The Understanding of Severe Local Storms Has Advanced Greatly Based on Numerous Theoretical

REPORT OF THE FIRST STUDY CONFERENCE ON AVIATION WEATHER HAZARDS

Kelvin K. Droegemeier School of Meteorology and Center for Analysis and Prediction of Storms University of Oklahoma University of Oklahoma, Norman, OK 73019 David Braaten Department of Physics and Astronomy University of Kansas Lawrence, KS 66045 David Rodenhuis NOAA/NCEP Aviation Weather Center Kansas City, MO 64106

1. PREFACE in preparation by the Office of the Federal Coordinator of Meteorology. It is perhaps appropriate that a number of The FAA Aviation Weather Research Program attendees flying to the First Study Conference on and its associated nine Product Development Teams Aviation Weather Hazards -- including the keynote (PDTs; Sankey et al., 1997) represent the principal speaker -- were diverted from their destination airport, mechanism by which needs are prioritized and applied or encountered significant flight delays, due to an research is conducted to meet them. Most of the intense mesoscale convective system that moved research and development is carried out at national through the southern Great Plains on 4 October 1998. laboratories, and operational testing is performed in That event underscored the importance of weather to collaboration with both providers and users of weather the entire aviation system, as well as the need for rapid information. implementation of technology to mitigate disruption Despite notable progress, concerns have been and exposure of the flying public, as well as military raised regarding the FAAs activities in aviation weather aviators, to hazardous conditions. research in the context of safety, the transfer of new technologies into the operational system, and the delivery of information to end users (GAO, 1998). One 2. INTRODUCTION notable cause appears to be communication and organizational barriers between the FAA and National The impact of weather on the safety and Weather Service (NWS), as noted in a recent efficiency of the national air transportation system in comprehensive review of the Aviation Weather Center the US is well known (e.g., NRC, 1995). The costs (AWC) conducted by the University Corporation for associated with delays alone are on the order of $5 Atmospheric Research (UCAR) on behalf of the billion per year, 65% of which are generally attributed National Centers for Environmental Prediction (NCEP). to weather (Evans, 1997). Contributing factors include In response to this and other extreme surface weather (e.g., fog, high winds, freezing recommendations, particularly the need for the AWC to precipitation), along with thunderstorms and their establish strong ties with the university community associated wind shear and turbulence at all flight levels. similar to those now in place at many of the other The other major consideration -- aviation safety, is of NCEP centers, the AWC, in partnership with the course the most important. National Transportation Department of Physics and Astronomy at the University Safety Board statistics from 1983 to 1995 show that of Kansas (KU) and the Center for Analysis and 33% of all commercial carrier accidents were attributed Prediction of Storms (CAPS) at the University of to weather, with 33% of all fatal accidents being Oklahoma (OU), organized the First Study Conference weather-related (Salottolo, 1994). on Aviation Weather Hazards from 4-6 October 1998 The Federal Aviation Administration (FAA) on the KU campus. and other agencies have aggressively pursued the aviation weather problem in response to needs 3. CONFERENCE GOALS articulated by all facets of the aviation community. The principal goal of the Study Conference, ______which was co-sponsored by NOAA/NWS, the FAA, the Corresponding Author Address: Prof. Kelvin US Weather Research Program, and the NSF EPSCoR Droegemeier, 100 East Boyd, Norman, OK 73019 (Experimental Program to Stimulate Competitive ([email protected]) Research), was to address one of the 5 research Numerous strategic plans have been prepared (e.g., priorities of the NOAA/NWS Strategic Plan: "Locally NRC, 1994; NRC, 1995; NAWPC, 1997), and the draft hazardous weather, especially severe convection, winter of a National Aviation Weather Initiatives plan is now weather, and phenomena that affect aviation." The Conference brought together administrative leaders, continues to focus on institutional arrangements for faculty scientists, and operational users and providers of moving research quickly into operations, and points to a aviation weather information in an effort to number of successes including the globally-relocatable complement and support the many activities now MM5 mesoscale window model system, which was underway by the FAA PDTs. adapted in collaboration with NCAR, Argonne National Of particular significance during the Laboratory, and other groups. Conference, and its many discussion sessions, was the The Air Force is also expending considerable identification of basic research topics of high priority to effort to provide an integrated view of the weather to aviation weather that can be rapidly prototyped and the end user via the Military Aircrew Information tested/implemented quickly and in the most cost System. This comprehensive framework integrates all effective manner possible while maintaining high sources of information and provides customized intellectual standards and satisfying the immediate and decision making resources tailored to the needs of the practical needs of the users. The integration of war fighter. universities into these activities, and the leveraging of Maj. Babcock closed the presentation by the considerable State and Federal investments in noting that the easy goals have been met, and that in university infrastructure and research, was a light of constrained resources, the challenge for the foundational theme of the Conference. future will be the development of effective partnerships and mechanisms for coordination so as to leverage 4. STRUCTURE community resources in the most effective manner possible. The National Aviation Weather Initiatives The Conference was organized around the Program, now in draft form, will provide a framework following sessions: for such partnerships and will involve all major funding agencies, along with universities and the private sector.  