Pacific Predictability: Perspective of a NWS Forecast Office

1. Pacific Predictability:  Perspective of a NWS Forecast Office Brad Colman NOAA/National Weather Service Seattle, Washington Brad.Colman@noaa.gov

2. 2nd THORPEX CORE OBJECTIVE Contribute to the design and demonstration of interactive forecast systems that allow information to flow interactively among forecast users, numerical forecast models, data-assimilation systems and observations to maximize forecast skill. [As an example, targeted observing strategies incorporate dynamical information from the numerical forecast model itself to identify when, where, and what types of observations would provide the greatest improvement to specific weather forecasts of societal, economic, and environmental interest.]

3. 4th THORPEX CORE OBJECTIVE Develop and apply new methods that enhance the utility and value of weather forecasts to society, economies and environmental stewardship through: (i) user-specific probabilistic forecast products; (ii) the introduction of interactive procedures that make the forecast system more responsive to user needs; (iii) the design of and training in the use of user-specific forecast products. Research will identify and assess the societal/economic costs and benefits of THORPEX recommendations for implementing interactive forecast systems and improvements in the global observing system.

4. National Digital Forecast Database • Mosaic forecasts for the entire country or regional domains • Public, marine, fire weather, and other programs • Flexible, GIS format, graphics, etc. It’s aggressive and represents a major paradigm shift in the way NWS forecasters produce their forecasts.

5. National Digital Forecast Database targets a spectrum of weather information users The public, emergency managers and city planners use WWW graphic products for detailed forecasts • More weather data • Higher resolution forecasts • Visual displays of probability • User-defined products create business opportunities Different Products for Different Customers Commercial weather companies & emergency managers use grids to generate tailored products TODAY...RAIN LIKELY. SNOW LIKELY ABOVE 2500 FEET. SNOW ACCUMULATION BY LATE AFTERNOON 1 TO 2 INCHES ABOVE 2500 FEET. COLDER WITH HIGHS 35 TO 40. SOUTHEAST WIND 5 TO 10 MPH SHIFTING TO THE SOUTHWESTEARLY THIS AFTERNOON. CHANCE OF PRECIPITATION 70%. Radio stations & public read text forecasts

6. NDFD Resolution and elements • Spatial resolution: 5 km grids for now 2.5 km grids are being considered • Temporal resolution: 3 hourly for days 1-3 6 hourly for days 4-7 as available from CPC beyond day 7 • Update frequency: every hour • All forecast parameters: Tx, Tn, T, Td, wind, sky, QPF, PoP, precip type, etc.

7. National products and services are derived from a local digital database Database kept current through coordinated local updates Standard formats of gridded and derived graphical products Follow standard time and space conventions National (NDFD) vs Local (LDFD) Databases

8. Interactive Forecast Preparation System (IFPS) • Numerical weather prediction inputs • Relatively coarse horizontal and vertical presentations • “SmartInit” process to downscale and generate sensible elements • Integration of point MOS guidance • Forecaster inputs and adjustments • Generally iterative (w/o fresh model data) • Graphical editing tools • “SmartTool” scripts • Grid editing and coordination • Basic building block for the weather element grids is 5 x 5 km spatial and 1 hour temporal • On-line chat • Poor objective techniques for some parameters like sky cover, precip type, etc.

9. Considerations: • System is predominately deterministic in presentation • No gradation in spatial scale Day 1  Day 7 • Minimal gradation in temporal scale • Strong motivation was to present “realistic” weather • “point-and-click” interface drove system to very fine scale • Growing client base • Forecast process is resource intensive

11. Separating processes and scales…

12. 48-h forecasts from 5 Ensemble Members Initialized 0000 UTC, Monday, 8 January 2001

13. Importance of Upstream Initial Conditions Sailboats that broke free from their mooring lines litter the East Beach area of Santa Barbara, California, at sunrise following an overnight storm.

14. Probabilities in NDFD (proposed) • Percent probability of frozen precipitation • Percent probability of freezing precipitation • Percent probability of thunderstorms • Exceedance forecasts for preset confidence levels: • Max QPF • Max wind speed • Max wave height • Extreme max temp (summer) • Extreme min temp (winter) • Max snow amount

15. Critical Questions • Given the current NWS operational framework, what is the optimal way to incorporate uncertainty information into the forecast process? • On a day-to-day basis, what confidence information can be provided to the forecaster to help them decide whether to follow a new solution? How much detail to include? • What can be done to separate out forced or climate signals from transients? Can the two parts be intelligently presented? • What can be learned from existing NWP methodologies as far as benefits and limitations of a particular approach to presenting uncertainty information? What method leads to the most specific and decisive actions? • To what extent can the existing NWS forecast system accommodate growing demands for uncertainty information? • Quantitative precipitation forecasts are among the most challenging. Can we skillfully determine limits, exceedance values, etc.? • What are appropriate measures to assess the skill of forecasts on these spatial and temporal scales?