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Mostly Cloudy

Started by dvferyance, November 26, 2018, 06:18:04 PM

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dvferyance

What drives me nuts with weather forecasters this is something I can never understand. Why do they use the term mostly cloudy for a day when the skies are completely 100% overcast? Most is not the same thing as all. Why don't they ever use the term completely cloudy ever? That would be more accurate. When I think I most I think of around 75-80% not 100%.


SSOWorld

Not mostly cloudy, partly sunny.
Scott O.

Not all who wander are lost...
Ah, the open skies, wind at my back, warm sun on my... wait, where the hell am I?!
As a matter of fact, I do own the road.
Raise your what?

Wisconsin - out-multiplexing your state since 1918.

formulanone

Weatherman-speak for "you might glance upon a tiny spot in the sky at 3:44pm that's blue, but it will be gone in a moment or two"

But I can't help thinking of this:


jeffandnicole

Quote from: dvferyance on November 26, 2018, 06:18:04 PM
What drives me nuts with weather forecasters this is something I can never understand. Why do they use the term mostly cloudy for a day when the skies are completely 100% overcast? Most is not the same thing as all. Why don't they ever use the term completely cloudy ever? That would be more accurate. When I think I most I think of around 75-80% not 100%.

Because weather forecasts are looking at a wide region, or a very specific location.  If the majority of the area will be cloudy but some breaks in the clouds elsewhere within the general region, or if they use a specific location such as the airport where the clouds break up on occasion, it gets the forecast 'Mostly Cloudy'.

I know there's certain percentages of viewable sky that equates to Mostly Sunny, Partly Sunny, Partly Cloudy, Mostly Cloudy, Fair, etc, but forget where I saw that.

And, I mentioned on the other thread that the forecasters are often wrong.  Your comment is another reason why I continue to agree with that statement. It's not as disasterous as calling for rain and getting a snowstorm instead, but they were still wrong.

frankenroad

This thread reminds me of the time that my father-in-law, who lived in the Berkshires of Western Massachusetts, called us one October Saturday to inform us that he had just shoveled 6 inches of "partly cloudy" off of his driveway!
2di's clinched: 44, 66, 68, 71, 72, 74, 78, 83, 84(east), 86(east), 88(east), 96

Highways I've lived on M-43, M-185, US-127

kphoger

I've seen plenty of forecasts that simply say "cloudy" with no qualifier.
Keep right except to pass.  Yes.  You.
Visit scenic Orleans County, NY!
Male pronouns, please.

Quote from: Philip K. DickIf you can control the meaning of words, you can control the people who must use them.

Scott5114

My current NWS forecast is "Overcast", for that matter.
uncontrollable freak sardine salad chef

Pink Jazz


As far as METARs go:

       
  • SKC - Clear or Sunny
  • CLR - Clear below 12000 feet (used for automated stations)
  • FEW - Mostly Clear or Mostly Sunny
  • SCT - Partly Cloudy or Partly Sunny
  • BKN - Mostly Cloudy
  • OVC - Cloudy or Overcast
Also, the term "Fair" typically corresponds to cloud cover of FEW or less.

wxfree

99% is "mostly" cloudy.  "Most" means more than half but not the whole thing.  There's also the issue of area.  A television forecaster is trying to describe conditions across an area.  A mostly cloudy day may be completely cloudy where you are while a place 20 miles away may be mostly cloudy for most of the day and mostly clear for a few hours.  There's no good way to describe conditions as they change through the day across a large area with a single term.  "Variable cloudiness" would be correct, but not very informative.

NWS issues forecasts in grids.  Around here, the grids are squares about 1.3 miles wide.  I would assume that's a uniform size they use everywhere, but they might be different if they're based on a fraction of a degree of longitude.  This small size makes the forecast simpler.  Still, "mostly cloudy" would be correct if it's cloudy all day except for a few breaks for a few minutes.  I don't know what the standard is for rounding up to "cloudy" but I do know that small breaks can't be predicted very well.  The sky cover forecast is in percentages for hourly periods.  I don't know if they call 99% "cloudy."