Operational Needs and Improvements of the Aviation Community b. Operational Needs and Improvements of the Aviation Community  Where We're Going & How We're Doing W. Qualley, Manager of Weather Services at  Icing and Visibility American Airlines, provided the opening remarks for this session. He noted that commercial airlines have  Operational Modeling several aviation hazard concerns, most of which are well-known and well-studied. Although the relative  Thunderstorms, Turbulence, and Gravity Waves importance of each varies among the airlines, depending in part upon their operating philosophy, they Each session was opened by an invited presentation, the are generally as follows (in rough order of importance): purpose of which was to overview the topic and provide turbulence (clear-air and convective induced), icing, a list of high-priority issues as a preface to the shorter, volcanic ash, and convective weather (initiation, topically more in-depth talks that followed (the movement and dissipation). Another -- ceiling and program, abstracts, and list of attendees can be found visibility -- is less of a safety issue but is certainly an on the world wide web at http://chinook.phsx.ukans.edu efficiency concern. /~braaten/hazwx.html. A plenary discussion period Because each airline responds differently to a followed each session, and on the last day a final given weather situation (snow, thunderstorms, low plenary was held to summarize findings and establish visibility), airlines are willing to invest directly in plans for the future. research relating to their particular needs, and The conference keynote address, originally indirectly, through FAA and other government scheduled for Sunday evening, October 4, was delayed agencies, in research on issues which affect all of by weather and delivered the next morning by Major commercial aviation in a similar way, such as Mike Babcock, Office of the Federal Coordinator, on turbulence. With increasing use of the internet, behalf of Brig. General Fred Lewis, Director of Air operational forecasters now have more tools, including Force Weather. Mike Eilts, Assistant Director of the experimental ones, than ever before. At times they are National Severe Storms Laboratory, delivered the overwhelmed by the number of forecast models and dinner address on Monday evening, October 5, products available, and it will probably be a number of describing the capabilities of and future plans for the years before forecasters have learned enough about the NSSL Warning Decision Support System (WDSS). nuances of each model to be able to determine which works best in a given weather situation. Although the 5. SESSION SUMMARIES duties of the operational forecaster will change dramatically in the years ahead, it will be quite some a. Keynote Address time before the need for them is gone entirely. R. Reinking noted that the use of advanced Maj. Babcock overviewed the structure and short-wavelength radars (K and X band) holds ever mission of the Air Weather Service, noting that the increasing promise for detecting supercooled drops in previous strategy of "cope and avoid" has been clouds, and that while the WSR-88D and TDWR are dismissed in favor of one that involves "anticipating exceptionally important systems, they are not the and exploiting" the weather. The US Air Force solution to all problems. He further demonstrated the viability of multi-parameter radars to detect icing that per NWS policy. The ADDS source code will be might pose a danger to aircraft. provided to vendors in the near future. Competition and cooperation were the key It was noted during this session that airlines phrases of the presentation given by T. Fahey, manager and various air traffic control elements typically use of meteorology at Northwest Airlines. He stressed that, different information and displays. A key goal during among users of weather information -- particularly the past year was the generation of a consensus forecast commercial airlines -- similarities are more common among several airlines and the FAA as part of SWAP than differences, and cooperation is effective only if '98 (Severe Weather Avoidance Planning). In this both sides benefit at equal value. He cited Eastern manner, presenter A. Shantz of NCAR noted that every Airlines, where competition led to failure, and Pan Am, group was "reading from the same sheet of music," where conciliation resulted in a similar outcome. He thereby improving overall system efficiency. Another also commented on the rather severe problem of similar venture is Collaborative Decision Making duplication of effort, the lack of coordination among (CDM), a joint effort among the FAA, ATC, Command CWSUs (cited also in the UCAR review of the AWC), Center, and airlines that seeks to share information so and a severe under-utilization of resources. The AWC that