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ATM OCN 100 - Summer 2002 LECTURES 32 & 33. THUNDERSTORMS: MESOSCALE CONVECTIVE SYSTEMS A. INTRODUCTION Practical Questions What is a thunderstorm? Why do thunderstorms occur? Definitions (where...). MADISON’S CURRENT WEATHER. Madison Weather at 1000 AM CDT - PowerPoint PPT Presentation
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ATM OCN 100 Summer 2002ATM OCN 100 Summer 2002 11
ATM OCN 100 - Summer 2002ATM OCN 100 - Summer 2002LECTURES 32 & 33LECTURES 32 & 33
THUNDERSTORMS:THUNDERSTORMS: MESOSCALE CONVECTIVE SYSTEMSMESOSCALE CONVECTIVE SYSTEMS
A. INTRODUCTIONA. INTRODUCTION– Practical QuestionsPractical Questions
What is a thunderstorm?What is a thunderstorm? Why do thunderstorms occur?Why do thunderstorms occur?
– Definitions Definitions (where...)(where...)
MADISON’S CURRENT WEATHERMADISON’S CURRENT WEATHER
Madison Weather at 1000 AM CDT WED AUG 8 2001 Updated twice an hour at :05 and :25
Sky/Weather: SUNNY Temperature: 83 F (28 C) Dew Point: 71 F (21 C) Relative Humidity: 67% Wind: W7 MPH Barometer: 30.04F
ATM OCN 100 Summer 2002ATM OCN 100 Summer 2002 33
Surface Weather Map from Today Surface Weather Map from Today with with IsobarsIsobars & Fronts & Fronts
ATM OCN 100 Summer 2002ATM OCN 100 Summer 2002 44
Current Temperatures (Current Temperatures (ooF) & IsothermsF) & Isotherms
ATM OCN 100 Summer 2002ATM OCN 100 Summer 2002 55
Current Dewpoints Current Dewpoints ((ooF) F)
ATM OCN 100 Summer 2002ATM OCN 100 Summer 2002 77
Current Winds Aloft at 34,000 Ft.Current Winds Aloft at 34,000 Ft.
ATM OCN 100 Summer 2002ATM OCN 100 Summer 2002 88
Tomorrow’s 7AM ForecastTomorrow’s 7AM Forecast
ATM OCN 100 Summer 2002ATM OCN 100 Summer 2002 1010
A. INTRODUCTION A. INTRODUCTION (con’t.)(con’t.)
DefinitionsDefinitions– AA thunderstorm thunderstorm - contains thunder;- contains thunder;
– A A thunderstorm day thunderstorm day -- a day with thunder. a day with thunder.
A Mesoscale PhenomenonA Mesoscale Phenomenon
ATM OCN 100 Summer 2002ATM OCN 100 Summer 2002 1111
CumulonimbusCumulonimbus
ATM OCN 100 Summer 2002ATM OCN 100 Summer 2002 1212
Thunderstorm Hazards-Thunderstorm Hazards-
Lightning Lightning
Lightning is a killer (with more than 80 deaths in US per year)!
ATM OCN 100 Summer 2002ATM OCN 100 Summer 2002 1313
ATM OCN 100 Summer 2002ATM OCN 100 Summer 2002 1414
Thunderstorm Hazards-Thunderstorm Hazards-
Lightning Lightning
Lightning is a killer (with more than 80 deaths in US per year)!
ATM OCN 100 Summer 2002ATM OCN 100 Summer 2002 1515
Historical Thunderstorm Charge Historical Thunderstorm Charge ModelModel
ATM OCN 100 Summer 2002ATM OCN 100 Summer 2002 1616
New Conceptual Model of Charge New Conceptual Model of Charge Structure in Deep Convection from Structure in Deep Convection from
Balloon DataBalloon Data
ATM OCN 100 Summer 2002ATM OCN 100 Summer 2002 1717
Thunderstorm Hazards-Thunderstorm Hazards-Flash FloodsFlash Floods
Flash Flooding is a killerFlash Flooding is a killer (with more than 120 deaths in US(with more than 120 deaths in US per year)! per year)!
