Severe Convective Storms Severe Convective Storms An OverviewAn Overview

Doswell C.A. III, 2001: Severe Convective Doswell C.A. III, 2001: Severe Convective Storms – An OverviewStorms – An Overview

Severe Convective Storms, Meteor. Severe Convective Storms, Meteor. Monogr., 28, no. 50, Amer. Meteor. Soc., Monogr., 28, no. 50, Amer. Meteor. Soc., 13-2613-26

General OutlineGeneral OutlineI.I. Severe ConvectionSevere Convection

- classification, problems, issues- classification, problems, issues- distinction between non- and severe - distinction between non- and severe

convection convectionII.II. Observations of Severe ConvectionObservations of Severe Convection

- large-scale- large-scale- mesoscale- mesoscale

III.III. Prediction of Severe ConvectionPrediction of Severe Convection- current accuracy- current accuracy- goals for severe convective storm - goals for severe convective storm

forecasting, to mitigate threats forecasting, to mitigate threats

Severe ConvectionSevere ConvectionClassification and problemsClassification and problems

>=3/4 in. hail>=3/4 in. hail >=50 knot sustained wind gusts>=50 knot sustained wind gusts TornadoTornado

Should the Should the averageaverage hail size and wind gust be hail size and wind gust be reported as reported as ““severesevere”” instead of the single largest size instead of the single largest size reported?reported?

Precipitation not officially defined beyond severePrecipitation not officially defined beyond severe Flash floods and heavy rain consideration must Flash floods and heavy rain consideration must

include areasinclude areas’’ hydrological circumstances hydrological circumstances Hales 2-tiered system for severe thresholdsHales 2-tiered system for severe thresholds

Observations of Severe ConvectionObservations of Severe ConvectionLarge-ScaleLarge-Scale

– Rawinsonde observations are primaryRawinsonde observations are primary– PROBLEMS: PROBLEMS:

- significant gaps worldwide- significant gaps worldwide

- limiting analysis to the few - limiting analysis to the few ““oubreakoubreak”” events events

– Fig 10: Chart idealizing significant synoptic Fig 10: Chart idealizing significant synoptic features in an outbreak of severe convective features in an outbreak of severe convective stormsstorms

Observations of Severe ConvectionObservations of Severe Convection

Ingredients-based approachIngredients-based approach– conditional instabilityconditional instability– moisture moisture – a source of lifta source of lift

V.S. Characteristic pattern aloneV.S. Characteristic pattern alone

Observations of Severe ConvectionObservations of Severe ConvectionMesoscaleMesoscale

Satellite images (qualitative)Satellite images (qualitative) Radar, limitedRadar, limited Important aspect: Convective OutflowImportant aspect: Convective Outflow Processes Processes

– free free ““internalinternal”” instabilities instabilities– forced forced ““externalexternal”” processes processes– frontsfronts– gravity wavesgravity waves

Prediction of Severe ConvectionPrediction of Severe Convection~Current accuracy levels~Current accuracy levels

ProgressProgress Advances in forecasting severe storms and Advances in forecasting severe storms and

tornadoes, SEE FIG. 12tornadoes, SEE FIG. 12 Increased prediction accuracyIncreased prediction accuracy Better public awareness and communicationBetter public awareness and communication

FrustrationsFrustrations Not as much attention to non tornadic eventsNot as much attention to non tornadic events Flash floods/heavy convection not offically Flash floods/heavy convection not offically ““severesevere”” Hail formation and short-range forecastsHail formation and short-range forecasts

Prediction of Severe ConvectionPrediction of Severe Convection~Lessening the threats posed~Lessening the threats posed

Needed outside North AmericaNeeded outside North America– systemic reporting systemic reporting – A way to including events in climatological A way to including events in climatological

databasedatabase– sufficient planning for possible severe events in sufficient planning for possible severe events in

areaarea’’s where threat is rares where threat is rare– public awareness, appropriate reactionspublic awareness, appropriate reactions

Prospects and Unsolved ProblemsProspects and Unsolved Problems

ForecastingForecasting– Improvements in observing systems (ie radar) Improvements in observing systems (ie radar)

and related forecasting systemsand related forecasting systems– Difficulties/ less progressDifficulties/ less progress

Tornadic vs nontornadic supercell differentiationTornadic vs nontornadic supercell differentiation Forecasting nonsupercell tornado situationsForecasting nonsupercell tornado situations System to forecast and mitigate flash flood damageSystem to forecast and mitigate flash flood damage

Prospects and Unsolved ProblemsProspects and Unsolved Problems

Weather Modification possibilitiesWeather Modification possibilities– Public appealPublic appeal– Lack of many severe convective weather Lack of many severe convective weather

processesprocesses New ObservationsNew Observations

– Doppler RADARs are likely only a beginningDoppler RADARs are likely only a beginning– Dual polarization observations possibleDual polarization observations possible– Satellite remote sensor improvementsSatellite remote sensor improvements

Economic difficultiesEconomic difficulties

Severe ConvectionSevere ConvectionFinal thoughtsFinal thoughts

Mesoscale and smaller eventsMesoscale and smaller events ““ChaoticChaotic”” systems systems Important unobservablesImportant unobservables

– Resources neededResources needed

Severe Convective StormsSevere Convective Storms

This is the paradox of all science: we are both This is the paradox of all science: we are both excited and frustrated by what we do excited and frustrated by what we do notnot know, even as we create new know, even as we create new understandingunderstanding””..

- - Charles A Doswell III, May 2000Charles A Doswell III, May 2000