all airspace system management elements -- from has about 50 staff, and 6 or 7 commercial airlines have the Command Center down to the pilot -- are working meteorology staffs. There exist 21 CWSUs and some from the same common framework of information. The 120 NWS Forecast Offices. Can duplication be effort seeks to pre-empt FAA capacity alerts, with the reduced and efficiency increased? view that a pro-active approach by the airlines will R. Baker of UPS described the automated prevent the shut-down of a particular region, thus aircraft reporting system and its use in operations. In preventing the alert from being needed. contrast to some other airlines, UPS is impacted F. Mosher of the AWC closed this session significantly by fog and frost, and the automated reports with a discussion of the future needs of aviation help considerably. The new humidity sensor, though weather. One of the most important is improved not without technical problems, works exceptionally numerical guidance, which will take the form of models well when operational, though as fleet sizes increase, having spatial resolutions down to 5 km within the next the cost to provide these and standard MDCRS data few years. Although continued rapid improvements in may become prohibitively large. It is important that the computing and networking capacity will guarantee such community continue to advocate these data and show capability, the observing systems are not improving their value in forecasting, especially numerical models. their spatial resolution at the same rate. Techniques for The final presentation of this session was using Doppler radar, profiler, and commercial aircraft given by D. Norquist, Air Force Research Laboratory, data will thus be critical for the future of aviation who demonstrated a notable success story in rapid weather forecasting. prototyping -- the diagnosis of cloud ceiling from The installation of in situ devices for mesoscale model output. The US Air Force is pursuing measuring turbulence and icing intensity will be a number of strategies in this regard, including a important for tactical avoidance as well as forecast statistical regression based on the most recent 10 days verification, and the conversion of data into of gridded output. The top 20 predictors are selected in information, and its rapid dissemination to both a "dynamic MOS" approach, and strategies now exist meteorologists and non-meteorologists, is a particular for discriminating among cloud type, cloud altitude, etc. challenge for the future. Finally, the roles of the These experiments are being performed with the MM5 Federal Government and private sector need to be model at 48 km resolution, and efforts will soon be clearly defined, and policies regarding the use of the directed toward a fully dynamic/prognostic approach. internet as a formal delivery system must be revisited in light of user preference for the internet as well as the c. Where We're Going & How We're Doing attractive nature of its bandwidth and low cost. The phrase "operationalization of technology", d. Icing and Visibility i.e., the move of technology into operationally useful forms, became a key phrase of the Conference after Prof. P. Wang of the University of Wisconsin- being introduced by Col. C. French, Air Force Weather Madison opened this session by reviewing the basics of Agency (AFWA) Commander. One of the key aspects cloud physics and supercooled drop behavior in the of this capability is verification, and L. Sherretz of the context of aviation. He noted that a connection NOAA Forecast Systems Laboratory (FSL) described between research and engineering is needed to fully the FSL Real Time Verification System (RTVS) and address the aircraft icing problem, i.e., a link between Aviation Digital Data Services (ADDS), both of which the study of drop structures and their interactions with are being tested and will eventually be maintained the flow stream around airfoils. Research-model operationally by the AWC. ADDS provides route- parameterizations need to be streamlined and simplified specific graphics of key aviation weather parameters to for use in operational forecast models, and those same pilots, dispatchers, weather vendors, and FAA parameterizations need to be verified by in situ automated systems, and also enables the user to provide observations as well as remotely sensed variables (e.g., quick feedback to the developers. The ADDS is now from a multi-parameter radar). available on the internet (adds.awc-kc.noaa.gov), L. Kelley overviewed the Alaska Aviation though the internet is not a formal delivery mechanism Experimental Forecast Facility and described their efforts to evolve a complete aviation weather hazards system. He highlighted the very strong collaborations evaluated using pilot reports, and the results indicated among various groups in Alaska, particularly the human that "synoptically-based" techniques were superior to factors efforts underway at the University of Alaska. those which relied upon model grid scale microphysical J. Hilliker of the Pennsylvania State University parameterizations, e.g., representations of ended the session by discussing a technique for supersaturation in clouds. forecasting marine stratus burnoff. This statistical Maj. P. Roohr of AFWA closed the session by approach uses surface observations from sites near the describing AFWAs application of MM5 as a multi- forecast location, and results show that it is superior to window model -- one of the notable success stories in persistence, climatology, and MOS. Further, it is Air Force weather during the