Note: This post talks about the impact of the Blob on winter weather in the Tri-Cities and is part of a series on my thoughts for the upcoming winter. Other posts in this series can be found here.
THE BLOB
The Blob is an area of persistent, unusually warm sea surface temperatures (SSTs) in the Gulf of Alaska. It has waxed and waned for the last couple of years and has been a player in our regional weather pattern during the entire six years of its existence. Unfortunately, what future impacts we might expect from it aren’t well-understood thanks to its short existence.
The Blob is directly linked to persistent high pressure that develops over the Gulf of Alaska. You can think of this weather pattern as a double-whammy with the two major drivers being wave direction and wave size – both of which are determined by the wind pattern. High pressure brings less wind and less wind brings smaller and fewer waves. Part of why waves are important for the Blob is because they bring up colder water from below, lowering the water temperature at the surface. Unfortunately (or fortunately, if you like the Blob), these lighter winds result in smaller waves that aren’t able to bring the colder water to the surface.
On top of the waves not being strong enough to mix in colder water from below, the light winds that do form produce waves that bring in warmer water from the south. Wind circulates clockwise around high-pressure systems in the Northern Hemisphere. On the south side of the high-pressure center, the wind will be blowing out of the east. Waves are created as the wind moves across the ocean, but instead of going the same direction as the wind, the waves move away at a right angle (a simplified idea of this is shown in the graphic above). In this situation, the waves travel from south-to-north and with them come warmer water.
IMPACTS FROM THE BLOB (MAYBE)
When I discussed the Blob with Rik and Stacy on 98.3 The Key a few weeks ago, I said it was the big variable in how our winter goes. This is because the Blob has done a couple of very different things for our weather during its short tenure in the Pacific. As far as I can tell, most of the winters during the Blob’s life have been accompanied by slightly above-average winter precipitation in the Tri-Cities.
Temperatures; however, have been quite varied. If you were to take an average of all the temperatures observed throughout the winter, a normal winter in the Tri-Cities would come out at (or near) 35.9° (and for stats nerds, the standard deviation is 2.8°). I’m going to briefly mention two recent winters here that were both pretty well removed from that figure (though neither were more than two standard deviations from normal).
The first is the winter of 2014-2015, which came in at an average of 38.4°. I can remember driving over Snoqualmie Pass in March 2015 while heading over to Seattle and finding the valley floor to be snow-free. This is in stark contrast to other years. Those who have been driving over the pass for years can probably recall snow up there as late as May or even June. As Dr. Cliff Mass noted in a blog post in 2015, the Blob warmed the air above it, which then moved across the Pacific Northwest, keeping snow levels unusually high in the Cascades.
The second is this past winter (2018-2019). If you were here, I’m sure you remember it – especially the record-breaking snow that came in February and March. The average ended up coming out to 32.8°, which is impressively low since December and January were relatively mild. Elevated sea surface temperatures in the Gulf of Alaska helped to strengthen the area of high pressure above it. This, in turn, forced the jet stream (strong winds at about 30,000 feet) north into Alaska and surging south through British Columbia straight into the Pacific Northwest bringing with it a parade of storms that didn’t have the chance to warm up over the ocean.
So why did I say maybe? It’s hard to determine if these patterns are primarily caused by the Blob itself, or by the weather pattern that birthed it. I’m sure it’s some combination of the two, but more research needs to be done on the subject.
FORECASTING THE BLOB
Since the Blob is dependent on a persistent ridge of high pressure, predicting its future is reasonably straightforward. If we’re expecting active weather in the Gulf of Alaska, it can be expected that the Blob will weaken; if it’s going to be relatively calm, it will probably persist and maybe strengthen.
The Blob has been weakening since our stormy pattern started in September, especially near the British Columbia coast. With the current weather pattern, strong storms have been moving along the Aleutian Islands. The one shown at the right (above on mobile) is producing wind gusts to around 80 mph with waves higher than 30 feet tall in some places. That is certainly bringing up cooler water from below the surface to cripple the Blob.
Long-range models seem to keep the stormy Aleutian trend in place for at least the next couple of weeks, while the ridge over the Western United States adjusts itself and slowly weakens. Dr. Mass expects the Blob to continue to weaken through the stormy season – a sentiment echoed by other speakers at the Winter Weather Conference I attended in Portland last month.
The featured image for this post is sea surface temperature anomalies for the Gulf of Alaska showing water temperatures up to 4°C above average on November 12. From earth.nullschool.net.
