A Multiscale Examination of A Multiscale Examination of a Mesoscale Cyclogenesis a Mesoscale Cyclogenesis

Event in a Polar Air StreamEvent in a Polar Air Stream

Tom Galarneau, Dan Keyser, and Lance Tom Galarneau, Dan Keyser, and Lance BosartBosart

Department of Earth and Atmospheric Department of Earth and Atmospheric SciencesSciences

University at Albany, SUNYUniversity at Albany, SUNY

8th Northeast Regional Operational Workshop, Albany, NY8th Northeast Regional Operational Workshop, Albany, NY

1 November 20061 November 2006

MotivationMotivation Heavy snow with thunder reported Heavy snow with thunder reported

across eastern PA, NJ, and LI on 5 April across eastern PA, NJ, and LI on 5 April 20062006

Review during “Friday Map Discussion” Review during “Friday Map Discussion” revealed two comma-cloud structures revealed two comma-cloud structures and led to arguments on whether these and led to arguments on whether these were true polar lowswere true polar lows

Investigation in graduate “Extratropical Investigation in graduate “Extratropical Cyclones” class (spring 2006) indicated Cyclones” class (spring 2006) indicated the involvement of a coherent the involvement of a coherent tropopause disturbance (CTD) in the tropopause disturbance (CTD) in the evolution of the polar lowsevolution of the polar lows

X

CTDPolar Low 1Polar Low 2

Storm Tracks

00Z/25

06Z/05

CTD StructureCTD Structure

Fig. 11a from Hakim (2000) Fig. 10c from Hakim (2000)

DT (K)DT anomaly (K)

Ertel PV (PVU) (K)

CTD ExampleCTD Example

Hakim (2000)

300 hPa Height, Temp,

DT , Wind, 850 hPa

The Polar Low The Polar Low SpectrumSpectrum Rasmussen and Turner (2003)Reed (1979)

Adapted from Rasmussen and Turner (2003); originally suggested by Emanuel in 1986

Cold lowOrographic

Boundary-layer front

Comma cloudReverse shear

Forward shear

Trough system

Polar Low TimelinePolar Low Timeline

1950 1975

1976 2000+

1960

1990

High latitudeTC-like lows

Instability lowsnear Norway

Instability lowsobtain fronts

Cold air depressionsnear British Isles

Lows occur in coldunstable air massover warm ocean

1st comprehensiveobservational studyusing sfc/upper air

Baroclinic instabilitysuggested mechanism

Conditional Instabilityof Second Kind (CISK)suggested mechanism

Norwegian PolarLows Project 1983–85-Aircraft obs; climo; modeling

Satellite studies ofcomma clouds

Comma clouds vs.‘real’ polar lows

Polar lows in NPAC,Sea of Japan, SH

Studies usingScatterometer data

Polar lowClassification(1985–96)

Idealizedsimulations

Aircraft obs ofAntarctic polar low

CTDsWISHEprocesses

Intense polar lows dubbed“Arctic hurricanes”

Polar Low TimelinePolar Low Timeline

1950 1975

1976 2000+

1960

1990

High latitudeTC-like lows

Instability lowsnear Norway

Instability lowsobtain fronts

Cold air depressionsnear British Isles

Lows occur in coldunstable air massover warm ocean

1st comprehensiveobservational studyusing sfc/upper air

Baroclinic instabilitysuggested mechanism

Conditional Instabilityof Second Kind (CISK)suggested mechanism

Norwegian PolarLows Project 1983–85-Aircraft obs; climo; modeling

Satellite studies ofcomma clouds

Comma clouds vs.‘real’ polar lows

Polar lows in NPAC,Sea of Japan, SH

Studies usingScatterometer data

Polar lowClassification(1985–96)

Idealizedsimulations

Aircraft obs ofAntarctic polar low

CTDsWISHEprocesses

Intense polar lows dubbed“Arctic hurricanes”

Pre-CTD

Businger and Reed (1989) Businger and Reed (1989) ClassificationClassification

Short-wave/jet streak type (baroclinic)Short-wave/jet streak type (baroclinic) Form in polar air mass in wake of synoptic-Form in polar air mass in wake of synoptic-

scale cyclone in region of cyclonic vorticity scale cyclone in region of cyclonic vorticity advectionadvection

Comma-cloud structureComma-cloud structure Arctic front type (baroclinic)Arctic front type (baroclinic)

Form along continental arctic-maritime polar Form along continental arctic-maritime polar air mass boundariesair mass boundaries

Comma-cloud structureComma-cloud structure Cold low type (warm core)Cold low type (warm core)

Form in arctic air masses over warm oceansForm in arctic air masses over warm oceans Spiral-cloud structureSpiral-cloud structure

GoalsGoals Examine large-scale environmentExamine large-scale environment Document evolution of CTD and Document evolution of CTD and

two polar lowstwo polar lows Relate to classification scheme in Relate to classification scheme in

polar low spectrumpolar low spectrum

Data SourcesData Sources 1.01.0 GFS analyses GFS analyses 32 km North American Regional 32 km North American Regional

ReanalysisReanalysis UAlbany surface/upper-air archiveUAlbany surface/upper-air archive GIBBS and RAL satellite archiveGIBBS and RAL satellite archive NCDC WSR-88D Level-II radar archiveNCDC WSR-88D Level-II radar archive National Lightning Detection NetworkNational Lightning Detection Network Dynamic tropopause (DT) defined as 1.5 Dynamic tropopause (DT) defined as 1.5

