Strange Skew-T sounding

Everskyward

Everskyward

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Everskyward
I was reading the thread about the inversion in Nebraska where Jesse posted the sounding. On a whim I got the local current sounding and it looks like this.

20120630-kag7j94rm3g9jksxmktj8tyb7s.png


How does that happen, with the dew point to the right (greater than) the temperature? Or is this an error?
 
My guess is there was a huge temp inversion and the air was super saturated at that level in the atmosphere. :dunno::dunno:
 
Definite depiction of where cloud base will be.
But I didn't think that dew point could ever get above the air temp, that's definitely 100% plus for moisture saturation.
 
The atmosphere is making that 110% effort . . .
 
Looks about right for the bases but not sure the dewpoint can exceed observed temp. Went up to 10,500 from BGD to FTG and the bases were well above me. Also had lots of virga between COS and DEN. It wasn't the normal tendrils of virga but more like puffy precip endings...
 
Jim Logajan said:
Supersaturated air. Check this link:

http://mrcc.isws.illinois.edu/resources_links/link_weatherfaq_other.htm#

Click on the "What is the difference between dew point ..." link.
Click to expand...
OK, thanks!

Here's another explanation.

Supersaturation
Supersaturation of more than 1-2% relative to water is rarely seen in the atmosphere.[5] For high levels of supersaturation there must be no condensation nuclei for the water vapor to condense on.

Supersaturation can also occur relative to ice. This is much more common in the atmosphere than supersaturation relative to water. Water droplets are able to maintain supersaturation relative to ice (remain as liquid water droplets and not freeze) because of the high surface tension of each microdroplet, which prevents them from expanding to form larger ice crystals. Without ice nuclei supercooled liquid water droplets can exist down to about −40 °C (−40 °F), at which point they will spontaneously freeze.
Click to expand...
My guess is that it would be this supersaturation relative to ice. I have known for a long time that this occurs but it never dawned on me what it would look like on one of these charts.
 
Everskyward said:
My guess is that it would be this supersaturation relative to ice. I have known for a long time that this occurs but it never dawned on me what it would look like on one of these charts.
Click to expand...

Why ice? I notice the graph shows a temperature of over 20 C at 20,000 ft. Also, there is quite a large jump in temperature at 15,000 ft. I'm not sure what to make of all that.

I wonder if the Colorado fires cause some unusual readings if the radiosonde passed through the smoke?
 
Jim Logajan said:
Why ice? I notice the graph shows a temperature of over 20 C at 20,000 ft. Also, there is quite a large jump in temperature at 15,000 ft. I'm not sure what to make of all that.
Click to expand...
Where do you see a temperature of 20 C at 20,000 ft? It looks to me more like -10 C.

Also, the jump at 15,000 ft is in the dew point (temp = thick red curve, dp = thick blue curve).
 
At 10,500 it was about 70 F degrees which isn't that far off from the prediction. The prediction also shows quite a temperature drop from 10 to 15,000. I wonder what the physics of that particular phenomena are?
 
azure said:
Where do you see a temperature of 20 C at 20,000 ft? It looks to me more like -10 C.

Also, the jump at 15,000 ft is in the dew point (temp = thick red curve, dp = thick blue curve).
Click to expand...

Oops! I made two errors - reversed the lines and used the wrong axis for temperature. I obviously misremembered how to read skew-t charts! :redface:
 
Jim Logajan said:
Oops! I made two errors - reversed the lines and used the wrong axis for temperature. I obviously misremembered how to read skew-t charts! :redface:
Click to expand...

There's a heck of a lot of info in a skew-t so it is easy to get confused. They are just model runs but maybe the model isn't too bad...
 
scottd said:
Nope. This is something that can occur in the RUC analysis, and is specifically caused by the cloud analysis in the model. This can happen while trying to conserve a parameter in the model called theta-v. The temperature is reduced and can "overshoot" the dewpoint, resulting in what appears to be supersaturation.
Click to expand...

Sounds like something is missing in the model - and there's never a good programmer around to put that "something" in when ya figger it out!
 
scottd said:
Nope. This is something that can occur in the RUC analysis, and is specifically caused by the cloud analysis in the model. This can happen while trying to conserve a parameter in the model called theta-v. The temperature is reduced and can "overshoot" the dewpoint, resulting in what appears to be supersaturation.
Click to expand...
Ok thanks!
 
scottd said:
Nope. This is something that can occur in the RUC analysis, and is specifically caused by the cloud analysis in the model. This can happen while trying to conserve a parameter in the model called theta-v. The temperature is reduced and can "overshoot" the dewpoint, resulting in what appears to be supersaturation.
Click to expand...

Thank you for the correction and explanation.

scottd said:
The Skew-T presented by the OP is from a model analysis, not from a rawinsonde observation.
Click to expand...

Is it a rawinsonde or radiosonde? I had learned the latter term decades ago, but have to admit first seeing rawinsonde only a few years ago. (First time I saw it I thought it was a typo.) I see the definition at Wikipedia seems to indicate the equipment on a balloon used for Skew-t observations probably makes them radiosondes rather than rawinsondes. However, I've come across incorrect information on Wikipedia technical articles a little more often than I think should be the case.
 
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