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

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)

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

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

Data Kona Low Tracks 43 Kona low cases Caruso & Businger 2006: Cool season, 1980-2002 10-45N, 175E-130W Upper-level low MUST pass south of 30N & surface low forms

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

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

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

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

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

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

Downstream Development

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

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

Warm Conveyor Belt Diabatic Heating Specific Humidity Pressure

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

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

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

Questions?