Drought in California

How Did We Get Here and What Can We Expect This Year?

November 7th 2014

APWA Sacramento Chapter Meeting

Alan HaynesService Coordination HydrologistNOAA / National Weather Service

California-Nevada River Forecast CenterSacramento, CA

How Did We Get into a Drought?

High Year to Year Variability

8-Station Index (2012-2014)

5-Station Index (2012-2014)

Oct2011

Oct2012

Oct2013

Cumulative Effects on Storage

Cumulative Effects on Storage

Blocking Semi-permanent upper level high pressure

October 2013 to April 2014 COLD

Warm Dry

HL

Departure from NormalWeather Pattern (storm track)

Sources of Knowledge of Future Conditions

Climate-Based Information

Observed Weather

Streamflow

Weather Forecasts0-15 Days

Immediate Past

Hydrologic Model States-soil moisture-snowpack

-Climate forecasts-Hydrologic ensemble forecasts using past weather inputs

Sources of Knowledge of Future Conditions

• Biggest source of skill in predicting water supply is the accumulated snowpack

• Some knowledge from weather forecasts

• Climate forecasts provide limited information – mainly from ENSO signal (i.e., El Nino)

So What About El Nino?

1950 1960 1970 1980 1990 2000 201048

49

50

51

52

53

54

55

8 Station Index Water Year Totals

Strong El Nino Moderate El Nino Weak El NinoEl Nino Average Period of Record Average

10 Holding Steady/Some Improvement

9 Drought Continuing

Water Year (Oct 1 – Sep 30)

Drought Busting3

Impact of El Nino on Water Supply

El Nino Evolution

El Nino Evolution

El Nino Strength Forecast

Strong

Moderate

Weak

Three Month OutlookTemperature

Precipitation

Summary

• Drought brought about by cumulative multi-year precipitation shortages

• Droughts are historically broken by a very wet year

• California starting year with dry antecedent conditions and low reservoir levels

• ENSO-neutral conditions continue, for now

• El Nino favored to begin in the next 1-2 months and last into spring 2015

• Chance of El Nino conditions is near 60-65%

• El Nino not likely to help much in ending the drought

Questions?