USWRP Multi-Agency Cool- Season QPF Workshop Co-Chairs Marty Ralph (NOAA/ETL) Bob Rauber (Univ. Illinois)

Workshop Focus Regional differences in precipitation processes and QPF methods Precipitation type forecasting and QPF of snow, freezing rain, sleet QPF for winter flood prone areas such as West Coast and Southern Appalachians Winter QPF in areas with significant mesoscale forcing (e.g. Atlantic coastal plain, Appalachians, Great Lakes, Front Range, coastal and interior western mountains hour Cool-Season forecast problem

THE END PRODUCT OF THE WORKSHOP An implementation plan for the USWRP that sets out the scientific objectives of each component of the cool season QPF problem Final report is available at: 10” rain Feb. 25, 2004, SSM/I Integrated Water Vapor (green 1-2 cm, orange 3-4 cm)

GROUP 1: RESEARCH AND FIELD STUDIES Co-leaders:Ron Stewart, McGill University Jeff Waldstreicher, NOAA/NWS Eastern Region SSD Recommended Physical Process Studies 4D structure of systems above the boundary layer (i.e., in the free troposphere) The rain-freezing rain-snow transition region Regional mesoscale boundary layer forcing (particularly orographic and lake effects) Moisture sources and transport into winter systems Predictability of cool season precipitation

GROUP 2: DATA ASSIMILIATION AND NWP ADVANCES Co-leaders:Tom Schlatter, NOAA/FSL Brian Jewett, University of Illinois at Urbana/Champaign Recommended parameterization improvements Cloud microphysics – the thermodynamic conditions and presence of microscopic particulates within a cloud determine the origin and subsequent growth of hydrometeors Boundary layer – winds in the sub-cloud layer transport hydrometeors laterally, and changes of phase can strongly alter the sub-cloud temperature and humidity profiles Land surface – antecedent conditions at and near the ground affect potential for freezing rain Convection – when near-surface temperature is just above freezing the intensity of precipitation can mark the difference between rain and snow.

GROUP 3: OBSERVING SYSTEMS, TEST BEDS Co-leaders:Dave Reynolds, NOAA/NWSFO Monterey Dave Kingsmill, NOAA/ETL Key Applications for Observations Nowcasting Data Assimilation Verification Required types of observation platforms In-situ Ground-based remote sensors Space-based remote sensors

GROUP 4: USERS, USER NEEDS Co-leaders:Roy Rasmussen, NCAR Paul Pisano, Federal Highway Administration Steps for development of cool season QPF products: Determine and validate user needs for cool season QPF products. Evaluate the social, environmental and security impacts of the winter QPF product. Develop operational concept and prototype(s) based on needs. Define science needs, and conduct research to meet them Test and evaluate prototypes through the use of testbeds and demonstration projects. Revise system based on user response (iterate). Transfer technology to operations based on the operational concept defined earlier in the process.

Core Recommendation #1 Establish a National Hydrometeorological Test-bed (HMT) From the working group reports, a consensus emerged that a test-bed approach should be implemented using two long-term regional efforts. HMT-East focus on winter storms along the East Coast of the United States, with freezing rain, coastal cyclones (e.g., Nor’easters), heavy snow, and lake effects as priorities HMT-West focus on water resource related issues in the West, with flood control, water supply, orographic effects and atmospheric rivers (concentrated regions of strong horizontal water vapor transport) as priorities HMT: Linking Research and Operations - Longer-term, continuous activities that are required to optimize operational impacts are the focus of HMT. - The HMT infrastructure then provides a foundation upon which to conduct episodic major field programs that are required to address certain key research and forecasting problems

Cool-season QPF multi-agency workshop report, May 2004

Core Recommendations #’s 2 & 3 Develop Probabilistic Methods - must address major regional differences - specify the size, position, orientation, timing, and amount of precipitation within regions of snowfall and mixed precipitation, - specify location of boundaries separating precipitation types Advance mesoscale data assimilation and modeling - community effort to develop the WRF system should be the focus of work to improve cool season QPF - for the next 2-3 yrs is continue enhancement of 3DVAR while pros & cons of EnKF and 4DVAR are explored - results of assimilation experiments may be strongly scale- dependent, i.e., methods that work well in global models may not work well in mesoscale models with more sophisticated physics

Temporary Oversampling in Testbeds can Provide AOR Data