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November 2011 Obs/Forecasting Discussion


WxUSAF

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I'm not a big believer in Nov patterns being a precursor to winter but I really don't like the high pressure parked in the goa pretty much through the entire run of the GFS (euro supports this too). We really don't want to see that during djf. Zwts made a great post about the pdo in another thread. Since we pretty much need a +PNA during a nina to get the ns vorts to take a favorable track, any high parked in the goa is going to deny that. If we have to rely on blocking this winter then it could be a frustrating one.

I'm in no way saying I think the prog -pna through the first half of the month is a big deal but it is also don't like a persistent high in the goa and a -pna setting up.

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I'm not a big believer in Nov patterns being a precursor to winter but I really don't like the high pressure parked in the goa pretty much through the entire run of the GFS (euro supports this too). We really don't want to see that during djf. Zwts made a great post about the pdo in another thread. Since we pretty much need a +PNA during a nina to get the ns vorts to take a favorable track, any high parked in the goa is going to deny that. If we have to rely on blocking this winter then it could be a frustrating one.

I'm in no way saying I think the prog -pna through the first half of the month is a big deal but it is also don't like a persistent high in the goa and a -pna setting up.

come on Bob, there's no reason to let weather patterns get in the way of our snow this winter :arrowhead:

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Just about the worst case -nao scenario we can have. No biggie though. Just posting to remind myself that looking at one index doesn't tell the story.

actually, I sorta like that map

I believe Stormchaser Chuck did a study a few years back that showed a -NAO in OCT is bad, but a -NAO in NOV is good for NAO state of the coming winter

I could see a few storms trying to attack that High Pressure in the winter which would mean wintry storms

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At least the -AO/-NAO combo will be in place whenever that cold air is ready to be released into the eastern U.S. Just gotta weaken the -PNA/+EPO combo and it'll be cold blast city.

Exactly. I wasn't posting to be negative about things. Just showing what a crappy -nao looks like. It's best to get the persistent -pna/+epo pattern out of the way before our real window of opportunity starts.

Do you think the transition will happen gradually or flip kinda quick? I evision a gradual change during late Nov and then potentially some pretty cold stuff locked in during early Dec.

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Exactly. I wasn't posting to be negative about things. Just showing what a crappy -nao looks like. It's best to get the persistent -pna/+epo pattern out of the way before our real window of opportunity starts.

Do you think the transition will happen gradually or flip kinda quick? I evision a gradual change during late Nov and then potentially some pretty cold stuff locked in during early Dec.

When this cold air comes in it likes to come in as a "quick" blast... say on the order of 2 days transitioning from above normal to well below normal. What happens in situations like this is the cold arctic air gets "bottled up" in western Canada, then a huge high pressure will come along and carry the cold through the central and eastern US.

Last year we had a fairly tumultuous period in late November before the PNA flipped to the positive phase and locked in the cold starting December 2nd.

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When this cold air comes in it likes to come in as a "quick" blast... say on the order of 2 days transitioning from above normal to well below normal. What happens in situations like this is the cold arctic air gets "bottled up" in western Canada, then a huge high pressure will come along and carry the cold through the central and eastern US.

Last year we had a fairly tumultuous period in late November before the PNA flipped to the positive phase and locked in the cold starting December 2nd.

Makes complete sense. The -pna will start to relax later this month and we'll probably go progressive for a bit. Hopefully after that the ridge w trough e sets up and the spokes of re-inforcing cold shots start to spin through. Then, on Dec 5th, a ns vort digs around the base and tracks just south of RIC and off the VA beach coast as it explodes and we're in perfect alignment for the deform band...........lol

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12z GFS backs off the idea of the big -NAO ridge, but also backs off on the persistent deep -PNA. Net result is a run that would bring temps that probably average to about seasonable over the next 2 weeks.

Ensemble mean is still in favor of the -NAO and -PNA with associated SE ridge.

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A very dry start for November so far IMBY. Going on 10 days with very little precip. A few showers midweek and it's dry again for a while.

6z Gfs is a complete disaster.71 on thanksgiving day. Awful start to winter. Not ready to cancel yet but

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The CPC analogs for D+11 have 1955 as one of their analogs for the upcoming pattern. The analogs don't take into account the enso state and only use the 500 h pattern, The years given were with the yearly snowfall at DCA were

1973-1974 16.7

1970-1971 11.7

1955-1956 11.3

1994-1995 10.1

2003-2004 12.4

1988-1989 5.7

All the years had 2 centered mean periods showing up except the 1988 and 1994 years.

http://www.cpc.ncep.noaa.gov/products/predictions/short_range/tools/gifs/500hgt_comp_sup814.gif

I've always like somewhere in the 12-16 inch range for snow for DC this year. Now I'd probably amend it to 10-16. For the CWG game I picked 14.2 which I think probably will be too high. Still the analog years were not complete disasters, even 1955-1956 which I think had two big New England snows.

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The CPC analogs for D+11 have 1955 as one of their analogs for the upcoming pattern. The analogs don't take into account the enso state and only use the 500 h pattern, The years given were with the yearly snowfall at DCA were

1973-1974 16.7

1970-1971 11.7

1955-1956 11.3

1994-1995 10.1

2003-2004 12.4

1988-1989 5.7

All the years had 2 centered mean periods showing up except the 1988 and 1994 years.

http://www.cpc.ncep....comp_sup814.gif

I've always like somewhere in the 12-16 inch range for snow for DC this year. Now I'd probably amend it to 10-16. For the CWG game I picked 14.2 which I think probably will be too high. Still the analog years were not complete disasters, even 1955-1956 which I think had two big New England snows.

Wes, I'm sure those words will bring comfort to JI

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I'll say this much, I never did like snow in OCT around here

looking back at all the years Baltimore reported a trace or more snow in OCT, snowfall during the winters was decidedly sub-par with only a couple decently AN

we'll see; maybe a road trip year

Edit: oh yeah, I forgot to mention that 10/72 was a year that reported a trace of snow

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I'll say this much, I never did like snow in OCT around here

looking back at all the years Baltimore reported a trace or more snow in OCT, snowfall during the winters was decidedly sub-par with only a couple decently AN

we'll see; maybe a road trip year

Edit: oh yeah, I forgot to mention that 10/72 was a year that reported a trace of snow

Am I sensing a downtick in optimism???

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Wes, I'm sure those words will bring comfort to JI

LOL, Ji is already almost ready to tip over the edge already. the analogs don't take into account the enso state so they really don't have much skill at providing a prediction for the winter. I do think 1955-1956 has enough similarities to probably give it some weight for those who like analogs.

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The presence of the SE ridge for now leaves me sanguine. I love this kind of fall November weather, and if it sticks around the entire month, that's cool.

I don't disagree with respect to the sensible weather, but I would prefer that the month was wet vs. dry because I believe (fwiw) that wet NOVs more often than not precede decent winters

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