Weathereze is getting as bad as leagleze to translate

flhrci

flhrci

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David
Take a look at today's convective outlook and the portion's I have highlighted. I cannot translate these parts. I am clueless as to what the heck they are saying.

David


Kansas City MO [SPC] convective outlook, prepared on the 19th at 11:55am EDT
(1555Z).
Day 1 convective outlook.
National Weather Service storm prediction center Norman Oklahoma.
6:55am EDT (1055Z) AM CDT {Saturday, satellite} April 19 4:08pm EDT (2008Z).
Valid the 19th at 12:30pm EDT (1630Z) - the 20th at 8:00am EDT (1200Z).
No severe thunderstorm areas forecast
.
Southeast
.
Cold upper low currently southern Illinois will track eastward across
Kentucky this.
Forecast period . dry slot rotating eastward across Tennessee valley to
{south, snow} of low.
Will aid in steepening lapse rates into central Appalachians and.
Inland portions of the mid Atlantic states this afternoon and.
Evening ..
Band of clouds / showers ahead of cold front now located from central.
Kentucky, southward into Georgia, will spread eastward ... moistening the
low levels Indiana, their.
Wake across the central Appalachians . air mass will then destabilize.
Ahead of upper low in Kentucky eastward to Appalachians during afternoon
{as, altostratus}.
Lapse rates steepen in the dry slot . while mid-level convective available
potential energy expected to.
Generally be at or below 500 J / KG given the limited moisture
40 - 50KT of.
Deep layer shear coupled with LOWERING freezing levels in advance of.
Upper low support thunderstorms by mid afternoon . a few storms.
Expected to reach to near severe levels with hail the primary threat.
Given mid level lapse rates in excess of 7C / KM and the LOWERING.
Freezing levels ..
Storms will likely evolve into more of a linear mode by this evening.
{as, altostratus} they spread east of the central Appalachians with a low
end wind.
Damage threat continuing ..
.. HALES / HURLBUT .. 04/19/2008.
 
500J per kg?! That's a definite No-Go!

(just kidding, I'm clueless on it)
 
CAPE (convective available potential energy) is a measure of instability. It is similar in purpose to the Lifted Index (LI) but a better measure because it looks at all heights of the atmosphere unlike LI which is a sample at one altitude I believe FL180.

While 500 J/KG suggests a fair amount of instability (especially where I live) most TS activity is above 1000.

Here is a map of CAPE values.

Remember basic weather, thunderstorms require and unstable atmosphere, moisture and a lifting action. CAPE is a good measure of stability.

Joe
 
Areeda said:
CAPE (convective available potential energy) is a measure of instability. It is similar in purpose to the Lifted Index (LI) but a better measure because it looks at all heights of the atmosphere unlike LI which is a sample at one altitude I believe FL180.

While 500 J/KG suggests a fair amount of instability (especially where I live) most TS activity is above 1000.

Here is a map of CAPE values.

Remember basic weather, thunderstorms require and unstable atmosphere, moisture and a lifting action. CAPE is a good measure of stability.

Joe
Click to expand...

Joe,

How did you learn this? In my PP, IR, COMM and now CFI training, I have never seen anything like it. I know of the lifted index and K index, and all the other stuff, but not this.

Thanks,

David
 
Buy Scott Dennenstaedt's $100 CD. It's really priceless. It should be embarassing to FAA. Really.

My Student blew the DPE away with his weather knowledge. The DPE asked me for some ground. :) :) One diagram with narration is worh a lot more than my description:

The CAPE, simply put is the area on a SkewT Log P between the Lifted Condensation Level of a surface parcel, when followed aloft along the line defining the wet lapse rate, till when the atmospheric temperature curve again intercepts said line. If the area is positive, e.g, as the parcel ascends at the saturated rate, and the atomspheric temperature is colder that dictated by the saturated lapse rate, the parcel will experience condensation and will give off latent heat of condensation, futher heating the column. If the integrated area is large, it'll really be a thunderboomer!
 
Last edited:
Okay, I give - where do I get Scott Dennenstaedt's $100 CD?

I admit to being less than weather savvy and am trying to cure that....
 
Thanks - and Scott, great article in IFR - I really enjoyed it, and agree with your statements about how little we know about Wx.

I live in the Chicago area and it consistently amazes me how dynamic our Wx is here, how different it can be north to south, and how dramatic the lake effect is. My home base, Waukegan, is a perfect example. Right by the lake, and always different than the other GA airports around the Class Bravo.
 
flhrci said:
How did you learn this? In my PP, IR, COMM and now CFI training, I have never seen anything like it. I know of the lifted index and K index, and all the other stuff, but not this.
Click to expand...
David - it was Scott's seminar and webinars. Like you I studied the FAA material and ended up with significant holes in my knowledge.

scottd said:
Better to say the LI is evaluated at 500 mb.
Click to expand...
Now you got me (again) isn't a pressure altitude of FL180 the same as 500 mb

scottd said:
BTW, the link Joe posted isn't "live" data...but a comparison from 2002.
Click to expand...
I usually use the data at http://http://twister.sbs.ohio-state.edu/severe/cape.html but it isn't available all the time, like right now. I searched aviation weather.gov and found that one. Thanks for letting me know not to use it.

scottd said:
(And he came to my two-day workshop, Under The Weather, where I beat him over the head with this stuff!)
Click to expand...
that's the real answer

scottd said:
Yes, the training that most pilots receive with respect to weather is poor at best. Sure, you know enough to pass the written and many DPEs know very little themselves - in fact many of my instrument students can run circles around the DPE's knowledge.
Click to expand...
The more I work on flight training the more I believe this is true for all of the knowledge areas at all levels of training. I'm not so sure it's a bad thing. Certainly you don't need a PhD in Meteorology, Aerodynamics and Aerospace Engineering plus a JD in Aviation Law to be a private pilot but it sure wouldn't hurt.

Joe
 
bbchien said:
The CAPE, simply put is the area on a SkewT Log P between the Lifted Condensation Level of a surface parcel, when followed aloft along the line defining the wet lapse rate, till when the atmospheric temperature curve again intercepts said line. If the area is positive, e.g, as the parcel ascends at the saturated rate, and the atomspheric temperature is colder that dictated by the saturated lapse rate, the parcel will experience condensation and will give off latent heat of condensation, futher heating the column. If the integrated area is large, it'll really be a thunderboomer!
Click to expand...

:):):):):)Alan Greenspan would be so proud!:):):):):)

Signed,
Still Cornfused
 
scottd said:
Joe,

On a standard day, 500 mb is actually a pressure altitude of 18,287 feet, not 18,000 feet (if I did my math correctly). If you adjust your altimeter to 29.92" Hg and fly at 18,000 feet on your altimeter, this doesn't mean that a barometer would measure exactly 500 mb on any given day.
Click to expand...
Thanks Scott, I get it now.

Joe
 
I have included a brief overview of the Skew-T diagram in both my private and advanced books, and I expect other authors to get on board (I've also included Scott's URL, which comes up just short of advertising...an ASA no-no). It is far too important a tool to be ignored simply because it is not on the written.

Bob Gardner
 
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