a five-year study of lightning paerns across southcentral ... · a five-year study of lightning...

AFive-YearStudyofLightningPa7ernsAcrossSouthcentralAlaska

RebeccaDuellandMa7hewClayNWSAnchorage

Background•  LightningandthunderstormclimatologiesofAlaskahavebeencreated,howeverthesourcesofthedatahavevariedandgenerallyimprovedwithHme.

•  ThunderstormClimatologyofAlaska,Grice&Comiskey,1976•  UseddatafromtheBLMThunderstormandWildfireSurveillanceProgram(radar,aircraTpatrols,fire-weatherobservingstaHons)1969-1974

•  ClimatologyCharacteris7csandObjec7vePredic7onofThunderstormsoverAlaska,Reap,1991•  BLMdatafrom1Maythrough30September1987-1989

Background

•  AlaskaLightningClimatologyandApplica7ontoWildfireScience,McGuineyetal.,2004•  BLMdata1986-2002

•  ClimatologyandtheIntra-SeasonalVaria7onofSummer7meCloud-to-GroundLightninginMainlandAlaska,BuckeyandBothwell,2009•  BLMdata2000-2007

GriceandComisky,1976 Reap1991

BuckeyandBothwell,2009

ThevastmajorityoflightningstrikesinAlaskaoccurovertheInterior

Background•  LightningacHvitypeaks3-6hoursaTerlocalnoon.–  ThisindicatesthattheconvecHonisdrivenprimarilybyintensesolarheaHngduringtheaTernoon.

– MostthunderstormsinAlaskaareairmassthunderstorms(notassociatedwithafrontorinstabilityline)(Grice&Comisky1976)

•  Mostthunderstormsoccuroverelevatedterrain.–  AreasofenhancedstaHcinstabilityandorographicforcing–  Lightningstrikesoverhigherterrainpeakearlierthanstrikesoverlowerterrain(Grice&Comisky1976,Reap1991)

ObjecHvesofThisStudy•  Whileotherstudieshavefocusstatewide,thisstudywillfocus

primarilyonSouthcentralAlaska.

•  PrimaryObjec7ve:ExaminefiveyearsoflightningtrendsoverSouthcentralAlaska

-  Howmanydaysayearcanweexpectthunderstormsinourdifferentforecastzones?

-  Whatweatherpa7ernsleadtothebiggestlightningevents?

Alaska'sseason-to-datewildfirestaHsHcsasofJune19

•  Wildfires:218Es7matedacresburned:153,441Ac7vefires:71Staffedfires:8Human-causedfires:156Lightning-causedfires:62Largestfirestodate:

1)LockwoodFire-22,346acres,GalenaZone,startedbylightningonJune62)PitkaForkFire-16,823acres,SouthwestArea,startedbylightningonJune43)Li7leYetnaFire-16,514acres,SouthwestArea,startedbylightningonJune44)ToikHillFire-16,471acres,GalenaZone,startedbylightningonJune65)BallCreekFire-13,924acres,SouthwestArea,startedbylightningonJune4

h7ps://fire.ak.blm.gov/content/aicc/sitreport/current.pdf

Image:AlaskaDepartmentofNaturalResources–DivisionofForestryFacebookPage

EastForkFire

AlaskaLightningDetecHonNetwork•  Changedtonewsystemin2012(TOA)

•  ReporHng2.25HmesthelightningstrikescomparedtooldVaisalasensors

•  Thisisdueincreasedefficiency,longerrangedetecHonandstatewidesensorcoverage

•  16Sensors•  14inAlaska,2inCanada

Credit:AlaskaInteragencyCoordinaHonCenter

•  LightningAcHvityLevel(LAL)isusedtodescribethearealcoverageofthunderstorms,notthenumberofthunderstormsorlightningstrikes.

LALValue Descrip7on ArealCoverage

1 Nothunderstormsexpected 0%

2 Isolatedthunderstorms 5%to25%

3 Widelysca7eredthunderstorms 25%to40%

4 Sca7eredthunderstorms 40%to55%

5 Numerousthunderstorms 55%orgreater

6 DryLightning LALof3anddrythunderstorms

present

WhatisLAL?

Methodology•  Downloadedandplo7edALDNdataandclippedthedataforSouthcentralAlaska•  RemovedCloudtoCloudLightningstrikes

•  Createda10X10kmgridwithinArcMap•  CalculatedtheNumberofinstancesoflightningstrikespergrid

10kmLightningGridforSouthcentralAlaska2012-2016

Smoothed10kmLightningGridforSouthcentralAlaska2012-2016

•  Usingnearestneighborsmoothing,wecansmooththedatatomakeiteasiertoread

ThunderstormDaysbyGeographicArea

ZoneNumber AverageThunderstormDays/Year

101(Anchorage) 6days/year111(MatanuskaValley) 14.8days/year

121(WesternKenaiPeninsula) 16.8days/year

125(WesternPrinceWilliamSound) 23.8days/day

141(CopperRiverBasin) 76.6days/year145(SusitnaValley) 60.2days/year

ThunderstormDaysvsAverageHighTemperature

Year AverageHighTemp

#ofT-StormDays

2012 62.4°F 1

2013 67.3°F 4

2014 64.6°F 5

2015 68.0°F 9

2016 67.5°F 11


#ofT-StormDays

2012 63.6°F 5

2013 68.0°F 7

2014 64.9°F 14

2015 67.7°F 21

2016 67.9°F 27

Anchorage MatanuskaValley(Palmer)



