El Nino, The Blob, and Winter Weather in the Pacific Northwest

Enter El Nino & The Blob

An El Nino is already in progress, and it’s looking like a pretty good one. Sea surface temperature anomalies in the Nino 3.4 region have been above 0.5°C for seven of the last eight 3-month periods, and it currently sits at a very respectable +1.0°C. For reference, 1.0°C is the highest May/June/July positive anomaly since 1997 – which you may remember as the beginning of the strongest El Nino we’ve ever measured (1997/1998).

SST anoms

Figure 1: August global sea surface temperature (SST) anomalies from 2015 (top) and 1997 (bottom). Yellow and red are positive, blues are negative.

The current SST anomalies across the globe (Figure 1, top) do look strikingly similar to how they did in August of 1997 (Figure 1, bottom). Two things that are different are 1. the SST anomalies along the equator in the east Pacific are not currently as extreme as in 1997 and 2. An area of very warm water off the Pacific Northwest coast, which has been named “The Blob,” is much warmer and much larger this year than in 1997.

So, what’s going to happen? In short, we don’t know, exactly. First, we have to forecast the evolution of El Nino correctly. Second, the actual weather that results from each El Nino isn’t always the same. And, third, we aren’t sure what affect The Blob might have on all of this, because we haven’t really seen such a large Blob before.

The Evolution of El Nino

The track record of predicting the state of ENSO in the future isn’t perfect. What long range forecast is? The latest model forecasts predict a strong El Nino lasting into 2016, all experts seem to agree on some version of this scenario, and it sure looks like it to me.

What Will The Weather Do?

If we believe these El Nino forecasts, and I do, the next challenge is to say what that means. Unfortunately, the news isn’t really better on that front. Because no two El Ninos are ever the same, and because the effects of El Nino on the global circulation pattern (and vice versa) are so complex, there is really nothing we can say, specifically.

For example, despite the common belief that El Ninos are always stormy and wet and California, it isn’t always so. To see what I mean, consider the following charts, which show the precipitation patterns that have resulted from all El Ninos we’ve measured.

ENSO impacts

Figure 2: ENSO precipitation anomalies for historical El Ninos – from strong at the top to weak at the bottom.

See? It isn’t the same for all El Ninos, not even for all strong El Ninos. What we can say is that most El Ninos are wet and stormy in California, but not all. The NWS Climate Prediction Center said it well in their latest ENSO post: “El Nino ’tilts the odds’ for weather and climate impacts.” Which is to say that it tilts the odds that we’ll see impacts like this:

Average El Nino Impacts

Figure 3: Impacts averaged over all El Ninos for North America

What About Blob?

This is where it gets interesting. I plan to flesh this out in a following post, but recent research from my alma mater, the University of Washington, suggests that The Blob is caused by persistent high pressure over the northeast Pacific which is caused by abnormally high water temperatures in the tropical west Pacific. Unusually warm water was present in the west Pacific last winter as the Blob formed.

This has interesting implications, because if this El Nino evolves like its evil twin from 1997, the warm water in the tropical west Pacific may disappear, which should cause The Blob to disappear. It did in 1997. Here is the SST anomaly from Dec 30, 1997:

SST Anoms Dec 30, 1997

Figure 4: SST Anomalies on Dec 30, 1997

You can see that by the end of 1997, the Blob was completely gone and had been replaced by cooler than normal SSTs over the entire NE Pacific. Furthermore, the waters in the tropical west Pacific had also cooled below normal, which was almost certainly an artifact of the development of the strong El Nino in 1997/1998.

If this happens again this time, we might be able to expect impacts from this El Nino like the ones we saw in 1997. Precipitation anomalies from 1997/98 El Nino are shown in Figure 5, below. Unfortunately, I don’t have SST data from the 1982/83 El Nino. It was also a very strong El Nino, and I’d sure like to compare it to our current situation, because that one was outlandishly wet up and down the Pacific Coast.

