The Intense Arctic Cyclone of Early August 2012: Analysis of a Rare Event

On 03 August 2012, a cyclone formed over central Siberia and progressed northeastwards. By 0000 UTC 05 August, the cyclone reached the Arctic Ocean with a mean sea-level pressure (MSLP) of 984 hPa. Once over the Arctic Ocean, the cyclone rapidly intensified and reached a minimum pressure of 962 hPa on 06 August near 83°N and 170°W. Subsequently, the cyclone slowly weakened, and by 0000 UTC 10 August it once again had a minimum MSLP of 984 hPa. A motivation for this presentation is the likelihood that this cyclone is one of the most intense storm systems to ever impact the Arctic Ocean in the modern data era.

A climatology of Arctic cyclones to include cyclone intensities, frequencies, and tracks will be created for 1979-2013 for each season. A motivation behind this part of the study is to determine whether or not there is a relationship between rapidly decreasing areal coverage of Arctic sea-ice and changes in storm intensity, frequency or track. The purpose of this presentation will be to present the results of a climatological analysis of Arctic Ocean cyclones for 1979 to 2013 and how the most recent intense storm of August 2012 fits into this climatology. We will also present the results of a detailed diagnostic analysis of the intense cyclone of early August 2012.

An anomalously strong 850 hPa baroclinic zone existed over north-central Russia prior to the development of the intense August 2012 cyclone. The corresponding 850 hPa temperature anomalies were between -2°C and -4°C poleward of 70°N and upwards of +8-9 °C over eastern Russia near 60°N. This enhanced baroclinicity aided in developing an anomalously strong 300 hPa polar jet along the coast of northeastern Russia (25-30 m s-1) that helped to intensify the cyclone. Subsequently, the cyclone intensified most rapidly as it traversed the ice-free waters of the Arctic Ocean. How much of an influence latent and sensible heat fluxes had in destabilizing the lower atmosphere and making it more conducive to cyclogenesis will be discussed during this presentation. The intense cyclone of early August 2012 featured very warm air at 850 hPa (> 15 C) that was collocated with high values of precipitable water (> 35 mm) within the warm-sector of the storm poleward of 70°N. Climatological trends of the elements associated with the impressive intense cyclogenesis event will also be discussed.