Operational Forecasting Use of Objective Analysis Techniques

Operational Forecasting Use of Objective Analysis Techniques:

Analysis Chart Production using 'On-Screen' Methods, Short Period MSLP forecasts based on 'Model Correction', & Convection Initiation Forecasts based on Streamline Analysis

Over the last year, the National Meteorological Centre (NMC) of the UK Met. Office (UKMO) has converted the production of analysis charts from pencil-and-paper to mouse-and-screen. The main product to undergo such a radical transformation is the 'ASXX' - a mean-sea-level-pressure (MSLP) analysis of the North Atlantic and Europe area, issued every 6 hours. Other analysis products are also created 'on-screen', using the 'Horace' workstation system (on a UNIX platform).

As well as the chart production, Objective Analysis techniques are used in the NMC to provide short period forecasts of MSLP up to 3 hours ahead. Through analysis of the latest observed MSLP values and the latest observed MSLP tendencies, corrections can be applied to model fields to adjust them toward 'reality'. This type of field modification is used to provide input to aviation forecasts of the lowest expected MSLP (QNH) value in 20 different regions across the British Isles - for the purpose of setting altimeters. These semi-automated forecasts are verified automatically in real time, and the results are presented graphically to the forecaster.

Another application of Objective Analysis in the forecasting environment has been the development of various methods of displaying streamlines, such that convergence lines and points are clearly visualised. This analysis can be carried out on observed winds or on forecast winds, and helps to pinpoint to forecasters the areas where convection may be triggered. Clearly other factors also play a part in the initiation of showers, but generally a strong correlation with radar images has been found.