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December 2011 General Disc/Obs

Ellinwood

By Ellinwood,
in Mid Atlantic

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Ian

Ian

Posted
Posted

Flood watch, instead of Flood warning, for main-stem river flooding (Potomac River at Pt. of Rocks)? I don't recall this happening in the recent past, but I could be totally wrong... does anyone remember other instances?

looks like it's forecast to go up to just below flood stage

http://water.weather.gov/ahps2/hydrograph.php?wfo=lwx&gage=porm2&view=1,1,1,1,1,1,1,1

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Bob Chill

Bob Chill

Posted
Posted

Yet another morning where IAD goes into the icebox, DCA doesn't, and I overlook my green backyard and the frozen field at a lower elevation behind it. 34.0 for my low. Still one freeze and (not) counting this season.

You got a heck of a microclimate going on. I'm pretty surprised you didn't get into the upper 20's last night.

My street follows a stream valley. There is typically a 2-4 degree difference between mby and the elementary school and it is only half a mile away. When I walk the dog in the fall shortly after the sun goes down it's crazy feeling how erratic the initial cooldown is.

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H2O

H2O

Posted
Posted

Yet another morning where IAD goes into the icebox, DCA doesn't, and I overlook my green backyard and the frozen field at a lower elevation behind it. 34.0 for my low. Still one freeze and (not) counting this season.

I did hit 32 this morning but not confident it was right

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Ian

Ian

Posted
Posted

You trolling at tad????.

gfs has likes that 3 storm volley over a few days.. first two well northwest and third kinda crappy but potential for something. i guess 1/2" of snow is better than none? tongue.png of course you might be a weenie even looking that far out.

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usedtobe

usedtobe

Posted
Posted

Wes I dont believe the new GFS,however this basic pattern has been in place for close to 4 months since Irene..it has to break sometimes..even the cold snowy patterns change..last year,1977,ect..Can you remember a pattern of any kind lasting this long?

To me the low pressure over the lakes at both 850 and the surface suggests that the xmas day storm as it is modeled would probably be rain across dc despite the marginal 850 temps and thickness. That was the reason for the are you trolling comment. Yes, I can remember and Don

s stats suggest when the ao is over 4 Sd that the positive AO lasts for 40 days or so. Bob Chill's stats suggest that even when we get a negative ao this winter it might not be long lasting. My guess for a break in the pattern is in Jan. The GFS xmas storm really isn't much of a pattern change.

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KEITH L.I

KEITH L.I

Posted
Posted

To me the low pressure over the lakes at both 850 and the surface suggests that the xmas day storm as it is modeled would probably be rain across dc despite the marginal 850 temps and thickness. That was the reason for the are you trolling comment. Yes, I can remember and Don

s stats suggest when the ao is over 4 Sd that the positive AO lasts for 40 days or so. Bob Chill's stats suggest that even when we get a negative ao this winter it might not be long lasting. My guess for a break in the pattern is in Jan. The GFS xmas storm really isn't much of a pattern change.

AO has been positive since August along with NAO..only a few day dip at times..i mean you have to feel the rubberband will break at some occasion

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usedtobe

usedtobe

Posted
Posted

gfs has likes that 3 storm volley over a few days.. first two well northwest and third kinda crappy but potential for something. i guess 1/2" of snow is better than none? tongue.png of course you might be a weenie even looking that far out.

I don't see it as being much different than our last non storm. Really marginal looking with a really crummy surface and more importantly, 850 pattern. Light precipitation with soutwesterly 850 winds without a true arctic shot usually is not snow. Of course that far out the pattern is probably going to keep changing each run. .

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usedtobe

usedtobe

Posted
Posted

AO has been positive since August along with NAO..only a few day dip at times..i mean you have to feel the rubberband will break at some occasion

Did you look at Bob Chill's look at 12 Decembers in which the average NAO was strongly positive. Only one had a negative nao in Jan. while the stratospheric polar vortex has weakened slightly compared to climo it still is forecast to remain stronger than normal. Without a cause, I don't think there is such a thing as a rubber band effect. Maybe you get a monster storm to change the pattern by bringing a warm shot into the polar regions. I'm not saying the pattern won't change, for sure it will sometime. My gues is xmas is too early.

