an unusual pathway to oceanic cyclogenesis linking “perfect storms” in the north atlantic ocean
DESCRIPTION
An Unusual Pathway to Oceanic Cyclogenesis Linking “Perfect Storms” in the North Atlantic Ocean. Jason M. Cordeira and Lance F. Bosart Department of Earth and Atmospheric Sciences, University at Albany, Albany, NY. NROW IX 7-8 November 2007. Email: [email protected]. - PowerPoint PPT PresentationTRANSCRIPT
An Unusual Pathway to Oceanic CyclogenesisLinking “Perfect Storms” in the North Atlantic Ocean
Jason M. Cordeira and Lance F. BosartDepartment of Earth and Atmospheric Sciences, University at Albany, Albany, NY
NROW IX 7-8 November 2007
Supported by:NSF Grant ATM-0304254
Email:[email protected]
The “Perfect Storm” of 1991 -Motivation (1/2)
30
30-Oct29-Oct28-Oct27-Oct 31-Oct
Buoy 44137 Max. Wave Height
Canadian moored buoys
Nova Scotia
•Strong winds–67 kt Chatham, MA
–55 kt Blue Hill Observatory
•Coastal flooding / High waves–30 m Southeast of Nova Scotia (see below)
–8 m offshore MA
Sig. Wave HeightWind Speed
The “Perfect Storm” of 1991 -Motivation (2/2)
Subsequent to the development of the Perfect Storm (PS1) a second strong cyclone (PS2) formed along the surface warm front in a region of deep moist convection (dmc)… L
PS2 moved into the North Atlantic where it interacted with an upper-level potential vorticity (PV) anomaly and merged with an existing cyclone…
dmc
Tropicalmoisture
MSLP: 50 hPa / 24 hours
HurricaneGrace
Outline
I. Brief large-scale overview
II. PS1: MSLP/PV Continuity
III. PS1: Intensification
IV. PS2: MSLP Continuity
V. PS2: Development and PV Continuity
VI. PS2: Analysis of rapid deepening phase
VII. Summarizing Analysis and Conclusions
VIII. Future Work and Thoughts
PS1 / Perfect Storm 1PS2 / Perfect Storm 2HG / Hurricane Grace
PV / Potential VorticityDT / Dynamic Tropopause (2.0 PVU)MSLP / Mean Sea Level Pressure
All plots: 1.125 ECMWF-ERA40
The “Perfect Storms” of Research
PS3PS2
PS1
HG
Unique TrackHeavy Snow
Role of HGUnique TrackTropical Transition
Development from PS1Rapid Deepening
This presentation will focus on PS2: Development from PS1 and rapid deepening
Brief large-scale flow evolution
1525 Oct 2504 Oct/Nov 500-hPa Geopotential height and anomaly (dam)
PSs
-Large-scale flow reconfiguration manifested by time-mean 500-hPa flow and the PNA index
-Meridional amplification of the NA flow pattern
PS1 -MSLP Continuity
PS1
Hurricane Grace
29 Oct 00Z 30 Oct 00Z
26/00
27/00
28/00
29/00
29/00
30/00
31/00
01/00
02/00500-hPa Backward Trajectory
MSLP MSLP
36h
72h
Ending 30 Oct 12Z36h
PS1 -PV Anomaly Continuity
29/0
0Z29
/12Z
30/0
0Z
A
C’
B
PV1Merger of C’ and D
Fracture of B C,D
Fracture of C C’,E
21
22
23
24
25
2627
28
29
31
01
21
22
23
24
25
26
27
0226
C
D 30
2627
2829
PVHG
Merger of PVHG and PV1
E
DT (K), 850-925 (10-4 s-1)
PS1 -Intensification (1/3)
29 October:
00Z 12Z
850 hPa (K), Wind Barb (kt), 2-D Frontogenesis (K km-1 3h-1)
Frontogenesis Scale:
Hurricane Grace PS1
PS1 -Intensification (2/3)
30 October:
00Z 12Z
850 hPa (K), Wind Barb (kt), 2-d Frontogenesis (K km-1 3h-1)
Frontogenesis Scale:
PS1
PS1 -Intensification (3/3)
850 hPa Height (dam), ( 10-5 s-1), Wind barb (kt)
29/00Z 29/12Z 30/00Z
Hurricane Grace PS1
The “Perfect Storms” of 1991 -MSLP Continuity
PS1
PS2
Hurricane Grace
29/00
30/00
30/00
31/00
01/00
26/00
27/00
28/00
29/00
31/00
01/00
02/00
Bac
kwar
d T
raje
ctor
y
01/00Z
999 hPa
949 hPa
31/1130
36h72h
72h
PS2 - Development
A.
1. Intense warm frontogenesis
2. Southerly moisture transport
B.
3. Strong low-level vorticity generation.
4. Strong deformation zone
Northeast
Northeast
Next: look at the role of deep moist convection in strengthening the low-level cyclonic vorticity maximum.
