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?