Overview
AutoNowCaster (ANC) has been integrated into the operational Multi-Radar/Multi-Sensor (MRMS) system running at NCEP. ANC's forecast products will be disseminated to the Aviation Weather Center (AWC) and to NWS's Weather Forecast Offices (WFOs). MDL will be maintaining the operational ANC including bugs fixes and software updates.
Background
From 2005 to 2010, the National Center for Atmospheric Research (NCAR), in collaboration with the National Weather Service, conducted a demonstration of the AutoNowCaster (ANC) system at the Dallas-Fort Worth Weather Forecast Office (Roberts et al. 2012). ANC was transferred from NCAR to the MDL, and it has been running at the MDL since 2010. In 2013, MDL conducted an objective analysis assessment of both the performance of ANC's convective likelihood and how it can be used as a tool to aid thunderstorm nowcasting (Ba et al., pending publication ). Since 2013, the ANC forecast products have been distributed to the Aviation Weather Center (AWC) via LDM. SIGMET forecasters from 2013's AWC summer experiment found the ANC convective likelihood provided good situational awareness to the overall storm environment.
Forecast Products
The primary forecast products of ANC are the Convective Likelihood Field and the Final Thunderstorm Nowcast.
The products of the AutoNowCaster can be seen at: https://mrms.nssl.noaa.gov/qvs/product_viewer
-
Convective Likelihood Field
ANC's convective likelihood field is obtained from fuzzy logic rules derived from knowledge of storm initiation and evolution obtained from research, field experiments, and exploratory tests conducted over several years (Wilson and Mueller, 1993; Wilson and Megenhardt, 1997; Roberts and Rutledge, 2003). ANC assimilates Weather Surveillance Radar-1988 Doppler (WSR-88D), surface, satellite, sounding, and Numerical Weather Prediction (NWP) data to analyze characteristic features of the atmosphere and produce nowcasts of convective likelihood. The analyses, which include evaluations of convective instability, surface mass convergence, and trigger mechanisms, are used to produce interest fields which are advected forward in time 60 minutes and converted into dimensionless likelihood fields using relationship functions developed by experts who have insight into the relevant physical processes (Mueller et al., 2003). These likelihood fields have a dynamic range from -1 to 1, where increasing positive values indicate regions of increasing likelihood of storm initiation and/or sustainment, and vice-versa. The likelihood fields are then weighted using values determined by subject matter experts, and all the weighted likelihood fields are summed to produce a convective likelihood field which is then filtered and smoothed. Values of the convective likelihood field >= 0.7 are considered indicative of convective initiation in the next 60 minutes.
-
Final Thunderstorm Nowcast
ANC's Final Thunderstorm Nowcast depicts (1) the 60-minute extrapolation of storms, including growth and decay, where a storm is defined to exist anywhere radar reflectivity >= 35 dBZ, and (2) areas where new storms are likely to initiate, with three levels of increasingly likely initiation represented by 25, 30, and 32 dBZ, respectively. ANC's Final Thunderstorm Nowcast provides forecasters valuable information about the evolution of both thunderstorms and the convective environment in the next 60 minutes.
References
Ba, M., L. Xin, J. Crockett, and S. Smith, 2017: Evaluation of NCAR's AutoNowCaster for Operational Application within the National Weather Service. Wea. Forecasting, 32, 1477–1490. doi:10.1175/WAF-D-16-0173.1
Mueller, C., T. Saxen, R. Roberts, J. Wilson, T. Betancourt, S. Dettling, N. Oien, and J. Yee, 2003: NCAR Auto-Nowcast System. Wea. Forecasting, 18, 545-561.
Roberts R. D., A. R. S. Anderson, E. Nelson, B. G. Brown, J. W. Wilson, M. Pocernich, and T. Saxen, 2012: Impacts of Forecaster Involvement on Convective Storm Initiation and Evolution Nowcasting. Wea. Forecasting, 27, 1061-1089.
Wilson, J. W., and C. K. Mueller, 1993: Nowcasts of thunderstorm initiation and evolution. Wea. Forecasting, 8, 113-131.
Wilson, J. W., and D. L. Megenhardt, 1997: Thunderstorm initiation, organization, and lifetime associated with Florida boundary layer convergence lines. Mon. Wea. Rev., 125, 1507-1525.
An Example of ANC Product
ANC Convective Initiation Likelihood with radar observation at valid time. Color indicates the likelihood of initiation, with increasing positive values used to indicate regions of increasing likelihood of storm initiation. White contours show radar reflectivities >= 35 dBZ; the dotted green line is the boundary entered by a forecaster; it represents the cold front that prevailed during this event.