Precipitation anomalies from the 1997/1998 El Nino

Figure 5: Precipitation anomalies from the 1997/1998 El Nino

Of course, the destruction of the The Blob in 1997/1998 is no assurance that it will happen the same way this time. After all, The Blob is much more pronounced this year than back in 1997. I’m just saying that there are reasons to think it could happen this way again. This also has implications for the eastern part of our continent which was ravaged by cold and snow over the last couple of winters. I’ll explain my theory on this in my next post.

What About The Pacific Northwest?

Unfortunately, there is no clear signal for what to expect in the Pacific Northwest during an El Nino. As we saw in Figure 2 (above), precipitation in the PacNW can vary from very wet to very dry, even during strong El Ninos. I’ve poured over rainfall/snowfall records for many locations from California to BC, and below is a bullet list of the most interesting things I found.

Conclusion

We are in the midst of a developing strong El Nino. Conditions right now are very similar to August 1997, which was the strongest El Nino that we’ve ever measured. Because no two El Ninos are exactly alike and The Blob may complicate things, we can’t say exactly what will happen. But the scales should be tipped toward wet weather across the southern U.S. this winter, with warmer than normal weather to the north. In the north, precipitation could amount to anything.

Interesting Things I Found From Past El Ninos

I’ve analyzed climate data from many sites over the western U.S. back to 1950 (the period for which I have SST data to compare to). Here are some of the things I found interesting:

  • Seattle, Portland, and Medford get much less snow during El Ninos than non El Nino years, especially since 1982 (what I call the modern era). Prior to 1982, they got a lot more snow overall, including during El Nino years.
  • In the modern era, Medford, OR has gotten only 1.5 inches of snow during all strong El Nino years combined. In non-El Nino years during the same period, they’ve averaged almost 4 inches per year. Prior to 1982, Medford did have some above average snow years during El Ninos.
  • Seattle, WA* averages just 1.6 inches of snow during El Nino years and 6.7 inches in non El Nino years in the modern era. During strong El Ninos, it’s even worse with an average of just 0.8 inch.
  • Ironically, the biggest snow season since 1950 in Seattle* occurred during the 1968-69 El Nino. I was born in Seattle, during this season! :)
  • Portland, OR has averaged just 1.1 inches of snow during modern era El Ninos versus 6.0 inches during non El Nino years. They also haven’t received any snow during strong El Ninos in the modern era.
  • Spokane, WA has received an average of 25.1 inches of snow during all El Ninos in the modern era. This is less than half of the average during non-El Nino years in the same period (51.8″).
  • Snowfall in the mountains during El Ninos is generally much less than during non El Nino years in the north. As we move south, the difference diminishes until it’s basically gone in California. See the following chart. I didn’t get a chance to look for mountain locations further south, but I suspect I’d find a reversal of that trend.
Average snowfall during

Figure 6: Average snowfall during El Nino years (blue) and non El Nino years (red) since 1950. **Records missing between 1989 and 1998. ^Data ends in 2000.



 


 

I get these records from the Western Regional Climate Center. I do the math myself. :)

*This is based on a reconstruction I made of Puget Sound snowfall. In the decade between roughly 1997 and 2007, climate records for Western Washington (snow record, in particular) are very sketchy to non-existent. I have no idea why the records are missing, but I made my own record using a composite of records from around the area. See here for more details.

Share

A Reconstruction Of The Snow Record For Seattle, WA

sea-snow-chart-max

Purpose

In doing research about snowfall during El Nino years in the Pacific Northwest, I found records up north – the Seattle area, in particular – severely lacking. I checked several official sites, and it was always the same: large periods of the record missing. In particular, snow data was missing from the very important 1997-98 Super El Nino period. I don’t know why this is, but it is very frustrating.

So, lacking official records, I took it upon myself to make my own record, which is shown below.

Methods

My method was very simple: I scoured all the records around the Puget Sound and simply patched them together. By doing this, I got reliable data from some site for each year. Then, for each year of my record, I took the average snow for all sites that had data for that year. I also made one with the maximum snowfall for the year. I don’t know if this would be considered a proper way to do a reconstruction by smart people, but, frankly, I don’t care. It suited my purposes, and I feel fairly comfortable that it is a useful dataset.

