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A climatology of the 100- and 250-hPa 45°–75°N zonal-mean meridional eddy heat flux anomaly, hereafter heat flux anomaly, was created to examine its variability following cool-season (i.e., October–April) blocks and extratropical cyclones. The goal is to elucidate the dynamical and environmental differences between synoptic events followed by the most extreme heat flux anomalies. The analysis was conducted with the National Aeronautics and Space Administration’s Modern-Era Retrospective Analysis for Research and Applications, version 2 reanalysis. The results show that, on average, European blocks and west Pacific cyclones are followed by positive heat flux anomalies while west Pacific blocks and Atlantic extratropical cyclones are followed by negative heat flux anomalies. However, there was a large range of the 11-day-average heat flux anomaly following the events. Events in each region were further partitioned by their 100-hPa heat flux anomaly for a temporal and spatial analysis of the top and bottom quartile of events. Top-quartile events exhibited a baroclinic wave structure with height from the troposphere through the stratosphere, whereas bottom-quartile events were associated with a barotropic wave structure with height; these structures are significant at the 5% level. The results suggest that the sign of the heat flux anomaly is not dependent on the location of the synoptic event alone, but that there are common climatological and anomalous wave patterns surrounding the synoptic events that result in positive or negative heat flux anomaly. Regardless of event region, the precursor stratospheric structure is a key indicator in whether an event is followed by positive or negative 100-hPa heat flux anomalies.

Cool-season occurrences of blocks, extratropical cyclones that undergo explosive cyclogenesis, and tropical cyclones (TCs) that undergo extratropical transition (ET) from 1980 to 2015 are analyzed using the National Aeronautics and Space Administration’s Modern-Era Retrospective Analysis for Research and Applications, version 2, dataset. These synoptic events are first examined in a climatological analysis that includes identifying consecutive synoptic events, namely, blocks that follow bombs or ET events as well as extratropical cyclones that follow ET events. These synoptic events are then analyzed with respect to three tropical modes of variability: the Madden–Julian oscillation (MJO), El Niño–Southern Oscillation, and the stratospheric quasi-biennial oscillation (QBO). The QBO was considered from both a momentum and thermal point of view, using the equatorial 30-hPa zonal-mean wind and the equatorial zonal wind shear between 30 and 50 hPa, respectively. The results show that in the seven days prior to cool-season blocks and ET events, there is a statistically significant frequency minimum in MJO phases 7 and 3, respectively. With respect to the QBO, there is a statistically significant frequency maximum in neutral QBO conditions during bomb onset and a frequency minimum during ET onset. When stratifying bombs by latitude, there is a significant reduction in Arctic (i.e., poleward of 55°N) bomb onset during easterly QBO conditions. The results show that both tropospheric and stratospheric tropical modes of variability can modulate the frequency of extratropical synoptic events to a similar degree.