Author Topic: Short term 10F temp rise  (Read 1510 times)

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Offline shimon

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Short term 10F temp rise
« on: November 17, 2022, 11:47:36 AM »
We've been waking up for the past 10 days to temps right around freezing and usually around 6am the temp is constant or dropping slightly.  But this morning woke up to 42F temps and then around 7am it quickly dropped back to freezing.  Looking at the data on WU, I noticed a brief spell of strong wind and a rise in pressure telling me a warm front moved in...but then why did the temperature drop suddenly?  Is there a name for this phenomenon?  I know just the basics of weather but this has me stumped.  And I have a second outdoor temp sensor that was showing the same readings so it's not a glitch in my Davis weather station.  This post talks about about a short temp drop but not sure if it's part of the same phenomenon: https://www.wxforum.net/index.php?topic=43538.0

Below is a screenshot of my weather page from this morning and then below are the two previous days for comparison.  WU page is KWASEDRO8.

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« Last Edit: November 17, 2022, 11:49:59 AM by shimon »

Offline ocala

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Re: Short term 10F temp rise
« Reply #1 on: November 17, 2022, 07:31:50 PM »
Don't have a clue but maybe that little rain shower you had about the same time brought down colder air from above?
Stuff like this is exactly why we have weather stations.   :-)
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Offline miraculon

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Re: Short term 10F temp rise
« Reply #2 on: November 18, 2022, 08:51:08 AM »
I live a few blocks inland from Lake Huron. Mostly in the summer, we will start the day with a SW wind (offshore) and as the land heats up, the local "low'" will cause a wind shift to an onshore breeze. Temperature changes of  10-12F occur as a result of this almost on a daily basis. I know that this doesn't apply in your case, but rapid temperature changes can occur and this is an example of one cause.

As the post that you link mentions, this can be due to local topography or a local condition such as the downdraft of cold air that ocala mentions.

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Offline shimon

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Re: Short term 10F temp rise
« Reply #3 on: November 18, 2022, 09:04:38 AM »
Don't have a clue but maybe that little rain shower you had about the same time brought down colder air from above?
Stuff like this is exactly why we have weather stations.   :-)

Thanks...but no rain.  Haven't seen a cloud all week.  We get a lot of dew/frost overnight and usually once it warms up, there is enough in the rain catcher to trigger 0.01".

Offline shimon

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Re: Short term 10F temp rise
« Reply #4 on: November 18, 2022, 09:06:59 AM »
I live a few blocks inland from Lake Huron. Mostly in the summer, we will start the day with a SW wind (offshore) and as the land heats up, the local "low'" will cause a wind shift to an onshore breeze. Temperature changes of  10-12F occur as a result of this almost on a daily basis. I know that this doesn't apply in your case, but rapid temperature changes can occur and this is an example of one cause.

As the post that you link mentions, this can be due to local topography or a local condition such as the downdraft of cold air that ocala mentions.

Greg H.

Thanks.  I've seen lots of rapid temperature changes but I don't recall ever seeing a rapid 10F rise and then drop over a short period.  I was hoping there was a technical name for this phenomenon.  I'll keep searching and looking around...if I find something I'll post my findings.

Offline CW7491

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Re: Short term 10F temp rise
« Reply #5 on: November 18, 2022, 11:49:52 AM »
shimon,

I used to live out in WA for a few years and it's a very interesting place to live with a weather station because you often see some huge variations due to extreme microclimates. Proximity to the sound and to the Cascades will do interesting things with just slight wind shifts. This looks like what happened in your case. If you notice, winds were very light out of the SW to WSW when your temps were down near freezing, but then the wind picked up and shifted to the north. Looking at your location, this north wind comes down a narrow valley from the Cascade foothills whereas the SW to WSW wind comes out of the Skagit Valley and the Puget Sound.

