Subseasonal variability of Rossby wave breaking and impacts on tropical cyclones during the North Atlantic warm season

Significant anomalies in sea level pressure, tropospheric wind, and humidity fields are found over the tropical-subtropical Atlantic within 8 days of an AWB activity peak. Such anomalies may lead to suppressed TC activity on the subseasonal time scale, but a significant negative correlation between the subseasonal variability of AWB and Atlantic basinwide TC activity does not exist every year, likely due to the modulation of TCs by other factors.

It is also found that AWB occurrence may be modulated by the Madden-Julian oscillation (MJO). In particular, AWB occurrence over the tropical-subtropical west Atlantic is reduced in phases 2 and 3 and enhanced in phases 6 and 7 based on the Real-Time Multivariate MJO (RMM) index. The impacts of AWB on the predictive skill of Atlantic TCs are examined using the Global Ensemble Forecasting System (GEFS) reforecasts with a forecast lead time up to 2 weeks.