Use of NWP and EPS Products in support of Location-specific Forecasts

First International Workshop on Prevention and Migration of Meteorological Disasters in Southeast Asia Use of NWP and EPS Products in support of Location-specific Forecasts Edwin S.T. Lai Hong Kong Observatory Hong Kong, China Kyoto, Japan, 5 March 2008

Presentation Outline Use of NWP Products in support of Location- specific Forecasts Use of EPS Products in support of Location- specific Forecasts Trial Operation of the JMA s Non-hydrostatic Model (NHM) in HKO The Way Forward

History of Adapting JMA Models 1. HKO first adapted an operational NWP model (Limited Area Model) from JMA in 1986. 2. The Regional Spectral Model (RSM) was adapted from JMA in 1997 and was put into operation in 1999, named as the Operational Regional Spectral Model (ORSM). 3. Message passing interface version of RSM was put into trial operation in 2004. 4. JMA Non-hydrostatic Model (NHM) has been under experimentation and development for operational support of HKO s nowcasting system since 2004. 5. Alternate exchange visits between JMA experts and HKO staff takes place annually.

Overview of NWP models in HKO Operational Regional Spectral Model (ORSM) Hydrostatic primitive equation model 60 and 20 km horizontal resolution 36 vertical levels 3D-OI data assimilation MPI-RSM Identical dynamical and physical frameworks as ORSM 40 vertical levels Message passing interface programming paradigm for parallel computation NHM Fully compressible non-hydrostatic governing equations Explicit cloud microphysics processes For nowcasting support WRF Fully compressible non-hydrostatic governing equations For research and specific applications (e.g. Olympic FDP)

Operational NWP Model Suite in HKO 60km ORSM + 3DOI 20km ORSM + 3DOI 5km NHM + LAPS Initial & B.C. Initial & B.C. LAPS LAPS (Local Analysis and Prediction System) : Resolution: 10 km, 5 km & 1km For nowcast application and initialization of hydrometeors for NHM

Need for post-processing processing NWP forecasts are subject to errors Systematic errors due to unrealistic description of orography, deficiencies in physical parameterization and boundary layer representation Non-systematic errors due to forecast errors in the synoptic domain (e.g. fronts and air masses moving too slowly or rapidly) Post-processing techniques could be used to compensate and reduce systematic errors (or biases) by developing statistical relationships between NWP output and the desired forecast quantities.

Location-specific Temperature Forecasts ORSM grid point outputs are calibrated against observation data at specific sites through Kalman filter (KF) or linear regression. Calibration 20-km ORSM grid point outputs Min/Max temperature forecasts at specific sites over Hong Kong

Post-processing of Temperature Forecast Time Series The calibration of temperature forecasts at DMO 3-hourly interval can adequately correct biases observed in the diurnal trends. Observations KF

Time-lagged Ensemble of ORSM A time-lagged ensemble approach is applied to ORSM output to estimate the spread and distribution of temperature and precipitation forecasts. A composite display in the form of meteograms updated every 3 hours is generated for reference by forecasters. Temperature Hourly Rainfall

ORSM Applications for the Meteorological Community ORSM TC forecast guidance disseminated to WMO Members via GTS twice a day (00 &12 UTC base time) whenever a TC is located with 10-30N, 105-125E. RAII pilot project on the provision of cityspecific NWP products to developing countries.

RAII Pilot Project on the Provision of NWP City-specific Forecasts Background A challenge for the public weather services of developing countries is the provision of weather forecasts up to a few days ahead. With recent advances in NWP, NWP products can provide very good guidance for Members in the provision of such forecasts. A key issue is how to make relevant NWP products available to the NMHSs concerned in order to enable them to provide cityspecific forecasts up to several days ahead and to show this as a benefit of operating observing stations.

Difficulties encountered The substantial resources and technical know-how required to receive, decode and process the NWP data before it becomes useful to forecasting pose a major roadblock. The growing data volume also imposes a significant burden on Members telecommunications capacity. NWP forecast charts currently available on the Internet normally have no location-specific features. They are, therefore, not directly applicable to public weather services that are typically tied to cities and towns.

Opportunities Operational NWP models have matured in the past decade. Advanced NWP centres operating global and regional models are now capable of routinely generating readily usable location-specific forecast products for selected cities up to a few days ahead. Location-specific forecasts such as time-cross-sections could be directly applied in the formulation of city forecasts which are the most visible aspect of the work of NMHSs. Time series of essential meteorological elements such as temperatures, wind, relative humidity and rainfall several days ahead would provide a concise way of presenting the numerical model output. With the maturity of the Internet technology, Internet graphic capability is now available to NMHSs of most developing countries.

Benefits With ready access to such city-specific model outputs, NMHSs of developing countries could cross the technological bridge and benefit directly from latest advances in NWP. It would enable these Members to improve their public weather services, enhance their visibility and strengthen their role as the sole official voice in weather warnings in their respective countries.