Here are the sites I used in the reconstruction: Bothel, Jackson Park, Seattle Naval Air Station, NWS Sand Point, UW, Seattle City Office, Portage Bay, Boeing Field, SeaTac, Kent, Bremerton, Tacoma City Hall, Puyallup, McMillin Reservoir, Wauna, Shelton, Olympia, Quilcene Everett, and Vashon Island. You can find all these data at the Western Regional Climate Center.

My Seattle-area Snowfall Reconstruction Chart (averaging method)

sea-snow-chart-avg

My Seattle-area Snowfall Reconstruction Chart (maximum method)

sea-snow-chart-max

My Seattle-area Snowfall Reconstruction Data

Season Avg Snow In Puget Sound (inches) Max
1950-51 14 27
1951-52 9 25
1952-53 1 3
1953-54 18 30
1954-55 6 16
1955-56 20 40
1956-57 17 25
1957-58 1 1
1958-59 8 21
1959-60 7 16
1960-61 4 9
1961-62 9 16
1962-63 2 4
1963-64 2 4
1964-65 20 44
1965-66 14 42
1966-67 6 11
1967-68 12 25
1968-69 42 82
1969-70 2 3
1970-71 17 36
1971-72 23 55
1972-73 6 10
1973-74 4 10
1974-75 8 23
1975-76 4 16
1976-77 1 3
1977-78 2 5
1978-79 9 19
1979-80 15 36
1980-81 2 4
1981-82 7 22
1982-83 0 0
1983-84 2 5
1984-85 11 19
1985-86 15 25
1986-87 2 4
1987-88 1 1
1988-89 13 30
1989-90 11 29
1990-91 6 10
1991-92 0 0
1992-93 8 14
1993-94 1 2
1994-95 5 9
1995-96 4 11
1996-97 16 23
1997-98 3 4
1998-99 4 7
1999-00 1 1
2000-01 5 10
2001-02 1 1
2002-03 0 0
2003-04 17 17
2004-05 0 0
2005-06 3 9
2006-07 5 6
2007-08 3 6
2008-09 16 28
2009-10 0 0
2010-11 7 10
2011-12 12 17
2012-13 0 1
2013-14 3 4
2014-15 1 1
Share

We May Finally Break The Heat Wave

GFS 10-day

We’ve had a stretch of heat over the Pacific Northwest the likes of which I can scarcely remember from growing up in the area and which I’ve certainly not seen in the 4 years I’ve lived in southern Oregon. Temperatures reached 110F at times at my house over the last couple of weeks, and many records have been broken. In fact, one site in Washington State may have broken the all-time state record.

But it looks like we may finally get a break in the heat wave over the next week or so. A monster ridge of high pressure has been the culprit in the heat wave, but some long range models show the ridge retrograding offshore and allowing a trough to drop in over the PacNW. Here is the GFS 500 mb ensemble mean and spread for 10 days from now:

GFS 10-day

GFS Ensemble Mean (lines) and spread (fill), Valid 09July2015

The spread is actually pretty low for that far out, and thus troughing seems like a good bet over the west coast. This probably wouldn’t mean cool weather, but at least the oppressive heat we’ve seen should be gone.

The fly in the ointment, however, is the European Forecast. I don’t have access to its ensembles right now, but its deterministic forecast shows a brief troughy interlude followed by the ridge rebounding over the area.

Of course, we’ll have to wait and see, but at least there is some hope for those of us who don’t like living in ovens.

Share

Potential Wind Storm In PacNW

We’ve been through a lot of boring weather through early winter, but we’re finally getting some storms again.

 

Share

McMinnville, OR Tornado Rated EF1

Following up on the post I made yesterday about the tornado touchdown in McMinnville, OR, the NWS survey team rated it as an EF1. This means the damage was indicative of winds of 86-90 mph.

I have seen some video of the tornado (here and here) but they aren’t great. In fact, I can’t really see much at all. But the following photo was posted on the NWS Portland Facebook page, and it shows the tornado pretty well.

Tor pic

Tornado near McMinnville, OR on 13Jun2013. Photo taken by Bonnie Helpenstell and grabbed from NWS Portland Facebook page.

