for tornadoes, lightning, high winds, freez- consisting of a plaque and a colorful windsock, was given to ing precipitation, and . W. F. Rostek (of Purdue University) for his paper (co- The session provided a unique blend of papers on the im- authored with J. T. Snow) titled "Surface Roughness Effects portance to the severe-weather forecaster of integrating sur- on Tornado-like Vortices." face, upper-air and satellite data. Prediction of severe storms The untiring efforts of R. W. Przybylinski, Chairman of is best accomplished by careful selection and evaluation of the Local Arrangements Committee, of J. T. Curran, Meteor- parameters using a spectrum of analysis tools, coupled with ologist-in-charge of the Indianapolis National Weather Serv- an understanding of convective dynamics. ice Forecast Office, of about 20 members of the Central Indi- ana Chapter of the American Meteorological Society, and of 3. Award winners the students of the program at Purdue It has become a tradition at the conferences on severe local University were also recognized. It was because of their good storms to present awards for best graphics accompanying an work that the conference was an unqualified success. •

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