User-driven Climate Forecasts in the Southeast U.S. David F. Zierden Assistant State Climatologist Center for Ocean-Atmospheric Prediction Studies The Florida State University Tallahassee, FL

World Map

ENSO Impacts in the Southeast La Niña Dry Fall, Winter, and Spring Greatly increases Atlantic hurricanes Increases tornadoes in the deep south Greatly increases wildfire activity EL Niño Very wet winter and spring Greatly reduces Atlantic hurricanes decreases tornadoes in the tornado alley Neutral ENSO phase increases the risk of severe freezes by 3:1 odds.

ENSO Effects on Precipitation

ENSO Effects on Temperature

Impact Freezes of the last century Freeze Date ENSO State *Dec 1894 Neutral Feb 1899 Neutral Dec 1934 Neutral Jan 1940 Neutral *Dec 1961 Neutral Jan 1977 El Nino Jan 1981 Neutral *Dec 1983 Neutral Jan 1985 Neutral *Dec 1989 Neutral Jan 1997 Neutral * High Impact

ENSO and Florida Freeze Probabilites

Return Frequencies

Extended Freeze Events

Late Season Freezes

La Niña and Wildfires n La Niña brings drier than normal conditions (30%-40%) and warmer temperatures from November through April. n Wildfire activity is increased throughout the wildfire season. n The increased activity can be expected during nearly all La Niña episodes. Anomalous Wildfire activity (acres burned) during La Niña episodes April

Mallory Swamp Fire during the last La Niña

Forecasting Potential Wildfire Activity n Forecast based on the Keetch-Byram Drought Index (KBDI). n Historical weather observations from the NWS Coop network provides coverage at nearly county level. n Forecast is presented in probabilistic terms. n “Bootstrapping” used to generate probability distributions for each station.

KBDI Forecast Method

Wildfire Threat forecast The end product is a monthly, county-by-county forecast of the KBDI.The end product is a monthly, county-by-county forecast of the KBDI. Graphic shows the probability of at least 7 days in the month being above or below critical thresholds.Graphic shows the probability of at least 7 days in the month being above or below critical thresholds. Thresholds were determined with input from forestry and wildfire experts.Thresholds were determined with input from forestry and wildfire experts. Forecast was based on the Neutral ENSO phase.Forecast was based on the Neutral ENSO phase.

More uses for climate forecasts that just wildfire n Harvesting - cannot harvest in low areas during El Nino winters. n Planting - Survival rate low during La Nina n Managed Forests - Herbicides, pesticides, prescribed burns

For More Information: Visit Our Websites COAPS: COAPS: Florida Climate Center: Florida Climate Center: Florida Automated Weather Network: fawn.ifas.ufl.edu

Determining Probability Distributions using “Bootstrapped” Data n Begin with the CURRENT KBDI value at the beginning of the forecast cycle. n Use over 50 years of DAILY observations at each station (13 El Nino, 13 La Nina, and 28 neutral). n Constuct a “bootstrapped” month by randomly selecting temperature and precipitation values each day from the group with similar ENSO phase. n Repeat until you have 1,000 realizations of the specific ENSO phase in each month.