Severe Convective Storms An Overview  Doswell C.A. III, 2001: Severe Convective Storms – An Overview  Severe Convective Storms, Meteor. Monogr., 28, no. 50, Amer. Meteor. Soc., 13-26

General Outline I.Severe Convection - classification, problems, issues - distinction between non- and severe convection II.Observations of Severe Convection - large-scale - mesoscale III.Prediction of Severe Convection - current accuracy - goals for severe convective storm forecasting, to mitigate threats

Severe Convection Classification and problems  >=3/4 in. hail  >=50 knot sustained wind gusts  Tornado  Should the average hail size and wind gust be reported as “severe” instead of the single largest size reported?  Precipitation not officially defined beyond severe  Flash floods and heavy rain consideration must include areas’ hydrological circumstances  Hales 2-tiered system for severe thresholds

Observations of Severe Convection Large-Scale –Rawinsonde observations are primary –PROBLEMS: - significant gaps worldwide - limiting analysis to the few “oubreak” events –Fig 10: Chart idealizing significant synoptic features in an outbreak of severe convective storms

Observations of Severe Convection  Ingredients-based approach –conditional instability –moisture –a source of lift  V.S. Characteristic pattern alone

Observations of Severe Convection Mesoscale  Satellite images (qualitative)  Radar, limited  Important aspect: Convective Outflow  Processes –free “internal” instabilities –forced “external” processes –fronts –gravity waves

Prediction of Severe Convection ~Current accuracy levels  Progress  Advances in forecasting severe storms and tornadoes, SEE FIG. 12  Increased prediction accuracy  Better public awareness and communication  Frustrations  Not as much attention to non tornadic events  Flash floods/heavy convection not offically “severe”  Hail formation and short-range forecasts

Prediction of Severe Convection ~Lessening the threats posed  Needed outside North America –systemic reporting –A way to including events in climatological database –sufficient planning for possible severe events in area’s where threat is rare –public awareness, appropriate reactions

Prospects and Unsolved Problems  Forecasting –Improvements in observing systems (ie radar) and related forecasting systems –Difficulties/ less progress  Tornadic vs nontornadic supercell differentiation  Forecasting nonsupercell tornado situations  System to forecast and mitigate flash flood damage

Prospects and Unsolved Problems  Weather Modification possibilities –Public appeal –Lack of many severe convective weather processes  New Observations –Doppler RADARs are likely only a beginning –Dual polarization observations possible –Satellite remote sensor improvements  Economic difficulties

Severe Convection Final thoughts  Mesoscale and smaller events  “Chaotic” systems  Important unobservables –Resources needed

Severe Convective Storms This is the paradox of all science: we are both excited and frustrated by what we do not know, even as we create new understanding”. - Charles A Doswell III, May 2000