Mt Whitney Webcam
Mt Williamson Webcam
Feature Topics
Who's Online
0 registered (), 9 Guests and 54 Spiders online.
Key: Admin, Global Mod, Mod
Forum Stats
3270 Members
13 Forums
5344 Topics
49604 Posts

Max Online: 382 @ 11/07/12 05:45 AM
Topic Options
#42919 - 06/04/15 02:08 PM How accurate is Mountain Forecast?
Ernest Offline


Registered: 05/19/15
Posts: 20
Loc: Los Angeles, CA
I'm curious as to how accurate the forecasts are for this particular website? I've been seeing weather reports one day forecasting up to 11 inches of rain and then I check back the next day and it's less than an inch.

I'm just curious as to how they receive their data and information because at this point it just seems more like a site to get hikers more anxious than they need to be.

Thanks!

Top
#42920 - 06/04/15 02:13 PM Re: How accurate is Mountain Forecast? [Re: Ernest]
Harvey Lankford Offline


Registered: 11/10/09
Posts: 989
Loc: Richmond, Virginia

In the few days we were there the weather had been neither hot, cloudless, nor settled, and though we were assured by the residents - as one always is - that such conditions had never been known before, the fact remained that they existed then.

Famous British explorer and dry-wit author HW (Bill) Tilman,
Two Mountains and a River, in
HW Tilman. The Seven Mountain-Travel Books, p. 555

Top
#42924 - 06/04/15 02:46 PM Re: How accurate is Mountain Forecast? [Re: Ernest]
Snacking Bear Offline


Registered: 08/09/11
Posts: 448
Loc: Saugus, CA
I've found them to be the best reports with the most reasonable accuracy of any other source.

Weather is subject to radical shifts. The closer meteorologists get to a given date, the better able they are to make a better prediction.

You might be complaining far more (and subject to dire circumstance) if they forecast 2 in. of rain and 20% chance of showers two weeks out, and you end up getting 8 in. of rain on the day.

As a hiker/mountaineer you should hope for the best and prepare for the worst. I can certainly identify with your frustration, but weather forecasts have little to do with the anxiety of the spectator, and much more with conservative estimations in the name of safety.
_________________________
@jjoshuagregory (Twitter & Instagram) for landscape and mountain photo spamming...

Top
#42925 - 06/04/15 03:12 PM Re: How accurate is Mountain Forecast? [Re: Ernest]
Bob West Offline


Registered: 11/13/09
Posts: 780
Loc: Bishop, CA, USA
The NOAA website will probably give a "reasonably accurate" forecast, leaving wiggle room for local variations. Case in point: the forecast given yesterday for the Eastern Sierra, from NOAA, changed somewhat after a few hours of computer assisted deliberation.

In the USAF, we called our met guys "weather guessers". A retired Air Force met man friend of mine is often skeptical of some forecasters, who might have a hidden agenda...like bringing the skiers to mountain X in hopes of Big Snow. He calls those forecasts "ravings of a diseased mind". LOL.

The moral of the story is one needs to be ready for whatever the mountains give us in terms of weather.




Edited by Bob West (06/04/15 03:15 PM)

Top
#42927 - 06/04/15 03:45 PM Re: How accurate is Mountain Forecast? [Re: Snacking Bear]
Ernest Offline


Registered: 05/19/15
Posts: 20
Loc: Los Angeles, CA
Thank you so much for the replies. I totally agree with your statement that it is better to be over-prepared than being blindsided by the unpredictable weather on Whitney. And I was not at all frustrated, just unsure of how to prepare for the upcoming trip to the mountain due to the variation in weather forecasts.

It makes sense due to its location and other circumstances, that there are many variables which would come into play when making these forecasts. I was just a bit shocked that the variations itself would swing wildly from one prediction to another. Time will tell of course and I will be patiently waiting until the day approaches.

Top
#42928 - 06/04/15 03:59 PM Re: How accurate is Mountain Forecast? [Re: Ernest]
+ @ti2d Offline


Registered: 10/22/09
Posts: 805
Loc: Oh Cursed, USA
Originally Posted By: Ernest
I'm curious as to how accurate the forecasts are for this particular website? I've been seeing weather reports one day forecasting up to 11 inches of rain and then I check back the next day and it's less than an inch.

I'm just curious as to how they receive their data and information because at this point it just seems more like a site to get hikers more anxious than they need to be.

Thanks!


Since when is a forecast accurate? whistle
_________________________
Have fun and enjoy the Gr8 Yd Opn.

Top
#42933 - 06/04/15 10:02 PM Re: How accurate is Mountain Forecast? [Re: Ernest]
SierraNevada Offline


Registered: 09/05/11
Posts: 1100
Loc: NorCal
If you're talking about mountain-forecast.com I think they're pretty good for detailed info on mountain peaks. From what I gather, they combine regional computer forecast models with historic data and local sensor information on the peaks they forecast for. I use them a lot in the winter for backcountry and frontcountry resorts. I've found them to be useful for getting a sense of temperature variation with elevation, when an inversion layer might be happening (warming high on the mountain), the freezing elevation etc. They post precise numbers, but everyone should realize there's a range of error associated with any forecast. NOAA's pinpoint map algorithm seems to be pretty much interpolation for elevation and a few other geographic effects with a lot less detail than the mountain-forecast.com.

These forecasts all struggle when the computer models diverge, which often happens when a storm is approaching or moving out or generally unsettled conditions. For a good technical discussion of Eastern Sierra computer models, trends, and forecasts, try Howard Sheckter in Mammoth. He doesn't post every day, but he gives you a big picture sense of what's being predicted and why. He's usually really good about picking up monsoonal trends and other Eastern Sierra local effects that you should be aware of before heading out.

