1. The Challenge of Convective Forecasting: Forecasting Issues by NCAR Colloquium on the Challenge of Convective Forecasting: 10-21 July 2006 Lance F. Bosart Department of Earth and Atmospheric Sciences The University at Albany/SUNY/ES-227 1400 Washington Avenue Albany, NY 12222

2. What has happened? Why did it happen? What is happening now? Why is it happening? What is going to happen? Why is it going to happen? Forecasting Philosophy: Bosart (2003)

3. Disconnect between research and operations. Inadequate technology transfer mechanisms. Inadequate communication processes. Inadequate representation of mesoscale weather systems. Why Does The Forecast Gap Exist?

4. Mesoscale Forecasting Roadblocks: A Personal Perspective Communications bottlenecks. Inadequate use of event-driven forecasts. Problems that make it difficult for weather scientists to address messy operational issues. Inadequate computer resources. Managerial infatuation with technology for technology’s sake independent of forecaster needs. Inadequate managerial appreciation of how human skills and resources are needed to extract the maximum operational advantage from technological advances. Inadequate technology transfer (e.g., use of mesoscale model “information”) into the operational sector.

5. What Are Some Forecast Needs? Matching forecast and observed variability. Mesoscale substructure within cyclones. Analysis, synthesis, and understanding. Rain versus snow versus freezing rain. Convection, convection, convection. Boundaries rule. Uncertainty rules.

6. "Customer Concern": Coupled jets. Cold fronts aloft. QPF distribution within a cyclone. Severe weather and mesoscale heavy rains and flooding. Weak cyclones (death by a 1000 tiny cuts) Behind the Concern: The weather that people care about lies, like the devil, in the mesoscale details and not in the S1 score or the AC coefficient.

7. 1.How to use time-to-space conversion processes to analyze and deduce important mesoscale storm structures. 2.How to blend disparate datasets and sources to yield a meteorological “story” not available from an individual dataset/source alone. What Ted Fujita Taught Us What Ed Danielsen Taught Us 1.How to understand cyclone lifecycles from a Lagrangian perspective. 2.How to visualize the mesoscale importance of the dry slot. 3.How to appreciate how wet and dry depositions patterns could be used to understand mesoscale cyclone structure from the PV/isentropic perspective.

8. Mesoanalyses generally unavailable. Inadequate synthesis of disparate observations. Degradation of routine surface synoptic analyses. Quality problems with web-based analyses. Inadequate student education and training. Why Can Mesoscale Weather Systems "Hide"?

9. Mesoscale Philosophy: Circa 1980 Analyze and represent synoptic scale features and synoptic scale boundaries correctly and forecast models will have a chance to simulate properly some mesoscale weather systems that depend upon these boundaries for their existence. As model resolution has continued to improve, this concept has proved useful in the forecasting of mesoscale weather systems that are: (1) significantly influenced by terrain, (2) dependent upon diurnally varying differential heating and roughness, and (3) associated with pre-existing low-level boundaries.

10. Continue to be poorly forecast by models Downstream ridging Downstream jet development Enhanced cyclonic vorticity advection over cyclone center Examples: (a)Hurricanes: David (1979) Floyd (1999) (b)Midlatitude cyclones: 12-14 March 1993 Superstorm 25-26 January 2000 "Surprise" snowstorm Bulk Upscale Effects of Deep Moist Convection

11. Downstream ridge and jet development. Tracton (1973) Fritsch and Maddox (1981) Anthes (1983) Boyle and Bosart (1986) Uccellini (1990) Bosart and Lackmann (1995) Zhang and Bao (1996a,b) Dickinson et al. (1997) Bosart (1999) Zhang et al. (1999a,b) Hurricanes Agnes (1972), Fran (1996), and Floyd (1999) Boundary layer preconditioning (moistening and destabilizing). Numerous authors Low-level PV growth. Numerous authors Convection, Downstream Ridge/Jet Development, and Cyclogenesis:

12. Features such as coastal fronts, inverted troughs, dry lines/troughs, cold fronts aloft, moisture ribbons all play important roles in cyclone precipitation distribution. Widespread convection in the warm sectors of cyclones may "rob" the region poleward of the warm front of stratiform precipitation. Lateral shear profiles and the associated deformation characteristics of the large-scale flow contribute significantly to cyclone structure and life cycles. Forecasting relatively low-latitude subsynoptic-scale cyclogenesis is very sensitive to diabatic processes and the representation of PV anomalies near the surface and near the DT. Nonconservation of PV on the DT provides a good way to "view" mesoscale aspects of diabatic processes. Representation of low-level PV anomalies demands a better use of surface observations. Mesoscale Lessons From Cyclone Studies

13. Ridges can play important roles in setting up positive PV advection and influencing mesoscale precipitation distribution. Precipitation distribution relative to the track of landfalling tropical cyclones depends strongly on the flow characteristics. Multiple genesis events may precede major cyclogenesis and in the presence of exceptionally strong forcing aloft rapid surface intensification may occur away from the primary baroclinic zones. The degree to which mesoscale processes associated with orographic forcing contributes to cyclogenesis is seasonally dependent. Mesoscale Lessons From Cyclone Studies (Continued)

14. Origin and evolution of mesoscale ascending sheets of air. Origin, evolution, and impact of coherent tropopause disturbances. Understanding and representing upscale effects of deep convection. Understanding how low-level boundaries preferentially impact mesoscale substructure and deep convection near boundaries and in cyclones. Understanding how "preconditioning" influences cyclone/frontal development. Understanding origin and evolution of mesoscale substructure (especially deep convection) within cyclones. What Are Some Important Scientific Issues?

16. a) PV distribution is known. b) A balance relationship is assumed. c) Bottom/top boundary temperatures are known.

28. Forecasting Strategies Lift Instability Moisture Boundaries When forecasting always remember to go out on a….. “LIMB!”