The role of uncertainty in waveguide perturbations on midlatitude predictability with DOWNSTREAM

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The principal investigator of this proposal will assess whether changes to the structure of the jet stream that occur in conjunction with the development of cyclones are significant sources of weather forecast errors further downstream. These events can result in poorly forecast extreme weather events. The project will contribute to the future US workforce through the training of a graduate student in state-of-the-art approaches to predictability, data assimilation, and synoptic/mesoscale meteorology. A successful project will develop understanding that can lead to improved weather forecasts, and in turn provide greater lead time for warnings and reduced loss of life and property due to certain mid-latitude extreme weather events.The goal of this proposal is to evaluate the hypothesis that waveguide perturbations associated with midlatitude cyclones and the extratropical transition of tropical cyclones (ET) are an important source of downstream forecast errors. The first phase of this proposal involves evaluating this hypothesis by comparing the downstream predictability following the development of midlatitude cyclones and ET and comparing it to a predictability climatology using 31 years of ensemble forecasts from the NOAA Earth System Research Laboratory 2nd generation reforecast project. Moreover, this study will evaluate hypotheses regarding the predictability of midlatitude vs. ET cyclones and how this predictability varies depending on the magnitude of the waveguide perturbation. In addition, this study will evaluate hypotheses related to how uncertainty in the outflow and thermodynamic profile in the vicinity of waveguide perturbations impact the downstream predictability. The role of the outflow on the downstream state will be evaluated by comparing the sensitivity of forecast metrics related to the downstream state to the outflow against the sensitivity of the forecast metrics to other aspects of the state. The role of the outflow will be confirmed by performing a series of perturbed initial condition experiments where aspects of the initial-time outflow properties are modified, and then evaluating the impact on the downstream state.