Drought in California How Did We Get Here and What Can We Expect This Year? November 7th 2014 APWA...

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?