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An Unusual Pathway to Oceanic Cyclogenesis Linking “Perfect Storms” in the North Atlantic Ocean

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: cordeira@atmos.albany.edu.

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An Unusual Pathway to Oceanic Cyclogenesis Linking “Perfect Storms” in the North Atlantic Ocean

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  1. An Unusual Pathway to Oceanic CyclogenesisLinking “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:cordeira@atmos.albany.edu Supported by:NSF Grant ATM-0304254

  2. The “Perfect Storm” of 1991 -Motivation (1/2) • Coastal flooding / High waves • 30 m Southeast of Nova Scotia (see below) • 8 m offshore MA • Strong winds • 67kt Chatham, MA • 55kt Blue Hill Observatory Buoy 44137 Max. Wave Height Sig. Wave HeightWind Speed 30 Nova Scotia 27-Oct 28-Oct 29-Oct 30-Oct 31-Oct Canadian moored buoys

  3. 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)… dmc L Tropicalmoisture HurricaneGrace PS2 moved into the North Atlantic where it interacted with an upper-level potential vorticity (PV) anomaly and merged with an existing cyclone… MSLP: 50 hPa / 24 hours

  4. Outline Brief large-scale overview PS1: MSLP/PV Continuity PS1: Intensification PS2: MSLP Continuity PS2: Development and PV Continuity PS2: Analysis of rapid deepening phase Summarizing Analysis and Conclusions Future Work and Thoughts All plots: 1.125 ECMWF-ERA40 PS1 / Perfect Storm 1PS2 / Perfect Storm 2HG / Hurricane Grace PV / Potential VorticityDT / Dynamic Tropopause (2.0 PVU)MSLP / Mean Sea Level Pressure

  5. The “Perfect Storms” of Research PS2 PS3 Unique TrackHeavy Snow PS1 Development from PS1Rapid Deepening Role of HGUnique TrackTropical Transition HG This presentation will focus on PS2: Development from PS1 and rapid deepening

  6. Brief large-scale flow evolution 500-hPa Geopotential height and anomaly (dam) 1525 Oct 2504 Oct/Nov -Large-scale flow reconfiguration manifested by time-mean 500-hPaflow and the PNA index -Meridional amplification of the NA flow pattern PSs

  7. PS1 -MSLP Continuity 30 Oct 00Z 29 Oct 00Z PS1 MSLP MSLP 29/00 500-hPa Backward Trajectory 31/00 02/00 Ending 30 Oct 12Z 36h 30/00 01/00 29/00 28/00 Hurricane Grace 72h 27/00 26/00 36h

  8. PS1 -PV Anomaly Continuity 29/00Z 21 A 21 B 22 22 23 23 24 29/12Z Fracture of C  C’,E E 24 C 25 27 C’ 28 PV1 25 26 27 26 29 26 Merger of C’ and D 02 D 30 Merger of PVHG and PV1 Fracture of B  C,D 31 01 29 PVHG 30/00Z 28 27 26 DT  (K), 850-925  (10-4 s-1)

  9. PS1 -Intensification (1/3) 850 hPa  (K), Wind Barb (kt), 2-D Frontogenesis (K km-1 3h-1) 29 October: 12Z 00Z Frontogenesis Scale: Hurricane Grace PS1

  10. PS1 -Intensification (2/3) 850 hPa  (K), Wind Barb (kt), 2-d Frontogenesis (K km-1 3h-1) 30 October: 12Z 00Z Frontogenesis Scale: PS1

  11. PS1 -Intensification (3/3) 850 hPa Height (dam),  ( 10-5 s-1), Wind barb (kt) 29/00Z 29/12Z 30/00Z Hurricane Grace PS1

  12. The “Perfect Storms” of 1991 -MSLP Continuity PS2 31/00 949 hPa 01/00 999 hPa 31/1130 PS1 30/00 29/00 31/00 02/00 72h 36h 30/00 01/00 29/00 Hurricane Grace Backward Trajectory 72h 01/00Z 28/00 27/00 26/00

  13. PS2 - Development A. B. Northeast Northeast Intense warm frontogenesis Southerly moisture transport Strong low-level vorticity generation. Strong deformation zone Next: look at the role of deep moist convection in strengthening the low-level cyclonic vorticity maximum.

