Homework 1: Due at Beginning of Class, September 9, 2011). (Students Reviewing These Papers Are Released from this Homework)
Reading 1: The Distinction between Large-scale and Mesoscale Contribution to Severe Convection: A Case Study Example (pdf)
1. Doswell discusses the setting for the Topeka, KS tornado event of May 6, 1983. Despite the fact that the synoptic setting was quite favorable for severe thunderstorm development, Doswell states: "...while the lapse rate field reveals low values of dry static stability in eastern Kansas and southwestern Missouri, there are two major obstacles to convective development in the Topeka area:..." What are these two obstacles?
There were two major obstacles to convective initiation: (a) a strong capping inversion; and (b) inadequate surface moisture (mixing ratios as inferred from the dew point field).
2. What role does consideration of wind shear have in the problem of forecasting convection?
The vertical wind shear influences the type of convection but not whether convection will occur. Convective initiation is a separate forecasting issue.
3. What is Doswell's conception of "large-scale processes"?
According to Doswell, large scale processes are characterized by simplifcations to the equations of motion such that air flow is dry adiabatic, in hydrostatic and (nearly) in geostrophic balance. Such flow is then quasi-geostrophic and the vertical motion fields and evolution of the height field can be understood on the basis of the quasigeostrophic omega and height tendency equations.
4. What is Doswell's definition of a "mesoscale process"?
According to Doswell, a mesoscale (or smaller scale) process is one that initiates parcel lifting. Thus, the terminology "...a short wave will trigger the thunderstorms..." is inaccurate, since the dynamics of short waves is such that they can be understood on the basis of quasigeostrophic theory.
Reading 2: Doswell, C.A. III, 2001: Severe convective storms -- An overview. Severe Convective Storms, Meteor. Monogr., 28, no. 50, Amer. Meteor. Soc., 1-26. (PDF)
1. According to Doswell, what is the primary observational tool for assessing the large-scale structure of the atmosphre?
The primary observational tool for assessing the large-scale structure of the atmosphere is the radiosonde network.
2. In the subtropical and polar regions of the planet, synoptic-scale processes are dominated by what, according to Doswell?
In the region of the world poleward of the tropics, synoptic-scale processes are dominated by those that are quasigeostrophic.
3. What observation does Doswell have about changes in the level of accuracy in tornado and severe weather forecasting?
Clear progress has been made, but there are frustrations centering on the remaining issues in the area of convective initiation, the last few steps of the supercell cascade that distinguishes tornadic from non-tornadic supercells, non-supercell tornadoes, hail formation, and convective wind gusts.
4. What are the three prongs in Doswell's approach to severe weather disaster mitigation?
The three prongs are: (a) forecast verification and establishment of a baseline climatology of severe weather events; (b) application of scientific forecasting approaches; and (c) making sure the public has clear knowledge of how to mitigate the hazards associated witht eh forecasted severe weather event.