PS2 - Development (deep moist convection)
850 hPa Winds
A
A’
PV1
A
A’
GIBBS VIS
29/12ZTake NS cross section across surface warm front
Frontogenesis [K km-1 3h-1], θ [K], ω [μb s-1], [10-5 s-1]
A A’
925 hPa θe
340K
PS2 - Development (deep moist convection) 29/12Z
Warm / MoistCold / Dry
Ascending tropical air originating from H. Grace.
Deep moist convection along surface warm front latent heat release
Diabatic heating PV redistribution and low-level vorticity generation
e [K], θ [K], ω [μb s-1], [10-5 s-1]
A A’
PS2 - Development (deep moist convection) 29/12Z
Warm / MoistCold / Dry
Ascending tropical air originating from H. Grace.
Deep moist convection along surface warm front latent heat release
Diabatic heating PV redistribution and low-level vorticity generation
PS2 - Development (low-level vorticity generation)
Diabatic heating: 1. generates a low-level
positive PV anomaly 2. erodes upper
tropospheric PV
Low-level PV anomaly: 1. + anomaly2. + anomaly
Upper-level PV anomaly: 1. anomaly2. anomaly
Adapted: Martin 2006
A
C’
B
PV1Merger of C’ and D
Fracture of B C,D
21
22
23
24
25
2627
28
29
31
01
21
22
23
24
25
26
27
0226
C
D
2627
29PVHG
Merger of PVHG and PV1
28
30
Perfect Storm 2 - PV Anomaly Continuity
PV Anomaly E:Fracture from CModest cyclogenesis to the west of GB (980 hPa)
PV Anomaly F:Arctic originInto North Atlantic behind “E”.
How did PS2 respond to “F”?
Recall: PS2 formed as a low-level diabatically generated/enhanced vortex.
F
E
PV2Merger of E and F
Fracture of C C’,E
28
29
30
31
3029
2827
26
Fracture of F24
25
PS2 - Rapid deepening MSLP
PV (PVU), (10-5 s-1), (K)
29/12Z
10/29 10/30 10/31 11/01 11/02
DT (K), 850-925 (10-5 s-1)
F
F
N S
PS2 - Rapid deepening MSLP
10/29 10/30 10/31 11/01 11/02
PV (PVU), (10-5 s-1), (K)
DT (K), 850-925 (10-5 s-1)
F F
29/18ZN S
PS2 - Rapid deepening MSLP
10/29 10/30 10/31 11/01 11/02
PV (PVU), (10-5 s-1), (K)
DT (K), 850-925 (10-5 s-1)
FF
E
30/00ZN S
PS2 - Rapid deepening MSLP
10/29 10/30 10/31 11/01 11/02
PV (PVU), (10-5 s-1), (K)
DT (K), 850-925 (10-5 s-1)
FF
E
30/06ZNW SE
PS2 - Rapid deepening MSLP
10/29 10/30 10/31 11/01 11/02
PV (PVU), (10-5 s-1), (K)
DT (K), 850-925 (10-5 s-1)
F F
E
30/12ZW E
PS2 - Rapid deepening MSLP
10/29 10/30 10/31 11/01 11/02
PV (PVU), (10-5 s-1), (K)
DT (K), 850-925 (10-5 s-1)
FFE
30/18ZN S
PS2 - Rapid deepening MSLP
10/29 10/30 10/31 11/01 11/02
PV (PVU), (10-5 s-1), (K)
DT (K), 850-925 (10-5 s-1)
FF
E
31/00ZNW SE
Summary / Conclusions
• PS1 formed in confluent air streams representing midlatitude and tropical (HG) source regions.– Trajectory analysis and PV continuity
500-hPa Backward TrajectoryEnding 30 Oct 12Z
36h
72h
36h
• Deep moist convection along the surface warm front produced intense diabatic heating– PV redistribution and low-level PV generation– Strong low-level vorticity maximum - PS2
Summary / Conclusions
850 Z (dam), ( 10-5 s-
1)
dmc
Tropicalmoisture
PS1 Schematic
L
PV1
.
• Strong tropospheric deformation steered PS1 westward and PS2 eastward into North Atlantic.
Summary / Conclusions
PS1 PS2
850 hPa Z (dam), ( 10-5 s-1), Wind barb (kt) DT (K) and Wind (kt), 850-925 ( 10-4 s-1)
PV1
F
..
• PS2 phases with upper-level PV anomaly F of Arctic origin– MSLP decreases 50 hPa / 24 hours
Summary / Conclusions
30/12Z
PV, , MSLP
10/29 10/30 10/31 11/01 11/02
DT , L.L.
F
F
E
Thoughts…
.
• What happens without Hurricane Grace?– Limited tropical moisture and low-level vorticity– How much deep moist convection results?– What is the resulting strength of PS1?– What is the resulting strength of PS2?
Comments?Questions?