The potential long-range predictability of precipitation over New Zealand

It is assumed that the interannual variance of seasonal precipitation total s is made up of a component reflecting daily weather variations which, as a result, is unpredictable beyond deterministic predictability limits of abo ut 2 weeks. The second component is any additional variance that is, at lea st, potentially predictable. The first component is considered noise and is estimated using a statistical model whose parameters are determined from d aily, within season, precipitation. Estimates are compared with the total v ariance and where the total variance exceeds the estimated noise it is conc luded that there is potential for long-range prediction. Results indicate t hat only 30% or less of the total variance at stations is potentially predi ctable. 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.