PVUPVU

1445Z/05 GOES-12 Visible

12

1745Z/05 GOES-12 Visible

12

2045Z/05 GOES-12 Visible

12

VIS1145Z

VIS1445Z

VIS1845Z

CTD Track CTD Track MapMap

DT (K) and wind (kts) at 0000 UTC 5 April 2006

XXX

XXX

XXXXX

00Z/04

00Z/25

00Z/03

00Z/30

340 K isotherm on DT

50 40 30607080

Large-Scale SummaryLarge-Scale Summary CTD extracted from high latitudes CTD extracted from high latitudes

via two ridging episodesvia two ridging episodes Ridging near 160Ridging near 160W on 30 MarchW on 30 March Ridging over Intermountain West on 2-4 Ridging over Intermountain West on 2-4

AprilApril Two polar lows developed in Two polar lows developed in

association with CTD on 5 April in association with CTD on 5 April in wake of synoptic-scale surface wake of synoptic-scale surface cyclonecyclone

00Z/05

DT (K), Wind (kts), 850 hPa (10-5 s-1)

03Z/05

DT (K), Wind (kts), 850 hPa (10-5 s-1)

06Z/05

DT (K), Wind (kts), 850 hPa (10-5 s-1)

09Z/05

DT (K), Wind (kts), 850 hPa (10-5 s-1)

12Z/05

DT (K), Wind (kts), 850 hPa (10-5 s-1)

15Z/05

DT (K), Wind (kts), 850 hPa (10-5 s-1)

18Z/05

DT (K), Wind (kts), 850 hPa (10-5 s-1)

21Z/05

DT (K), Wind (kts), 850 hPa (10-5 s-1)

00Z/06

DT (K), Wind (kts), 850 hPa (10-5 s-1)

00Z/05

925 hPa e (K), 925–500 hPa wind shear (kts),850–500 hPa lapse rate (C km-1), cloud-to-ground lightning

1

03Z/05

925 hPa e (K), 925–500 hPa wind shear (kts),850–500 hPa lapse rate (C km-1), cloud-to-ground lightning

1

06Z/05

925 hPa e (K), 925–500 hPa wind shear (kts),850–500 hPa lapse rate (C km-1), cloud-to-ground lightning

12

09Z/05

925 hPa e (K), 925–500 hPa wind shear (kts),850–500 hPa lapse rate (C km-1), cloud-to-ground lightning

12

12Z/05

925 hPa e (K), 925–500 hPa wind shear (kts),850–500 hPa lapse rate (C km-1), cloud-to-ground lightning

12

ALB OKX

12Z/05

100

200

300

500

700

8501000

100

200

300

500

700

8501000

-30 -20 -10 0 10 20 30 40 50 -30 -20 -10 0 10 20 30 40 50

0.5 GFSOBS

925 hPa e (K), 925–500 hPa wind shear (kts),850–500 hPa lapse rate (C km-1), cloud-to-ground lightning

12

15Z/05

925 hPa e (K), 925–500 hPa wind shear (kts),850–500 hPa lapse rate (C km-1), cloud-to-ground lightning

12

18Z/05

925 hPa e (K), 925–500 hPa wind shear (kts),850–500 hPa lapse rate (C km-1), cloud-to-ground lightning

12

21Z/05

925 hPa e (K), 925–500 hPa wind shear (kts),850–500 hPa lapse rate (C km-1), cloud-to-ground lightning

1

2

00Z/06

925 hPa e (K), 925–500 hPa wind shear (kts),850–500 hPa lapse rate (C km-1), cloud-to-ground lightning

1

2

-2

8

4

2

0

-2

10

6

14

12

10

9800

02

04

06

08

10

12

06

06

12

SLP (hPa) (C)

06Z/05

1

2

06Z/05

1

2

02

2

12

10

8

6

4

-2

0

0

1412

04

14

12

10

08

06

04

10

SLP (hPa) (C)

1145Z

12Z/05

12

12Z/05

1

12

2

04

14

12

10

8

6

4

64

2

2

2

2

16

12 10

08

06

04

16

14

10

SLP (hPa) (C)

1445Z

15Z/05

12

15Z/05

2

2

04

2

4

68

4

2

6

4

2

8

10

12

14

16

1820

22

16

6

02

06

06

04

08

10

12

14

SLP (hPa) (C)

1845Z

18Z/05

1

2

18Z/05

2

2

10

2

2

10

8

6

4

4

4

6

12

16

20

12

08

06

04

02

10

SLP (hPa) (C)

21Z/05

SummarySummary Two polar lows developed in wake of Two polar lows developed in wake of

synoptic-scale surface cyclonesynoptic-scale surface cyclone Formed downstream of CTD Formed downstream of CTD Formed in surface baroclinic regionFormed in surface baroclinic region Formed in moist-adiabatic environmentFormed in moist-adiabatic environment

Surface frontal structure developed Surface frontal structure developed during polar low evolutionduring polar low evolution

Surface pressure minima formed Surface pressure minima formed beneath comma heads during polar low beneath comma heads during polar low evolutionevolution

Concluding RemarksConcluding Remarks The two polar lows exhibit characteristics of The two polar lows exhibit characteristics of

short-wave/jet streak type described in Businger short-wave/jet streak type described in Businger and Reed (1989).and Reed (1989).

Are short waves discussed in previous polar low Are short waves discussed in previous polar low literature possibly CTDs?literature possibly CTDs?

Are moist-adiabatic environments associated Are moist-adiabatic environments associated with CTDs over land analogous to those with CTDs over land analogous to those resulting from flow of arctic air over warm resulting from flow of arctic air over warm ocean?ocean?

Can strong CTDs induce low-level vertical Can strong CTDs induce low-level vertical motion maxima and thus contribute to robust motion maxima and thus contribute to robust surface cyclogenesis via enhanced vortex surface cyclogenesis via enhanced vortex stretching?stretching?