Geoff Roest
MS in Geosciences
San Francisco State University
QUASIGEOSTROPHIC DIAGNOSIS OF AN
EXPLOSIVELY DEVELOPING CYCLONE ALONG THE NORTHERN
CALIFORNIA COAST
OUTLINE
• Introduction
• Background
• Project Plan
• Rainfall, wind, and tornado data
• Qualitative Estimate of quasigeostrophic controls
• Quantitative Estimate of quasigeostrophic controls
• Hypotheses/objectives
CYCLOGENESIS
INTRODUCTION BACKGROUND PROJECT PLAN OBJECTIVES
(Petterssen 1956)
• Major storm brought damaging winds and flooding rains
• Explosively developed prior to making landfall
• Developed eye-like feature, Thunderstorms
• At least 1 tornado
FEB. 19TH, 1993 STORM
INTRODUCTION BACKGROUND PROJECT PLAN OBJECTIVES
FEB. 19TH, 1993 STORM
INTRODUCTION BACKGROUND PROJECT PLAN OBJECTIVES
NWS BULLETINS FROM STORM
INTRODUCTION BACKGROUND PROJECT PLAN OBJECTIVES
• Storms of this strength not unheard of in Eastern Pacific, but unusual
• Rapid development was noteworthy
• Significant impact on Northern California
FEB. 19TH, 1993 STORM
(Sanders and Gyakym 1980)
INTRODUCTION BACKGROUND PROJECT PLAN OBJECTIVES
FROM SANDERS AND GYAKUM (1980)
• “Meteorological bomb” (aka “Explosively developing cyclone) – a cyclone that deepens at 12 mb in 12 hrs
• Feb 1993 storm – 13 mb in 14 hrs
• Climatology
• Often cold season, maritime events
• Downstream from mobile 500 mb trough and planetary wave trough
• Are largely baroclinic events
INTRODUCTION BACKGROUND PROJECT PLAN OBJECTIVES
ADDITIONAL CRITERION FOR EXPLOSIVE CYCLOGENESIS
• Allen et al. (2010) discussed importance of relative pressure fall:
• Cyclone’s central pressure fall is important, but what if ambient atmospheric pressure decreases at same rate?
INTRODUCTION BACKGROUND PROJECT PLAN OBJECTIVES
• Estimated forcing on the basis of quasigeostrophic diagnosis
• Findings
• Unusually strong baroclinicity
• Strong, persistant warm air advection
• Diabatic heating
• Sensible heating
• Latent heating
CASE STUDY OF EXPLOSIVE CYCLOGENESIS
INTRODUCTION BACKGROUND PROJECT PLAN OBJECTIVES
Reed and Albright 1986
DESCRIPTION OF CYCLONE, EFFECTS
• Gathering rainfall and wind data from:
• National Climatic Data Center (NCDC)
• Western Region Climate Center (WRCC)
• National Weather Service statements and reports
INTRODUCTION BACKGROUND PROJECT PLAN OBJECTIVES
• Reconstruct pressure field, height field, etc. using:
• Weather observations from land, buoys
• NCEP Reanalysis
• Tornadic thunderstorm
• Thermodynamic environment
• Shear environment
SYNOPTIC DISCUSSION OF CYCLONE
INTRODUCTION BACKGROUND PROJECT PLAN OBJECTIVES
REASONS FOR DEVELOPMENT
• Quasigeostrophic theory –forcing mechanisms for vertical velocity
INTRODUCTION BACKGROUND PROJECT PLAN OBJECTIVES
(Bluestein 1992, pp. 330)
REASONS FOR DEVELOPMENT
• Sutcliffe Petterssen Development Equation (Palmen and Newton, 1969, pp. 316-326)
• Can reconstruct development of storm using finite difference approximation on weather maps
INTRODUCTION BACKGROUND PROJECT PLAN OBJECTIVES
• Diabatic heating
• Sensible heating (Allen et al. 2010)
• Latent heating (Reed et al. 1988)
• Static stability
• Lapse rates/lifted indices
• Moisture fluxes from ocean
PROJECT PLAN
INTRODUCTION BACKGROUND PROJECT PLAN OBJECTIVES
(NOAA)
• Conditional symmetric instability (CSI) (Bennetts and Hoskins, 1979)
• Function of momentum and θe
• Conservation of momentum and entropy
• Not considered by static stability parameter
PROJECT PLAN
INTRODUCTION BACKGROUND PROJECT PLAN OBJECTIVES
(Reed and Albright 1986)
• Hypotheses
• Dynamic environment supportive of explosive cyclogenesis
• Atmosphere was strongly conditionally unstable
• CSI contributed to cumulus convection
• Objectives
• Study extreme event using quasigeostrophic theory
• Estimate relative contribution of each term in Sutcliffe-Petterssen Development Equation to explosive development
INTRODUCTION BACKGROUND PROJECT PLAN OBJECTIVES
REFERENCES• Allen, J. T., A. B. Pezza, and M. T. Black, 2010: Explosive Cyclogenesis: A Global Climatology Comparing Multiple
Reanalyses. Journal of Climate, 23, 6468–6484.
• Bennetts, D. A., and B. J. Hoskins, 1979: Conditional symmetric instability - a possibleexplanation for frontal rainbands. Quarterly Journal of the Royal Meteorological Society ,105, 945–962.
• Holton, J. R., 1992: An Introduction to Dynamic Meteorology . 3rd ed. Academic Press, 511 pp.
• Monteverdi, J. P., E. Jan Null, Kathy L. Pagan, and Ernest Daghir, Explosively-developingcyclone with “eye”: Extratropical “hurricane” along the West Coast?
• National Weather Service, 1993: Northern and Central California Weather Summary . National Weather Service San Francisco, CA.
• National Weather Service, 1993: Storm Report for 2/19/93. National Weather ServiceEureka, CA.
• Palman, E., and C. W. Newton, 1969: Atmospheric circulation systems: their structure and physical interpretation . Vol. 13. International Geophysics Series, Academic Press, 624 pp.
• Petterssen, S., 1956: Weather Analysis and Forecasting . McGraw-Hill Publishing Company. Vol. 1. 428 pp.
• Reed, R. J., and M. D. Albright, 1986: A Case Study of Explosive Cyclogenesis in the Eastern Pacific. Monthly Weather Review, 114, 2297–2319.
• ——, M. D. Albright, A. J. Sammons, and P. Undén, 1988: The Role of Latent Heat Release in Explosive Cyclogenesis: Three Examples Based on ECMWF OperationalForecasts. Weather and Forecasting, 3, 217–229.
• Sanders, F., and J. R. Gyakum, 1980: Synoptic-Dynamic Climatology of the “Bomb”. Monthly Weather Review, 108, 1589–1606.
• Stumpf, C. J., 2012: A Comprehensive Survey of Buoyancy and Shear Parameters forCalifornia Tornadoes: 1951-2011. San Francisco State University, 167 pp.