past decade. At the inexpensive, requires no model data, and can be applied present time, the AFWA runs eight 36 km windows (48 at any location. hr forecasts) and eight 12 km nests (24 hour forecasts) using a 70-node IBM SP2. The initial and boundary e. Operational Modeling conditions are derived from NOGAPS, the NCEP aviation model, or the Eta, and a considerable number Bill Cotton of the Colorado State University (10 Gbytes/day) of aviation-specific products are overviewed the current real time configuration of the produced including aviation impact variables Regional Atmospheric Modeling System (RAMS), (turbulence, icing, meteograms, cloud products). which involves initialization from the Eta model using Extensive verification is performed in real time, and 2-way nesting with the finest grid at 12 km resolution. emphasis is now being placed on grids of even higher At the present time, no cloud-radiation interactions are resolution. included, though full surface physics are utilized. Considerable effort has been directed toward the f. Thunderstorms, Turbulence, and Gravity Waves development of advanced microphysical parameterizations, though the computational load for D. McCann of the AWC started the session the prediction of drop and CCN spectra can be as much with a talk that asked an important question: "Is CAT as 100 times that for more conventional bulk schemes. caused by wind shear?" He discussed the various terms He noted that computational resources continue to in the kinetic energy budget equation and noted that improve dramatically, with workstations networked via dissipation may be the best indicator of turbulence that fast switches representing one way for obtaining an aircraft will "feel." The discussion focused on the significant capacity at low cost. simplification of such turbulence models and the extent K. Droegemeier, University of Oklahoma, to which over-simplification may result in "throwing overviewed the CAPS real time forecast system - the out the baby with the bath water." The issue of scale- Advanced Regional Prediction System (ARPS), which dependence of TKE was also discussed, along with the has been running on a daily basis for the past several fact that wind shear and the Richardson number are not years. Currently, the system produces 5 forecasts per always well correlated -- thus limiting the performance day -- all with full physics -- including 4 at 27 km of the former as an indicator of turbulence. McCann resolution and one nest at 9 km resolution. The ARPS proposed using the inverse Froude number to categorize Data Analysis System (ADAS) also runs continuously, turbulence intensity, noting that turbulence and gravity and every hour both produce over 2000 products, many waves are not necessarily synonymous (unless the customized for aviation via Project Hub-CAPS with waves break). American Airlines (see http://www.hubcaps.ou.edu). C. Mueller of NCAR described the National He noted that, in contrast to virtually all other Convective Weather Forecast Product as a means for groups, CAPS not only runs high-resolution grids, but addressing the 0-2 hour forecast time frame. This also assimilates high-resolution data from the WSR- product is aimed at dispatchers and the ATC, and has 88D, satellites, profilers, and surface networks. been used in test mode by Delta, Northwest, and the Further, CAPS is about to ingest commercial aircraft AWC. One drawback is that it appears to work best for reports. Droegemeier closed the presentation by the most predictable events, e.g., squall lines; however, showing forecasts made with no radar data, with NIDS such events also have the greatest impact on an airport. data only, and with WSR-88D full Level II (base) data. She also noted that lightning improves data In the particular case shown, the storm could not be latency and provides information in traditionally data- forecast properly without Level II data. This result sparse regions (e.g., oceans). In the future, a national helped stimulate Project CRAFT (Collaborative Radar product is envisioned that spans many scales -- from Acquisition and Field Test), which is a joint effort terminal to regional to national, and will involve among UCAR/Unidata, the Universities of Oklahoma moving to regional models at resolutions down to 5 and Washington, and the Oklahoma State Regents for km. Higher Education to set up a prototype real time WSR- B. Sharman discussed enroute turbulence 88D Level II data ingest system for 8 radars across the prediction at NCAR, noting that the goals are southern Great Plains. determined largely by the associated PDT: the E. Kemp of the University of Oklahoma development of in situ measurements, the improvement continued the discussion of ARPS real time forecasts, of forecasting techniques, and the creation of focusing on verification of aviation impact variables via operational warnings for low-altitude turbulence. a joint USAF/COMET project at Tinker AFB in Given that turbulence cannot presently be predicted Oklahoma City. A large number of icing algorithms explicitly by numerical models, emphasis is being given developed at NCAR, FSL, AFWA, and the AWC were to identifying linkages between turbulence and the System. Early results suggest that most algorithms larger scales which presumably force it. perform similarly despite vastly different formulations. The NASA Aviation Safety Program is D. MacGorman ended this session by seeking to quantify turbulence using ACARS. They are describing how lightning data are applied to air traffic now using the RUC and applying various measures of operations. Three-dimensional