  14. A A’ PS2 - Development (deep moist convection) 29/12Z Take NS cross section across surface warm front PV1 GIBBS VIS A A’ 850 hPa Winds

  15. 29/12Z PS2 - Development (deep moist convection) Frontogenesis [K km-1 3h-1], θ [K], ω [μb s-1],  [10-5 s-1] 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 925 hPa θe 340K Cold / Dry Warm / Moist A A’

  16. 29/12Z PS2 - Development (deep moist convection) e [K], θ [K], ω [μb s-1],  [10-5 s-1] 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 Cold / Dry Warm / Moist A A’

  17. PS2 - Development (low-level vorticity generation) Upper-level PV anomaly:  anomaly  anomaly Diabatic heating: generates a low-level positive PV anomaly erodes upper tropospheric PV Low-level PV anomaly: + anomaly + anomaly Adapted: Martin 2006

  18. Perfect Storm 2 - PV Anomaly Continuity PV Anomaly E:Fracture from CModest cyclogenesis to the west of GB (980 hPa) PV Anomaly F:Arctic originInto North Atlantic behind “E”. How did PS2 respond to “F”? Recall: PS2 formed as a low-level diabatically generated/enhanced vortex. 21 A F 21 PV2 B 24 30 Fracture of F 22 22 31 25 Merger of E and F 23 26 23 27 28 24 29 Fracture of C  C’,E 30 29 E 24 C 28 25 27 C’ 28 PV1 25 26 27 26 29 26 Merger of C’ and D 02 D 30 Merger of PVHG and PV1 Fracture of B  C,D 31 01 29 PVHG 28 27 26

  19. MSLP PS2 - Rapid deepening PV (PVU),  (10-5 s-1),  (K) F 10/29 10/30 10/31 11/01 11/02 F DT  (K), 850-925  (10-5 s-1) N S 29/12Z

  20. MSLP PS2 - Rapid deepening PV (PVU),  (10-5 s-1),  (K) 10/29 10/30 10/31 11/01 11/02 F F DT  (K), 850-925  (10-5 s-1) N S 29/18Z

  21. MSLP PS2 - Rapid deepening PV (PVU),  (10-5 s-1),  (K) 10/29 10/30 10/31 11/01 11/02 E F F DT  (K), 850-925  (10-5 s-1) N S 30/00Z

  22. MSLP PS2 - Rapid deepening PV (PVU),  (10-5 s-1),  (K) 10/29 10/30 10/31 11/01 11/02 E F F DT  (K), 850-925  (10-5 s-1) NW SE 30/06Z

  23. MSLP PS2 - Rapid deepening PV (PVU),  (10-5 s-1),  (K) 10/29 10/30 10/31 11/01 11/02 E F F DT  (K), 850-925  (10-5 s-1) W E 30/12Z

  24. MSLP PS2 - Rapid deepening PV (PVU),  (10-5 s-1),  (K) 10/29 10/30 10/31 11/01 11/02 E F F DT  (K), 850-925  (10-5 s-1) N S 30/18Z

  25. MSLP PS2 - Rapid deepening PV (PVU),  (10-5 s-1),  (K) 10/29 10/30 10/31 11/01 11/02 F E F DT  (K), 850-925  (10-5 s-1) NW SE 31/00Z

  26. Summary / Conclusions • PS1 formed in confluent air streams representing midlatitude and tropical (HG) source regions. • Trajectory analysis and PV continuity 500-hPa Backward Trajectory Ending 30 Oct 12Z 36h 72h 36h

  27. PV1 dmc L Tropicalmoisture PS1 Schematic Summary / Conclusions • 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 850 Z (dam),  ( 10-5 s-1)

  28. Summary / Conclusions . • Strong troposphericdeformation steered PS1 westwardand PS2 eastward into North Atlantic. F PV1 850 hPa Z (dam),  ( 10-5 s-1), Wind barb (kt) DT  (K) and Wind (kt), 850-925  ( 10-4 s-1) PS1 PS2

  29. Summary / Conclusions .. • PS2 phases with upper-level PV anomaly F of Arctic origin • MSLP decreases 50 hPa / 24 hours PV, ,  MSLP 11/01 10/29 10/30 10/31 11/02 F E F 30/12Z DT , L.L. 

  30. 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? cordeira@atmos.albany.edu

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