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.

A straightforward model for the spatial calculation of the time of fog clearance is presented which is based on thermodynamic equations, spatial data sets such as NOAA-AVHRR satellite data, Digital Elevation Model, and horizontal and vertical meteorological observations. The model has been tested on two days with extended fog layers within the study area. The local validation of the model reveals an accuracy in fog clearance of 4 minutes by comparing the model result with meteorological observations. A spatial validation by means of a reference NOAA overpass indicates an under-estimation of the fog-covered area by the model of 2.9% at the time of the reference image. Five minutes before reference time, the spatial correspondence of the modelled and the reference fog coverage increases to 98.9%. The temporal deviation of uncoinciding pixels between reference and modelled fog image at reference time is less than ±30 minutes in 68% of the total number of fog-covered pixels and therefore matches the accuracy of local tephigram methods. However, for individual pixels a time error of up to ±60 minutes occurs for the time of fog clearance. Time errors are probably mainly due to an inaccurate estimation of fog thickness.

During the last two weeks of March 1980 an intense heat wave developed in central and northern Argentina, with its greatest intensity over the city of Buenos Aires. The sequence of temperature anomalies showed the importance of this heat wave. During the period of maximum intensity the daily minimum temperatures were over 27 °C and the apparent temperatures over 30 °C. It was the most intense heat wave of the last two decades and the only one that has occurred in March. The intensity of the event is shown by the high values of several biometeorological indices that indicate dangerous levels of thermal stress on people. The persistence of an anticyclonic circulation at all tropospheric levels and the extension of the barotropic zone to the south led to the maintenance of high values of temperature and humidity. The advective effect added to the intense solar radiation was the most important cause of the high temperatures.

To provide ice warnings for road maintenance, a forecasting model has been developed that computes the state of the road several hours in advance. The model, which is called HS4Cast, runs autonomously and does not need human input. The current version of the forecast model features a fuzzy logic engine that determines the best forecast by evaluating certain patterns in the measured parameters. Using this forecast engine, predictions up to 24 hours in advance are possible with reasonable accuracy. If available, additional forecasts from a weather centre may be imported into the model so that the effects of precipitation are taken into account, this further reduces forecast errors. Statistics summarising the model's performance are presented using data from several measurement sites along an Austrian motorway, where HS4Cast has been in use since about 1990.

Predicting rainfall along the New South Wales (NSW) coast is a major forecasting problem because of sharp gradients in rainfall amounts with the heaviest falls on the coastal fringe decreasing rapidly inland. On some occasions the rainfall pattern is less spatially coherent and consists of isolated maxima. Both rainfall patterns are associated with mesoscale coastal ridging. The first rainfall pattern arises from coastal ridging occurring in combination with an offshore trough. In the first case study presented here, a typical ridge-trough system was aligned parallel to the coast, and located just offshore, with the observed rainfall heaviest at the coast, decreasing rapidly from over 60 mm to near zero 30 km inland. The model captured well the southward temporal evolution of the maximum relative humidity values and rainfall. The second rainfall pattern occurs when shallow coastal ridging interacts with downdrafts from thunderstorm activity over the ranges to the west. The second case study was one in which convergence and condensation generated a quasi-stationary line of thunderstorms, resulting in flash flooding. The model precipitation rates and accumulations matched very closely those of the squall line, as revealed by radar precipitation intensities and the observed rainfall.

In February and March 1996, the French NWP model Arpège was run to give operational forecasts five days ahead. These forecasts were a part of preparations for FASTEX (Fronts and Atlantic Storm-Track Experiment), whose field phase took place in 1997. The extensive collection and availability of model output during this period gave an excellent opportunity to study in real time the behaviour of different NWP models during the period of the year when strong winds and rapid changes in weather conditions are frequent. In this paper, we study a case where the ECMWF model predicted an incorrect pressure gradient at Northeast Iceland, while Arpège correctly simulated the gradient. The model errors are connected to anomalies in the mid-tropospheric vorticity field, which is in general quite different in the two models. The differences in the vorticity fields are discussed in relation to orographic effects.

In this paper we review work undertaken on sea clutter illustrated by previously unpublished observations made with an S-band radar during a research project in South Wales carried out during the winter of 1976/77. The implications for detection with C-band Doppler radar are considered.

The basic statistics of aerological variables obtained from radiosonde data at Ezeiza, Buenos Aires, Argentina, for 1986 are examined, and their relationships with occurrence and non-occurrence of daily local precipitation are analysed. The resulting samples are statistically different for nearly all the variables. Nevertheless, thermodynamic variables at the 700 mb level and the K-Whiting instability index yield the best correlations with rainfall, though it is noted that they are diagnostic and not prognostic variables. 500 mb relative vorticity at selected gridpoints is included in the analysis, given the effectiveness of this dynamic field to recognise favourable patterns for daily precipitation occurrence. Some experiments using these potential predictors to specify occurrence or non-occurrence of the event within a 24-hour period are presented.