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November 2011 Obs/Forecasting Discussion


WxUSAF

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if the computer progs through the end of the month come close to being right with qpf, driest as in 01/02 and 07/08 look to be out, and that's a good sign

Are you suggesting that there is a correlation between a dry November and a lack of winter snow in DC? The driest November (1981) was followed by 22.5 inches of snow in 1981-1982, and the second driest (1965) was followed by 28.4 inches in 1965-1966.

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Are you suggesting that there is a correlation between a dry November and a lack of winter snow in DC? The driest November (1981) was followed by 22.5 inches of snow in 1981-1982, and the second driest (1965) was followed by 28.4 inches in 1965-1966.

I have not studied any relationships of patterns between seasons, but intuitively it would seem that a warm autumn would increase the odds of a cold winter, as a dry autumn would increase the odds of a wet winter. I know that in the large data set available there are probably analogs found to support any claim, but how about a statistical analysis of the odds of such occurring?

Personally, I'm relieved to see this warm weather in Nov, as I think it gives us a better chance of colder-than-normal conditions to follow in D/J. I know that we were quite cool in Oct (-2.2F) and that had me worried.

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Are you suggesting that there is a correlation between a dry November and a lack of winter snow in DC? The driest November (1981) was followed by 22.5 inches of snow in 1981-1982, and the second driest (1965) was followed by 28.4 inches in 1965-1966.

I believe the examples you gave are exceptions to a general rule that dry NOV do not bode well for the winter

I recall checking on it in the past, but I can't say there have been any studies

obviously, it does not always correlate, but it certainly did in 01/02 and 07/08

I would also note that our general winter weather (all things considered) has changed quite a bit since 1965 and 1981 and the recent years I mentioned likely carry more weight as being more in line with current patterns

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There is an incredibly weak negative correlation (R2 = 0.0037) between Fall DCA precip and Winter DCA precip (wetter Fall = drier Winter), but it is basically a shotgun blast graph that isn't even worth posting.

I don't dispute your numbers, but I'm just talking the month of NOV which I assume include other months of fall

plus, maybe I should have mentioned that I am talking snow and cold vs. precip in general

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12z GFS ensemble mean actually looks like it's going in a good direction late in the run. Yeah, it's still fantasy-land time, but weakens the Gulf of Alaska trough dramatically, keeps a -NAO, shows some weak troughing over us and hints of ridging out west.

I'm kinda glad you posted this because I was looking at the run and thinking the same thing. I know it's fantasy land but it does break down the -pna around day 9 or so and then moves things along in a semi decent pattern. It at least opens the door for the possibility of a decent pattern in early Dec. I hope future runs keep breaking down the disgusting epo / pna combo in the same general timeframe and not just pushing it later and later.

The one saving grace of the atrocious PAC is that it's stuck in a stable crappy pattern in Nov and not Dec. Losing 6 weeks of a 12 week window would keep the weenie suicide hotline ringing off the hook.

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I'm kinda glad you posted this because I was looking at the run and thinking the same thing. I know it's fantasy land but it does break down the -pna around day 9 or so and then moves things along in a semi decent pattern. It at least opens the door for the possibility of a decent pattern in early Dec. I hope future runs keep breaking down the disgusting epo / pna combo in the same general timeframe and not just pushing it later and later.

The one saving grace of the atrocious PAC is that it's stuck in a stable crappy pattern in Nov and not Dec. Losing 6 weeks of a 12 week window would keep the weenie suicide hotline ringing off the hook.

If support starts from run to run showing this then I will buy it but until then it is still, to me, doing the delayed but not denied right now. We need a flip point to fix itself more or less.

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12z NAM and GFS support some flakes (that won't accumulate) in the air for the DC region tomorrow... it'll be light rates, but freezing level is plenty low enough (around 950mb or lower) for flakes to reach the surface despite the warm-ish surface temps:

post-96-0-15936300-1321475797.png

post-96-0-77054800-1321475808.png

Keep in mind that the soundings are for 1pm tomorrow.

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Numbers ripped from the LWX climo site. Simple November precip vs seasonal snowfall at DCA.

Thanks for the effort! Have you ever found any good previous/following correlations? For example, previous month's precipitation/following season snowfall, previous season's precipitation/following season snowfall, previous month's temperature/following season snowfall, previous season's temperature/following season snowfall, previous month's precipitation/following season temperature, previous month's temperature/following season temperature, etc.

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Looks like the rain dried all up around the hood....I'm stuck up in Philly this week but will be in Princeton tomorrow...maybe I see some flakes up there...maybe not...ugh I miss my pillow

Lots of leaves waiting for you to be raked up. Have fun in Ivy league town Princeton.

.43 in the guage here since midnight.

49* here now

LWX: Head to the highest points to see any snow in the mountains

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Anybody see a better look from the longer range? Seems to be improving to me. Also, the EC has a couple of interesting tidbits around day 7 to 10 time frame. It's so hard to get an idea from it because of the data that's available. But, it seems to me, that it is also starting to take on a more interesting look, along with its ens. mean. Thoughts pros?

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Anybody see a better look from the longer range? Seems to be improving to me. Also, the EC has a couple of interesting tidbits around day 7 to 10 time frame. It's so hard to get an idea from it because of the data that's available. But, it seems to me, that it is also starting to take on a more interesting look, along with its ens. mean. Thoughts pros?

The 192 hr storm on last night's Euro has no support on the ensembles so I wouldn't give it much credence. Just look at the ensemble mean from last night's euro or at the GEFS ensembles. They look nothing like the operational. It does look like we will a trasnitory cold shot but basically, the Pacific still needs to improve. By 336 hrs, the ensemble mean does show some ridging in western Canada which would be an improvement but it you look at the ensembles at that time range they are all over the place. The mjo is forecast to be in some of the warmer looking phases at that time so I'm not sure I'd yet buy the somewhat colder look though as I posted yesterday, I do think there will be a transitory cold shot.

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Both the euro and gfs break down the -pna around hr 192. They look pretty similar @ 500 around the 192-240 timeframe. The euro looks really tasty but there's no sense in taking it seriously. Either way, it's really nice to see ridging out west and consensus starting to build.

AO doesn't look to go negative anytime soon so real cold air isn't likely before Dec.

EDIT: Adding the pna forcast from cpc. Me likely.

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Both the euro and gfs break down the -pna around hr 192. They look pretty similar @ 500 around the 192-240 timeframe. The euro looks really tasty but there's no sense in taking it seriously. Either way, it's really nice to see ridging out west and consensus starting to build.

AO doesn't look to go negative anytime soon so real cold air isn't likely before Dec.

That's an important point. While the NCEP ensemble do show a negative NAO index, it look more like an artifact of how it's measured that a true block with a high over Greenland into iceland and a low to the south. Plus the AO forecasts at 14 days are a little more robust than the NAo forecast. The models are still showing a positive EPO in the longer time ranges but its magnitude drops quite a bit towards the end of the period.

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