LDAR systems have turbulence intensity which are weighted depending on been available for many years, but due to their how well they verify with observations. The combined comparatively short range and high cost relative to index -- the Integrated Turbulence Forecasting other systems, have seen limited use. One notable Algorithm -- has proven superior to any single attribute of lightning data is their low algorithm. Eventually the system will include fuzzy bandwidth/volume, rapid availability, and capability of logic. mapping flashes in 3-D. A new VLF system developed Donna Tucker, University of Kansas, in England (RDI Sferics Network) -- which can cover overviewed numerical simulations of low-level vast geographic areas -- appears to hold promise and turbulence generated by convective storms, mostly in has been tested, but is not currently operational. The the cold-air outflow, with emphasis on downdraft proposed Geostationary Lightning Mapping System forcing (evaporation versus melting). She commented represents a new capability, and the assimilation of on the importance of hydrometeor determination in the lightning data into mesoscale and storm-scale models prediction of hazardous low-level turbulence, and represents a tremendous opportunity for the future. reminded the audience that such turbulence can be found significant distances away from the parent storm. g. Dinner Presentation K. Droegemeier described results from a series of convective storm simulations in which spatial Mike Eilts reported in his Monday evening resolutions as high as 250 m were used in 3-D to dinner presentation on the NSSL prototype Warning capture explicitly the turbulence generated both within Decision Support System (WDSS) that has been tested the storm and in its near environment (convection- in NWS Weather Forecast Offices since 1994. The induced turbulence). Comparative experiments using 2 concept behind WDSS is similar to decision support km resolution -- which is very fine compared to current systems that have been built for other professions (e.g., operational models -- were shown to be inadequate for financial managers, insurance industry), where the resolving the turbulence, and the turbulent kinetic ultimate goal is to put the required information in the energy was shown to be a factor of 4 smaller relative to hands of the decision maker in a timely fashion. For the 250 m grid case. meteorologists making warning decisions, this means Large values of TKE were found well outside gathering data from all available weather sensors and the precipitation regions in the 250 m simulations, using image processing, artificial intelligence, and mostly downstream in the anvil, indicating that expert systems to help interpret data and turn them into reflectivity alone is not a good indicator of turbulence useful information. These data and information are intensity. A number of measures of turbulence, then easily accessible to the meteorologist through an including dissipation and the Richardson number, were interactive display. Statistically, the WDSS has shown compared in all simulations, with the former being to increase significantly the lead-time and skill of superior in a qualitative manner. It was noted that tornado and severe storm warnings at NWS Offices. while gravity waves (e.g., mountain waves) may be The NSSL has also developed the Common turbulent to an aircraft flying through them, they Operations Development Environment (CODE), which themselves are not turbulence except in regions of is a software tool the facilitates the development of new breaking. applications easily while allowing them to be run using D. Rhoda presented a video of ITWS showing archived data and/or real-time data. CODE was aircraft tracks superposed on convective echoes and stimulated by the need for an infrastructure that will navigational aids in the terminal area. Clearly depicted significantly streamline the technology transfer process was the dynamic nature of air traffic management, to NWS operational systems (e.g., WSR-88D and especially during heavy weather, and the potential value AWIPS). Thus, NSSL plans to develop CODE using for up-linking terminal weather depictions during the Applications Programmer Interfaces (API) from both final phases of flight (when pilots may be too busy to AWIPS and the WSR-88D. By doing so, all of the effectively manage the on-board radar, and when applications and display concepts developed and tested ground clutter limits its usefulness). in CODE should work directly on the operational The forecasting of upper tropospheric systems with little or no re-coding. turbulence using numerical model guidance was the principal focus of A. Marroquin's presentation, and 6. CONFERENCE SUMMARY, numerous comparisons among algorithms were made. RECOMMENDATIONS, AND PLANS The FSL diagnostic turbulence forecasting algorithms have been formulated to handle shear, gravity wave In light of space limitations, we summarize in breaking, and convection, and Marroquin commented bullet form the principal outcomes of the various that missing in the community is a coherent effort to plenary discussions. evaluate competing algorithms and fully understand their physical bases. For this purpose, the FSL has  The role of universities in aviation research and created the Algorithm Development and Verification development needs to be clarified and strengthened. Universities receive little direct funding from the FAA in aviation weather, and be-released National Aviation Weather Initiatives their representation on PDTs is notably thin. Program document.

