Stephan B. Smith*, Thomas M. Graziano1, Richard A. Lane1,
William O. Alexander1, Michael D. Eilts2, J.T. Johnson2,
James W. Wilson3, Rita D. Roberts3, Donald W. Burgess4,
David H. Kitzmiller*, Robert E. Saffle5, Robert C. Elvander1,
Steven M. Zubrick6, Joseph T. Schaefer7, Steven J. Weiss7, and David A. Imy7

* Techniques Development Laboratory
National Weather Service, NOAA
Silver Spring, Maryland

1 Office of Meteorology
National Weather Service, NOAA
Silver Spring, Maryland

2 National Severe Storms Laboratory
Environmental Research Laboratories, NOAA
Norman, Oklahoma

3 Research Applications Program
National Center for Atmospheric Research
Boulder, Colorado

4 WSR-88D Operational Support Facility
National Weather Service, NOAA
Norman, Oklahoma

5 Advanced Development and Demonstration Laboratory
National Weather Service, NOAA
Silver Spring, Maryland

6 Forecast Office
National Weather Service, NOAA
Sterling, Virginia

7 Storm Prediction Center
National Weather Service, NOAA
Norman, Oklahoma


As part of its modernization, the National Weather Service (NWS) is employing new observing systems and technologies to better accomplish its mission of issuing timely warnings of severe weather and flash floods. Providing WSR-88D Doppler radar, GOES-Next satellite imagery, lightning location data, and Automated Surface Observing System (ASOS) observations to forecasters in the form of userfriendly displays in the Advanced Weather Interactive Processing System (AWIPS) can improve the accuracy and timeliness of warnings. However, the enormous volume and great variety of data can potentially overwhelm the forecaster tasked with monitoring and issuing warnings for many storms. There is a need, therefore, to provide automated storm detection, phenomenon classification, severity monitoring, and nowcasting that would allow the forecaster to make better informed warning decisions.

This paper provides a brief overview of a new collaborative effort involving the NWS, the National Severe Storms Laboratory (NSSL), and National Center for Atmospheric Research (NCAR), the main goal of which is the development of an automated convection guidance package for AWIPS called the System for Convection Analysis and Nowcasting (SCAN). More information is available from the SCAN homepage at


The goals of SCAN are (1) to detect, analyze, and monitor convection and generate short-term probabilistic forecasts and warning guidance automatically within AWIPS and (2) to combine previous research and development efforts into one integrated approach to forecasting convection.


SCAN is divided into two basic functionalities: (1) that of detecting and monitoring convection and (2) that of forecasting it (Fig. 1). The former will be composed of a variety of algorithms driven primarily by the array of high resolution observing systems of the modernized weather service. The goal of these algorithms is to automatically diagnose and classify the severity of thunderstorms as well as their potential to produce heavy rain. The forecast component of SCAN is divided into two subcomponents. The Short-Range component will provide gridded guidance (e.g. MOS, River Forecast Center flood guidance, and the National Center for Environmental Prediction (NCEP) products) which focuses on time frames suitable for the formulation of watches and advisories (1-6 hours). The Nowcast component will provide expert system generated, 0-1 hour forecasts of thunderstorms tailored to the issuance of "short-fuse" warnings. 

This framework has the advantage of allowing for improvements in, and additions to, the individual components without affecting the overall system functionality. This will be important, for example, in implementing new hybrid detection algorithms that operate off of fully integrated, remote-sensor data.

There are many motivations for developing SCAN. First, it supports the modernized end-to-end forecast process by making optimal use of the enormous volume and great variety of advanced observational data, model output, and valueadded guidance within AWIPS, as well as yielding a more efficient, effective, and consistent means of issuing timely and accurate watch/ warning/advisory products. Second, SCAN establishes a mechanism for the implementation of well-tested research applications in AWIPS. Third, it represents a vehicle in which to implement high resolution, short-term probabilistic quantitative precipitation forecast guidance for risk based flash flood forecasting. Finally, SCAN supports NWS watch decentralization by creating a means for local modification of watch guidance issued by the NCEP's Storm Prediction Center (SPC), and by integrating SPC and SCAN products to generate warning guidance.


During the 1997 convective season, a SCAN prototype consisting of an integration of NSSL's Warning Decision Support System (Eilts 1997), NCAR's Thunderstorm Auto-nowcaster (Mueller et al. 1997) and the NWS's Thunderstorm Product (Smith and Churma 1996) was tested at the Washington D.C.-Baltimore forecast office in Sterling, Virginia. The purpose of the field test was to integrate these software applications and examine the usefulness of the combined products as a tool for the short-term and warning forecaster. The SPC provided probabilistic DAY-3 convective outlooks for the SCAN area primarily to assist in travel planning and staffing coordination for the larger convective events. Results of this and additional field tests will be implemented into baseline AWIPS in a stepwise fashion beginning in early 1999. This cycle of field testing/risk reduction followed by AWIPS implementation is designed to accelerate the rate of technology transfer into NWS forecast offices and to bring rapidly to bear the fruit of applied research onto the NWS's most critical mission, watches and warnings.


The authors would like to thank the programmers and meteorologists at TDL, NSSL, and NCAR for their skilled work in programming and developing the SCAN prototype. We would also like to thank the forecasters and operational staff at Sterling for their cooperation and assistance in organizing and carrying out the 1997 field test. The SPC outlook forecasters are gratefully acknowledged for the their professional expertise in preparation of the SCAN Day-3 convective outlooks. SCAN is funded by the NWS, the National Science Foundation, and the U.S. Weather Research Program.


Eilts, M. D., 1997: Overview of the Warning Decision Support System. Preprints 28th Conf. on Radar Meteorology. Austin, Amer. Meteor. Soc. 402-403.

Mueller, C., R. D. Roberts, and S. G. Henry, 1997: Thunderstorm automated nowcast system realtime demonstrations. Preprints 28th Conf. Radar Meteorology. Austin, Amer. Meteor. Soc., 406-407.

Smith, S. B., and M. E. Churma, 1996: An overview of the AWIPS Thunderstorm Product. Preprints 15th Conf. on Weather Analysis and Forecasting. Norfolk, Amer. Meteor. Soc. 297-300.