If you go to your local forecast page on the NWS web site, there's a link to a graphical hourly forecast that shows the exact percentage of sky cover, and precise numbers for other elements, tailored to your location.  If go to the the main graphical forecast page (it uses a map and not a graph, but I suppose they consider the map to be a graphic feature), you can select an element and see the exact number for that element for each grid point for a selected hour.  In addition to the precision, it's neat to see things like cold spots and warm spots.

https://digital.weather.gov/

I've never viewed the site on a small device.  If you view it on a computer, you it will show you the numerical value for each grid point you move the mouse to.
I'd like to buy a vowel, Alex.  What is E?

Hurricane Rex

If I had to come up with a system:
Cloud cover:
1-25%: Mostly sunny
26-50%: Partly cloudy
50-75%: partly sunny
76-99%: mostly cloudy.

LG-TP260

ODOT, raise the speed limit and fix our traffic problems.

Road and weather geek for life.

Running till I die.

Pink Jazz

Quote from: Hurricane Rex on January 13, 2019, 08:35:11 PM
If I had to come up with a system:
Cloud cover:
1-25%: Mostly sunny
26-50%: Partly cloudy
50-75%: partly sunny
76-99%: mostly cloudy.

LG-TP260

This won't work because of nighttime conditions.  Partly cloudy and partly sunny are the same according to NWS to accommodate nighttime conditions, with partly sunny being exclusive to daytime and partly cloudy usable either during daytime or nighttime.

froggie

(jumping in late)

Quote from: Pink Jazz on December 02, 2018, 02:59:29 PM

As far as METARs go:

       
  • SKC - Clear or Sunny
  • CLR - Clear below 12000 feet (used for automated stations)
  • FEW - Mostly Clear or Mostly Sunny
  • SCT - Partly Cloudy or Partly Sunny
  • BKN - Mostly Cloudy
  • OVC - Cloudy or Overcast
Also, the term "Fair" typically corresponds to cloud cover of FEW or less.

Partly Sunny refers more to BKN where your total sky cover is 5/8 - 6/8.

Hurricane Rex



Quote from: Pink Jazz on January 14, 2019, 11:08:20 AM
Quote from: Hurricane Rex on January 13, 2019, 08:35:11 PM
If I had to come up with a system:
Cloud cover:
1-25%: Mostly sunny
26-50%: Partly cloudy
50-75%: partly sunny
76-99%: mostly cloudy.

uaeless crap tapatalk has put in.

This won't work because of nighttime conditions.  Partly cloudy and partly sunny are the same according to NWS to accommodate nighttime conditions, with partly sunny being exclusive to daytime and partly cloudy usable either during daytime or nighttime.

Ok then, partly/mostly clear during the nighttime. I do want to say that I assumed when I put sunny in, people would know that this is a daytime scale and you'd adjust for nighttime.

LG-TP260

ODOT, raise the speed limit and fix our traffic problems.

Road and weather geek for life.

Running till I die.

kphoger

I think there should be a "partly moony".
Keep right except to pass.  Yes.  You.
Visit scenic Orleans County, NY!
Male pronouns, please.

Quote from: Philip K. DickIf you can control the meaning of words, you can control the people who must use them.

ET21

Quote from: kphoger on January 14, 2019, 02:04:15 PM
I think there should be a "partly moony".

Chance of moon 40%
The local weatherman, trust me I can be 99.9% right!
"Show where you're going, without forgetting where you're from"

Clinched:
IL: I-88, I-180, I-190, I-290, I-294, I-355, IL-390
IN: I-80, I-94
SD: I-190
WI: I-90, I-94
MI: I-94, I-196
MN: I-90

Hurricane Rex

Quote from: ET21 on January 14, 2019, 02:53:24 PM
Quote from: kphoger on January 14, 2019, 02:04:15 PM
I think there should be a "partly moony".

Chance of moon 40%
If its totally clear, but its a new moon, then its a contradiction (chance od moon 0%).

LG-TP260

ODOT, raise the speed limit and fix our traffic problems.

Road and weather geek for life.

Running till I die.

