Latest HUXt Ensemble Forecast

A 5-day probabilistic forecast of the near-Earth solar wind speed and CME arrival times and speeds.

Forecast guide

The HUXt ensemble forecast takes two data inputs:

  • UK Met Office (UKMO) estimate of the solar wind speed close to the Sun (at 21.5 rS). This comes from the WSA model driven with daily-updated magnetograms.
  • UKMO estimates of CME properties (speed, direction, width) at  21.5 rS, from fitting the cone model to coronagraph observations

These are the two standard inputs to the WSA-Enlil solar wind model, which is used to produce the standard SWPC and UKMO forecasts. We perturb both inputs (solar wind and CME properties) within some reasonable ranges to generate large ensembles of different initial conditions at 21.5 rS. Each is propagated to Earth using HUXt, which is intended to capture the uncertainty in the forecast conditions at Earth.

Dashboard panel descriptions

Top-left: Time series of solar wind speed, for the model spin-up period (grey) and the forecast interval (white). The black line is the “deterministic” forecast – HUXt run with the WSA solution and CME parameters, without any perturbation. This should be similar to the standard WSA-Enlil forecast. The white line is the HUXt ensemble median, the blue/purple coloured bands are percentiles of the ensemble. When the bands are narrow/broad, the forecast has high/low confidence. The observed real-time solar wind speed from DSCOVR is shown in red for the last 5 days, but these are increasingly unreliable owing to issues with DSCOVR.

Middle-left: Time series of CME arrival probability at Earth. It’s the fraction of ensemble members that predict a particular CME will arrival at Earth within a particular time window. The total area under a given curve is a measure of the confidence that CME will arrive at Earth. A narrow peak suggests a high confidence in the arrival time. A broader peak suggests low confidence in the arrival time.


Bottom-left: Table of the Earth-directed CME properties and forecast arrival times/speeds


Top-right: Summary of the input data. The colour map shows the WSA solar wind speed at 21.5 rS in HEEQ coordinates. Overlaid are the positions and widths of CMEs identified by Met Office observers. Those with a possibility of Earth impact are assigned a colour used in other panels.


Bottom-right: The probability density of CME arrival speeds, for the Earth-impacting CMEs only. The total area under the curve is a measure of the confidence a CME will arrive at Earth. A narrow/broad peak suggests a high/low confidence in the arrival speed.


Additional information

This forecasting system was developed as part of the Space Weather Empirial Ensembles Package (SWEEP) project. HUXt is an open-source solar wind numerical model which is described in Barnard and Owens (2022) and Owens et al. (2020).

Download the latest forecast data here: data_wsa_huxt_forecast_latest.h5. Please note that these forecast data are licensed under CC BY 4.0

Experimental BRaVDA-HUXt Ensemble Forecast

A probabilistic 5-day forecast of the near Earth solar wind speed and CME arrival times and speeds

BRaVDA-HUXt forecast guide

This BRaVDA-HUXt ensemble forecast is still under development and is therefore less tested and stable than the HUXt ensemble. In this forecast, the BRaVDA data assimilation scheme is used to assimilate the real-time in-situ solar wind speed data from DSCOVR and STEREO-A. The output of the BRaVDA assimilation is an improved inner boundary condition for use with the HUXt ensemble forecast.