Skew T from better days.

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elyjs
Posts: 150
Joined: Mon May 09, 2011 5:24 pm
USHPA Rating: P2

Skew T from better days.

Postby elyjs » Wed Oct 22, 2014 9:42 pm

Every once in a while I will snag a screenshot of a good forecast before I fly. Here is an awesome late summer day. It will be May before we see anything like this again.

Image

http://xc.rmhpa.org/flight/878

scotts
Posts: 308
Joined: Wed Aug 28, 2013 9:15 pm
USHPA Rating: P4
Location: Mesa, AZ

Re: Skew T from better days.

Postby scotts » Thu Oct 23, 2014 9:30 am

"Inverted V" == good! They often mention it in the weather discussion as well. Here are a few link to an article explaining the skew-T with free flying in mind:

https://www.prolific.com/qwiki.cgi?mode ... E8M1H9M5QT

when you have extra time bored at work, rainy/snowy no fly days, spend some time reading more articles searching "paragliding skew-T", "hang fliding skew T", etc. If you find a good one, post it up for the rest of us too. It should eventually pay off for your flying, as Rick said last night at the meeting.

cheers!
Scott S.
P4; skywalk Chilli3S; Mesa, AZ of all places!
Get busy living!

Kiernan
Posts: 483
Joined: Tue Mar 29, 2005 4:40 pm
Location: Denver

Re: Skew T from better days.

Postby Kiernan » Fri Oct 24, 2014 5:04 pm

Inverted V sounding is not really so good. And I don't think this screenshot is of a real inverted V.

This from weatherprediction.com: "Named Inverted-V since the dewpoint depression decreases significantly with height
Most common in interior Western U.S. (especially interior Southwest U.S.)
Sounding has dry air (low RH) in lower troposphere with nearly saturated air (high RH) in middle troposphere
Convection tends to be high based since Convective Condensation Level is at a high elevation
Most common severe weather: Strong winds > 58 mph; this is due to negative buoyancy of evaporationally cooled air aloft that causes it to accelerate toward the surface
Gust fronts from inverted-V storms can have a large temperature gradient from one side to the other due to evaporative cooling
Hail and tornadoes are not common due to the dry boundary layer, high cloud base and unorganized wind shear"


The sounding shows dry air (low RH) low down but not "nearly saturated air" (high RH) higher up.
I think the inverted V is where the dewpoint line and temperature line actually meet, so it's a true inverted V shape. In this screenshot The dewpoint is pretty constant from surface to 700mb. The difference btwn. dewpoint and atmosphere temp. at 700 mb is about 12C, so the air isn't near saturated. Then dewpoint sort of follows the temperature curve. So I don't see any convective clouds developing. I think on a proper inverted V the dewpoint would follow the mixing ratio line until it meets the atmosphere temperature and stay close to the temp. line above the point where they meet.

On inverted V days at Lookout there have been strong gusty outflow winds from high base thunderstorms. Not something I'd look for when I want to fly. The screenshot on the other hand shows me a really nice day probably with lift up to 10K and east winds to the same level.

Scott, I like the link you posted on the skew-T. I'm still trying to figure it out so that I can actually use it every flying day.

scotts
Posts: 308
Joined: Wed Aug 28, 2013 9:15 pm
USHPA Rating: P4
Location: Mesa, AZ

Re: Skew T from better days.

Postby scotts » Fri Oct 24, 2014 5:38 pm

Hmmm... thanks for the correction and additional info!
Scott S.
P4; skywalk Chilli3S; Mesa, AZ of all places!
Get busy living!

scotts
Posts: 308
Joined: Wed Aug 28, 2013 9:15 pm
USHPA Rating: P4
Location: Mesa, AZ

Practical Use of Meteorological Models and Visualization Tools for Soaring Forecasts

Postby scotts » Tue Apr 12, 2016 7:40 am

Found this excellent presentation on skew-t, soundings, and modeling from a link on http://rucsoundings.noaa.gov

Practical Use of Meteorological Models and Visulization Tools for Soaring Forecasters Presentation by Walt Rogers at the 2016 Soaring Society of American National Convention (Greenville NC).
http://rucsoundings.noaa.gov/Greenville ... tation.pdf

Can we get Walt to give a talk at a future club meeting?
The more pilots we have looking at this stuff daily, the better. It really has almost all the info we need at one source. Its the second thing I look at every day I'm considering flying, the first being just the general forecast at weather.gov. Its also great when you are at some other site in a different state as you just punch in the closest airport code and since you are use to the format already, you can process it quickly to make your flying decisions.

There are some really great graphics in the referenced presentation which show how the thermal layer progresses throughout a typical day cycle as well.
Scott S.
P4; skywalk Chilli3S; Mesa, AZ of all places!
Get busy living!


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