Met Office Unified Model Tropical Cyclone Performance Following Major Changes to the Initialization Scheme and a Model Upgrade

Abstract

The Met Office has used various schemes to initialize tropical cyclones (TCs) in its numerical weather prediction models since the 1980s. The scheme introduced in 1994 was particularly successful in reducing track forecast errors in the model. Following modifications in 2007 the scheme was still beneficial, although to a lesser degree than before. In 2012 a new trial was conducted that showed that the scheme now had a detrimental impact on TC track forecasts. As a consequence of this, the scheme was switched off. The Met Office Unified Model (MetUM) underwent a major upgrade in 2014 including a new dynamical core, changes to the model physics, an increase in horizontal resolution, and changes to satellite data usage. An evaluation of the impact of this change on TC forecasts found a positive impact both on track and particularly intensity forecasts. Following implementation of the new model formulation in 2014, a new scheme for initialization of TCs in the MetUM was developed that involved the assimilation of central pressure estimates from TC warning centers. A trial showed that this had a positive impact on both track and intensity predictions from the model. Operational results from the MetUM in 2014 and 2015 showed that the combined impact of the model upgrade and new TC initialization scheme was a dramatic cut in both TC track forecast errors and intensity forecast bias.

The effect of atmosphere–ocean coupling on the prediction of 2016 western North Pacific tropical cyclones

“…Global numerical weather prediction (NWP) models, the weather‐timescale general circulation models (GCMs), are widely used as operational tools to predict TC activity. TC track prediction in NWP models has been substantially improved over the past decades , due to improved simulation of the large‐scale environment through better and higher‐resolution models and better model initializations based on more advanced data assimilation schemes (Heming, ). However, large errors remain in TC predictions by global NWP models (Hodges and Emerton, ; Heming, ; Yamaguchi et al, ; Hodges and Klingaman, 2019, submitted, personal communication).…”

“…TC track prediction in NWP models has been substantially improved over the past decades , due to improved simulation of the large‐scale environment through better and higher‐resolution models and better model initializations based on more advanced data assimilation schemes (Heming, ). However, large errors remain in TC predictions by global NWP models (Hodges and Emerton, ; Heming, ; Yamaguchi et al, ; Hodges and Klingaman, 2019, submitted, personal communication). For example, in the west Pacific, the state‐of‐the‐art UK Met Office and European Centre for Medium‐Range Weather Forecasts (ECMWF) global NWP systems have mean location errors that grow from 50 to 400 km during the five‐day forecast (Yamaguchi et al, ).…”

“…This article investigates the added value of air–sea coupling in the UK Met Office operational global NWP model for predicting TCs, with a focus on the WNP basin. The WNP basin is chosen because it is an area where NWP models have large TC prediction errors (Hodges and Emerton, ; Heming, ; Yamaguchi et al, ). The UK Met Office operational global atmosphere‐only NWP model is compared with two newly developed coupled models for seven‐day reforecasts of the 2016 WNP TC season.…”

MJO modulation and its ability to predict boreal summer tropical cyclone genesis over the northwest Pacific in Met Office Hadley Centre and Beijing Climate Center seasonal prediction systems

“…Many studies have shown that improvements in model initialization and resolution have contributed greatly to advancements in TC prediction (Hendricks et al , ; Osuri et al, ; Heming, ). In the hindcast experiments of this article, the lower GPI forecast skill in BCC_CSM1.2 since the first forecast lead day implies that further improvements in the initialization scheme and reanalysis data choosing may contribute to more skilful GPI forecasts using this model.…”

Assimilation of SMOS L‐band wind speeds: impact on Met Office global NWP and tropical cyclone predictions

“…Met Office tropical cyclone (TC) forecasts have shown significant improvement in recent years (Heming, ). Upgrades to the model dynamics, physics, and horizontal resolution in 2014 led to a positive impact on both track and intensity errors.…”