1. Downstream Development and Kona Low Genesis
Rich Moore
Naval Postgraduate School
14th Cyclone Workshop
Collaborators: Prof. Huw Davies and Dr. Olivia Martius
ETH-Zurich

2. Kona Lows Subtropical cyclones in the central Pacific
Exert a significant impact upon the climate of Hawaii
Destructive weather, including flash floods, high winds, large surf and severe thunderstorms
Caruso and Businger (2006)

3. breaking extratropical wave
Kona Low Genesis
breaking extratropical wave
positive PV anomaly
Caruso and Businger (2006)

4. Kona Low Research
Midlatitude jet structure, characteristics of the cut-off low and local conditions (Morrison and Businger 2001, Martin and Otkin 2004, Otkin and Martin 2004a,b, Caruso and Businger 2006)
GOAL: mechanisms responsible for the the wave breaking itself

5. Data Kona Low Tracks 43 Kona low cases Caruso & Businger 2006:
Cool season,
10-45N, 175E-130W
Upper-level low MUST pass south of 30N & surface low forms

6. Methodology
ERA-40 data
Create composite fields centered on the time and location of the mature storm
Monte Carlo analysis to determine statistical significance
Case study

7. Downstream Development
Propagation of a growing wave packet along a tropopause-level wave guide
Orlanski and Sheldon (1993)

8. Downstream Development
250 V Wind:
+ anomaly
- anomaly
Dynamic Tropopause(2 PVU)

9. Upstream Precursor Disturbance
Sea Level Pressure
Dynamic Tropopause(2 PVU)

10. The Most Destructive Kona Low
24-28 Feb. 1997
High surf, large hail (13 mm in diameter)
Winds > 50 mph
Heavy rains and flooding
Over 4 million USD in damage

11. The Most Destructive Kona Low
250 V Wind:
+ anomaly
- anomaly
Dynamic Tropopause(2 PVU)

12. Downstream Development

13. The Most Destructive Kona Low
Sea Level Pressure
Dynamic Tropopause(2 PVU)

14. Lagrangian Flow & Diabatic Processes
36 hour backward trajectories from negative PV anomaly

15. Warm Conveyor Belt
Diabatic Heating
Specific Humidity
Pressure

16. Summary – Kona Low Further research questions:
Upstream cyclone precursor, atmospheric block
Diabatic vs. adiabatic processes

17. West African Flooding Algeria November 2001 L PV on 320K SLP
IR meteosat L
For are real case
Typical morphology associated typically with streamers
Subsidence plus dry air from stratosphere within streamer and along western flak
Reduced stability plus upgliding along isentropes => strong convection along eastern flank
Wind field not only at upper-levels but extending down into the lower troposphere if strong anomaly
wind on 850hPa
precipitation

18. Tropical Transition PV on 350K Shading: 900 mb vorticity
Hurricane Maria 2005

19. Questions?