Seasonal Prediction Carl Schreck History El NioLa Nia

Seasonal Prediction Carl Schreck History El Niño/La Niña Climate Modes 1

Seasonal Hurricane Prediction History El Niño/La Niña Climate Modes 2

Users § Emergency Managers q Raises public awareness § Reinsurance Industry q q Companies that insure the companies you buy insurance from Risk Prediction Initiative (RPI 2. 0) is a leader in bringing new forecast methods to the industry § Energy Traders q q Oil and natural gas drilling in the Gulf is vulnerable Futures prices respond to the seasonal forecasts History El Niño/La Niña Climate Modes 3

History § Bill Gray (Colorado State University) discovered the basic hurricane ingredients in the 1960 s § Many of those ingredients can be driven by large scale climate modes § Climate modes in winter and springtime can predict hurricane activity for upcoming season History El Niño/La Niña Climate Modes 4

Gray’s Seasonal Predictors (Initial) § West African Rainfall q Intense rainfall produced stronger easterly waves § Sea level pressure anomaly in Caribbean q Lower = more activity § 200 mb zonal wind anomaly in Caribbean q q If positive, more vertical wind shear over area, less activity Tended to persist from spring into hurricane season § ENSO Warm phase created more wind shear over Atlantic, less TC Landsea and Gray (1992, BAMS) activity History El Niño/La Niña Climate Modes q 5

Klotzbach/Gray Predictors (since 2010) § January-March Atlantic SST § March Atlantic SLP § February-March Pacific SLP § ECMWF ENSO forecast History El Niño/La Niña Climate Modes 6

The Future of Seasonal Prediction? § Physics-based dynamical models are getting better at seasonal prediction § Ensembles of these models provide estimate the range of possible outcomes § Generally not as good as statistical forecasts…yet Schemm et al. (2012, CDPW) History El Niño/La Niña Climate Modes 7

El Niño–Southern Oscillation (ENSO) History El Niño/La Niña Climate Modes 8

Characteristics of La Niña § Anomalous low (high) pressure in the western (eastern) Pacific § Stronger than normal trade winds across Pacific § Dry (Wet) conditions in the east (west) Pacific § Deep thermocline in the west – shallow in the east Courtesy of C. C. Hennon, UNC Asheville History El Niño/La Niña Climate Modes 9

Characteristics of El Niño § Anomalous low (high) pressure in the eastern (western) Pacific § Weak or even reversed trade winds across Pacific § Dry (Wet) conditions in the west (east) Pacific § Deep thermocline in the east – upwelling capped Courtesy of C. C. Hennon, UNC Asheville History El Niño/La Niña Climate Modes 10

Determining the phase of ENSO x Darwin x Tahiti § Southern Oscillation Index (SOI) q q Tracks the see-saw in pressure between western Pacific/Indian Ocean and central Pacific Uses pressure observations from Tahiti and Darwin, Australia § Sea-surface Temperature (SST) based methods q Average SST anomalies over various regions of the Pacific History El Niño/La Niña Climate Modes 11

Impact on Hurricanes iri. columbia. edu History El Niño/La Niña Climate Modes 12

Recent ENSO Conditions cpc. ncep. noaa. gov History El Niño/La Niña Climate Modes 13

ENSO Forecasting § Dynamical Models q q Starts with the current state of the atmosphere/ocean on a grid Uses physics approx. to predict its evolution § Statistical Models q Based on current atmospheric and ocean conditions § All models struggle during January–May q “Spring Barrier” § Better forecasts in April through June when conditions are already developing History El Niño/La Niña Climate Modes 14

Main Development Region SLP/SST/VWS History El Niño/La Niña Climate Modes 15

Atlantic Multi-Decadal Oscillation (AMO) Trenberth & Shea (2006, GRL) § Atlantic SSTs vary with a period of 60– 80 years § Hurricane activity follows a similar pattern § Recent warmth is a combination of climate change and the AMO § Thought to be driven by thermohaline circulation, but we don’t know History El Niño/La Niña Climate Modes 16

Atlantic Meridional Mode (AMM) Kossin and Vimont (2007, BAMS) Genesis locations, SST anomalies (shading) and Shear anomalies (contours) § Dipole of SST between the North and South Atlantic AMM loading pattern TNA ≈ TNA – TSA § Closely related to the AMO q But AMM has a stronger relationship with Hurricane activity TSA History El Niño/La Niña Climate Modes 17

Global/N. Hem. /S. Hem. Temperature data. giss. nasa. gov § Surface temperatures from around the globe get distributed into the atmosphere § Key Climate Change Debate: § Hurricane Ingredient: Conditionally unstable atmosphere q Warm air rises, but only if it’s warmer than its surroundings q Do Hurricanes respond to Total or Relative changes in SST? History El Niño/La Niña Climate Modes 18

Solar Flux § Sun goes through 11 year cycles in its output § These cycles affect surface temperatures § Not clear how Solar flux would be a better predictor than temperature § But empirical relationships can lead to new discoveries History El Niño/La Niña Climate Modes 19

Midlatitude Teleconnection Patterns § Based on the locations of high and low pressure centers Arctic Oscillation (AO) North Atlantic Oscillation (NAO) § Related to variations in the jet stream § Not clear how they affect hurricanes q q Pacific–North American Pattern (PNA) East Pacific/North Pacific Oscillation (EPO) Variations in shear? Downstream variations in the Bermuda High? cpc. ncep. noaa. gov History El Niño/La Niña Climate Modes 20

Ingredients Deep Warm Ocean Layer Conditionally Unstable Atmosphere Summary Climate Modes MDR Sea Surface Temperature MDR Sea-Level Pressure MDR Vertical Wind Shear Moist Mid-Troposphere El Niño/La Niña Pre-existing Convection Atlantic Multi-decadal Oscillation (AMO) Weak Vertical Shear Cyclonic Low-Level Vorticity Atlantic Meridional Mode (AMM) Global/Hemispheric Surface Temperature History El Niño/La Niña Climate Modes 21