FactorsthatInfluencetheGrowthofSupercellsintoMCSa8erSunsetKeenanEure1,JohnM.Peters2,RussShumacher2

1.UniversityofMaryland,CollegePark,CollegePark,MD2.ColoradoStateUniversity,FortCollins,CO

IntroducKon•  Discrete,tornadoproducingsupercellso8enoccurina8ernoon

(stormswithrotaKngupdra8s)•  ColdairouNlowsfromindividualcellsmergeandhelpform

MesoscaleConvecKveSystem(MCS)•  O8enproducesflashflooding

•  ConvecKontransiKonsfromsurfacebasedtoelevated•  Lowest1-2kmofatmospherecools&stabilizesassunsetsand

warmairadvectsormovehorizontallyovercoolair(belowle8)•  Southerlyfastmovingwinds,orlowleveljet(LLJ)hasa

maximumatnight(belowright)•  Lowlevelwindshear&ascentincrease

Methods•  25casesofsupercelltoMCStransiKon(MCSevents)•  25casesofsupercellswithnoMCSa8erwards(Nullevents)•  AnalyzedhourlyRapidRefresh(RAP)modeldataforeachcase

toanalyzethefollowingfrom18Zto9Z:•  Meridionalwindcomponent–verKcalorsoutherlywind

component,toseethechangeintheLLJ•  PotenKaltemperatureadvecKon–allowsustoseewarmair

advecKon;indicaKveoflowlevelascentorrisingmoKon•  Divergence–similartopotenKaltemperatureadvecKon,

negaKvedivergenceshowsrisingmoKon/ascent•  Bulkwindshear–Thechangeofthexandywindcomponents

withheight•  ConvecKveAvailablePotenKalEnergy(CAPE)–measureof

instabilityforstormgrowthanddevelopment•  DeltaZLevelofFreeConvecKon(LFC)–heightanairparcel

needstoreachtotheLFC,whereaparcelbecomesbuoyantandcontributestostormgrowth&development

•  Tookcoordinatesforeachcasetomakeagridofareainfocus•  Averagedvariablesoverthexandycoordinatesovereachlevel

ofatmosphere(37values,1foreachheight,37totalforeachhour)

•  ProducedKmevs.heightplotsforeachparameterlistedabove•  Createdplotsshowingdifferencebetweenspecifiedhourand

21Z,since21Zwastypicallythemostunstable&generallythemeanKmeoftornadoes

•  Timevsheightmadeforeachcase,thencreatedcompositesoraveragesoftheMCSandnullcases,respecKvely

•  PosiKvechangesinpotenKaltemperatureadvecKoninthe0Zto

5Zwindow(inthelowest1-2km)fortheMCScasesversusminimaloralmostnegaKvechangeindicatesmorelowlevelascentfortheMCScases

•  SharpnegaKvechangesindivergencebetween0Zto6-7ZinMCScasesequatestoconvergence;asairconvergencesitleadstorisingmoKonaswell

•  MeridionalwindcomponentchangeisindicaKveofastrongerLLJnocturnalmaximumforMCScases,comparedtoanabsenceofthisfornullcases

•  CAPEvaluesfairlysimilarbetweenMCScasesandnullcases•  DeltaZLFCvalues,orheightsparKcularlyhigherfornullcases,

meaningthattheseparcelsneededtoreachahigherheighttoreachtheirinstabilitylevel(LFC),whethertheparcelwasfromthegroundorelevated

Corfidi, Stephen F., Sarah J. Corfidi, and David M. Schultz. "Elevated Convection and Castellanus: Ambiguities, Significance, and Questions." Weather and Forecasting 23 (n.d.): 1280-303. 26 Apr. 2008. Web. 21 July 2016. Du, Yu, and Richard Rotunno. "A Simple Analytical Model of the Nocturnal Low-Level Jet over the Great Plains of the United States." American Meteorological Society 71 (2014): 3673-684. 22 Sept. 2014. Web. 21 July 2016. Markowski, Paul, and Yvette Richardson. Mesoscale Meteorology in Midlatitudes. N.p.: n.p., n.d. 17 Mar. 2010. Web. 21 July 2016. Moore, James T., Fred H. Glass, Charles E. Graves, Scott M. Rochette, and Marc J. Singer. "The Environment of Warm-Season Elevated Thunderstorms Associated with Heavy Rainfall over the Central United States." American Meteorological Society 18 (2003): 861-78. 1 Oct. 2003. Web. 21 July 2016. Nielsen, Erik R., and Gregory R. Herman. "Double Impact: When Both Tornadoes and Flash Floods Threaten the Same Place at the Same Time." American Meteorological Society 30 (2015): 1673-693. 17 Sept. 2015. Web. 21 July 2016. Parker, Matthew D. "Response of Simulated Squall Lines to Low-Level Cooling." American Meteorological Society 65 (2008): 1323-341. 1 Apr. 2008. Web. 21 July 2016. Peters, John M., and Russ S. Schumacher. "Dynamics Governing a Simulated Mesoscale Convective System with a Training Convective Line." American Meteorological Society 73 (2015): 2643-664. American Meteorological Society. American Meteorological Society, 24 June 2016. Web. 21 July 2016. Schumacher, Russ S., and Richard H. Johnson. "Organization and Environmental Properties of Extreme-Rain-Producing Mesoscale Convective Systems." American Meteorological Society 133 (2005): 961-76. Web.

