• Bengtsson, L., 1985: Medium-range forecasting—The experience of ECMWF. Bull. Amer. Meteor. Soc, 66 , 11331146.

  • Brankovic, C., , and T. N. Palmer, 1997: Atmospheric seasonal predictability and estimates of ensemble size. Mon. Wea. Rev, 125 , 859874.

    • Search Google Scholar
    • Export Citation
  • Branstator, G., , A. Mai, , and D. P. Baumhefner, 1993: Identification of highly predictable flow elements for spatial filtering of medium- and extended-range numerical forecasts. Mon. Wea. Rev, 121 , 17861802.

    • Search Google Scholar
    • Export Citation
  • Bretherton, C. S., , C. Smith, , and J. M. Wallace, 1992: An intercomparison of methods for finding coupled patterns in climate data. J. Climate, 5 , 541560.

    • Search Google Scholar
    • Export Citation
  • Bromwich, D. H., , and T. R. Parish, 1998: Meteorology of the Antarctic. Meteorology of the Southern Hemisphere, D. J. Karoly and D. G. Vincent, Eds., Amer. Meteor. Soc., 175–200.

    • Search Google Scholar
    • Export Citation
  • Buizza, R., 1997: Potential forecast skill of ensemble prediction and spread and skill distributions of the ECMWF ensemble prediction system. Mon. Wea. Rev, 125 , 99119.

    • Search Google Scholar
    • Export Citation
  • Dalcher, A., , and E. Kalnay, 1987: Error growth and predictability in operational ECMWF forecasts. Tellus, 39A , 474491.

  • ECMWF Data Services, 1999: The description of the evolution of the ECMWF forecasting system and corresponding archive. Attachment to the description of the ECMWF/WCRP Level III-A Global Atmospheric Data Archive ECMWF/WCRP, 122 pp. [Available from ECMWF, Reading, Berkshire, RG2 9AX, United Kingdom.].

    • Search Google Scholar
    • Export Citation
  • Hurrell, J. W., , H. van Loon, , and D. J. Shea, 1998: Mean state of the troposphere. Meteorology of the Southern Hemisphere, D. J. Kamly and D. G. Vincent Eds., Amer. Meteor. Soc., 1–46.

    • Search Google Scholar
    • Export Citation
  • Jolliffe, I. T., 1986: Principal Component Analysis. Springer-Verlag, 271 pp.

  • Kalnay, E., and Coauthors,. 1996: The NCEP/NCAR 40-year reanalysis project. Bull. Amer. Meteor. Soc, 77 , 437471.

  • Kalnay, E., , S. J. Lord, , and R. D. McPherson, 1998: Maturity of operational numerical weather prediction: Medium range. Bull. Amer. Meteor. Soc, 79 , 27532769.

    • Search Google Scholar
    • Export Citation
  • Kidson, J. W., 1988: Interannual variations in the Southern Hemisphere circulation. J. Climate, 1 , 11771198.

  • Kidson, J. W., 1991: Intraseasonal variations in the Southern Hemisphere circulation. J. Climate, 4 , 939953.

  • Kidson, J. W., 1999: Principal modes of Southern Hemisphere low-frequency variability obtained from NCEP-NCAR reanalyses. J. Climate, 12 , 28082830.

    • Search Google Scholar
    • Export Citation
  • Kidson, J. W., , and I. G. Watterson, 1999: The structure and predictability of the “high-latitude mode” in the CSIRO9 general circulation model. J. Atmos. Sci, 56 , 38593873.

    • Search Google Scholar
    • Export Citation
  • Kiladis, G. N., , and K. C. Mo, 1998: Interannual and intraseasonal variability in the Southern Hemisphere. Meteorology of the Southern Hemisphere, D. J. Karoly and D. G. Vincent, Eds., Amer. Meteor. Soc., 307–336.

    • Search Google Scholar
    • Export Citation
  • Lorenz, E. N., 1963: Deterministic nonperiodic flow. J. Atmos. Sci, 20 , 130141.