Progress of the Pilot Project Pilot Project Co-ordination Group Established following the decision of 13 th Session of RAII in Dec 2004 Now with 15 Members participating 3 Members are providing products for the project Japan, Republic of Korea and Hong Kong, China Project s participants began to obtain the NWP products via the respective website of the product providers in Jan 2006 A WMO VCP training course on use and interpretation of NWP city-specific products was conducted in Hong Kong in late 2006 (another being planned for late 2008) A software has been developed and provided to users to carry out post-processing and verification of the NWP products in Dec 2007

Progress of the Pilot Project As at February 2008, forecast times series of a total of 160 cities are now available to the project s participants. Project s participants: Bangladesh, Bhutan, Cambodia, Iran, Kazakhstan, Kyrgyz, Lao, Mongolia, Myanmar, Nepal, Oman, Vietnam. Black dots represent cities with NWP forecasts provided by ORSM of HKO

Sample Product from Japan

Forecast Post-processing and Verification Tool for the City-specific NWP Products To facilitate the recipients to adapt the model outputs for their own specific applications, a software program in the form of a spreadsheet has been developed for users to carry out post-processing and verification of NWP forecasts The spreadsheet can conduct forecast verification and present the results in graphical format. An Excel spreadsheet that can automatically post-process the ORSM model outputs of temperature forecasts

The Next Phase of the RAII Pilot Project on the Provision of NWP City-specific Forecasts Several possibilities in taking the project forward to the next phase: Provision of potential hazardous weather alerts to NMHSs based on pre-determined criteria and NWP outputs Multi-model or time-lagged super-ensemble based on the model outputs generated by the contributing NWP products providers Centralize portal for easy access and navigation among the products from various NWP sources

Example Warning of rainstorms based on ORSM output In HKO, alerts on rainstorms are automatically generated based on the pre-determined criteria and the ORSM rainfall forecasts. The alert messages are visually display in a Combined Rainstorm Warning Panel for reference by forecasters. These criteria are derived from calibration of model output with actual rainfall observations

Use of Ensemble Prediction Systems (EPS) in HKO EPS grid point outputs from JMA and ECMWF are routinely received at HKO. A composite display in the form of meteograms is generated for forecasters reference. HK

Post-processing of EPS outputs for Location-specific Probabilistic Forecasts (Sloughter( et al. 2006) The method has proved to be particularly effective for improving the reliability of the probability forecasts and reducing the over-forecast bias as evident in the DMO point forecasts PoPDMO_0.5 HKO Climatology PoPcal_3 0.26 布賴爾評分 Brier Score (Brier Score) 0.24 0.22 0.2 0.18 Observed relative frequency 0.16 0.14 0 1 2 3 4 5 6 7 8 9 10 預報期 ( 天 ) Forecast period (day)

Application of EPS in TC Track Forecast Time series of accumulated TC strike probability at specific points, as derived from JMA EPS data, allow decision makers to critically assess the timing of TC passage with respect to the location of interest.

Non-Hydrostatic Model (NHM) Trial operation since April 2004 Based on JMA-NHM (Saito et al. 2006) Numerical guidance of severe weather in very short term Configuration: 5 km horizontal resolution 121x121 horizontal grid points; 45 vertical levels Hourly update Initial condition: 20-km RSM + LAPS moisture initialization on cloud hydrometeors Boundary condition: 20-km RSM Forecast range = 12 hours More sophisticated treatment of cloud and precipitation processes: Kain-Fritsch parameterization + cloud microphysics

NHM with LAPS moisture initialization: T+7hr initialized at 15 UTC 7 May 2004 Data ingested in LAPS: Conventional obs, radar (ref.+doppler vel.), satellite (IR), GPS PWV, GD AWS etc Forecast using 20-km ORSM as initial

Development of NHM to support high-resolution regional scale numerical guidance Example: 72 hour forecast initialized at 00 UTC 23 Nov 2007 by 20-km NHM JMA GSM as initial and boundary conditions Potential benefits on location-specific forecasts using NHM due to more advanced physical processes are used:- Supplement guidance from global models Data assimilation with regional or local observations ingested into model High-impact weather tropical cyclone motion and intensity short-range QPF haze episodes

Application of NHM in very-short short-range range precipitation prediction extrapolation effective in advective cases NWP-Nowcast Blending SWIRLS NHM Guidance on dynamic evolution of precipitation systems in rapidly changing cases Browning(1998), Lin et al (2004) high resolution, rapidly updated very-short-range QPF RAPIDS Rainstorm Analysis and Prediction Integrated Dataprocessing System

prevailing wind direction 24 hr backward trajectories for air parcels reaching HK based on 5-km 5 NHM run initialized at (a) 00 UTC 1 Jan; (b) 12 UTC 1 Jan; and (c) 12 UTC 2 Jan 2004

Roadmap of NWP Development at HKO

Roadmap for all concerned - Where do we go from here? Met. service still waiting to take off Join the RAII project or ask for one! Met. service taking off Focus on fine-resolution models and identify niche areas for local applications Met. centres flying high Share model data (forecast, EPS and ANALYSIS) and products (location-specific) Academics and research institutes Support your met. service and find an outlet for your research efforts

An initiative to promote a wider use of NWP techniques For NMHSs with some NWP capacity, a bilateral collaborative effort between major NWP centers and NMHSs can be implemented with positive feedback to create a win-win situation. Benefit: NMHSs obtain quality analyzed fields from NWP centers to operate or experiment with limited area model in support of shortrange forecasting system or other specialized applications. NMHSs Local observations Analyzed fields NWP Centers Benefit: NWP centers have reliable sources of local observations to complement the synoptic obs and remote sensing data to ensure and enhance the quality of analyzed fields from global models.

Thank You!