Comparison of Weather Charts   
GRIB-/MOS-/ENS-Data Verification by HINDCAST  

What is the intention of www.vorticity.de? What's it all about?

vorticity.de does not want to compete with current Diagnosis Systems such as wxcharts windy ventusky visualweather oder NinJo

Neither does vorticity.de want to reduce modern synoptics to the theory of the ideal cyclone or bring the visualization back to the old-style visualization of 16-FAX-Charts nor does vorticity.de want to go back to maybe 'good old times' - because we have 'even better times' today!

The intention of vorticity.de is to bridge the gap between traditional synoptics and the current state of synoptic and modern forecast techniques, so to say state-of-the art instead of art-of-the-state.

This is mainly achieved by combining various meteorological charts to arrays of charts to make the synoptic interpretation easier and to allow new ways of interpretation and verification.

Especially the visual comparison of classical and GRIB products and the comparison of analysis charts and forecast charts of different lead times for identical valid times (HINDCAST) are normally difficult to be accomplished because the required charts are nostly not available in normal operations, neither the MSLP forecast charts issued four days ago with lead timne H+108 of DWD and UK MET nor the GFS GRIB forecast charts worldwide which have been issued one week ago with lead times up to H+180.

Progress in meteorological research during the last decades, especially in the fields of Numerical Weather Prediction (NWV), Ensemble Forecast ENS (Ensemble Technology) Statistical Weather Forecasting MOS (Model Output Statistics) and data representation of GRIB conmpared to classical forecast has made products available that enable even forecasters with minor synoptic knowledge to keep up in the normal forecasting business. Nevertheless, understanding these products is important for their appropriate and critical interpretation and to identify their limits.

This synoptic understanding enables the forecaster to anticipate alternative developments and to be prepared accordingly. It is, however, important to resist the temptation of trying to improve automatic forecast products and actually making them worse - which is a well known process called disimpürovement.

The subjective verification of forecast charts by visual comparison with the analysis chart for the same validtime allows the judgement, whether or not the forecast chart gave the right clue to predict the actual situation correctly. To allow this 'visual verification', old forecast charts with a leadtime of 36/60/84/108 hours to the actual analysis valid time are necessary - I doubt whether these 'VOID' products are available to the forecaster.

This type of verification is not meant to replace important standard verification parameters for NWP-products such as Anomaly-Correlation-Coefficient (ACC), but to complement it. Objective verification is mandatory for Inter-NWP-model-comparison and has been established as SOP, Standard Operational Procedure.

The main goal is to allow the immediate verification here and today - 365 times per year and not for selected casestudies only with a bias depending on the intention behind: The selection of very poor forecasts to show low performance of the models or of excellent forecasts to show their brilliant performance.

Meanwhile there are authentic experiences with young meteorologists (BS, MS, even Ph.D.) who know the difference between a High and a Low, but know the geostrophic wind by name only. These colleagues may enter a more scientific career (most likely not), but they will never get the thorough understanding of synoptics. This results in a loss of genuine synoptic Know-How which is a pity because ikt is required to improve Postprocessing procedures in future. Just interpreting NWP models might cover daily operational requirements, but does not result in improvement of direct model output fore better forecasts.
Understanding current Hi-Tec Forecast products is important to 'stay in the loop', to check the plausibility of the forecast, to identify its limits and to anticipate possible alternative developments and be prepared for them.

This may not result in disimprovement of automatic products (well known phenomenon!)

The subjective visual verification of forecast and analysis charts with identical valid time (HINDCAST) allows an immediate information whether or not the forecast chart gave the correct information to the forecaster to make a correct forecast - twice daily, 00 and 12 UTC, 365 day per year - not just for case studies with a bias according to the intention of the person who make the case study: either poor forecasts to show how poor the model and postprocessing products perform - or cases of excellent forecasts to show the opposite.

It is not intended to replace important standard verification parameters for an objective verification of NWP-products like Anomaly-correlation-coefficient 500 hPa, just to offer continuous near-realtime verification options if required.

Procedures for an objective verification of forecast products have become Standard Operational procedures at all major National Meteorological Centers

Comments, critics, suggestions or requests more than welcome!: bernd.richter(et)web.de