One of the reasons Northwest weather is so temperate in summer is the cool coastal waters off our coast.
And this year, we start the summer with surface waters cooler than normal.
This is illustrated by the sea surface temperature anomalies (differences) from normal (below), with blue indicating cooler than normal water.
Below is a map of sea surface temperatures off the U.S. West Coast (°C). The purple and blue colors indicate the coldest temperatures. You will need a sweater to enjoy a coastal stroll!
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One reason is the upwelling of cold water from below, as illustrated by the figure below. Such upwelling is forced by northerly (from the north) winds along the West Coast.
Importantly, these northerly winds have been stronger than normal for the past month.
Why?
Because of stronger-than-normal surface high pressure offshore of the northwest. This is demonstrated by the figure below, which shows the sea-level pressure anomaly (difference) from normal over the past month.
The red area indicates a much higher-than-normal high-pressure area offshore.
Since winds move clockwise around high-pressure areas in the Northern Hemisphere, this implies enhanced northerly flow along the coast, something shown explicitly in the figure below (which shows the wind differences from normal of the past month).
With this persistent pressure/wind pattern in place, the current 5-day forecasts are for colder than normal conditions over western Washington, Oregon, and British Columbia (blue and green indicate colder than normal conditions)
Keep your sweaters handy!
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It seems like the cooler waters should take a little steam out of any systems that happen to make a push toward us.
ReplyDeleteTo add on to my original comment, now I'm wondering how many times Seattle has had a summer that's been significantly cooler and dryer than average. I'd like to know the setup that would make a scenario like that possible.
DeleteWhat I do remember is the very hot summer of the BLOB (2015) beginning with dry weather, but the back half of that summer turned wet and I believe the total precipitation for that summer ended up above normal.
Do you mean 2019 for the blob? While temps during the day generally did not get much beyond the low 80's, the overnight low was sitting around 65F and made for uncomfortable nights and muggy too, with it being often 70+ percent. Then the rains came and the major thunderstorm in early Sept that knocked power out for many, myself included early that evening.
DeleteLooks like El Niño is present and strong already. Looks like official forecast is for strong El Niño with 63% probability. Some places call for 4C anomaly that never happened before. What it you take on it?
ReplyDeleteThe media is hyping this up more than I have ever seen them hype an El Nino or La Nina situation before. At the time of this writing, the Weather.com app even has a banner link up similar to those used when wind, snow, flood, and other types of official weather warnings are in place touting it. The level of hype strikes me as being completely unnecessary, at least at this point in time.
DeleteI asked about this and Cliff responded, it'll not last as most storms of this ilk are not sustainable, if we get anything at all, outside of a normal El Nino.
DeleteThis should keep the Times from belly aching all this here global warming tommyrot
ReplyDeleteWhat are your thoughts on the major news outlet’s reports on a building El Niño. You previously wrote about the inaccurate drought reports. Do your thoughts change with the recent reports?
ReplyDeleteHe has already replied to a similar question and thinks if it happens, it'll not be as hyped as most such systems of this magnitude don't last long.
DeleteDoes the recent report from news outlets on El Niño change your thoughts on drought? Does this cooling instance help?
ReplyDeleteThe cooler temperatures we've been having lately are most appreciated! Thank you, Professor Mass, for explaining the science behind it.
ReplyDeleteReminds me The pint size javalina hogs are feasting on the prickly pears in the Sonoran about now. Them critters eat better then us, I have to buy these by the pound at the green barn in Lynden
ReplyDelete