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. 19 TH, 1993 STORM INTRODUCTION BACKGROUND PROJECT PLAN OBJECTIVES

FEB. 19 TH, 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. 19 TH, 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 ) 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 θ e 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 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: San Francisco State University, 167 pp.