ATM OCN 100 Summer 2002ATM OCN 100 Summer 2002 1818
Thunderstorm Hazards-Thunderstorm Hazards-TornadoesTornadoes
Tornadoes are killers (with more than 60 deaths in US per year)!
ATM OCN 100 Summer 2002ATM OCN 100 Summer 2002 1919
Funnel CloudFunnel Cloud
When funnel clouds touch the ground they become…….
ATM OCN 100 Summer 2002ATM OCN 100 Summer 2002 2020
TornadoesTornadoes
ATM OCN 100 Summer 2002ATM OCN 100 Summer 2002 2121
Thunderstorm Hazards-Thunderstorm Hazards-High Winds (Straight line)High Winds (Straight line)
ATM OCN 100 Summer 2002ATM OCN 100 Summer 2002 2222
Thunderstorm Hazards-Thunderstorm Hazards-Large HailLarge Hail
ATM OCN 100 Summer 2002ATM OCN 100 Summer 2002 2323
B. THUNDERSTORM GENESISB. THUNDERSTORM GENESIS
Essential IngredientsEssential Ingredients
– Low Level MoistureLow Level Moisture
– Unstable Atmospheric Lapse RateUnstable Atmospheric Lapse Rate
– Trigger (Trigger (or or Kicker)Kicker) Initial Setting & Initiation ProcessesInitial Setting & Initiation Processes
– Free ConvectionFree Convection
– Forced ConvectionForced Convection
ATM OCN 100 Summer 2002ATM OCN 100 Summer 2002 2424
When Convection?When Convection?
ATM OCN 100 Summer 2002ATM OCN 100 Summer 2002 2525
STABLE CONDITIONSSTABLE CONDITIONSCompare Compare EnvironmentEnvironment with with DALRDALR
Colder parcel sinks & returns to startColder parcel sinks & returns to start
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TEMPERATURE (C)
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ATM OCN 100 Summer 2002ATM OCN 100 Summer 2002 2626
ABSOLUTELY STABLE CONDITIONSABSOLUTELY STABLE CONDITIONSCompare Compare EnvironmentEnvironment with with SALRSALR & & DALRDALR
Colder parcel sinks & returns to startColder parcel sinks & returns to start
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ATM OCN 100 Summer 2002ATM OCN 100 Summer 2002 2727
UNSTABLE CONDITIONSUNSTABLE CONDITIONS
Compare Compare EnvironmentEnvironment with with DALRDALR Warmer parcel continues upward Warmer parcel continues upward
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ATM OCN 100 Summer 2002ATM OCN 100 Summer 2002 2828
ABSOLUTELY UNSTABLE CONDITIONSABSOLUTELY UNSTABLE CONDITIONS
Compare Compare EnvironmentEnvironment with with SALRSALR & & DALRDALR Warmer parcel continues upwardWarmer parcel continues upward
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ATM OCN 100 Summer 2002ATM OCN 100 Summer 2002 2929
If STABLE CONDITIONS for DryIf STABLE CONDITIONS for DryCompare Compare EnvironmentEnvironment with with DALRDALR
Colder parcel sinks & returns to startColder parcel sinks & returns to start
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TEMPERATURE (C)
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ATM OCN 100 Summer 2002ATM OCN 100 Summer 2002 3030
But UNSTABLE CONDITIONS for HumidBut UNSTABLE CONDITIONS for HumidCompare Compare EnvironmentEnvironment with with SALRSALR Warmer parcel continues upwardWarmer parcel continues upward
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ATM OCN 100 Summer 2002ATM OCN 100 Summer 2002 3131
CONDITIONALLY STABLE CONDITIONSCONDITIONALLY STABLE CONDITIONSCompare Compare EnvironmentEnvironment with with SALRSALR & & DALRDALR
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ATM OCN 100 Summer 2002ATM OCN 100 Summer 2002 3232
Stability CriteriaStability CriteriaSee Fig. 6.14 Moran & Morgan (1997)See Fig. 6.14 Moran & Morgan (1997)
ATM OCN 100 Summer 2002ATM OCN 100 Summer 2002 3333
STABILITY CRITERIASTABILITY CRITERIA Absolutely StableAbsolutely Stable
– Layer lapse rate less than saturation Layer lapse rate less than saturation adiabatic lapse rate.adiabatic lapse rate.
