Direct computer simulation of intense tropical cyclones (TCs) in weather models is limited by computational expense. Intense TCs are rare and have small‐scale structures, making it difficult to produce large ensembles of storms at high resolution. Further, models often fail to capture the process of rapid intensification, which is a distinguishing feature of many intense TCs. Understanding rapid intensification is especially important in the context of global warming, which may increase the frequency of intense TCs. To better leverage computational resources for the study of rapid intensification, we introduce an action minimization algorithm applied to the Weather Research and Forecasting and WRFPLUS models. Action minimization nudges the model into forming more intense TCs than it otherwise would; it does so via the maximum likelihood path in a stochastic formulation of the model, thereby allowing targeted study of intensification mechanisms. We apply action minimization to simulations of Hurricanes Danny (2015) and Fred (2009) at 6‐km resolution to demonstrate that the algorithm consistently intensifies TCs via physically plausible pathways. We show an approximately tenfold computational savings using action minimization to study the tail of the TC intensification distribution. Further, for Hurricanes Danny and Fred, action minimization produces perturbations that preferentially reduce low‐level shear as compared to upper‐level shear, at least above a threshold of approximately 4 m/s. We also demonstrate that asymmetric, time‐dependent patterns of heating can cause significant TC intensification beyond symmetric, azimuthally averaged heating and find a regime of nonlinear response to asymmetric heating that has not been extensively studied in previous work.
Tropical cyclones (TCs) cause negative sea surface temperature anomalies by vertical mixing and other processes. Such cold wakes can cover substantial areas and persist for a month or longer. It has long been hypothesized that cold wakes left behind by intense TCs reduce the likelihood of subsequent TC development. Here, we combine satellite observations, a global atmospheric model, and a high‐resolution TC downscaling model to test this hypothesis and examine the feedback of cold wakes on subsequent TC tracks and intensities. Overall, cold wakes reduce the frequency of weak to moderate events but increase the incidence of very intense events. There is large spatial heterogeneity in the TC response, such as a southward shift of track density in response to cold wakes similar to that generated by Florence (2018). Cold wakes may be important for modeling and forecasting TCs, interpreting historical records and understanding feedbacks in a changing climate.
more » « less- Award ID(s):
- 1854956
- NSF-PAR ID:
- 10368950
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Geophysical Research Letters
- Volume:
- 48
- Issue:
- 7
- ISSN:
- 0094-8276
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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