Is SKEW-T still important to soaring pilots ?

[crosscou...@gmail.com]

Having used XC skies and now Topmeteo, I wonder what's the need to get the forecasted SKEW -T diagram to points along your task.
Will you as, a pilot, get any better prediction of soaring conditions if you use both ?
Dan

[Tony]

i still like to use the forecast skew-t to help estimate the trigger time and temperature. also helps get a good idea of how the cu will develop during the day. whether they will spread out and create overcast or thin out as the boundary layer lifts into dryer air aloft, or blow up into thunderstorms.

[Phil Chidekel]

Within the bounds of science, people can interpret a SKEW-T differently. I like that. I think it's easier to "fact check" a SKEW-T against actual observations, and discern whether a certain sounding is actually a reasonable interpretation of a slice of atmosphere for a specific day/situation.

Blipmaps and topmeteo are a computer's interpretation of a SKEW-T. I like to interpret it myself and compare it with the computer.

[JS]

It's fun to task "using the pretty colors" but perhaps easier to visualise wind shear at an inversion using SKEW-T, and if it'll be worth groveling in the inversion to get on top of it.
Jim

[John Cochrane]

Pretty maps tell you what is supposed to happen. Skew T tells you why -- and helps you to figure out why it's not happening.

For example a "top of lift" occasioned by a very shallow intersection of adiabatic parcel with the surrounding air is a very different forecast than one with a hard inversion.

Skew T shows the vertical profile of wind and direction.

Skew T shows you how close you are to things not in the graphical forecast. How close to OD/not OD? How close to cirrus formation?

John Cochrane

[BobW]

Succinctly stated.

I saw my first lapse rate diagram as a sketch on a napkin by my officemate
before I'd ever been to a glider field; its predictive power was immediately
apparent to me. (I still have it! And, I eventually learned the NWS had
something called a Skewed-T plot.) Perhaps that's why I still prefer to
generate my own daily forecasts from as primary data as is obtainable on any
given day (sometimes, eyeballs-only!).

Bob - a "Why?" kinda guy - W.

[Dave Springford]

and Skew-T is free, an important consideration for glider pilots :)

If you know how to interpret the Skew-T (or T-Phi) diagram then you can get all the information that the graphical forecasts provide and more. It just takes more effort and knowledge. (Which seems to be going the way predicted in Idiocracy.)

[Papa3]

Well... the SKEW-T logP is one of the most information rich diagrams one can find. If you know how to really "read" one, you can figure out lift strength, height, cloudbase, and winds from a single view at a glance. It takes me about 5 seconds to look at one to decide if it's a good day or not. That said, the modern interfaces in XCSkies, DrJack, etc. allow you to get a broader view of weather at a macro level including fantastic trend information. "North looks like it should have higher bases and more Cu than South" or "it's obvious that the models think the encroaching front shuts things down by late afternoon." HRRR is becoming incredibly useful for my forecasting as well.

So, the answer for me is "Yes, it's still very important." But since they are a point forecast, they aren't the only thing I look at.

[crosscou...@gmail.com]

Papa3, what is HRRR ???

[herbk...@gmail.com]

High Resolution Rapid Refresh
http://rapidrefresh.noaa.gov/HRRRncep/
Get ready to be overloaded with data.

[Don Johnstone]

At 13:35 01 March 2016, crosscou...@gmail.com wrote:
>Papa3, what is HRRR ???

High Resolution Rapid Refresh - A browser for viewing weather data
in a graphical form

>On Monday, February 29, 2016 at 8:33:35 PM UTC-5, Papa3
wrote:
>> Well... the SKEW-T logP is one of the most information rich
diagrams one

>=

>can find. If you know how to really "read" one, you can figure out
lift

>st=

>rength, height, cloudbase, and winds from a single view at a
glance. It

>ta=

>kes me about 5 seconds to look at one to decide if it's a good day
or not.

>=

> That said, the modern interfaces in XCSkies, DrJack, etc. allow
you to

>ge=

>t a broader view of weather at a macro level including fantastic
trend

>info=

>rmation. "North looks like it should have higher bases and more
Cu than

>S=

>outh" or "it's obvious that the models think the encroaching front
shuts

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>ings down by late afternoon." HRRR is becoming incredibly useful
for my

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>recasting as well. =20
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>> So, the answer for me is "Yes, it's still very important." But
since

>the=

[Papa3]

Not just a "browser" but a fundamentally different model. It's been exceptionally useful in task setting giving resolution down to very fine level. UI takes some getting used to, but you only care about a couple of values anyway.

http://ruc.noaa.gov/hrrr/

[son_of_flubber]

I've been using skew-T to get better at 'reading the sky'.