Absolutely UnstableAbsolutely Unstable– Layer lapse rate greater than dry adiabatic Layer lapse rate greater than dry adiabatic
lapse rate.lapse rate. Conditionally UnstableConditionally Unstable
– Layer lapse rate lies between dry & Layer lapse rate lies between dry & saturation adiabatic lapse rates.saturation adiabatic lapse rates.
ATM OCN 100 Summer 2002ATM OCN 100 Summer 2002 3434
STATIC STABILITY STATIC STABILITY (con’t.)(con’t.)
• Processes which change static stability Processes which change static stability (instability)(instability)
• Cool below, but warm above Cool below, but warm above (stabilize)(stabilize)• Warm below, but cool above Warm below, but cool above (destabilize)(destabilize)
• Visual stability indicatorsVisual stability indicators
ATM OCN 100 Summer 2002ATM OCN 100 Summer 2002 3535
MammatusMammatus
These pocket clouds form from sinking air ahead of the most severe thunderstorms. If you see these….run for cover!!!!
ATM OCN 100 Summer 2002ATM OCN 100 Summer 2002 3636
ATM OCN 100 Summer 2002ATM OCN 100 Summer 2002 3737
Hail StonesHail Stones
ATM OCN 100 Summer 2002ATM OCN 100 Summer 2002 3838
Hail StormHail Storm
ATM OCN 100 Summer 2002ATM OCN 100 Summer 2002 3939
THE “TRIGGER”THE “TRIGGER” Free ConvectionFree Convection
– Air ascends due to destabilization;Air ascends due to destabilization;– Heat surface and/or cool aloft.Heat surface and/or cool aloft.
Orographic LiftingOrographic Lifting– Air ascends mountain slopes.Air ascends mountain slopes.
Frontal LiftingFrontal Lifting– Air ascends along cold front.Air ascends along cold front.
Dynamic LiftingDynamic Lifting– Upper level motions induce lifting.Upper level motions induce lifting.
ATM OCN 100 Summer 2002ATM OCN 100 Summer 2002 4040
C. THUNDERSTORM TYPESC. THUNDERSTORM TYPES Single-Cell ThunderstormsSingle-Cell Thunderstorms
– ““Air Mass” ThunderstormsAir Mass” Thunderstorms
– Orographic ThunderstormsOrographic Thunderstorms Frontal ThunderstormsFrontal Thunderstorms Squall-Line ThunderstormsSquall-Line Thunderstorms Mesoscale Convective Complexes (MCC)Mesoscale Convective Complexes (MCC) Multiple-Cell ThunderstormsMultiple-Cell Thunderstorms
ATM OCN 100 Summer 2002ATM OCN 100 Summer 2002 4141
D. THUNDERSTORM CLIMATOLOGYD. THUNDERSTORM CLIMATOLOGY
Geographical & Seasonal DistributionGeographical & Seasonal Distribution Time of DayTime of Day Duration of ThunderstormsDuration of Thunderstorms Reported Thunderstorm IntensitiesReported Thunderstorm Intensities
ATM OCN 100 Summer 2002ATM OCN 100 Summer 2002 4242
Thunderstorm ClimatologyThunderstorm Climatology
See Fig. 13.9, Moran & Morgan (1997)See Fig. 13.9, Moran & Morgan (1997)
ATM OCN 100 Summer 2002ATM OCN 100 Summer 2002 4545
E. CHARACTERISTICS OF E. CHARACTERISTICS OF THUNDERSTORMSTHUNDERSTORMS
The Thunderstorm Cell ModelThe Thunderstorm Cell Model Life Cycle of a Non-Severe Life Cycle of a Non-Severe
Thunderstorm CellThunderstorm Cell– Where…Where…
ATM OCN 100 Summer 2002ATM OCN 100 Summer 2002 4646
Cumulus Stage in thunderstorm life cycleCumulus Stage in thunderstorm life cycle See Fig. 13.2a, Moran & Morgan (1997)See Fig. 13.2a, Moran & Morgan (1997)
