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Metrics Tropical Cyclone “size” willPanel | ||||
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NEWS!
Please note that with cycle 47r1 the model identifiers will change.
A test environment for time-critical applications is now available.
Please note that to prepare for the cycle upgrade changes to dissemination requirements will not be possible between 09:00 UTC on 29 June 2020 and 09:00 UTC on 01 July 2020.
Meteorological content
The changes in this model cycle cover the Data Assimilation, treatment of observations and improvements to the model itself
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AssimilationLWDA uses first guess from Early Delivery
Weak-constraint 4D-Var
Revision of skin temperature background errors in the context of TOVS sink variable
Timestep for last 4D-Var minimisation
ObservationsATMS observation error correlations
Channel-specific aerosol rejections for IR sounders
Spline interpolation in the 2D GPS-RO bending angle operator
ModelSurface albedo changes
Update to greenhouse gases and total solar irradiance
Quintic interpolation in semi-Lagrangian advection
Drag coefficient for very strong winds
Convection scheme
Tangent-linear physics
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Meteorological impact
New metrics for Tropical cyclones
- Metrics of Tropical Cyclone (TC) “size” will supplement the existing forecasts of TC track and intensity (minimum central mean sea level pressure and maximum wind around a TC).
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TC “size” will be represented by radii for mean 10m wind thresholds of 18, 26 and 32 m/s (34, 50 and 64 knots) to denote the furthest distance (in metres) away from the centre of the TC at which each of the wind speed thresholds are exceeded. Each of these are computed for each of four earth-relative quadrants, i.e. in NE, SE, SW and NW, delivering a total of 12 “size metrics” for each TC at each time step. To arrive at these metrics the code scans, in outwards fashion, all model gridpoints within each quadrant. Values are computed for the HRES and ENS for all TCs that are either present in the initial conditions, or that develop during the forecast integrations (i.e. TC “genesis”). The new values, which we will call “wind radii”, are included as supplementary information within the BUFR message that currently contains the TC tracks (pairs of latitudes and longitudes) and the TC intensities (minimum pressure and overall maximum wind speed). Implementation of the TC wind radii product was motivated by continuing model developments such as the recent re-tuning of the Charnock parameter for very high wind speeds, which goes live in model cycle 47r1, and which improves lower tropospheric wind speeds around intense storms. Computation of the wind radii values is executed after the TC tracking, in a post-processing step, using code developed by NOAA which is available in the public domain. The wind radii values are non-zero wherever the wind thresholds are exceeded, otherwise they are set to zero. If the track is missing at specific time step(s) then values are replaced by a missing value indicator. No changes were made to the TC tracker software. |
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EFIFor the computation of EFI and SOT in IFS cycle 47r1 mxcape6 and mxcapes6 will be used instead of cape and capes, respectively. This change is aiming for a better sampling in the computation of the 24-hour maxima needed for the EFI. In effect with the change we extract the maximum within 24 hourly values, instead of using 4 6-hourly values. Additional details: The EFI (and SOT) for CAPE and CAPE-shear start using mxcape6 and mxcapes6 parameters |
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Each tropical cyclone identified in an IFS forecast has 10m mean wind attributes associated. In previous cycles this was just the maximum within the cyclone circulation, now there are also TC size metrics (see above). Historically such metrics were adjusted upwards, compared to raw model values, by multiplying by 1.08, in part to provide more realistic values. This dates back to a time when model resolution was much lower than it is now. With cycle 47r1 we have chosen to remove this adjustment factor. This decision coincides with a concurrent model change that increases the 10m winds slightly in extreme conditions (see meteorological content section).
ECMWF output that references such values includes the TC BUFR files, and on the web the TC-related Lagrangian meteograms. The TC classifications used for TC strike probabilities (and their ecCharts counterparts) are also impacted.
It is unlikely that users will notice a difference.
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Convective inhibitionFor Convective Inhibition (CIN) the following two changes will be implemented:
This will provide an estimate for CIN which is much more in line with parcel theory and forecasting practice and will improve usability for diagnosing deep moist convection. Additional details: Changes in CIN to concur with forecasting practice |
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These events are intended for testing technical aspects only and should not be used for Time Critical activities.
Options 2 and 3
Option 2 or 3 time-critical applications can be tested with theIFS Cycle 47r1 test data retrieved from MARS or received in Dissemination.ResourcesWebinar on 'Cycle 47r1 performance and products'
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