Predictability of Atlantic Hurricane Activity by the NMME Coupled Models

We propose to investigate, and then implement into a real-time forecast system, the response of the CFS CGCM to the Madden-Julian Oscillation (MJO) in north Atlantic hurricane activity. The very high resolution (T382) version of CFS will be used, as it has already been found to reproduce the interannual variations of hurricane activity level and individual hurricane tracks quite effectively over a multidecadal hindcast period.

Seasonal Atlantic hurricane activity level is known to vary in response to environmental variables such as the ENSO state, the sea surface temperature (SST) in the Main Development Region (MDR), and the state of the north Atlantic multidecadal oscillation. Relatively recently, dynamical tools have been used to predict hurricane activity with some success, defining individual cyclones and quantifying their seasonal total energy. The MJO phase and strength is also definable, and some statistical and dynamical predictability for the MJO is discernible out to the first 2-3 weeks. The MJO is also found capable of affecting the genesis and strength of tropical cyclones in both the Pacific and Atlantic oceans, and this MJO-cyclone relationship is reproducible in some dynamical models. We plan to capture these relationships in a real-time hurricane prediction system that can distinguish preferred timings and locations of hurricane activity up to 2-3 weeks.

Four main tasks of the project will be to (1) assess the extent and quality of MJO representation in the T382 CFS model; (2) examine the relationship between the model’s MJO and its hurricane activity compared with that found in observations, and statistically correct systematic errors; (3) repeat steps (I) and (2) for the standard (T 126) CFS version 2 model and for the other models in the NMME experiment, and test multimodel ensemble prediction; and (4) assuming favorable results from (l), (2) and/or (3), implement a real-time hurricane forecast system using the T382 CFS and/or other models in the NMME.

Better prediction of the seasonal Atlantic hurricane activity level, and of preferred subregions for hurricane activity in the medium-range timescale (first few weeks) due to the MJO, is relevant to U.S. economic, safety and national security issues–disaster management, water management, health, and protection of life and property. An example of the level of hurricane forecast detail potentially resulting from the proposed work would be: “During week 1, hurricanes are more likely to emerge in the Gulf of Mexico or in the vicinity of Cuba than near or north of the Leeward Islands, while during week 2 they are most likely in the subregion south of Haiti, the Dominican Republic, Puerto Rico and Virgin Islands, and relatively unlikely in the western Gulf of Mexico. ” Such intraseasonal specificity, still not targeting individual hurricanes, would complement the overall seasonal prediction of hurricane activity to render the suite of time scales more seamless. This work is also more generally relevant to the Next Generation Strategic Plan, as better Atlantic hurricane predictions lead to more valued, relied-upon climate services for the benefit of hurricane-sensitive human activities (e.g., coastal sustainability). The combination of the effects of climate change and the year-to-year variations in hurricane activity has potential for the hazard of record-breaking extremes in coastal region inundation and storm surge.