Weather Blog

How a breeze 75,000 feet up might indicate a hot summer for Seattle

How a breeze 75,000 feet up might indicate a hot summer for Seattle
FILE -- Alki Beach in West Seattle packed with people enjoying the sunshine on a hot Seattle day.

You've likely heard the old tale of how a butterfly flapping its wings in China can make it rain here on a weekend, but what if I told you a moderate breeze high above the clouds around the equator could be the reason we just had a very wet spring? Or lend credence to other forecasts that we've got a hot summer looming?

Jason Phelps, now a graduate student at Utah State University after completing his undergraduate Atmospheric Sciences at the University of Washington, is working on research that could help give long-range forecasters another tool in spotting upcoming weather trends over several months.

Right now, many of those long range forecasts are aided by research in certain oscillations in the atmosphere that occur somewhat regularly over a period of months to decades.

You've likely heard of El Nino -- technically the "El Nino, Southern Oscillation" (ENSO) that runs on a 3-7 year cycle. There's also the Pacific Decadal Oscillation (PDO) that measures periods of warm and cooler then normal water temperatures in the northern Pacific Ocean, and that runs on a 10-30 year cycle.

On shorter time scales of a few weeks, there's the Northern Atlantic Oscillation (NAO), the Arctic Oscillation (AO), the Pacific North America Pattern (PNA) and the Madden-Julian Oscillation (MJO).

Well, now adding to the alphabet weather soup comes the Quasi-Biennial Oscillation, or "QBO", which is what Phelps is now working on.

The QBO is a slowly oscillating wind about 15 miles high above the equatorial regions of Earth (where air pressure is 30 mb, or 0.89" of mercury) -- well above the daily grind of weather patterns. Research shows the wind slowly alternates between west and east over a period of 12-18 months, making a full cycle every 18-36 months (averaging about 2.2 years). 

The wind, which reaches peak speed of about 30-40 mph in either direction at its maximum, creates a chain reaction of events in lower altitudes which can eventually manifest itself in a stable weather pattern.

Phelps is working on showing correlations between that wind and long-term weather patterns along the West Coast. He's been mostly targeting Utah since he's based there but since he's a former KOMO Weather intern and has ties to Seattle, he's been plugging in his numbers for the Northwest as well and emailing them to me since last fall.

What he's found so far is that depending on what months the QBO reaches its maximum phase and whether it's in its positive (west) phase or negative (east) phase, the event does seem to account for overall weather patterns here with some regularity.

Most recently, the QBO had been holding in its peak positive phase from about last July through this March. When the QBO has been in its maximum positive phase during the October-to-January timeframe, Jason's research shows that in 12 of the past 14 times that has happened since 1960, there has been a significantly wetter February-May period in Western Washington. (One came up average, the other drier than normal.) The spring of 1972 -- home to many of the rainy records we just broke this spring -- was also a similar positive QBO pattern.

And in the 12 instances the opposite was true, it was significantly drier on five springs, moderately drier on three others, slightly wetter than normal on two and only one had a significantly wet spring.

When QBO is positive in July, it tends to have the opposite effect, bringing a dry fall to the West, as was the case here. He said our rather long QBO positive phase this year that both explains the dry fall and wet spring. He said it's also a good reason for the California drought.

He also says his latest research indicates that the QBO is affected by both the El Nino Oscillation and the PDO, making for sometimes longer shifts in the QBO. (Hey, I just unlocked my "Government Acronym Badge.")

Some forecasts going ahead

So now the fun part: What does QBO portend for us going forward? Phelps said when the positive phase holds for July-March, it typically goes negative for September through November.

Based on past trends, here is what he's thinking will happen this year:

We're drying out: As mentioned earlier the QBO would have suggested a wet February to April and it was right. Past trends suggest we'll dry out and become drier than normal for the early summer months, Phelps says.

An intense heat event: Phelps says QBOs that have had a long peak between July into winter have been followed by a summer with an intense heat wave, including 2009 (103°day with 7 90°+ days), 1986 (home to 4 90°+ days), 1991 (reached 99°), 1972 (6 days at 90° or hotter) and 1958 (9 days over 90°). In fact, of the eight last such QBO set ups, the following summers have had more 90°+ degree days than average in seven of them, and every one of those years but one had a day at 95° or hotter.

(Phelps does say not every hot year had this QBO set up though, including 1994 when Seattle hit 100°.)

Rainfall trends back toward normal toward end of summer: Past similar QBOs have had near normal rainfall amounts as summer nears its end and fall begins.

Strong El Nino brings a dry winter -- and super dry start to next spring?: Phelps says every time when the QBO phase is similar to this year, the following winter has had a very strong El Nino event. You might have heard that forecasters are calling for El Nino this winter -- the forecast models have been trending around a moderate event but Phelps thinks there is good likelihood we'll have a strong El Nino this winter. Normally, that would likely mean a warm, dry winter with less mountain snowpack.

However, while most El Ninos' winter-drying impacts usually peak around the start of winter, Phelps says his data suggests the peak might come later this winter. Past winters that fit his mold have been about 12-13 percent below normal for the December-February time frame, but 20 percent below normal for the February-April time frame - a dry signal about on par with how strong the wet signal was for this spring. He says we drift back closer to normal rainfall toward the end of spring.

Now again, this is all based on past history and other factors are in play, so don't take this as a set-in-stone forecast but where the odds might lean.

But it'll be interesting to see how his predictions shake out. Phelps has done well before. A few days after I wrote this blog in November citing the "Equal Chances" outlook for the winter, and coming amidst a very dry fall, Phelps sent me an email (dated November 21) that said his research suggested a wet winter, especially February. (He also says the data suggested a better chance of at least one major snow event though.)

Oh, by the way...

If you're interested in how Phelps' forecasts stack up against NOAA's long term 90 day forecasts, they're somewhat in agreement. NOAA's June-August forecast is still giving a strong signal toward a warmer than normal summer but unlike Phelps' forecast, isn't picking up on any dry signal.

It's the same story for winter -- warmer than normal, but no dry signal like Phelps indicates.