#ofT-StormDays

2012 59.9°F 10

2013 61.9°F 12

2014 61.8°F 15

2015 64.1°F 23

2016 64.7°F 24


#ofT-StormDays

2012 58.8°F 6

2013 63.3°F 14

2014 61.4°F 24

2015 63.6°F 30

2016 63.9°F 45

WesternKenaiPeninsula(Kenai)

WesternPrinceWilliamSound

(Seward)



#ofT-StormDays

2012 64.3°F 37

2013 71.7°F 69

2014 65.3°F 81

2015 68.2°F 80

2016 69.3°F 116


#ofT-StormDays

2012 63.7°F 34

2013 69.8°F 51

2014 65.6°F 66

2015 68.0°F 69

2016 68.4°F 81

CopperRiverBasin(Gulkanna)

SusitnaValley(Talkeetna)


0

2

4

6

8

10

12

6263646566676869

2012 2013 2014 2015 2016Num

bero

fThu

nderstormDays

AverageHighTem

perature(F)

Year

Anchorage

AverageHighTemperature #ofT-stormDays

30405060708090100110120

646566676869707172

2012 2013 2014 2015 2016

Num

bero

fThu

nderstormDays

AverageHighTem

perature(F)

Year

CopperRiverBasin(Gulkana)

AverageHighTemperature #ofT-stormDays

VeryweakcorrelaHonbetweenaveragehightemperaturesandthunderstormdays.-Likelya7ributedtoincreasedsensorsacrossAKdetecHngmorelightningstrikes.

LightningStaHsHcs

•  Greaterthan99%oflightningstrikesacrossSouthcentralAlaskaoccurbetweenthemonthsofJuneandAugust.

•  NumberoflightningstrikesacrosssouthernAlaskahavegenerallybeenincreasingeachyearwith2016themostacHveacrossallzones.

•  NodisHnctcorrelaHonbetweenaveragehightemperaturesandlightningstrikes.–  It’spossiblethatasmoresensorsareinstalled,thenumberofstrikesbeingdetectedgoesup.

–  Pastresearchshowsthatthunderstormsarediurnallydrivenwhichcouldhintatmorewarmoutliersnotpickedupby3monthaverage.

Thunderstormpa7ernsfortheKenaiMountainsandthewesternChugach

Mountains

Pa7ern1:NortherlyWave

500mbGeopotenHalHeight 500mbTemperature(°C)

MeanSeaLevelPressure(Pa) 925mbTemperature(°C)



Anchorage00ZSounding17June2015

Anchorage06ZSounding17June2015

Pa7ern2(EasterlyWave)

500mbGeopotenHalHeight 500mbTemperature(°C)


Pa7ern2(EasterlyWave)

6/16/2015LightningPlotforAnchorage

*Greenboxesindicatea5kmgridthathadatleastonerecordedlightningstrike

Pa[ern1:NortherlyWaves

6/20/2014LightningPlotforAnchorage

*Greenboxesindicatea5kmgridthathadatleastonerecordedlightningstrike

Pa[ern2:EasterlyWaves

LALComparisonforAnchorage

Date ForecastedLALAbove1500_

ActualLALAbove1500_

ForecastedLALBelow1500_

ActualLALBelow1500_

6/16/2015 6 3(6) 6 2

7/29/2014 1 2 1 2

6/20/2014 2 2 2 2

7/31/2015 2 2 1 1

Overall,forecastsforLALarequiterepresentaHveforAnchorage.-Itappearsthatevenundernortherlywaves(6/16/2015)thattheAnchoragebowlwillbehardpressedtoseeLALof6duetoarealcoveragewithmostthunderstormsresidingovertheChugachMountains.

Thunderstormpa7ernsfortheCopperRiverBasinand

WrangellMountains

500mbGeopoten7alHeight 500mbTemperature(°C)

References•  Buckey,D.R.andBothwell,P.D,2009:Climatologyandtheintra-seasonalvariaHonof

summerHmecloud-to-groundlightninginmainlandAlaska.FourthConferenceonMeteorologicalApplicaHonsofLightningData,Phoenix,AZ,Amer.Meteor.Soc.,7pp.

•  Grice,G.K.andA.L.Comisky,1976:ThunderstormClimatologyofAlaska.NOAATechnicalMemo.NWSAR-14,36pp.

•  Mesinger,F.,andCoauthors,2006:NorthAmericanRegionalReanalysis.Bull.Amer.Meteor.Soc.,87,343–360,doi:10.1175/BAMS-87-3-343

•  McGuineyE,ShulskiM,WendlerG(2004)AlaskalightningclimatologyandapplicaHontowildfirescience.Proceedings,ConferenceonMeteorologicalApplicaHonsofLightningData,85thAnnualAMS

•  Reap,R.M.,1991:ClimatologyCharacterisHcsandObjecHvePredicHonofThunderstormsoverAlaska.Wea.Forec.,6,309-19.

Acknowledgements

HistoricallightningdataprovidedbytheBureauofLandManagement,AlaskaFireService.

SynopHcImagesprovidedbytheNOAA/ESRL

PhysicalScienceDivision,BoulderColoradofromtheirWebsiteath7p://www.esrl.noaa.gov/psd/

DatausedforthesynopHcimagesfromthe

NorthAmericanRegionalReanalysis

a five-year study of lightning paerns across southcentral ... · a five-year study of lightning...

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