  • Lorenz, E. N., 1965: A study of the predictability of a 28-variable atmospheric model. Tellus, 17 , 321333.

  • Marques, R. F. C., , and V. B. Rao, 1999: A diagnosis of a long-lasting blocking event over the southeast Pacific Ocean. Mon. Wea. Rev, 127 , 17611776.

    • Search Google Scholar
    • Export Citation
  • Marques, R. F. C., , and V. B. Rao, 2000: Interannual variations of blockings in the Southern Hemisphere and their energetics. J. Geophys. Res, 105 , (D4),. 46254636.

    • Search Google Scholar
    • Export Citation
  • Mo, K. C., , and R. W. Higgins, 1998: The Pacific–South American modes and tropical convection during the Southern Hemisphere winter. Mon. Wea. Rev, 126 , 15811596.

    • Search Google Scholar
    • Export Citation
  • Molteni, F., , and T. N. Palmer, 1991: A real-time scheme for the prediction of forecast skill. Mon. Wea. Rev, 119 , 10881097.

  • O'Lenic, E. A., , and R. E. Liverzey, 1989: Relationships between systematic errors in medium range numerical forecasts and some of the principal modes of low-frequency variability of the Northern Hemisphere 700-mb circulation. Mon. Wea. Rev, 117 , 12621280.

    • Search Google Scholar
    • Export Citation
  • Palmer, T. N., 1988: Medium and extended range predictability and the stability of the Pacific/North American mode. Quart. J. Roy. Meteor. Soc, 114 , 691713.

    • Search Google Scholar
    • Export Citation
  • Palmer, T. N., , and S. Tibaldi, 1988: On the prediction of forecast skill. Mon. Wea. Rev, 116 , 24532480.

  • Renwick, J. A., 1995: Predictable and unpredictable elements of the northern wintertime 500-mb height field. Ph.D. thesis, University of Washington, Seattle, 168 pp. [Available from Bell & Howell Information and Learning, 300 North Zeeb Road, P.O. Box 1346, Ann Arbor, MI 48106–1346.].

    • Search Google Scholar
    • Export Citation
  • Renwick, J. A., 1998: ENSO-related variability in the frequency of South Pacific blocking. Mon. Wea. Rev, 126 , 31173123.

  • Renwick, J. A., , and J. M. Wallace, 1995: Predictable anomaly patterns and forecast skill of Northern Hemisphere wintertime 500-mb height fields. Mon. Wea. Rev, 123 , 21142131.

    • Search Google Scholar
    • Export Citation
  • Renwick, J. A., , and J. M. Wallace, 1996a: The influence of sampling variability upon model output error statistics. Mon. Wea. Rev, 124 , 19811991.

    • Search Google Scholar
    • Export Citation
  • Renwick, J. A., , and J. M. Wallace, 1996b: Relationships between North Pacific wintertime blocking, El niño, and the PNA pattern. Mon. Wea. Rev, 124 , 20712076.

    • Search Google Scholar
    • Export Citation
  • Renwick, J. A., , and M. J. Revell, 1999: Blocking over the South Pacific and Rossby wave propagation. Mon. Wea. Rev, 127 , 22332247.

  • Sinclair, M. R., 1996: A climatology of anticyclones and blocking for the Southern Hemisphere. Mon. Wea. Rev, 124 , 245263.

  • Thompson, D. W. J., , and J. M. Wallace, 2000: Annular modes in the extratropical circulation. Part I: Month-to-month variability. J. Climate, 13 , 10001016.

    • Search Google Scholar
    • Export Citation
  • Zheng, X., , H. Nakamura, , and J. A. Renwick, 2000: Potential predictability of seasonal means based on monthly time series of meteorological variables. J. Climate, 13 , 25912604.

