Forecasting Organized Severe Storms (FOSS) - Operations Proving Ground

In this section, Kim Runk introduces Ariel Cohen and the Forecasting Organized Severe Storms video lecture series.  Ariel contextualizes the role of deep, moist convection in instability mitigation as a part of the evolving global circulation.  He addresses the ingredients and representing parameters for organized, severe convection, and identifies how we can leverage meteorological datasets to assess the convective environment.  Special attention is placed on understanding vertical motion and how it can be inferred from chart analysis.

The cyclonic perturbation aloft and its interaction with antecedent baroclinicity explain the mutual overlap of moisture, lift, instability, and vertical wind shear supporting organized severe thunderstorms. This basic interaction is typified in numerous variants of recognizable patterns that the forecaster can use to assess severe-weather potential. This segment will specifically address the basic necessity for ascent to overlap with buoyant air in support of severe convection.

In this section, Ariel Cohen describes the various characteristics that distinguish three convective-environment regimes addressed in the Day-2 Convective Outlook preparation videos. These include convective threats evolving in a northwest-flow, recycled-moisture regime; with a tropical cyclone; and from a subtle midlevel disturbance. He demonstrates how the assessment regarding organized, severe-storm ingredients can be applied to any regime by performing a detailed investigation of governing conceptual models and related meteorological data.

Numerous conceptual models can be employed to identify severe-storm threat areas, and each of these conceptual models can be linked to signals amid the observed and numerically simulated synoptic and mesoscale environment. Knowledge of complex theoretical topics -- such as lapse-rate advection's manifestation on the local thermodynamic profile, and mesocyclone-maintenance and tornadogenesis theories -- can greatly aid forecasters in interrogating environment-depicting datasets to identify specific clues relevant to accurately expressing severe-storm potential. This segment will specifically address details and detection of meteorological environments favoring superposition of ascent and buoyant air, especially that characterized by surface-based effective inflow offering the greatest severe-thunderstorm potential.

In this section, Ariel Cohen explains how to anticipate convective mode, based on the orientation of convection-initiating boundaries relative to environmental kinematic profiles. These include considerations of boundary-relative cloud-layer mean winds, deep shear, and anvil-level storm-relative flow. He also addresses ways in which we can assess the propensity for convection to be surface based, leveraging the concept of the effective-inflow layer. This includes an assessment of the residence time of convection within the surface-based effective-inflow-layer air.

Baseline considerations of convective mode and effective-inflow bases are critical to distinguish between specific severe-storm hazards and their coverage and intensity. Other reality checks, including cyclone configuration and the inherited forecast, can play major roles in directing subsequent outlooks. This segment will address these key reality checks in preparing the convective outlook, along with a brief overview of the science behind General Thunderstorm preparation.

In this section, Ariel Cohen addresses the various convective hazards that emanate from organized, severe storms. This effectively links the meteorological assessment of convective mode and propensity for convection to be surface based with hazards, which serves as a foundation for related Impacts-based Decision Support Services. A discussion of tornadogenesis emanating from both supercells and quasi-linear convective systems is highlighted in this section. This section culminates with a discussion of the relationship between the assessment of convective hazards and Convective Outlook designations, philosophical elements of Convective Outlook preparation, along with a discussion of General Thunderstorm forecasting.

This segment will address big-picture subjects pertaining to the convective outlook. This includes the ways in which the previous outlook, internal and external collaboration, psychology, and personality potentially influence outlook decisions, and specifically how an awareness of these elements is key in terms of making sense of the final outlook and making any final changes before it is disseminated to the world.