ReferencesThisworkhasbeensupportedbytheNaKonalScienceFoundaKonResearchExperiencesforUndergraduatesSiteinClimateScienceatColoradoStateUniversityunderthecooperaKveagreementNo.AGS-1461270andAGS-PRF1524435.

FormoreinformaKon,contactkeure@umd.edu

IntroducKon

Methodology

Conclusions

Acknowledgements

References

Results

Discretesupercellsonthele8,organizedMCSontheright

MCScases Nullcases

18 19 20 21 22 23 0 1 2 3 4 5 6 7 8 90

500

1000

1500

2000

2500

3000

3500

4000

Time (Z)

Heig

ht a

bove

gro

und

leve

l (m

)

Potential Temp Advection Change from 21Z (K hr−1)

−1

−0.8

−0.6

−0.4

−0.2

0

0.2

0.4

0.6

0.8

1

18 19 20 21 22 23 0 1 2 3 4 5 6 7 8 90

500

1000

1500

2000

2500

3000

3500

4000

Time (Z)

Heigh

t abo

ve g

roun

d lev

el (m

)

Potential Temp Advection Change from 21Z (K hr−1)

−1

−0.8

−0.6

−0.4

−0.2

0

0.2

0.4

0.6

0.8

1

18 19 20 21 22 23 0 1 2 3 4 5 6 7 8 90

500

1000

1500

2000

2500

3000

3500

4000

Time (Z)

Heigh

t abo

ve g

roun

d lev

el (m

)

Divergence Change from 21Z (hr−1)

−0.1

−0.05

0

0.05

0.1

0.15

18 19 20 21 22 23 0 1 2 3 4 5 6 7 8 90

500

1000

1500

2000

2500

3000

3500

4000

Time (Z)

Heigh

t abo

ve g

roun

d lev

el (m

)

Divergence Change from 21Z (hr−1)

−0.1

−0.05

0

0.05

0.1

0.15

18 19 20 21 22 23 0 1 2 3 4 5 6 7 8 90

500

1000

1500

2000

2500

3000

3500

4000

Time (Z)

Heigh

t abo

ve g

roun

d lev

el (m

)

Meridional Wind Component Change from 21Z (m/s)

−10

−8

−6

−4

−2

0

2

4

6

8

10

18 19 20 21 22 23 0 1 2 3 4 5 6 7 8 90

500

1000

1500

2000

2500

3000

3500

4000

Time (Z)

Heigh

t abo

ve g

roun

d lev

el (m

)

Meridional Wind Component Change from 21Z (m/s)

−10

−8

−6

−4

−2

0

2

4

6

8

10

18 19 20 21 22 23 0 1 2 3 4 5 6 7 8 90

500

1000

1500

2000

2500

3000

3500

4000

Time (Z)

Heigh

t abo

ve g

roun

d lev

el (m

)

CAPE (J Kg−1) and Delta Z LFC (m)

1750

20002000

2250

2250

2250

2500

2500

500

2750

2750

3000

3000

3000

325032

3250350037504000

0

200

400

600

800

1000

1200

1400

1600

1800

2000

18 19 20 21 22 23 0 1 2 3 4 5 6 7 8 90

500

1000

1500

2000

2500

3000

3500

4000

Time (Z)

Heigh

t abo

ve g

roun

d lev

el (m

)

CAPE (J Kg−1) and Delta Z LFC (m)

30003250

3500

3750

3750

3750

4000

4000

4000

0

200

400

600

800

1000

1200

1400

1600

1800

2000

Caseanalyzedthatsawseveralflashfloodsandtornadoesincloseproximity