Page History

This The following is a description of the latest operational release of GloFAS v3.45. For For an overview of other GloFAS releases, please see: GloFAS versioning systemThe forecasts of GloFAS version 3.4 are available in pre-release mode from 16 November 2022 on the GloFAS Stage Platform: https://stage.globalfloods.eu/glofas-forecasting/. To access the GloFAS stage website, visit https://stage.globalfloods.eu/accounts/signup/ to create your account.

Summary

GloFAS version 3.4 introduces some important enhancements to the web products, including methodological, visual, and technical changes. The changes aim to aid user experience when interpreting the forecasts on the GloFAS map viewer. All changes implemented are summarised here:

STATIC tab

• The 'Upstream Area' static layer has been replaced by the 'LISFLOOD Drainage Network'. This layer now shows the rivers as vectors, with the thickness and colour of the lines indicating the drainage (or upstream) area.

HYDROLOGICAL tab

• 'Flood summary for days 1-3', 'Flood summary for days 4-10', 'Flood summary for days 11-30':
  • Flood summary maps are coloured according to the probabilities of exceeding 2- (yellow), 5- (red), and 20-year (purple) return period flood threshold within the given period, with the colour tone defined according to three probability of exceedance classes (30-50%, 50-75% and 75-100%).
• New 'Flood summary for days 1-30' layer, showing the flood summary over the full 30-day forecast horizon.
• '5 Year Return Period Exceedance' and '20 Year Return Period Exceedance'
  • Colour tone defined according to six probability of exceedance classes, defined by increments of 20% (instead of increments of 10%) to improve visibility.
• Major upgrade of the methodology used to generate the 'Reporting Point' layer :
  • Improved algorithm to generate the dynamic reporting points, resulting in more homogeneous coverage of the flooded river sections by the reporting points.
  • Dynamic reporting points remaining at the same location over consecutive forecasts and only removed when the flood signal disappears, allowing the user to trace the evolution of the forecast over the same river catchment.
  • Reporting point colours now only show the flood severity category (yellow, red or purple). This improves visibility and avoids the repetition of information already provided in the flood summary maps with the three probability-based subcategories.
  • Peak timing indicated on the reporting points as black border (within first 3 days) or greyed colours (beyond 10 days). This allows to quickly identify areas with flood expected in a short range (i.e. requiring more immediate action), or floods expected in more than 10 days.
  • Forecast tendency and peak date algorithms are defined according to the ensemble median, consistently with the reporting point flood categories, with a downward tendency highlighted if the discharge drops by at least 10% compared with the reference initial discharge value.
  • Discharge hydrograph vertical axis scale is defined according to the interquartile range of the ensemble forecast. This change avoids outliers dominating the hydrograph plots, thus improving visibility of the forecast especially in very dry areas. Maximum ensemble forecast values shown as a numerical value if they fall outside of the displayed range.
  • Forecast overview table simplified to show the combined flood signal of the three severity levels (2-, 5-, and 20-year), colour-coded according to the flood summary maps probability levels.

FLOOD RISK tab

• Upgraded methodology used to generate the 'Rapid Flood Mapping' layer 
  • Flood extent defined according to the probability of exceedance of the ensemble median (instead of the ensemble mean), consistently with the way flood severity is defined in the reporting points.

Map viewer features:

• Multi-tab feature which allows users to see pop-out windows for several queryable products in a single window.
• Improved functionalities in the pop-out windows for better user experience (dragging, closing and resizing).
• Revised web layer legends.
• Introduction of a stage Information System open to all following registration so that users can access new developments ahead of a release for monitoring.

Wiki

• Updated GloFAS -IS products documentation on the GloFAS wiki.

v3.5 integrates changes in its meteorological forcing used for the forecasts, with the use of the new version of the ECMWF-ENS ensemble forecasting system, introduced by IFS cycle 48r1. This change in the forcing data has the following impacts on GloFAS:

• Hydrological monitoring:
  • No change in the ECMWF-C3S ERA5- and ERA5-T-forced hydrological reanalysis simulations.
  • In the forecast initialisation (in the so-called fill-up, where ERA5-T is not yet available), the meteorological forcing resolution of ECMWF-ENS-CNTL has increased from 18 km to 9 km (similarly to the real time forecasts for days 1-15).
• Real time forecasts:
  • The spatial resolution of the forcing increases from 18 km to 9 km in the first 15 days of the 30-day forecast horizon, while the resolution of the extended-range forcing (days 16 to 30) remain unchanged at 36 km.
  • The extended-range ECMWF-ENS is produced every day in 48r1. Thus, the meteorological forcing for days 16-30 in GloFAS (which is blended after the first 15 days of higher resolution ENS) will always come from 1-day old forecast runs. Previously, it was coming from 1-4-day old forecast runs, depending on the day of the week, as the extended-range ENS was produced only on Mondays and Thursdays before 48r1.
• Reforecasts:
  • GloFAS v3.5 will not have a new 48r1-specific hydrological reforecast data set.
• Seasonal forecasts and seasonal reforecasts:
  • There is no impact on the seasonal hydrological modelling system.

More details on the 48r1 meteorological modelling changes can be found on the Implementation of IFS Cycle 48r1 page.

In addition, the v3.5 update also includes two additional reporting points in Bangladesh and NigeriaThis upgrade of GloFAS does not impact on the GloFAS modelling and data production/availability.

Technical details