Upper-level fronts, tropopause disturbances, and convection - Dr. Bogdan Antonescu and Prof. Geraint Vaughan - Centre for Atmospheric Science, University of Manchester, Manchester, UK
Forecasting convective storms is one of the most difficult forecast challenges. One feature that has been claimed to have a positive influence and a negative influence on convective storms are tropopause folds, layers of stratospheric air that have been intruded down into the troposphere. To determine the relationship between tropopause folds and convective storms, this talk presents first the main conceptual models for the evolution of the upper-level fronts and associated tropopause folding. "Potential vorticity thinking" represents the framework for this discussion, thus advocating once more the utility of "PV thinking" for operational forecasters, not only as means of understanding the atmospheric dynamics, but also as a useful tool in the forecast process. In the second part of the talk, we will try to disentangle the conflicting paradigms that tropopause folds both promote and suppress convection, by analyzing the influence of tropopause folds on the ingredients for deep, moist convection. At the end of the talk we present some tools that can be used by the operational forecasters to assess the influence of tropopause folds on convection.
Recording Bogdan Antonescu and Geraint Vaughan
Sting jets - Prof. Geraint Vaughan - Centre for Atmospheric Science, University of Manchester, Manchester, UK
The presentation will discuss the strong winds that are sometimes found in the southwest quadrant of a cyclone and which on occasion can cause damaging winds at the surface. A conceptual model will be presented showing how these winds are related to air streams in the cyclone. Evidence for a distinct airflow known as a 'sting jet' will be presented - this is a descending jet of air reaching the top of the boundary layer a little behind the cold front. Reference will be made to results from recent experimental field campaigns to study this phenomenon.
Recording Geraint Vaughan