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What exactly is a (thermal trough) and why does it create so much heat?


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I've read their descriptions but still don't understand how they create heat? I always thought it was the 4 corners high that is responsible for our summer time warm waves?

 

Also as a bonus what are Oregon's best summer time warm waves and what were the atmospheric conditions at those times  to the best of your knowledge?  

 

Just for fun here is the August 1981 heatwave.  

 

The first hot weather actually hinted in July 27th according to the Eugene Register Guard archives.  https://news.google.com/newspapers?nid=4pF9x-cDGsoC&dat=19810727&printsec=frontpage&hl=en7/27/81.  Sizzling weather likely to end Tuesday

7/28/1981: Some Like It Hot And Yesterday was all their's.https://news.google.com/newspapers?nid=4pF9x-cDGsoC&dat=19810728&printsec=frontpage&hl=en

 Temperatures hit the 100F mark and then some in many parts of Eugene Springfield area Monday although the official high reading was 98 degrees at the National Weather Service station at Mahlon airport.We were one of the few places that didn't reach 100 said Meteorologist Dave Parmenter 

 

Here is August 1981 event. August 7th: Passwords for Weekend "It's Hot!" Weather Forecaster Bill Isabell summed up the weekends weather today in a single word "Hot!" https://news.google.com/newspapers?nid=4pF9x-cDGsoC&dat=19810807&printsec=frontpage&hl=enTemperatures were expected to climb to 105 today and Saturday.  A large warm air mass stretching as far north as southeastern Alaska is causing the heatwave he said.
 

August 8th. https://news.google.com/newspapers?nid=4pF9x-cDGsoC&dat=19810808&printsec=frontpage&hl=en Sizzling Weekend Predicted For Valley:

 

August 9th:  https://news.google.com/newspapers?nid=4pF9x-cDGsoC&dat=19810809&printsec=frontpage&hl=enIt's Hot (103) - and may get hotter. Think that's bad? it was 114 in Medford! Bumper to Bumper Traffic besieged ocean beaches. Patients discharged from hospitals asked to be taken back.

 

August 10th Eugene Sweats Record - 108 Degrees.

 

Fahrenheit One Hundreds Eight That's not the title of a science fiction story with apologies to Ray Bradbury . It's science fact a story that was all too true for the willamette valley residents who on Sunday sweltered through the hottest temperature ever recorded in Eugene. The previous record was 106 set Aug 7,1972. Fahrenheit 108 was a sizzling story of mass migrations to sea level or ski level as people sought cooler climates. Of rushes to buy fans,air conditioners,ice,beer and pop. Of worried water department officials and 'panicked' forest firefighters.  And the story continues. At least two or three more chapters of scorching heat will be written in the interior of Oregon forecasters say.

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Thermal troughs don't create the heat, they're the result of it. Hot air rises, creating an area of surface low pressure which along the west coast resides generally east of the Cascades and coastal mountains of California throughout the warm season. With strong subsidence from upper level ridging, it can and will migrate west when the ridge axis orients itself along or just west of the coastline.

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My preferences can beat up your preferences’ dad.

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Thermal troughs don't create the heat, they're the result of it. Hot air rises, creating an area of surface low pressure which along the west coast resides generally east of the Cascades and coastal mountains of California throughout the warm season. With strong subsidence from upper level ridging, it can and will migrate west when the ridge axis orients itself along or just west of the coastline.

Just to add to this: The resulting low pressure also creates an area of decending air which helps to hold lower elevation overnight temps up compared to just a big dome of high pressure (rising air) which would allow the warm air to escape in the overnight hours more easily. This is a common occurrence in the foothill locations during the warm season but is more uncommon in the low elevations without a thermal trough. This is just another factor that can contribute to maximizing the airmass potential in the afternoon hours.

Cold Season 2023/24:

Total snowfall: 26"

Highest daily snowfall: 5"

Deepest snow depth: 12"

Coldest daily high: -20ºF

Coldest daily low: -42ºF

Number of subzero days: 5

Personal Weather Station on Wunderground: 

https://www.wunderground.com/personal-weather-station/dashboard?ID=KMTBOZEM152#history

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Just to add to this: The resulting low pressure also creates an area of decending air which helps to hold lower elevation overnight temps up compared to just a big dome of high pressure (rising air) which would allow the warm air to escape in the overnight hours more easily. This is a common occurrence in the foothill locations during the warm season but is more uncommon in the low elevations without a thermal trough. This is just another factor that can contribute to maximizing the airmass potential in the afternoon hours.

I think this is a little backward. The buoyancy associated with the surface heat is what creates the low surface pressures (rising air). Sinking air (subsidence) associated with high heights aloft support the surface heating.

 

The foothills stay sometimes freakishly warm at night during heatwaves due to their position at the bottom of the thermal belt. Surface temps recover thanks to decoupling here in the valleys, relatively speaking, while the thermal belt remains intact as recoveries are minimal starting around 950mb or so until heights fall/onshore flow increases.

My preferences can beat up your preferences’ dad.

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I think this is a little backward. The buoyancy associated with the surface heat is what creates the low surface pressures (rising air). Sinking air (subsidence) associated with high heights aloft support the surface heating.

 

The foothills stay sometimes freakishly warm at night during heatwaves due to their position at the bottom of the thermal belt. Surface temps recover thanks to decoupling here in the valleys, relatively speaking, while the thermal belt remains intact as recoveries are minimal starting around 950mb or so until heights fall/onshore flow increases.

 

You're totally right! I could on and on about what I meant to say or how it was a "typo" but the reality is I got the lifting action of lows and highs mixed up!  :wacko:

Cold Season 2023/24:

Total snowfall: 26"

Highest daily snowfall: 5"

Deepest snow depth: 12"

Coldest daily high: -20ºF

Coldest daily low: -42ºF

Number of subzero days: 5

Personal Weather Station on Wunderground: 

https://www.wunderground.com/personal-weather-station/dashboard?ID=KMTBOZEM152#history

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Thermal troughs don't create the heat, they're the result of it. Hot air rises, creating an area of surface low pressure which along the west coast resides generally east of the Cascades and coastal mountains of California throughout the warm season. With strong subsidence from upper level ridging, it can and will migrate west when the ridge axis orients itself along or just west of the coastline.

So that's the secret. Normally the upper ridging is east of us most of the summer.  What causes the ridge axis to usually shift to get the triple digit heat? 

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It gets hot when the thermal trough moves over the ocean and brings offshore flow to the coast. This article describes it well (if you can navigate through the advertisement attack unscathed).

 

http://komonews.com/weather/faq/what-is-the-dew-point-and-how-does-fog-form-12-26-2015

Your article links to dew point and fog which is (around here) a winter time occurrence.  Have we ever had fog in the valley in the summer?

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So that's the secret. Normally the upper ridging is east of us most of the summer. What causes the ridge axis to usually shift to get the triple digit heat?

That's just the waves of weather. A butterfly flaps its wings in North Korea and we get a heatwave out of it.

My preferences can beat up your preferences’ dad.

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