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gb
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Joined: 01 Jul 2010
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gb
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 Wed Mar 20, 2019 2:31 pm |
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| rossb wrote: | | You seem more concerned with trying to find inconsistencies with what I've been saying, as opposed to actually understanding my claim. Meanwhile, you keep making things up, and twisting around what I say. I keep rephrasing it, and you keep returning to the same straw men (e. g. snow forecasts, which have nothing to do with anything I've said). |
Of course the snow forecasts, and models and forecasters missing have everything to do with your claim that "short term forecasts" are 95% accurate. It is entirely situational and more reliable in summer. But, I can give another specific example: On August 3rd last year I did a late start for a trip to Glacier Peak to wait for the University of Washington MM5 and updated forecaster discussions to come out mid-morning. I was concerned about thunderstorms and smoke. The MM5 forecast just a couple of tiny areas of possible rainfall (T to.01") in the Cascades for August 4th, which matched the Discussion of a "slight chance of isolated thunderstorms". The smoke was more problematic and was at best a guess as no models went out to August 5th. August 3rd was mostly fair and warm, but not hot. On August 4th, I moved my camp up to 6500' after noticing that towering cumulonimbus clouds had not developed by 2:42PM, and in fact cumulus clouds seemed to be lessening. However, at 5:50pm a large thunderstorm rolled by with heavy rain about 4 miles away and the edge of towering cumulus just about above me. The broad storm covered at least twenty miles and passed by obliquely by about 6:30PM. However, a few cumulus begin to build to my SSE (bad direction given the wind) at about the same time, and by 7:19PM rain begin to spatter down and I retreated to the tent. For three hours there was an intense thunderstorm above me with strikes to 2000' and about 1-1/2" of rain until it broke around 10:30PM. Clearly the MM5 model and the Discussion based on it and other models missed by a mile. There were thunderstorms (complexes) with heavy rain and numerous strikes in all quadrants. 95%, no, short term forecast, yes.
| Quote: | | It is fairly simple. I can't always tell what the weather will be like, but quite often I can. Not 100% -- no one is perfect -- but around 95%. This is because I tend to focus on short term forecasts, and the discussion that surrounds them. Again, that does not mean I can always tell what the weather will be like. There are times when the weather is too unpredictable. But this shows up in the forecast discussions. So don't expect me to make a forecast every single day. But what I'm saying is that if I make a forecast, it is highly likely that it will be right. (Highly likely means 95% or better). |
The question about your 95% accuracy is what in doubt; that really has nothing to do with whether you choose to make a forecast or not. Summer in fair weather can certainly be 95% accurate. But, is also situational, which is my point. It didn't work on Glacier Peak with a nearby Cut-Off Low, and I mentioned it didn't work for me several times in January and to the forecasters chagrin with 2 out of 3 possible lowland snowstorm events in February.
| Quote: | | But I have no confidence in the least that you -- or anyone else for that matter -- is very good at making forecasts like the original one made in this post. You claimed that you knew what the weather was going to be like two weeks out. You had such extraordinary confidence that you posted it on this blog. This was not an "it might", but an "it will" forecast. Otherwise, why make it? Why come on the blog and say something like that, unless you have a lot of confidence. So either you simply didn't read the discussion about the long term forecasts (wherever that was), or you are putting way too much faith in them. Of course the long term forecasts are bound to be on target sometimes. They may even be better than simply flipping a coin. But you have given no evidence to support your case that you are capable of making those long term predictions with any reliability. In fact, you stumbled upon the opposite. You could have made a prediction at any time, and the one time you chose, it was a complete failure. |
I said "it appears likely that".....not that I knew. I posted it not because of absolute confidence or I would not have used the words "it appears likely that". Clearly, I posted it (as I stated) because it was a very topical subject. That appears to have completely escaped you.
But, in your paragraph you intentionally ignore the fact that the March 7 forecast through March 22nd was, as it turns out, accurate within 1-2C pretty much every day of the forecast save March 12th. Remember 4) above:
| Quote: | | 4) Long term, which you have now decided, to be 14 days, are of course, not generally reliable - but this depends on what you mean by reliable (as I said in my post), and it depends on the synopsis and dynamics in play. I gave two examples in my last post (which you chose to ignore) that on March 8th 2019 (and even before), the GFS model has proven very reliable for the forecast through March 19th, missed a week trough (still uncertain effects) on March 20th, but still shows reasonable accuracy March 21st and 22nd (ridge dominated, at times dirty). Overall, that is pretty dam good. I also gave you an explicit example in my last post of planning my trip to Colorado beginning September 15, 2018 for which I started studying about two weeks before. My last view of the model forecasts was September 14, 2018 and it was accurate (save for a weak trough that was 150 miles further south than forecast on September 24th, but was otherwise accurate to September 27th, including wind forecasts for smoke. That is again pretty dam good. So, the accuracy of long term forecasts - greater than 7 days or really 4-5 days is far more nuanced and is purely situational. Sometimes it is possible to have reasonable reliability and sometimes it is not. For instance, right now, I wouldn't bet a lick on a forecast (even crude) beyond March 22nd. In general, it will be cooler than present and may trend cooler until late in the month, and may be pretty wet or pretty dry, depending. It is too complex for accurate forecasting because of the positioning and shape of the trough and the tendency for higher pressure east. |
| Quote: | | You also haven't answered my question about long term forecasts. How often do you think you can nail a long term forecast? 9 out of 10? 6 out of 10? |
Pointless point. See the above paragraph and look for the bold. As to right now, I will make the bold statement that Washington may be a bit above average, or could yet be cool mostly through April 5th, but I don't have a clue how wet. But that it would appear all but Southern California may get significant rains.
Well, look at that, not surprisingly, the CPC has similar conclusions but with very low confidence.
https://www.cpc.ncep.noaa.gov/products/predictions/610day/fxus06.html
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