    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 10 10 1
PDF Downloads 4 4 0

Southern Hemisphere Medium-Range Forecast Skill and Predictability: A Comparison of Two Operational Models

View More View Less
  • 1 National Institute of Water and Atmospheric Research, Wellington, New Zealand
© Get Permissions
Restricted access

Abstract

The skill of two global numerical weather prediction models, the National Centers for Environmental Prediction (NCEP) medium-range forecast model and the European Centre for Medium-Range Weather Forecasts (ECMWF) operational model, has been assessed over the Southern Hemisphere extratropics for much of the 1990s. Forecast skill and circulation predictability are calculated in terms of predicted and observed 500-hPa height fields. The skill of both the NCEP and ECMWF models has increased steadily through the decade. The useful forecast range (mean anomaly correlation at least 0.6) extended out to about day 6 during the late 1990s compared to day 5 in the early 1990s. The ECMWF model generally performed best out to the useful forecast limit, but scores were insignificantly different beyond that. ECMWF forecasts show a gradual increase in variance with forecast interval, while NCEP forecasts show a decrease.

For both models, the most predictable wintertime circulation pattern, defined by a singular value decomposition analysis, is associated with wave propagation across the South Pacific and southern Atlantic Oceans, the so-called Pacific–South American pattern, analogous to results found for the Northern Hemisphere. At day 10, the predicted amplitude of the leading pattern correlates at 0.6 with the analysis amplitude, while average hemispheric anomaly correlations are less than 0.3. For the leading singular mode pair, the spatial patterns and summary statistics compare closely between models. The spatial pattern of the leading singular mode is very similar in form to the leading analysis EOF from either model. A study of forecast errors reveals that a pattern related to the “high-latitude mode” or Antarctic oscillation, associated with a zonally symmetric exchange of mass between mid- and high latitudes, is weakly associated with large forecast errors. Large errors tend to be associated with positive height anomalies over the Pole and weak westerlies near 55°S. The more predictable patterns exhibit stronger temporal persistence than do the least predictable. Applications of these results to operational forecasting are discussed.

Corresponding author address: James A. Renwick, National Institute of Water and Atmospheric Research Wellington, P.O. Box 14901, Wellington, New Zealand. Email: J.Renwick@niwa.cri.nz

Abstract

The skill of two global numerical weather prediction models, the National Centers for Environmental Prediction (NCEP) medium-range forecast model and the European Centre for Medium-Range Weather Forecasts (ECMWF) operational model, has been assessed over the Southern Hemisphere extratropics for much of the 1990s. Forecast skill and circulation predictability are calculated in terms of predicted and observed 500-hPa height fields. The skill of both the NCEP and ECMWF models has increased steadily through the decade. The useful forecast range (mean anomaly correlation at least 0.6) extended out to about day 6 during the late 1990s compared to day 5 in the early 1990s. The ECMWF model generally performed best out to the useful forecast limit, but scores were insignificantly different beyond that. ECMWF forecasts show a gradual increase in variance with forecast interval, while NCEP forecasts show a decrease.

For both models, the most predictable wintertime circulation pattern, defined by a singular value decomposition analysis, is associated with wave propagation across the South Pacific and southern Atlantic Oceans, the so-called Pacific–South American pattern, analogous to results found for the Northern Hemisphere. At day 10, the predicted amplitude of the leading pattern correlates at 0.6 with the analysis amplitude, while average hemispheric anomaly correlations are less than 0.3. For the leading singular mode pair, the spatial patterns and summary statistics compare closely between models. The spatial pattern of the leading singular mode is very similar in form to the leading analysis EOF from either model. A study of forecast errors reveals that a pattern related to the “high-latitude mode” or Antarctic oscillation, associated with a zonally symmetric exchange of mass between mid- and high latitudes, is weakly associated with large forecast errors. Large errors tend to be associated with positive height anomalies over the Pole and weak westerlies near 55°S. The more predictable patterns exhibit stronger temporal persistence than do the least predictable. Applications of these results to operational forecasting are discussed.

Corresponding author address: James A. Renwick, National Institute of Water and Atmospheric Research Wellington, P.O. Box 14901, Wellington, New Zealand. Email: J.Renwick@niwa.cri.nz

Save