7/24/2014

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Long range forecasts still portend warm summer -- and winter -- for Northwest

Long range forecasts still portend warm summer -- and winter -- for Northwest
Mt. Rainier as seen from Centennial Park on June 25, 2014. (Photo courtesy: Sigma Sreedharan Photographyā€ˇ)
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The monthly updates to the long-range seasonal forecasts came out a few days ago and sure enough, they are sticking to their guns of a warmer summer for the Pacific Northwest. But also new creeping into the forecast: A moderately strong signal now that the winter will experience a similar fate.

Now, you might be thinking: "Hey, wait a minute, they said the same thing about May and June and it was wrong!"

Actually, it was right. Despite May being a bit wetter than normal, it was indeed warmer than normal -- Seattle ended up a full 3.1 degrees above normal, buoyed by four days at 80 or warmer. Even June so far is running about a degree above normal, even though we have yet to reach 80 this month.

Look for the trend to continue through the summer months. (The warmer part, not the "not hitting 80" part.)

Here is the map for just July:



A solid warm signal for the Pacific Coast (and Alaska). No real signals for rainfall, although as I mentioned in a blog last month there are other signals we could be in for a dry July -- drier than the mostly dry it already is.

This warm signal now holds not just through summer, and not just through fall, and now, not just through winter! In fact, it holds alllll the way until their April-May-June forecast for 2015, when it goes back to equal chances.

This consistent warm signal comes to us courtesy of the expected El Nino for this fall and winter. NOAA forecasters now have 70 percent chance of El Nino by later this summer and 80 percent chance by fall.

El Nino's tend to make for a warm winter around here:


Image courtesy: Climate.gov

Forecast models are now leaning toward a weak-to-moderate El Nino. There were some signs earlier this spring we could be in for a very strong El Nino this winter, but ocean temperatures have backed off a bit.

So of course, largest impact if El Nino holds true this fall and winter is likely less mountain snow with higher snow levels and less frequent storms.

Again, these long-range forecast maps represent a "weighting of the die" -- as in if you have a 10-sided die, it'd be like 5 sides predict a warm month, 3 have a normal month, and 2 represent a cold month. So it's leaning odds toward a warmer month, just like data would suggest the Seattle Mariners have a better than average chance to win on a night that Felix Hernandez was starting. But as we've seen, even a dominating Felix start doesn't always translate to a win.

NOAA now actually breaks down these probabilities by 3-month period -- essentially putting a number to the map blobs. Here it is for Seattle:



The next updated forecast comes out the third week in July but I'm going to bet it'll be singing the same tune.

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