US 89

Quote from: Hurricane Rex on January 14, 2019, 03:20:34 PM
Quote from: ET21 on January 14, 2019, 02:53:24 PM
Quote from: kphoger on January 14, 2019, 02:04:15 PM
I think there should be a "partly moony".
Chance of moon 40%
If its totally clear, but its a new moon, then its a contradiction (chance od moon 0%).

And with no clouds and a first quarter moon, the chance of moon is 50%.

SSOWorld

Mostly Cloudy == "Threat" of sun outside.
Scott O.

Not all who wander are lost...
Ah, the open skies, wind at my back, warm sun on my... wait, where the hell am I?!
As a matter of fact, I do own the road.
Raise your what?

Wisconsin - out-multiplexing your state since 1918.

kphoger

Quote from: US 89 on January 14, 2019, 03:58:03 PM
And with no clouds and a first quarter moon, the chance of moon is 50%.

Huh?  The chance of moon would still be 100%, right?
Keep right except to pass.  Yes.  You.
Visit scenic Orleans County, NY!
Male pronouns, please.

Quote from: Philip K. DickIf you can control the meaning of words, you can control the people who must use them.

hotdogPi

Quote from: kphoger on January 15, 2019, 01:33:20 PM
Quote from: US 89 on January 14, 2019, 03:58:03 PM
And with no clouds and a first quarter moon, the chance of moon is 50%.

Huh?  The chance of moon would still be 100%, right?

It will be above the horizon for only half of the night. If the percentage is averaged over the entire night, it is 50%.
Clinched, minus I-93 (I'm missing a few miles and my file is incorrect)

Traveled, plus US 13, 44, and 50, and several state routes

I will be in Burlington VT for the eclipse.

kphoger

Quote from: 1 on January 15, 2019, 03:03:30 PM
Quote from: kphoger on January 15, 2019, 01:33:20 PM
Quote from: US 89 on January 14, 2019, 03:58:03 PM
And with no clouds and a first quarter moon, the chance of moon is 50%.

Huh?  The chance of moon would still be 100%, right?

It will be above the horizon for only half of the night. If the percentage is averaged over the entire night, it is 50%.

So, there's a 100% chance that the moon will be out during the night.

100% chance of rain doesn't mean it will rain 100% of the time.
Keep right except to pass.  Yes.  You.
Visit scenic Orleans County, NY!
Male pronouns, please.

Quote from: Philip K. DickIf you can control the meaning of words, you can control the people who must use them.

02 Park Ave

On my local NWS Weather Radio station, KIH28, here in South Jersey, I never hear the condition described as "sunny" any more.  Now it is characterized as being "fair" even with a cloudless sky.  I do hear "partly sunny" however.
C-o-H

Pink Jazz

#22
Quote from: froggie on January 14, 2019, 11:14:13 AM
(jumping in late)

Quote from: Pink Jazz on December 02, 2018, 02:59:29 PM

As far as METARs go:

       
  • SKC - Clear or Sunny
  • CLR - Clear below 12000 feet (used for automated stations)
  • FEW - Mostly Clear or Mostly Sunny
  • SCT - Partly Cloudy or Partly Sunny
  • BKN - Mostly Cloudy
  • OVC - Cloudy or Overcast
Also, the term "Fair" typically corresponds to cloud cover of FEW or less.

Partly Sunny refers more to BKN where your total sky cover is 5/8 - 6/8.



These are the official NWS definitions and according to the NWS Partly Sunny and Partly Cloudy are the same except Partly Cloudy can be used at night or day.

Quote from: 02 Park Ave on January 15, 2019, 04:51:14 PM
On my local NWS Weather Radio station, KIH28, here in South Jersey, I never hear the condition described as "sunny" any more.  Now it is characterized as being "fair" even with a cloudless sky.  I do hear "partly sunny" however.

Your station is probably an automated station which can only measure up to 12000 feet.  When no clouds are below 12000 feet the METAR will report CLR which means the sky is clear below 12000 feet.  "Fair" often covers the METAR sky cover reports of CLR and FEW.  Manual stations on the other hand are based on visual observation and on a cloudless sky the METAR will report SKC ("sky clear") which will be translated as Sunny or Clear.  When you hear Partly Sunny, the METAR is reporting SCT during the daytime.



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