The forecaster's tools

Weather evolves like nudged chaos, i.e. the predictability is limited, and human judgement remains an important input in the forecasting process. The information needed by a weather forecaster consists of the following three groups (1) -

1. Analysis of the most recent weather information:

• satellite and radar imagery (Note 15.A). These data are probably consulted most frequently. Most satellite images (visible, infrared and water vapour) are from geostationary satellites (Note 8.G), because they are continuous, allowing visualisation of time lapse evolution.
• Surface and upper-level charts and thermodynamic diagrams (Note 6.I) based mainly on station observations, radiosonde data, wind profilers, and aircraft measurements.

1. Prognostic material, based on NWP output (Note 15.H).

• surface and upper-level charts (for instance, those analysed in Exercise 13.2) of pressure, temperature, dewpoint, 3D wind, and variables derived from these (e.g. absolute vorticity); charts of vertically-integrated quantities (such as the Lifting Index, Note 7.G); and charts displaying other surfaces, such as isentropic surfaces (e.g. isentropic potential vorticity charts, Note 12.K).
• thermodynamic diagrams and wind profiles, especially during the thunderstorm season.
• NWP diagnostics for the location(s) of interest. The NWP has a fairly course resolution and does not know about the local climatic conditions of a place or region for which a forecast must be issued. NWP diagnostics are based on the statistical relation between weather at the nearest gridpoint in the NWP, and the actual weather at the location.

1. Forecast training

• Good grasp of synoptic, dynamic, and mesoscale meteorology, as well as radar and satellite data interpretation.
• Knowledge of the local weather (this typically takes two years of residence).

(1) Sturman, A. and N. Tapper 1996. Weather and Climate in Australia and New Zealand. (Oxford Univ Press) 476pp, after Targett 1994.