Seasonal Prediction

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

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

3. Users • Emergency Managers • Raises public awareness • Reinsurance Industry • Companies that insure the companies you buy insurance from • Risk Prediction Initiative (RPI2.0) is a leader in bringing new forecast methods to the industry • Energy Traders • Oil and natural gas drilling in the Gulf is vulnerable • Futures prices respond to the seasonal forecasts El Niño/La Niña History Climate Modes

4. History • Bill Gray (Colorado State University) discovered the basic hurricane ingredients in the 1960s • 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 El Niño/La Niña History Climate Modes

5. Gray’s Seasonal Predictors (Initial) • West African Rainfall • Intense rainfall produced stronger easterly waves • Sea level pressure anomaly in Caribbean • Lower = more activity • 200 mb zonal wind anomaly in Caribbean • 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 activity Landsea and Gray (1992, BAMS) El Niño/La Niña History Climate Modes

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

7. 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) El Niño/La Niña History Climate Modes

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

9. 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 El Niño/La Niña History Climate Modes Courtesy of C.C. Hennon, UNC Asheville

10. 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 El Niño/La Niña History Climate Modes

11. Determining the phase of ENSO x Darwin x Tahiti • Southern Oscillation Index (SOI) • 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 • Average SST anomalies over various regions of the Pacific El Niño/La Niña History Climate Modes

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

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

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

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

16. Atlantic Multi-Decadal Oscillation (AMO) • 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 the thermohaline circulation, but we don’t know Trenberth & Shea (2006, GRL) El Niño/La Niña History Climate Modes

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

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

19. 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 El Niño/La Niña History Climate Modes

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

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