Clear Sky Clocks - Forecast Accuracy (Humidity)

Clear Sky Clocks (CSC) has recently added a number of items to the
forecast, including wind, temperature and humidity.

The forecast of Saturday morning, 12/11, for Saturday night, predicted
humidity levels of 90 to 100 percent for much of Northern California,
including Fiddletown. In fact, humidity was much lower there; I spent
the night at Fiddletown and no dew appeared - not on my car windshield,
not on my table or on my charts, which were open all night.

I had noticed that the Weather Underground forecast
(ww.wunderground.com) called for humidity in the 60 percent range.

I wonder if anyone else has had a change to note the accuracy (or lack
of) of CSC's humidity forecast. Pl4ease post if you have.
Clear skies,
Shneor Sherman

Blue Canyon was forecasted by CSC to be a bust but my husband and a small
group of brave souls went up on Saturday, slogged through the snow and had
an AWESOME night of viewing. I think the CSC is a cool idea and Attila is a
cool guy for doing it but sometimes the CSC is off. Of course, it's a bit
like predicting the weather is it not? ;-)

Dawn Baird-Chleborad
www.astronerds.com


"shneor" wrote in message
oups.com...
I wonder if anyone else has had a change to note the accuracy (or lack
of) of CSC's humidity forecast. Pl4ease post if you have.
Clear skies,
Shneor Sherman

On 13 Dec 2004 07:28:03 -0800, "shneor" wrote:

I wonder if anyone else has had a change to note the accuracy (or lack
of) of CSC's humidity forecast. Pl4ease post if you have.

The forecast for my location bears no relation to reality. In fact, the current
values are wrong. It is quite common for values in the 70-90% range to be given
when the actual humidity is 30%. I've only seen the humidity go over 50% a few
times in the last decade; anytime I see a report that puts it over 35%, I'm
suspicious. Barring occasional fog, that just doesn't happen here. The model is
obviously failing to take something into consideration, perhaps the altitude.
You only have to go about 20 miles from here to get much wetter air.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

What was the configuration of the land you were observing from? At the
bottom of a hill you could be walking through a cloud created from the dew
and up top of that hill your equipment could be dry as a bone. That's
exaggerating a bit but you get the idea.

When observing I have a digital clock with temperature and a separate
humidity gauge. I'll write down all three figures for the start and end of
each observing session. Most of the time the clear sky clock still has the
last nights forecast displayed the next morning and these figures could be
compared to that to give you a better idea of it's accuracy. Of course
looking out the window will always be the best thing you can do.
--
I'd love to grab one of those digitized full weather stations and keep daily
recordings,
Michael A. Barlow

"shneor" wrote in message
oups.com...
Clear Sky Clocks (CSC) has recently added a number of items to the
forecast, including wind, temperature and humidity.

The forecast of Saturday morning, 12/11, for Saturday night, predicted
humidity levels of 90 to 100 percent for much of Northern California,
including Fiddletown. In fact, humidity was much lower there; I spent
the night at Fiddletown and no dew appeared - not on my car windshield,
not on my table or on my charts, which were open all night.

I had noticed that the Weather Underground forecast
(ww.wunderground.com) called for humidity in the 60 percent range.

I wonder if anyone else has had a change to note the accuracy (or lack
of) of CSC's humidity forecast. Pl4ease post if you have.
Clear skies,
Shneor Sherman

That's a very interesting observation. CSC claims accuracy to a 10-mile
diameter area. I have found CSC's seeing and cloudiness forecases to be
reasonably accurate most of the time, and the transparency forecast
correct at least half the time. In this case, the transparency forecast
was way off, too, as tranaparency was much better than the CSC
forecast. I wonder if there's a connection between the two (humidity
and transparency)?

Clear skies,
Shneor Sherman

Neither does it here as well. Also, their light pollution map must be
either 50 miles off or estimated with unreal equations. Where I live I can
look up and, when it is around, see M33 without optical aid. The "seven
sisters" is visible with 14 stars, and my eyes are not worth a hoot.

DustyDSOsometimes


"Chris L Peterson" wrote in message
...
On 13 Dec 2004 07:28:03 -0800, "shneor" wrote:

I wonder if anyone else has had a change to note the accuracy (or lack
of) of CSC's humidity forecast. Pl4ease post if you have.

The forecast for my location bears no relation to reality. In fact, the
current
values are wrong. It is quite common for values in the 70-90% range to be
given
when the actual humidity is 30%. I've only seen the humidity go over 50% a
few
times in the last decade; anytime I see a report that puts it over 35%,
I'm
suspicious. Barring occasional fog, that just doesn't happen here. The
model is
obviously failing to take something into consideration, perhaps the
altitude.
You only have to go about 20 miles from here to get much wetter air.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

On 13 Dec 2004 08:14:16 -0800, "shneor" wrote:

That's a very interesting observation. CSC claims accuracy to a 10-mile
diameter area. I have found CSC's seeing and cloudiness forecases to be
reasonably accurate most of the time, and the transparency forecast
correct at least half the time. In this case, the transparency forecast
was way off, too, as tranaparency was much better than the CSC
forecast. I wonder if there's a connection between the two (humidity
and transparency)?

I also find their other forecasts to be very accurate, certainly spot on well
over half the time.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

Maybe Attilla should get some feedback. This is a new feature for CSC.
I'll send him a note when I get a chance.

Shneor Sherman

"Dusty" wrote in message
...

Where I live I can look up and, when it is around, see M33 without
optical aid.

I hate you.

The "seven sisters" is visible with 14 stars, and

I hate you even more.............................

...............



































Only kidding :-)



G


Only A Gentleman Can Insult Me And A True Gentleman Never Will

I checked with Attilla, who forwarded my comments on to Allan Rahill,
who responded in some detail.
He said that there are problems for the Western US and British Columbia
mainly due to topography and the resolution limits of the weather
model. The model's resolution is 10 miles, so valleys are lower than
the model thinks, and mountains are higher. That's why the humidity
forecasts are not as accurate as we would like. As humidity affects
transparency, the transparency forecast is also less accurate that we
would like to see it. Allan is trying to tweak the model to see if
forecast accuracy will improve without causing other problems.

Attilla asked that forecast discrepancies be send to him (via his web
site, I assume, at cleardarksky.com).

Clear skies,
Shneor Sherman