Personally, I try to poll several different sources that use different models. Watch out for forecasts that just regurgitate the NWS - the consistency might impress you, but its really the same source. A good forecaster will interpret and discuss the variation in computer models and which ones do the best under the circumstances.

Top
#42938 - 06/04/15 11:42 PM Re: How accurate is Mountain Forecast? [Re: SierraNevada]
Steve C Offline


Registered: 09/22/09
Posts: 7235
Loc: Fresno, CA
I wrote this in another thread on 6/1, and since it has come up again...

Quote:
Regarding Mountain-forecast, every time a storm on Whitney is predicted, if you check the amount of snow predicted, they exaggerate the amount. For example, they are predicting 4 inches for this coming weekend; in contrast, the NOAA site calls for "A chance of snow showers." ...let's wait and see what actually comes in.

I haven't been keeping exact figures, but I am pretty sure if we kept track of the total predicted snows on Whitney over a year's time, it would add up to many feet.

Checking today, M-F called for 3.9" of snow. Checking the web cam for the day, NOTHING fell.
Personally, I don't give them much credence.

Top
#42965 - 06/05/15 07:15 PM Re: How accurate is Mountain Forecast? [Re: Steve C]
SierraNevada Offline


Registered: 09/05/11
Posts: 1100
Loc: NorCal
Steve, I respectfully disagree with your take on mountain-forecasts, although I've not followed them closely for Whitney. I've mainly used mountain-forecast in the winter time in NorCal and I've been happy with their info. I can't speak for the other 11,200 mountains they forecast, but I've found them to be worth including in my forecast information, together with avalanche reports, NOAA, accuweather, weatherunderground, Howard Sheckter, and even local TV news. There is no single forecast site that is always the best on all occasions.

I suspect that the highly precise reporting of mountain-forecast tends to make people confuse precision with accuracy. The reader needs to consider the precise numbers to be in the center of a range of accuracy. When you look at it that way, predicting 3.9" is not all that different than "snow showers." How many inches is a "shower" and is there a practical impact to me if its 2" or 3.9" ? Not really, I can deal 2" or 3.9" the same. By looking at multiple forecasts (from other computer models) one can get a sense of what that range might be around the 3.9," and a sense of what probability it has. In fact, it's just fine if a site is consistently overpredicting or underpredicting, a consistent bias is very helpful on its own. Just include that bias in your assessment together with the other sources.

Top
#42984 - 06/07/15 10:27 AM Re: How accurate is Mountain Forecast? [Re: SierraNevada]
wbtravis Offline


Registered: 09/22/09
Posts: 1239
Loc: Corner of Jack Benny and Roche...
NOAA works good enough. If you are looking for perfection, good luck searching for it.

I take forecasts for the Sierra with a liberal gain of salt. I have seen forecasts blow up too many times.

I take clothing for the lowest temperature I expect to see, both day hike and backpack plus rain gear. I have never had a surprise...including single digits twice on summit of Mt. Whitney in the summer.

What most do not plan for, which plan for all the time is wind. I have worn my shell pants to the summit two or three times during the summer.

Top
#42987 - 06/07/15 10:55 AM Re: How accurate is Mountain Forecast? [Re: wbtravis]
SierraNevada Offline


Registered: 09/05/11
Posts: 1100
Loc: NorCal
WB, I think you nailed the practicality of weather forecasts for the typical hiking season in the Sierra. Most people pay more attention heading into winter snow than trail hiking in August, so I believe forecasts should be more than a "grain a salt" sometimes. I'm a bit of a geek, researching the forecast from an atmospheric level (Howard Sheckter) down to precise freezing elevation levels (mountain-forecast) with NOAA, Accuweather and usual suspects in the middle. As always, hike your own hike.

If mountain-forecast is consistently over-predicting snow on a particular mountain, as some have indicated, than that's useful information for estimating the "worse case" in comparison with other sources. Mountain-forecast is pushing the science by taking point-forecasting to a new level, but I wouldn't throw them out with the bathwater. Here's their disclaimer:

"While this information may be indispensable in planning your ascent, please treat it critically and verify against other sources. Our weather algorithms are thoroughly tested and proven to work well for thousands of mountain ski resorts and surf breaks; however, the database of mountain locations may contain errors at this early stage. Please send your feedback it will be crucial for ironing out bugs and expanding the forecast coverage."


Edited by SierraNevada (06/07/15 11:02 AM)

Top
#42997 - 06/08/15 06:04 AM Re: How accurate is Mountain Forecast? [Re: SierraNevada]
Sierra Angler Offline


Registered: 05/10/13
Posts: 72
Loc: Lake Tahoe California
I use up to 10 weather forecast sites and the Windfinder for eyes ahead. As a Guide in the Sierras for 2 decades , this is the ONLY data we have to estimate the conditions for the trips . They interpret the raw NOAA DATA and then YOU interpret that condensed milk and Make Up your Idea( we say yogurt). The forecasts Have Been Off somewhat rather Badly as of late ( the last two Years) . Plan for the WORST and Enjoy what you GET , because that is it for that time .We Complain to the weather or God . The humans are a best guess Race , and they invented TP less than a Hundred Years ago...... before that it was a SPONGE on a STICK you dip in water , use then rinse ,dry, store. Don't get carried away with data or best Guess . Remember YOU are responsible for YOUR decisions , not Oprah . Cheers and stay SAFE Every One !! gst

Top
#43047 - 06/10/15 07:18 AM Re: How accurate is Mountain Forecast? [Re: Sierra Angler]
wbtravis Offline


Registered: 09/22/09
Posts: 1239
Loc: Corner of Jack Benny and Roche...
Responsible for your decisions...what a novel concept, especially in the mountains and this mountain in particular.

Top