Post on 22-Dec-2015
2011 Pacific Northwest Climate Recap
Jim Johnstone
JISAO – University of Washington
jajstone@uw.edu
1. Review of ENSO conditions (record La Niña)
2. Review of Pacific NW climate 2011 (Unusual spring conditions)
3. Re-development of La Niña in late 2011
4. La Niña and Pacific NW Climate
Niño 3.4 index
El Niño
La Niña
Niño 3.4 index
SST anomalies
January 3, 2011
El Niño
La Niña
Southern Oscillation Index
(SOI)
Sea-level pressure (SLP) anomalies
March 2011
La Niña
El Niño
Feb-Apr SOI
Strongest spring La Niña on record (to 1866)
Niño 3.4 index
SOI
El Niño
La Niña
La Niña
El Niño
Current SST anomalies
ENSO summary: 2011
Strong La Niña from summer 2010 to spring 2011
Record positive SOI in early spring (Feb-Apr)SST anomalies not as extreme
Decay to neutral conditions in May-June
Re-emergence of weak-moderate La Niña by July-August
Precipitation anomalies:
Oct-Dec 2010
Jan-Mar 2011
US Precip anomalies
Apr-Jun 2011
Pac NW Precipitation
Pacific NW Climate: 2011 (Washington, Oregon, Idaho)
Snow water content
Stevens Pass, WA
Mt Hood, OR
Hemlock Butte, ID
April-Jun 500 mb anomalies
(i.e. pressure)
US Tmax anomalies
Apr-Jun 2011
Record values
(back to 1900)
Texas drought
Pacific NW Tmax (persistently cool Feb-July)
Lowest Apr-Jun Tmax in Washington history (to 1900)
Airport cloud ceilings(hours per day)
SeaTac
Portland
Pacific NW Climate summary: 2011
Unusually wet, cloudy, cool conditions in late spring (April-July)
Late snowfall into April-May
Anomalous June snow pack (~2-5x normal)
Trough over Pacific NW, Ridge over SW North AmericaCool, wet PNW / hot, dry Texas
Did a strong early spring La Niña generate late spring cool/wet conditions over the Pacific NW?
Tmax
Apr-Jun 2011
Top 5 early spring La Niñas
1971
1974
2008
2000
1989
Precip
Apr-Jun 2011
Top 5 early spring La Niñas
1971
1974
2008
2000
1989
Did a strong early spring La Niña generate late spring cool/wet conditions over the Pacific NW?
Probably not – La Niña forcing of PNW climate not strong in late spring
What about the coming winter?
Winter La Niña composites (Dec-Feb)
Tmean
Strong events
Moderate events
Winter La Niña composites (Dec-Feb)
500 mb heights
Strong events
Moderate events
Winter La Niña composites (Dec-Feb)
Precipitation
Strong events
Moderate events
Developing La Niña conditions portend acool, wet winter.
Precipitation response is more consistent forstronger events.