- PATRICIA (EP20): 00 UTC 22 Oct 2015: 60 kt -> 150 kt in 24 hours (CHP6 predicted ~150 kt)
- MERANTI (WP16): 06 UTC 10 Sep 2016: 35 kt -> 155 kt in 60 hours (CHP6 predicted ~160 kt)
- MARIA (AL15): 12 UTC 17 Sep 2017: 60 kt -> 140 kt in 36 hours (CHP6 predicted ~135 kt)
While CHP6 is not a forecast model per se, since it is meant to show the sensitivity of the TC to very favorable environmental conditions relative to the other members of the CHIPS ensemble, the fact that it sometimes captures ERI events with 36-72 hour lead time when no other full physics model does, suggests that the dynamics of ERI are primarily axisymmetric and do not require a 3D full-physics framework. These examples of correct predictions of extreme RI events suggest that the general pathway of extreme rapid intensification can be captured by an axisymmetric numerical model, and that the MPIR may be achieved when the storm structure and latent heating distribution are axisymmetric in a favorable environment. When the MPIR limit is high for a given storm, extreme rapid intensification becomes possible.
The goals of this work are twofold: 1) to create and evaluate an initial version of forecast guidance for the upper bound rate at which TCs may intensify and examine the verification statistics for such a model, and 2) to examine high-resolution flight-level aircraft observations for several well-observed ERI cases to learn how the TC’s physical scale (radius of maximum winds), inertial stability, dynamic efficiency, and column-integrated diabatic heating evolve during ERI. Development of effective MPIR-based guidance could be extremely useful to operational forecasters who need to assess what the upper-bound intensification risk is for marginal tropical storms that are a few days away from landfall.