Crazy Temperature Spikes in Bellingham
Folks around Bellingham have been noting some wild temperature swings, with temperatures warming by 15-25F over an hour or two, before dropping back to the previous level. These features, known as "temperature spikes" in the weather business, are frequently noted in certain areas of the Northwest.
Let me illustrate what happened by showing you the temperatures at Bellingham during the past few days (see below). On 14th and 15th temperatures were in the teens, as uber cold air from the interior of British Columbia, pushed through the Fraser River Valley and then over Bellingham and northwest Washington. Temperatures slowly warmed on the 16th. But suddenly over one hour, temperatures surged 20F to 45F. Instant defrost. But then temperatures dropped just as suddenly two hours later, back to the low 20s. Startling.
On the 17th temperatures dropped back down to 15F and everything froze solid again. But that would not last long. First, temperature rose rapidly to around 30F and held around 30F for much of January 18. But later that day, temperatures surged 15F in one hour to 45F, rose to near 50F, and then dropped back to 35F over one hour. How weird is that?
So what is going on? How can temperature rise and fall tens of degrees in an hour?
To get a hint, let's plot the wind direction at Bellingham for the same period.
Ah ha! For most of the period, winds at Bellingham were from the northeast, associated with cold, arctic air flowing out of the Fraser River Valley. But look carefully. There was a switch to southeasterly winds early on the 16th when temperatures started to warm, and a sudden spike to easterly winds later on the 16th when the temperatures surged! And later on the 18th there was a sudden shift to southerly winds associated with the sudden warm-up on that day,
A better approach is to look at local weather maps before and after. At 1 AM on the 16th, cool northeasterly air was over the Bellingham.
A similar situation occurred two days later.
So why this big change on the 16th? As shown below (surface map at 10 PM that day), a strong low center approached on the 16th. On one hand this low produced a large pressure difference between high pressure in British Columbia and the low center, which would tend to produce cold northeasterly flow in the Fraser Valley. But the low center also resulted in strong southerly/southeasterly flow over the lowlands, and for a few hours that warmer, southerly flow was dominant--thus the surge in temperatures. After the low moved through, the cold northeasterlies returned to Bellingham.
Other areas of Washington State can also get large temperature swings. For example, shallow cold air in eastern Washington can be rapidly displaced by strong downslope flow from local mountains. And Portland can have rapid temperature changes depending on the air flow in the Columbia River Gorge.
You can imagine the future impacts of these huge temperature swings.
Let me illustrate what happened by showing you the temperatures at Bellingham during the past few days (see below). On 14th and 15th temperatures were in the teens, as uber cold air from the interior of British Columbia, pushed through the Fraser River Valley and then over Bellingham and northwest Washington. Temperatures slowly warmed on the 16th. But suddenly over one hour, temperatures surged 20F to 45F. Instant defrost. But then temperatures dropped just as suddenly two hours later, back to the low 20s. Startling.
On the 17th temperatures dropped back down to 15F and everything froze solid again. But that would not last long. First, temperature rose rapidly to around 30F and held around 30F for much of January 18. But later that day, temperatures surged 15F in one hour to 45F, rose to near 50F, and then dropped back to 35F over one hour. How weird is that?
So what is going on? How can temperature rise and fall tens of degrees in an hour?
To get a hint, let's plot the wind direction at Bellingham for the same period.
Ah ha! For most of the period, winds at Bellingham were from the northeast, associated with cold, arctic air flowing out of the Fraser River Valley. But look carefully. There was a switch to southeasterly winds early on the 16th when temperatures started to warm, and a sudden spike to easterly winds later on the 16th when the temperatures surged! And later on the 18th there was a sudden shift to southerly winds associated with the sudden warm-up on that day,
A better approach is to look at local weather maps before and after. At 1 AM on the 16th, cool northeasterly air was over the Bellingham.
But by 3 AM, strong southeasterly flow had surged in bringing warm air (see below). But the cool air was not far away. A meteorological battle was going on between cold and warm airstreams!
A similar situation occurred two days later.
So why this big change on the 16th? As shown below (surface map at 10 PM that day), a strong low center approached on the 16th. On one hand this low produced a large pressure difference between high pressure in British Columbia and the low center, which would tend to produce cold northeasterly flow in the Fraser Valley. But the low center also resulted in strong southerly/southeasterly flow over the lowlands, and for a few hours that warmer, southerly flow was dominant--thus the surge in temperatures. After the low moved through, the cold northeasterlies returned to Bellingham.
Other areas of Washington State can also get large temperature swings. For example, shallow cold air in eastern Washington can be rapidly displaced by strong downslope flow from local mountains. And Portland can have rapid temperature changes depending on the air flow in the Columbia River Gorge.
You can imagine the future impacts of these huge temperature swings.
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