To obtain representative relationships between rain intensity and radar reflectivity and make an accurate estimation of the rainfall amount in the Baiu season (the most important rainy season in eastern Asia), the precipitation types (convective, stratiform and mixed types) must first be classified. This is because the mechanism and efficiency of precipitation show distinct variations according to rain regimes. An objective classification method, bright band fraction (BBF) that focuses on the vertical structure of radar reflectivity field, was improved and applied to the Baiu precipitation of 1995 in the Kanto Plain, Japan. Samples of convective rainfall were further divided into patterns using an index effective efficiency (Ee) that represents the echo top height. For those types (and patterns) that had been divided, Z-R relations were established using a statistical method called the window probability matching method (WPMM). The shapes of the Z-R relations show a natural matching of the probability density function of radar reflectivity with that of rain intensity recorded by rain gauge. The results show that the classification of precipitation types is reasonable, and Z-R relations corresponding to the precipitation types are representative. Some facts which need special attention in the application of the WPMM are also revealed.

During 1994/95 a UK Overseas Development Administration (now Department for International Development - DFID) funded project was undertaken to predict ozone amount over Punta Arenas in southern Chile. A low-cost satellite receiver was installed to receive the digital data stream from the NOAA series of weather satellites. The ozone channel of the TIROS Operational Vertical Sounder instrument on the NOAA satellites was used to obtain maps of stratospheric ozone for the area around Punta Arenas in near real time. Also, a simple model was developed to predict the amount of column ozone from the forecast 100 hPa temperatures obtained from the UK Meteorological Office. These techniques used together made it possible to issue timely warnings to the general public of Punta Arenas before the Antarctic ozone hole moved across southern South America during the Austral spring.

The main developments in aviation forecasting over the 50 years up to 1985 are summarised. The importance of subsequent increasing Regional and World Area Forecasting commitments at the UK Meteorological Office is stressed, along with a demonstration of the more recent advances in forecasting low-level and middle/upper-level significant weather, respectively. Meteorological hazards requiring warnings (e.g. SIGMETS) and current aviation forecast output are considered, along with a glance into the future, cautioning that the trend towards fully automated products may be hindered by slower improvements in some aspects of model technology such as derived-field forecasts of fog and low cloud.

Decision-making in agricultural production is a complex process in which many risks need to be con-sidered for an informed decision to be made. In many parts of the world, weather and climate are one of the biggest production risks and uncertainty factors impacting on agricultural systems performance and management. Farmers around the world, especially those in the developing countries, have been trying to adapt to the variable weather and climate conditions through various risk-management strategies. Improved weather and climate information, supplied to the farming community in a timely manner, can greatly assist the farmers in their operational decisions.

We noted with interest the recent article by Reason & Jackson, which presented a modelling case study of the coastal ridging that occurs along the south-eastern coast of Australia. As the authors and others have pointed out, coastal ridging is a dominant feature of the weather over this region in the warmer months, and also occurs with varying degrees of regularity in other parts of the world. The paper by Reason & Jackson draws to some extent on an earlier publication of ours on the same topic (Speer & Leslie, 1997) and we would like the authors to respond to our comments on a number of alternative interpretations we appear to have of case study they chose. We offer our comments because the topic area is vital to the understanding and prediction of a significant component of the weather over the most populous part of the Australian continent. To that end, we feel that an exchange of views would be of considerable interest to readers of Meteorological Applications, particularly as we and the authors have generated a significant fraction of the published work on this topic, especially for southeastern Australia.

The increasing accuracy of data from meteorological satellites coupled with the scarcity of tropical raingauge data and the need for information regarding the fundamental tropical seasons (dry and wet), has led to the development of procedures for climatic analysis that incorporate satellite products. A previously designed procedure based on satellite outgoing longwave radiation and raingauge data is modified to characterise each calendar month of a neo-tropical region (Guri, 7.5° N, 62.5° W, 2.5° lat, 2.5° long, Jan 1974 – Dec 1996, Venezuela). The intensities (categories) of the two fundamental tropical seasons are explored by applying a further four-category procedure. Observed runs of categories lasting four, five and six years, not expected in the 23-year period (1974–1996), indicate that there is a degree of persistence. This persistence could provide industry with information that will allow improved annual planning.