In the winter months, there is a phenomenon you're probably familiar with called the Frasier Outflow. This develops when there is a large pressure gradient due to high pressure over the Frasier plateau in BC and east of the Cascades. The air pushes down the Frasier River valley and results in very strong winds in the Puget Sound area, particularly in Bellingham. Usually this wind is a very cold wind, but in this case, it looks like it was a relatively warm wind. Take a look what happened at the Bellingham Airport around 11p on 16Nov ... https://www.weather.gov/wrh/timeseries?site=KBLI&hours=72

It looks like you were sheltered from this wind due to the terrain to your north and east, but you started seeing some of it make it down that narrow valley around the time you saw the temp spike and then it dropped off again and shifted back to the SW and your temp dropped back down. This is ultra-localized, so pretty interesting to have a weather station on your property to measure it.

If you're interested in reading more about local phenomena in the Puget Sound area, I highly recommend following Cliff Mass' blog (Professor at UW) and after just checking, he sure enough wrote about this very event in his latest post ... https://cliffmass.blogspot.com
« Last Edit: November 18, 2022, 11:51:56 AM by CW7491 »

Offline CW2274

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Re: Short term 10F temp rise
« Reply #6 on: November 18, 2022, 07:28:10 PM »
A few months ago a member here, Randall, who only lives a couple miles from me as the crow flies, had a sudden increase of 12F higher than me, and this was at night as well. I was somewhat stupefied, then noticed he had a brisk east flow of wind, which comes off the Rincon Mts. My wind was dead calm. That caused down sloping winds, which compresses the air, making it much warmer. Happens here quite often. Think Santa Anna winds that Socal gets. Same thing. No idea if that applies here, though.

Offline CW7491

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Re: Short term 10F temp rise
« Reply #7 on: November 18, 2022, 08:07:52 PM »
Definitely can get downslope warming and upslope cooling in the PNW, but usually these events are high pressure air masses to the east, blocked by the Cascades, that force themselves through valleys and the airmass pours into the Puget Sound region like filling a bowl. Strong ones will effect the whole region, while weaker ones will result in localized winds near those cuts in the Cascades. Typically it is a winter phenomenon and results in the moderate maritime airmass being replaced by a bitter cold continental airmass.

Offline shimon

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Re: Short term 10F temp rise
« Reply #8 on: November 19, 2022, 10:24:36 AM »
shimon,

I used to live out in WA for a few years and it's a very interesting place to live with a weather station because you often see some huge variations due to extreme microclimates. Proximity to the sound and to the Cascades will do interesting things with just slight wind shifts. This looks like what happened in your case. If you notice, winds were very light out of the SW to WSW when your temps were down near freezing, but then the wind picked up and shifted to the north. Looking at your location, this north wind comes down a narrow valley from the Cascade foothills whereas the SW to WSW wind comes out of the Skagit Valley and the Puget Sound.

In the winter months, there is a phenomenon you're probably familiar with called the Frasier Outflow. This develops when there is a large pressure gradient due to high pressure over the Frasier plateau in BC and east of the Cascades. The air pushes down the Frasier River valley and results in very strong winds in the Puget Sound area, particularly in Bellingham. Usually this wind is a very cold wind, but in this case, it looks like it was a relatively warm wind. Take a look what happened at the Bellingham Airport around 11p on 16Nov ... https://www.weather.gov/wrh/timeseries?site=KBLI&hours=72

It looks like you were sheltered from this wind due to the terrain to your north and east, but you started seeing some of it make it down that narrow valley around the time you saw the temp spike and then it dropped off again and shifted back to the SW and your temp dropped back down. This is ultra-localized, so pretty interesting to have a weather station on your property to measure it.

If you're interested in reading more about local phenomena in the Puget Sound area, I highly recommend following Cliff Mass' blog (Professor at UW) and after just checking, he sure enough wrote about this very event in his latest post ... https://cliffmass.blogspot.com

Thank you for the informative, clear and excellent explanation.  Your analysis seems spot on.  I have perused the Cliff Mass Weather Blog previously but will take a closer look as I haven't visited it in a while.

 

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