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The relationship of tropical cyclones to MJO and ENSO in the S2S database

“It is very well established that tropical cyclones (TCs) are modulated globally by the Madden-Julian Oscillation (MJO) and the El Niño-Southern Oscillation (ENSO). Due to these relationships, TC activity is to some extent predictable on both intraseasonal and seasonal time scales. Given the recent effort to develop TC forecasts on intraseasonal time scales a comprehensive analysis of the skill of various models in simulating and predicting TC activity at these time scales is warranted. The S2S dataset includes many high-resolution global weather and climate models that have capability to simulate tropical cyclone activity well. It is the ideal dataset to explore in depth the skill of TC forecast models.

First, we will detect and track tropical cyclones (TCs) in the S2S model output to generate TC tracks for this dataset. We will then analyze various aspects of the TC climatology in the S2S models, e.g., genesis, tracks, seasonality, intensity. Given that TC seasonal forecasts still have limited skill, as was apparent in the Atlantic as recently as 2013, it is important to analyze how well the models in the S2S database simulate the ENSO-TC teleconnection. We propose to examine the relationship of ENSO to TCs globally within the S2S dataset. Our focus will be on the response to ENSO of the environmental variables that are relevant for TCs, as well as modulation of the models’ TCs by ENSO. We will also examine the predictability of the S2S models for TC seasonal forecasts on regional scales. The project will also address how well the models in the S2S database simulate the relationship between the MJO and TCs. First, we will examine how well the different models reproduce the observed modulation of TCs in the active phase of the MJO. Second, we will explore various aspects of this modulation in the models, for instance, if the models modulation by the MJO is dependent on the MJO strength or on the MJO Phase.

In all three aspects of this project – TC climatology, ENSO-TC relationship, and MJO-TC relationship – we will focus on the models’ skill in forecasting TC activity on subseasonal to seasonal time scales. Furthermore, we will examine how the individual models’ ability to simulate TC characteristics is dependent on each model’s configuration. Our contribution to the MAPP task force activities will focus on the skill of S2S TC forecasts.”

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