ATM OCN 100 Summer 2002ATM OCN 100 Summer 2002 4747
Mature Stage in thunderstorm life cycleMature Stage in thunderstorm life cycle See Fig. 13.2b, Moran & Morgan (1997)See Fig. 13.2b, Moran & Morgan (1997)
ATM OCN 100 Summer 2002ATM OCN 100 Summer 2002 4848
Dissipating Stage in thunderstorm life cycleDissipating Stage in thunderstorm life cycle See Fig. 13.2c, Moran & Morgan (1997)See Fig. 13.2c, Moran & Morgan (1997)
ATM OCN 100 Summer 2002ATM OCN 100 Summer 2002 5050
F. SEVERE THUNDERSTORMSF. SEVERE THUNDERSTORMS Official Criteria for Severe WeatherOfficial Criteria for Severe Weather
– Large hailLarge hail (3/4 inch or large diameter)(3/4 inch or large diameter);;
– and/orand/or
– Damaging WindsDamaging Winds (surface wind gusts of 58 mph (surface wind gusts of 58 mph oror greater) greater)..
Unofficial Criteria for Severe WeatherUnofficial Criteria for Severe Weather– Tornadoes, Heavy Precipitation, Flash Tornadoes, Heavy Precipitation, Flash
Flooding, Deadly LightningFlooding, Deadly Lightning
ATM OCN 100 Summer 2002ATM OCN 100 Summer 2002 5151
Vertical Cross section of Severe Vertical Cross section of Severe ThunderstormThunderstorm
See Fig. 13.11, Moran & Morgan (1997)See Fig. 13.11, Moran & Morgan (1997)
ATM OCN 100 Summer 2002ATM OCN 100 Summer 2002 5252
Ingredients for severe thunderstorm episodeIngredients for severe thunderstorm episodeSee Fig. 13.13, Moran & Morgan (1997)See Fig. 13.13, Moran & Morgan (1997)
ATM OCN 100 Summer 2002ATM OCN 100 Summer 2002 5353
F. SEVERE THUNDERSTORMS F. SEVERE THUNDERSTORMS (con’t.)(con’t.)
Types of Severe ThunderstormsTypes of Severe Thunderstorms Structure of Severe ThunderstormsStructure of Severe Thunderstorms Synoptic Situations Favoring Severe Synoptic Situations Favoring Severe
Thunderstorm WeatherThunderstorm Weather Movement of Severe Thunderstorm Movement of Severe Thunderstorm
CellsCells
ATM OCN 100 Summer 2002ATM OCN 100 Summer 2002 5454
NWS Watches & WarningsNWS Watches & Warnings
Severe thunderstorm Severe thunderstorm watchwatch– Issued by National Weather Service to Issued by National Weather Service to
alert public that conditions are favorable alert public that conditions are favorable for development of severe thunderstorms for development of severe thunderstorms (large hail &/or high winds).(large hail &/or high winds).
Severe thunderstorm Severe thunderstorm warningwarning – Issued by National Weather Service to Issued by National Weather Service to
warn public that a severe thunderstorm warn public that a severe thunderstorm has been sighted by storm spotters or has has been sighted by storm spotters or has been indicated by radar.been indicated by radar.
ATM OCN 100 Summer 2002ATM OCN 100 Summer 2002 5555
Hail ClimatologyHail Climatology
See Fig. 13.24, Moran & Morgan (1997)See Fig. 13.24, Moran & Morgan (1997)
ATM OCN 100 Summer 2002ATM OCN 100 Summer 2002 5656
Tornado ClimatologyTornado Climatology
See Fig. 14.4, Moran & Morgan (1997)See Fig. 14.4, Moran & Morgan (1997)
ATM OCN 100 Summer 2002ATM OCN 100 Summer 2002 5757
Cross-section of a Cross-section of a thunderstorm cellthunderstorm cell