1)Look at sky. Imagine what skew-T should look like. Look at skew-T.

2)Look at Skew-T. Imagine what sky should look like. Look at sky.

Fun and fascinating.

[crosscou...@gmail.com]

A quick look shows a resolution of the whole USA...Will try to find finer resolution after work. Dan

[SF]

Yes, being able to read a Skew-T is still important
IF
you want to do a reasonably accurate job of Forecasting for cross country or competitive flights.
IF
all you want to do is fly around the airport, or decide to make instructional flights, looking at the pretty colors is good enough.
Why?
Well XC Skies only generates the pretty colors every three hours. That makes it pretty hard to predict the beginning, and end of the day with reasonable accuracy. Model Update times on the sites with pretty colors lag what's available directly from http://rucsoundings.noaa.gov/. If you make an early morning forecast on the east coast, update time is important, and having one available every hour is important if you want to know when to launch and when to land. Model selection...All the models are lying to you, too some degree. The question is which one of them is lying to you the least? The most reliable model for this air mass, today, may not be available on the sites with the pretty colors.
I have not tried Topmeteo, but plan on doing so this spring. If the only model it uses is the NAM, we may have problems with it on the east coast. On the day of the flight the NAM is not your usual best choice of weather model to look at. Its pretty much all you have looking three days out (along with the GFS), but it's not known to be all that accurate for this afternoon.

Looking at the pretty colors is better than doing nothing, combine that with a quick look at the satellites for clouds, and the mixing height, and winds on the NOAA tabular forecast, and you will have something reasonably OK.



SF

[JS]

HRRR
At the top is Domain: Full.
Choose your region there.
Jim

[crosscou...@gmail.com]

Looks very impressive indeed. What typical values do you use for your task setting ? Dan

On Tuesday, March 1, 2016 at 2:28:53 PM UTC-5, Papa3 wrote:

[Papa3]

Not comprehensive, but:

- Planetary Boundary Layer (PBL) height
- Total cloud cover
- Low level cloud cover
- Lifted condensation level (LCL)
- Winds (10M, 850MB)

In particular, the HRRR seems to do an excellent job of handling clouds, both convective and upper air. For instance, if you're worried about a forecast cirrus shield moving in (or out), I've found that the Total Cloud cover really helps develop that situational awareness. "Looks like the north area might get shut down later, let's task the fleet there early and get them back to the south before it starts shutting down". Also very useful to use the cloudbase calculations from XCSoar or DrJack. On ridge days provides detailed view of wind field.

P3

[JS]

P3, have you found Windyty or ye olde Nullschool useful on ridge days?
Jim

[Papa3]

WindyTy is very "pretty", and it gives a great synoptic view of winds and the associated system. In fact, the UI is probably as good/better than anything out there for wind depiction over time. But, it's limited by the fact that the underlying model is only the GFS. Hopefully Walt Rogers will chime in here, but if someone ever wanted to do a project to create the ultimate forecasting tool for gliding, I think it would include meso-scale visualizations (like WindyTy, Dr.Jack) with point-forecast SkewT and related parcel analysis across models (like Bufkit or Bill Moninger's parcel analysis tools) as a point-and-click drill down. The way I think about forecasting for gliding is:

- Big picture/synoptic. Do I even need to dig deeper (along the lines of Doc's Weather forecasting rock if you recall: Rock is wet - it's raining, Can't see rock - it's snowing, Rock is gone -it's windy). Once I know whether it's worthwhile then...

- Meso-scale visualizations. I use Dr. Jack (NAM), HRRR, etc. to get a more detailed picture (lift strength and heights, clouds/cloudbase,wind direction and strength which quadrants look better, etc.)

- Point analysis: If I'm serious about the day, I look at Bufkit or just use the Moninger (Rucsoundings) sight to see what the underlying SkewT looks like, often comparing models. That last bit is important, as we are seeing more and more days here in the east where the models (GFS, NAM, RAP, HRRR) are diverging in one or more critical parameter. So, being able to compare and check for consistency also help instill confidence in the forecast.

Long answer to a short question.

p3

[Papa3]

[Martin Gregorie]

On Thu, 03 Mar 2016 10:27:53 -0800, Papa3 wrote:

> Long answer to a short question.
>

This is about the best 'quick looks' tool I've used:

http://rasp.inn.leedsmet.ac.uk/RASPtableGM9/RASPtableGM.html

This is a viewer for the UK RASP and also shows Predicted SkewT*LogP
Sounding Charts. Both RASP parameter maps and Skew T charts can be
examined on an hourly basis during daylight for today and to following 5
days, but I think its based on GFS forecasts.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
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