 In the 1995 NRC report, the FAA was urged to 7. ACKNOWLEDGEMENTS take leadership in aviation weather; the impression by attendees is that more more could be done to The Conference was sponsored by the Federal effectuate this leadership. The PDT structure in Aviation Administration, the National Oceanic and particular is viewed to inhibit new collaborators Atmospheric Administration, the National Weather and initiatives. Service, the US Weather Research Program, and the National Science Foundation EPSCoR Program.  The difference between data and information is Additional support was provided by the NSF through vitally important, and consideration must be given Grant ATM92-20009 to the Center for Analysis and to what is really needed versus what is technically Prediction of Storms at the University of Oklahoma, feasible. ITWS is one success story -- a system and by the College of Arts and Sciences at the that alerts decision makers when a threat exists, but University of Kansas. does not present a lot of extraneous information. 8. REFERENCES CITED  A clearer, more effective and shorter path to operations must be developed in order to Evans, J.E., 1997: Operational problems of convective effectively utilize the remarkable developments weather in the national airspace system. Convective made during the past several years in aviation Weather Forecasting Workshop, Long Beach, CA, Amer. weather. Meteor. Soc., A1-A14.

 The general and business aviation communities GAO, 1998: FAA has not fully implemented weather-related have received relatively little attention compared to recommendations. Report to the Subcommittee on commercial carriers, yet suffer significant loss and Technology, Committee on Science, US House of disruption due to weather. Although economics is Representatives, GAO/RCED-98-130, 72pp. a major driver for commercial aviation, both it and general aviation must deal with safety issues. NAWPC, 1997: National Aviation Weather Program Thus, safety should be a focal point for future Strategic Plan. Prepared by the Joint Action Group for research, and opportunities in this area exist, Aviation Weather, for the National Aviation Weather particularly at NASA. Program Council. OFCM Document FCM-P32-1997, 31pp.  The NWS and FAA need to establish a more effective partnership in aviation weather, led UCAR, 1998: Review team report on the NCEP Aviation perhaps by a coordinating group similar to the Weather Center, conducted by the University NEXRAD Technical Advisory Committee. Corporation for Atmospheric Research on behalf of NCEP, 24 pp.  The AWC needs a visiting scientist program, much like those at NCEP and NCAR, to bring NRC, 1994: Weather for those who fly. National Academy stimulation to its scientific development and Press, Washington, DC, 100 pp. operational testing activities. Such an effort could be used to stimulate faculty involvement in NRC, 1995: Aviation Weather Services: A Call for Federal aviation weather research. Action and Leadership. National Academy Press, Washington, DC, 109 pp.  The NWS needs to re-visit its policy on the internet as a product delivery mechanism. Salottolo, G., 1994: Presentation to the National Aviation Weather Services Committee at the National Academy Additional thoughts and comments from of Sciences, 1 September, Washington, DC. conference participants were received after the meeting adjourned and are posted on the web at the address Sankey, D.A. and co-authors, 1997: Strategy and direction of referenced in section 4. the Federal Aviation Administration's Aviation Weather Key basic science issues identified for further Research Program. Preprints, 7th Conf. on Aviation, study include microphysical processes of winter storms, Range, and Aerospace Metr., Feb. 2-7, Long Beach, the fundamental dynamics of turbulence (both "clear Amer. Metero. Soc., 7-10. air" and that induced by convection), the short-term predictability of storm-scale weather (0-6 hours) including the relative merits of full dynamic models versus statistical techniques, and the assimilation of high resolution data (radar, lightning, satellite, commercial aircraft) into numerical models for use in diagnosis and forecasting. A more complete discussion of these and other issues can be found in the soon-to-