Base of cumulous clouds

midlifeflyer

midlifeflyer

Touchdown! Greaser!
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Mini rant first thing in the morning…

On FB, I just came across a post linking a King Schools video with Martha going through the Temp - Dewpoint / 4.4 x 1000 calculation to estimate the cloud base.

Really?

Completely useless and ridiculous except for the knowledge test which, for some inconceivable reason, still uses °F when all reported weather uses °C.

Modern tools and reported bases aside, can you imagine getting a METAR or AWOS, converting both of those number to °F, then doing the subtraction, and then dividing by 4.4? How many errors will that introduce compared with taking the spread in °C and dividing by 2.4 (or for that matter 2.5)?

I guess it’s time for coffee.
 
midlifeflyer said:
Completely useless and ridiculous except for the knowledge test which, for some inconceivable reason, still uses °F when all reported weather uses °C
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And that's why King teaches it. They do also go over it for Celsius. But they're trying to get you to pass the knowledge test. And if they were able to get my dumb ass a 95, it clearly works.
 
midlifeflyer said:
Mini rant first thing in the morning…

On FB, I just came across a post linking a King Schools video with Martha going through the Temp - Dewpoint / 4.4 x 1000 calculation to estimate the cloud base.

Really?

Completely useless and ridiculous except for the knowledge test which, for some inconceivable reason, still uses °F when all reported weather uses °C.

Modern tools and reported bases aside, can you imagine getting a METAR or AWOS, converting both of those number to °F, then doing the subtraction, and then dividing by 4.4? How many errors will that introduce compared with taking the spread in °C and dividing by 2.4 (or for that matter 2.5)?

I guess it’s time for coffee.
Click to expand...
Get yo handy E6B out and the conversions are easy.
 
midlifeflyer said:
Mini rant first thing in the morning…

On FB, I just came across a post linking a King Schools video with Martha going through the Temp - Dewpoint / 4.4 x 1000 calculation to estimate the cloud base.

Really?

Completely useless and ridiculous except for the knowledge test which, for some inconceivable reason, still uses °F when all reported weather uses °C.

Modern tools and reported bases aside, can you imagine getting a METAR or AWOS, converting both of those number to °F, then doing the subtraction, and then dividing by 4.4? How many errors will that introduce compared with taking the spread in °C and dividing by 2.4 (or for that matter 2.5)?

I guess it’s time for coffee.
Click to expand...

Soooo, your issue is F vs C?
 
midlifeflyer said:
Mini rant first thing in the morning…

On FB, I just came across a post linking a King Schools video with Martha going through the Temp - Dewpoint / 4.4 x 1000 calculation to estimate the cloud base.

Really?

Completely useless and ridiculous except for the knowledge test which, for some inconceivable reason, still uses °F when all reported weather uses °C.

Modern tools and reported bases aside, can you imagine getting a METAR or AWOS, converting both of those number to °F, then doing the subtraction, and then dividing by 4.4? How many errors will that introduce compared with taking the spread in °C and dividing by 2.4 (or for that matter 2.5)?

I guess it’s time for coffee.
Click to expand...
That question is in there for the FSS specialists who do weather observations.
 
If you have the metar, you're not computing bases, you have them. The only time that formula might be useful is when you don't have any weather, and I'd argue that the American brain is much more wired to understand temperature in F than in C. Either way, I don't think I've ever used that formula outside the written test. Perhaps it was more useful in the days before the internet and tablet computers.

I do use the lapse rate to estimate what altitude I'll need to fly to get to a comfortable temperature in the summer... in which case F is again more useful to my lazy American brain.
 
Jim K said:
If you have the metar, you're not computing bases, you have them. The only time that formula might be useful is when you don't have any weather, and I'd argue that the American brain is much more wired to understand temperature in F than in C. Either way, I don't think I've ever used that formula outside the written test. Perhaps it was more useful in the days before the internet and tablet computers.

I do use the lapse rate to estimate what altitude I'll need to fly to get to a comfortable temperature in the summer... in which case F is again more useful to my lazy American brain.
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LOL.

The "lazy American brain" can barely do math at all, let alone
°F = (°C * 9/5) + 32​
twice (even with a calculator; have you seen those easy order of operation quizzes 85% of the people get wrong?) in addition to the subtraction. division, and multiplication to get to the exact same result in feet.

You don't even need to "understand "Celsius (which is kind of scary since all of our aviation weather is in Celsius). Just do much simpler arithmetic.
 
midlifeflyer said:
Modern tools and reported bases aside, can you imagine getting a METAR or AWOS, converting both of those number to °F, then doing the subtraction, and then dividing by 4.4?
Click to expand...
Yes, because Celsius (properly, Centigrade) means nothing to me, so I've already converted it.
How many errors will that introduce compared with taking the spread in °C and dividing by 2.4 (or for that matter 2.5)?
Click to expand...
You'll likely gasp when you find out I convert the temp by multiplying by 2 and adding 30.

