The Impact of Recently Implemented and Planned Changes to the Met Office Global Model on Tropical Cyclone Performance

The impact of changes to the Met Office Global Model (MOGM) made in 2014 and 2015 were discussed in the paper presented at the 32nd AMS Conference on Hurricanes and Tropical Meteorology in 2016. The model’s performance during the remainder of 2016 was similar to or an improvement on what was seen during the previous two years. Forecasts for the track of high profile Hurricane Matthew were very good with landfall over Haiti and the passage close to Florida well predicted. However, the rapid intensification early in its lifetime was not well captured.

In 2017 the horizontal resolution of the MOGM was increased from 17 km to 10 km at mid-latitudes. Results from trials of this change will be presented which include both a reduction in track forecast errors and intensity bias. Performance for high profile hurricanes such as Harvey, Irma and Maria, which occurred after the resolution change, will be presented.

The increase in resolution of the MOGM has accentuated the problem of over-deepening tropical cyclones which occurs on some occasions. It is expected that a coupled atmosphere-ocean model will have a positive impact on this. Trials are underway of a coupled version of the MOGM and initial results will be presented which show a further reduction in track forecast errors and intensity bias compared to the atmosphere-only model.