Meteorologists who work in the energy commodities market continue to investigate ways to enhance predictions of seasonal temperature anomalies using oceanic/atmospheric indices. This study examines the relationship of three climate indices - ENSO (El Niño/Southern Oscillation), PNA (Pacific North American) and NAO (North Atlantic Oscillation) - to heating degree day (HDD) totals accumulated in 11 cities in the Midwest and northeastern United States, to determine which, if any, has predictive power. The data covers the 48-year period between 1951/52 and 1998/99, and focuses on two periods either side of 1 January (i.e. the winter months of October-December and January-April). The index most strongly related to the HDD anomalies during both winter periods was NAO. NAO values were negative for cold (above-average HDD) anomalies occurring prior to and after 1 January, while the NAO values were generally positive during warm (below-average HDD) anomalies. During cold anomalies, the PNA values were generally positive in the three months before 1 January and negative afterwards, indicating that different atmospheric teleconnection patterns cause similar temperature anomalies in these regions. The relationship between the equatorial Pacific sea-surface temperatures (SST) data and temperature anomalies was the weakest. Confidence in these relationships increased when the extreme HDD anomaly years were examined. These results indicated that the relationships of climate indices to HDD anomalies exist and that these would be useful in developing and improving seasonal predictions for business applications.

A mesoscale model has been applied over the Greater Sydney region to an air pollution episode resulting from fire hazard reduction burns from 12 to 14 April 1997. The episode was characterised by two distinct events in a period of sustained light winds, which included humid sea breezes and land breezes. The first event occurred early in the period when the atmospheric circulation involved either weak sea breezes or no sea breeze at the coast. Described here are the meteorological conditions associated with the inter-regional transport of smoke from a prescribed, or hazard reduction, burn just north of Sydney, which concentrated smoke in the eastern part of the Sydney metropolitan area. The second event, which occurred late in the episode, was local in nature but was induced synoptically by the large-scale airflow by a change in wind direction that transported smoke and fog over a major highway. Also described are the meteorological conditions that contributed to the disruption of a major highway caused by a multiple vehicle pile-up just to the south-west of Sydney later in the period. Numerical model simulations using the University of New South Wales (UNSW) NWP model, which used archived real-time data, accurately predicted both the concentration of pollution in the eastern part of the Sydney metropolitan area in the first event and the hazardous smog formation and timing of the clearing south-west wind change in the second event.

Coastal ridging is an important component of the weather of south-eastern Australia during the summer. The mesoscale aspects of such an event are often not well forecast, and this can have serious implications for aviation, shipping, air quality and bushfire control. A previous study by Speer & Leslie (1997) identified three types of coastal ridging according to the associated synoptic conditions. In this study, a coastal ridging event, which appears to have aspects of all three types, is examined with the aid of mesoscale manual analyses, surface and radiosonde data and simulations with a mesoscale numerical model (Colorado State University Regional Atmospheric Modeling System).

It is found that the model is able to capture the salient features of the event but, on the east coast, tends to produce a weaker event than that observed. The model ridging also tends to lag the observed feature on the east coast by a few hours. It is suggested that these model deficiencies may relate to deficiencies in the lower atmosphere air mass characteristics, which, in turn, may relate to the surface parameterisations in the model.

Smoke pollution from controlled burning of forested areas can be amajor problem for populated areas, even those at some distance fromthe site of the burning. In particular, Perth, the largest city inWestern Australia, is affected by smoke from controlled forest burnsto the south of the city when meteorological conditions advect smokeover the city. Such controlled burns are extensively carried out onan annual basis in spring, early summer and late autumn by theWestern Australian Department of Conservation and Land Management(CALM) in the southwest forests, in order to reduce flammable fuelsand mitigate the undesirable social, economic, environmental andhuman problems caused by destructive wildfires. In this article,results are presented from a mesoscale model prediction of smoketrajectories from a controlled burn event that took place inNovember, 1995. In this example, two meteorological factors, astrong sea-breeze front and a mesoscale low pressure system,unexpectedly turned the smoke back from its initial trajectory overthe ocean to directly over Perth itself. The result was very highsmoke concentration levels over the city and associated healthconcerns to residents as well as disruption to transport includingthe closing of Perth airport. The mesoscale guidance was veryaccurate and can provide valuable guidance when run routinely.

In an attempt to improve short-range weather predictions in Central Europe, a research project was carried out in Austria which involves adapting the WELS weather prediction system to the Central European environment. This PC-based system is currently in operational use in parts of the United States, chiefly in support of winter highway maintenance operations. The system rests upon the concept of hybrid modelling: an independent, grid-based mesoscale forecast model, integrating the full set of prognostic equations, delivers a prediction which can, in combination with topographic properties, be visualised by a Graphical User Interface (GUI). This post-processing tool seems to have a promising future, especially because it includes the opportunity of adjusting the output of the prediction model; also, locally generated observations can be incorporated into the forecasting process. The use of the forecast-manipulation facilities is appropriate if the prediction seems to be off-track; the time-consuming rerun of the entire forecast model in the case of derailing predictions can be avoided.

Theories are good for the intellect, but are no more useful than a bit of practical experience. Perhaps the most significant thing about them is that they have been accorded quite unjustified status by engineers.