How much precision do you need when estimating cloud base? I don't need much.
 
C -> F and F -> is pretty easy to do in your head. Or just remember every 5C gets you an even integer degrees F and interpolate from there.
 
Lindberg said:
25°C is one quarter of the boiling temperature of water. Is that hot or cold? Beats me.
Click to expand...
depends if you think about 80°F is hot or cold.

So... when you are on the ground and the METAR or AWOS reports "temperature 30 dewpoint 20," even after all these years of hearing that, you really don't know whether it's hot or cold outside if you are in the air-conditioned FBO without Siri telling you? I can't do inches/feet/yards/miles to meters to save my life (drives me nuts when we watch tennis tournaments in other countries), but I know whether its hot or cold outside in either system

I know we are insane in this country about our metriphobia, but we really have no idea what standard meteorological reports have been telling us for decades?

Sorry I started this thread.
 
midlifeflyer said:
So... when you are on the ground and the METAR or AWOS reports "temperature 30 dewpoint 20," even after all these years of hearing that, you really don't know whether it's hot or cold outside if you are in the air-conditioned FBO without Siri telling you?
Click to expand...
I don't have a siri, but I know that 90° (30*2+30) is moderately hot.
And I noticed you converted 25 to 80, not 77, the actual value. So you agree that precision isn't important and nothing valuable is lost in quick conversions?
 
Lindberg said:
I don't have a siri, but I know that 90° (30*2+30) is moderately hot.
And I noticed you converted 25 to 80, not 77, the actual value. So you agree that precision isn't important and nothing valuable is lost in quick conversions?
Click to expand...
In his defense he said about 80. 77 (along with 78,79,81, 82) is about 80. If someone asks me what's it supposed to get to today, I'm gonna say about 80 (even though the forecast said 82)
 
Rockymountain said:
Yeah if we just all went with Kelvin we wouldn’t have that uncomfortable overlap between F and C where -40 in one is -40 in the other and they start diverging the other way. ;-)
Click to expand...

Most people don’t consider the overlap uncomfortable, they consider the temperature uncomfortable.

What they don’t know is that at -40 it’s a dry cold, so it doesn’t feel nearly as cold. (Say that in Phoenix and watch people’s eyes cross.)
 
Lindberg said:
I don't have a siri, but I know that 90° (30*2+30) is moderately hot.
And I noticed you converted 25 to 80, not 77, the actual value. So you agree that precision isn't important and nothing valuable is lost in quick conversions?
Click to expand...
Absolutely agree that quick conversions don't require precision to know whether it's cold or hot outside. I use the same C X2+30 as you when I want a ball park. Heck, if you can feel the 3 degree between 77 and 80, kudos to you.

OTOH, if I am going to go through the bother of calculating something (like those test questions), why would I bother to take introduce a potential error by including an unnecessary conversion formula when calculating with the raw data is actually easier?

Unless, of course I found "30-20 = " to be easier or more difficult depending on nothing more than the letters next to it.
 
I was in Norway doing military training, sitting in a snow cave one night. Had to go outside to pee. Asked my buddy how cold it was. Minus 40. F or C, I asked? Doesn't matter, he said. Blew my mind.
 

Seems absurd we’re still dealing with this issue. Carter was right. We should have switched in the ‘70s.
  • Mission: Mars Climate Orbiter
  • Agency: NASA
  • Launch Date: December 11, 1998
  • Failure Date: September 23, 1999
  • Cause of failure: A software error caused by one team using imperial units (pound-seconds) for force data, while another team expected metric units (newton-seconds).

I was making good progress in switching, as a personal challenge, but then I bought the Bushcat, which like all LSAs, is calibrated in mph. So I do t/d calcs & charting in sm, just to avoid conversion errors (minor as the may be at 90 mph). Although I could never get comfortable with meters instead of feet.
 
Tampa set a heat record on Monday. First time it has hit 100 in recorded history. Usually that is impossible because there is so much humidity. An unusually dry high pressure system made it possible.

Oddly, I was at my hangar changing my oil, and felt it was the most comfortable day of the summer.
 
Ed Haywood said:
Tampa set a heat record on Monday. First time it has hit 100 in recorded history. Usually that is impossible because there is so much humidity. An unusually dry high pressure system made it possible.

Oddly, I was at my hangar changing my oil, and felt it was the most comfortable day of the summer.
Click to expand...
That's funny.... yesterday, we had the hottest day of the year yet I was minimally sweating when preflighting/putting my plane back in the hangar. I figured that the RH must have been a bit lower than a few days prior...where I lost half of my plasma volume doing the same process. (well, I might be exaggerating a little ;) )
 
Here in south Texas it was 67* at 7am today. That broke a record low for the date set in 1946. Nearby hill country areas were even cooler with temps in the 50s.
 
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