Inland Northwest Climate Recap and Seasonal Outlook Dr. John Abatzoglou Department of Geography University of Idaho 10 th Annual Climate and Water Meeting: 2011 Water Year Idaho Department of Water Resources, Boise, ID

2009 Global Recap

2010 to date Jan-Sep 2010: Tied with 1998 for warmest on record

CPC Seasonal Outlook: Oct 2009 DJF MAM

Western US Winter Recap Oct-Mar Precip (% of Normal)1 April SWE (% of Norma) Westmap, WRCC NOAA

Well Behaved El Nino

700 mb Vector Wind Anomalies 1 Jan – 20 Mar 1983, 1998, 2010 Proxy for anomalies in winds, temperature (via advection) and precipitation in the mountainous West Well Behaved El Nino

The Great EL-to-La Flip of 2010 Historically about a third of El Nino events are followed by a La Nina The great flip of 2010 rivals that of 1973

The Great EL-to-La Flip of 2010

Oct-Mar Precip (% of Normal) Westmap, WRCC NOAA Apr-Jul Precip (% of Normal)

Idaho Recap

Notable Climate Oddities of (1) Balmy Jan-Mar (4-6F above normal) (2) The 75 day-long April (3) A “Cool” Summer (4) WY Near Normal T&P Idaho Recap

NOVDECJANFEB

MARCHAPRILMAYJUNE

SNOTEL

Seasonal Outlook Basis for Outlook –Long-lived boundary conditions (climate- memory) Long-term trends Soil moisture (summer) / snow cover (winter-spring) Ocean Temperatures –Statistical Tools Low-frequency Climate Variability (e.g., ENSO) –Climate Models CFS: Climate Forecast System

Global SST Departures ( o C) Sea surface temperatures (SST) were at least 2.0°C below-average east of the dateline in the tropical Pacific

Recent Evolution of ENSO Conditions SST Departures ( o C) El Niño La Niña Neutral La Niña is present across the equatorial Pacific Ocean.

ENSO Forecast 1.Observations in the NINO3.4 region indicate La Nina. 2.Atmospheric response (SOI), surface winds are in concert and reinforcing SST 3.Strong La Nina conditions, possibly strongest since Atmospheric manifestation of El Nino typically begin in Nov. Figure provided by the International Research Institute (IRI) for Climate and Society (updated 19 October 2010).

CFS: Monthly Outlook: Nov-Apr

CPC: Winter Outlook DJF

Implications for Idaho

Rain Gauge Calisthenics

La Nina’s Footprint in Idaho April SWE (% Departure from Normal) Composite (top 10 La Nina’s)

MEI vs. April 1 SWE La Niña neutral El Niño Northern IdahoCentral Idaho

Climate Risks Increased Risk of Wet/Cool Late Winter and Cool Spring Freezing Level m lower during La Nina Events La Nina signal strong through February - we’ve been tricked before…

Summary 1) La Nina generally associated with above normal precipitation across the state, impacts accentuated over the northern portion of the state Strongest in late winter due to the enhancement of the polar jet and direction of storm track over the northern tier of the US Increase in frequency of measurable precip days during La Nina and likelihood of heavier events, net 5-20% increase observed during past La Nina’s 2) La Nina generally associated with cooler than normal condition Particularly late winter-spring conditions Lower snow levels means more precipitation retained as snow 3) A strong La-Nina is likely to result in “real” winter for Idaho snowpack and favorable water supply outlook for 2011