The potential long-range predictability of precipitation over New Zealand

It is assumed that the interannual variance of seasonal precipitation totals is made up of a component reflecting daily weather variations which, as a result, is unpredictable beyond deterministic predictability limits of about 2 weeks. The second component is any additional variance that is, at least, potentially predictable. The first component is considered noise and is estimated using a statistical model whose parameters are determined from daily, within season, precipitation. Estimates are compared with the total variance and where the total variance exceeds the estimated noise it is concluded that there is potential for long-range prediction. Results indicate that only 30% or less of the total variance at stations is potentially predictable. Countrywide totals do not improve the situation. Persistence of the ENSO signal may be able to help realize a small fraction of the potential predictability or about 5% of the total variance. Copyright (C) 1999 Royal Meteorological Society.