NWS Spokane Fire Weather Latah County LEPC August 11th 2011 Bob Tobin

Let’s Start With What We Know

There was a 30 day period of normal to above normal temps Jan-Feb

Typical US Temperature, Precipitation and Jet Stream Patterns during La Niña Winters

We were in a strong La Nina pattern which is expected to weaken to near neutral if not weak El Nino through the summer.

What do we expect…The $64,000 question Nearly all models indicate that La Niña is passed it’s peak and quickly weakening, but will last well into the Northern Hemisphere spring 2011. Considerable uncertainty is evident during the Northern Hemisphere summer and fall, but a majority of models indicate ENSO-neutral conditions (Niño-3.4 SST anomalies between -0.5°C and +0.5°C ).

The CFS ensemble mean (black dashed line) predicts La Niña conditions through Northern Hemisphere have transitioned to neutral conditions, then a good chance of swinging back to a weak/moderate La Nina by winter 2011/2012.

I added the ENSO forecast through the summer 2011 from CPC. Here are some Analog years that fit 55-56, 73-74, 88-89, 07-08. 1989 now appears to be the best fit. Year DJF JFM FMA MAM AMJ MJJ JJA JAS ASO SON OND NDJ 1955 -1.0 -0.9 -1.4 -1.8 -2.0 -1.9 1956 -1.3 -0.7 -0.6 -0.8 1973 1.8 1.2 0.5 -0.1 -1.1 -1.7 -2.1 1974 -0.5 1988 0.7 0.1 -0.2 -1.2 -1.6 1989 -1.5 -0.4 -0.3 2007 0.8 0.4 2008 0.0 2009 0.2 0.6 0.9 1.5 2010 1.7 0.3 2011 -.06 I added the ENSO forecast through the summer 2011 from CPC.

Not big temperatures differences stick out For monthly average temperatures.

Mean troughing off the coast Wet thunderstorm potential high

4 Corner High rebuilds

Climate Precipitation outlook for Aug-Oct 2011

Climate Temperature outlook for Aug-Oct 2011

What happened in July/August of 1989, the year that had a fading “La Nina” event similar to 2011? Moist in some areas in Jul/Aug 1989 Cool over the region in Jul/Aug 1989

What happened in September of 1989, the year that had a fading “La Nina” event similar to 2011? Warmer than usual over WA and some of Oregon in Sep 1989 Drier than usual mainly over the west side in Sep 1989

Most Likely to happen in 2011 – Near record precipitation and snow and cooler than normal through late spring. This continued through July. July-August Cooler than usual most areas so far in July, particularly west side and Cascades. Fewer and shorter hot spells east side through Aug. Slow Start! As much as 4-5 weeks delay in start of fire season due to effects of lingering snowmelt and cool/wet weather. This means around the first week of August or later before significant fires are possible. Lightning strike count looks to be less than usual for the summer for Pac NW but potentially more Hurricanes . One to two periods of episodic lightning outbreaks will be possible. September warmer and drier then normal.

Large timber fires will not be possible at the lower-mid elevations until the first week of August or later, but may last into the middle of September. East of the Kettle mountains and north Idaho should experience average number of fire starts and below average number of acres. 1974: 1103 starts/ 9466 acres 1989: 1008 starts/ 14,699 acres Eastern Washington North Idaho 1999: 951starts / 13,128 acres 2008: 1,078 starts/ 77,769 acres. Avg:1071 starts/106,985.