The Prediction of Northern Hemisphere Tropical Cyclone Extended Life Cycles by the ECMWF Ensemble and Deterministic Prediction Systems. Part I: Tropical Cyclone Stage*

Abstract

This study has explored the prediction errors of tropical cyclones (TCs) in the European Centre for Medium-Range Weather Forecasts (ECMWF) Ensemble Prediction System (EPS) for the Northern Hemisphere summer period for five recent years. Results for the EPS are contrasted with those for the higher-resolution deterministic forecasts. Various metrics of location and intensity errors are considered and contrasted for verification based on IBTrACS and the numerical weather prediction (NWP) analysis (NWPa). Motivated by the aim of exploring extended TC life cycles, location and intensity measures are introduced based on lower-tropospheric vorticity, which is contrasted with traditional verification metrics. Results show that location errors are almost identical when verified against IBTrACS or the NWPa. However, intensity in the form of the mean sea level pressure (MSLP) minima and 10-m wind speed maxima is significantly underpredicted relative to IBTrACS. Using the NWPa for verification results in much better consistency between the different intensity error metrics and indicates that the lower-tropospheric vorticity provides a good indication of vortex strength, with error results showing similar relationships to those based on MSLP and 10-m wind speeds for the different forecast types. The interannual variation in forecast errors are discussed in relation to changes in the forecast and NWPa system and variations in forecast errors between different ocean basins are discussed in terms of the propagation characteristics of the TCs.

Sensitivity of Tropical Cyclone Formation to Resolution‐Dependent and Independent Tracking Schemes in High‐Resolution Climate Model Simulations

“…This comprises information from the different regional TC observing centers synthesized and merged together into a single data set (Knapp et al, 2010). For the years analyzed here, the IBTrACS data should have an almost complete representation of TC formation, although Knapp et al (2010) note small differences between the operational centers that compile the best track data in the total number of declared TCs (see also Hodges & Emerton, 2015;Ren et al, 2011). Here IBTrACS serves as ground truth for TC formation.…”

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

“…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, ).…”

The heated condensation framework as a convective trigger in the NCEP Climate Forecast System version 2

“…Location and intensity in both sets of tracks is based on lower-tropospheric vorticity. Error statistics based on this measure is shown to be consistent with more traditional verification metrics [see Hodges and Emerton, 2015]. In addition, 10 m wind speed and minimum sea level pressure (SLP) were compared against the IBTrACS (Figure 9) because these quantities are underestimated in the CFSR data due to the model's resolution [e.g., Manganello et al, 2012].…”

“…Tracks match if they overlap in time by any amount (accounting for differences in lifetimes between the IBTrACS and CFSR tracks), their mean separation is less than 48 geodesic, and are the track pair with minimum mean separation. This method achieves a high rate of identification of observed tracks in the analyses, with those missing being short-lived, weak systems [see Hodges and Emerton, 2015]. Likewise, to identify the same TCs in the forecast, the forecast tracks are matched against the CFSR tracks following a similar approach.…”