Analysis of the Outflow Interactions of 2015 Hurricanes Marty and Joaquin using Ensemble Techniques: a Perspective Informed by Observations from the TCI Experiment

The processes modulating the intensity of tropical cyclones (TC) have been the subject of significant research activity for decades, both on account of their intrinsic phenomenological interest as well as the role a greater understanding of them might play in improving TC forecasts. The Tropical Cyclone Intensity (TCI) field experiment collected a rich set of observations in 2015 which help shed important light on this longstanding research problem. Analysis of these observations reveals some evidence that the low potential vorticity (PV) and low inertial resistance dome built by east Pacific Hurricane Marty helped to enable the rapid intensification of Joaquin in the western Atlantic four days later.

To obtain a full 4-dimensional view of the evolving atmosphere during the period of interest, we employ Ensemble Kalman Filter (EnKF) data assimilation of the TCI observations using the University of Wisconsin Nonhydrostatic Modeling System (UW-NMS). This improves the definition of the PV and inertial frequency depictions in the context of a full ensemble numerical simulation of the two hurricanes, and allows detailed diagnosis of the processes governing their interaction. In particular, we demonstrate the impact of Marty’s outflow on the subsequent development of Joaquin using ensemble sensitivity analysis (ESA).