Title page for ETD etd-08112009-131703


Document Type Master's Dissertation
Author Moatshe, Peggy Seanokeng
URN etd-08112009-131703
Document Title Verification of South African Weather Service operational seasonal forecasts
Degree MSc
Department Geography, Geo-Informatics and Meteorology
Supervisor
Advisor Name Title
Prof W A Landman Supervisor
Keywords
  • South African Weather Service
  • Reliability Diagram
  • ROC
  • Relative Operating Characteristics
  • RD
  • seasonal forecast
Date 2009-04-17
Availability unrestricted
Abstract

The South African Weather Service rainfall seasonal forecasts are verified for the period of January-February-March to October-November-December 1998-2004. These forecasts are compiled using different models from different institutions. Probability seasonal forecasts can be evaluated using different skill measures, but in this study the Ranked Probability Skill Score (RPSS), Reliability Diagram (RD) and Relative Operating Characteristics (ROC) are used. The RPSS is presented in the form of maps whereas the RD and ROC are analyses are presented in the form of graphs. The aim of the study is to present skill estimates of operational seasonal forecasts issued at South African Weather Service

A limited number of forecasts show positive RPSS value throughout the validation period. From RD and ROC analysis, there is no skill in predicting the normal category as compared to below-normal and above-normal categories. Notwithstanding, the frequency diagrams show that the normal category was often given a large weight in the operational forecasts.

The value of verifying seasonal forecast accuracy from the userís perspective is important. The understanding of seasonal forecast performance helps decision makers to determine when and how to respond to expected climate anomalies. Therefore the frequent update of the seasonal forecast verification is important in order to help Users make better decisions.

Copyright © 2008, University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria.

Please cite as follows:

Moatshe, PS 2008, Verification of South African Weather Service operational seasonal forecasts, MSc dissertation, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-08112009-131703/ >

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