By the way, this tornado was entirely different than the big ones out in the central and eastern U.S. This kind is called a cold air funnel and is formed by processes different than the big ones that come from supercells. A violently rotating column of air reaching from a convective cloud to the ground is a tornado no matter what the mechanism. But they’re different. It will be easier to explain in a video, so I’ll do that some time.

Share

Tornado In McMinnville, OR

Funnel cloud from Harrisburg, OR today (13Jun2013)

An NWS storm survey team confirmed that a tornado touched down in McMinnville, OR this afternoon. They have yet to say what rating the tornado was on the F-scale, but there was significant damage to some buildings.

I have heard there is video of the whole thing, but I’ve yet to see it. I will post a link when it comes out. However, I did find this photo of a funnel cloud from Harrisburg, OR this afternoon:

Funnel cloud from Harrisburg, OR today (13Jun2013)

Funnel cloud from Harrisburg, OR today (13Jun2013)

Tornado confirmed and a cool photo of a funnel cloud…in western Oregon no less! Check.

Of course, that’s not enough for me. I like to investigate why these things happen (not surprising, I suppose, since it is my job to forecast these things). Here are the radar images from around the time of the reported tornado in McMinnville:

KRTX 0.5 degree reflectivity

KRTX 0.5 degree reflectivity valid 13Jun2013/2333Z

The cell that caused the twister is fairly obvious. It had a ~60dbz core which is pretty good, but at this distance from the radar, we are sampling at ~3,700 feet above ground level. In other words: we’re not seeing much, if any, of the portion of the cell that contained the tornado.

KRTX-0.5Z-V13JUN13-2333Z

The cell also had a **very** weak rotation at that level. Green indicates movement toward the radar (which is located in Portland – toward the upper right) and red is away. The values in there are pretty lame, like 10 knots in each direction, but that rotation is cyclonic. Again, though, we’re overshooting most of it at this range.

Finally, here is the sounding from Salem, OR. It is quite close by and, as luck would have it, taken at right around the same time:

2013061400.72694.skewt

There is some **weak** cyclonic rotation on this sounding as well – notice how the wind barbs show southerly wind at the surface and then it gradually turns toward the west/northwest with height (called veering). It’s also pretty moist in the low levels and there is some very marginal instability.

None of this information screams tornado, and I never would have forecast it to occur based solely on what I’ve seen so far. But it’s not hard to see how it happened in hindsight.

This is yet another learning experience and a pretty unusual and neat occurrence to boot.

Share

Tropical Storm Andrea Is Born

We are about to get our first named tropical storm of the season this afternoon. Hurricane hunter aircraft reportedly found a well-defined circulation with the cloud shield seen southwest of Tampa on the following satellite photo. She will be called Andrea. June seems a little early for this! :)

Visible

Visible satellite image of tropical system currently forming in the Gulf of  Mexico, valid 05Jun2013/2115Z. It will be called Andrea.

Share

Photos Of Wildfire In Grants Pass, OR today

Wildfire rolled up the hills just east of Grants Pass, OR this afternoon. My understanding is that it’s called the Beacon Hill Fire and was started by a truck throwing sparks as it move along I-5. It was close enough to my home that I was able to check it out for myself. I took the following photos from Grants Pass this afternoon.

20130531_170635

 

There was isolated extreme fire behavior, including pockets of torching. Luckily it wasn’t windier today. I wasn’t able to photograph the worst of it, but the I did get the one below. It’s not terribly dramatic, but those flames are half as tall as the nearby telephone pole. You can also see how close this was to Interstate-5. I would have loved to get in closer to see what was going on, but then I’d just be part of the problem. 😉

20130531_165007-c

Share

More Tornado Terror For OKC Area

Three hooks on radar within 50 miles of Oklahoma City, OK this evening.

Radar

0.5 degree reflectivity from OKC radar – valid 31May2013/725pm CDT. Yellow arrows point to hook echoes.

Share

Interactive Before/After Map of Tornado Damage In Moore, OK

This interactive map has a slider bar that you can use to scroll back and forth between the before and after damage photos. You can also zoom in and out. This really puts the unbelievable damage caused by the tornado into perspective.

Snapshot of application - click to go to the app

Snapshot of the app – click to go to the app itself

Share