DKSS-EPS 2020 - Storm surge ensemble prediction system
Ensemble sea level forecast, 51 hours ahead
Ensemble high water risk forecast, 51 hours ahead
Both
Ensemble spread indicator
Background
Sea level forecasts with uncertainty intervals are in demand. That has led to this exercise.
The one and same storm surge (i.e. ocean) model is forced by a number of weather model forecasts (ensembles),
which are similar but not identical. The result is displayed as sea level ensemble mean, minimum, maximum and spread,
for danish coastal stations.
Components
- DKSS storm surge model set-up (geography etc.)
- Atlantic surge model for boundaries
- ECMWF global deterministic NWP model
- HBM ocean model
- DMI-Harmonie COMEPS/NEA NWP ensemble prediction system
Ensembles
DKSS-EPS has 18 ensemble members, forced by the NWP ensemble prediction system DMI-COMEPS,
plus one deterministic member. 19 in total.
The perturbation lies with the weather forcing exclusively.
DMI-COMEPS ensemble members are all Harmonie-NEA.
The weather model ensemble forecast range is 57 hours. The COMEPS ensembles are
arranged to have 3 ensembles run every hour.
In a six-hour scedule, this produces 18 ensemble members, with forecast range relative
to the analysis time of latest member ranging from 57 hours (newest) to 51 hours (oldest).
With the storm surge ensembles run on a standard 6-hour schedule, 51 hours in then the
limiting range.
Graphics
The
ensemble graphics page shows sea level ensemble results for primary stations (no duplicate stations). We show
- deteministic forecast
- ensemble mean
- ensemble min
- ensemble max
- ensemble spread
The risk graphics page shows percentage of ensembles exceeding warning sea level for primary stations (no duplicate stations).
This page shows both.
Resources
- platform: Cray-XC50
- cpus: 128 (8 nodes)
- runtime: ~3.5 hours
- schedule: 6 hours
- forecast range: 51 hours
Future developments
Proper operationalisation. This is, until further notice, pre-operational, running on an R&D partition of the DMI Cray-hpc. And as such not monitored 24/7 by duty staff.
Schedule like COMEPS, running two ensembles every hour.
Jacob Woge Nielsen - 9 Nov 2020