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mattie g

mattie g

Posted
Posted

Did you look at Bob Chill's look at 12 Decembers in which the average NAO was strongly positive. Only one had a negative nao in Jan. while the stratospheric polar vortex has weakened slightly compared to climo it still is forecast to remain stronger than normal. Without a cause, I don't think there is such a thing as a rubber band effect. Maybe you get a monster storm to change the pattern by bringing a warm shot into the polar regions. I'm not saying the pattern won't change, for sure it will sometime. My gues is xmas is too early.

I need average to above-average in the Southeast for Christmastime. Golf and fishing are calling me big time since we didn't head down to the in-laws' in SC at Thanksgiving.

That said, I can't help but feel the pattern "averages" itself out by mid-March. Could mean a week or two of real cold, but not necessarily with the chance of snow to go with it. I'm thinking a week of well-below temps and a couple fairly transient shots of cold during a period of otherwise average temps, probably in a six-week period starting in mid to late January. That may or may not result in overall below normal temps for, say, February.

Of course, I have nothing to back this up. Just a layman's view and a "hunch."

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Bob Chill

Bob Chill

Posted
Posted

Did you look at Bob Chill's look at 12 Decembers in which the average NAO was strongly positive. Only one had a negative nao in Jan. while the stratospheric polar vortex has weakened slightly compared to climo it still is forecast to remain stronger than normal. Without a cause, I don't think there is such a thing as a rubber band effect. Maybe you get a monster storm to change the pattern by bringing a warm shot into the polar regions. I'm not saying the pattern won't change, for sure it will sometime. My gues is xmas is too early.

I have a bunch of garbled notes jotted down and I'm too lazy to dig deep in but I have noticed a couple of things that stand out. Generally speaking, when a sustained ao/nao signal develops (one way or the other) in Nov-Dec it does break during the winter but the break appears to be short lived before going back to the previous pattern. I don't really count spring and summer months when looking at sustained strong + or - patterns. I have generally been looking at nov - dec in particular.

The NAO is much more volitile than the AO so usuing the Nov-Dec signal doesn't work out as well as the AO. It's very clear from a purely statistical standpoint that when there is a strong + or - AO index in the Nov-Dec timeframe (especially Dec), it's fairly uncommon for more than one month out of the following Jan-Mar timeframe to have the opposite index. Last year was one of those exceptions. AO was negative from August all the way through January and we all know what happened from Feb on last year.

Another thing I've been thinking that is more of a wag than anything else is that the AO was negative a heck of alot more than positive during the 2005 through Jan of 2011. The long term -AO cycle (that I really don't know that much about) could have potentially switched on us in Feb of last year. Don't have a clue if that is right but it sure feels like the possibility of a longer term +AO cycle has started or at least the longer term -AO has ended for the time being. Who knows?

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Bob Chill

Bob Chill

Posted
Posted

I pulled the list of -AO Decembers with a monthly of -1.0 or more. Here is the list:

1950, 1952, 1958, 1961, 1963, 1966, 1969, 1976, 1978, 1981, 1985, 1995, 1996, 2000, 2001, 2002, 2005, 2009, 2010

Of course Dec will obiviously be cold but the progression of the Dec - Feb timeframe supports my earlier post in the other thread with the opposite AO index:

December:

Following Jans:

Following Febs:

The monthlies of my +AO Decembers look the same way but opposite of course. There appears to be a decent correlation with the state of the index in Dec (when the signal is strong) and how it plays of the following couple of months. It takes time to break it down either way. The list of years is pretty long with -AO Decembers. Some of the analogs are crappy matches but as a whole I think there is something there worth thinking about.

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usedtobe

usedtobe

Posted
Posted

I pulled the list of -AO Decembers with a monthly of -1.0 or more. Here is the list:

1950, 1952, 1958, 1961, 1963, 1966, 1969, 1976, 1978, 1981, 1985, 1995, 1996, 2000, 2001, 2002, 2005, 2009, 2010

Of course Dec will obiviously be cold but the progression of the Dec - Feb timeframe supports my earlier post in the other thread with the opposite AO index:

December:

Following Jans:

Following Febs:

The monthlies of my +AO Decembers look the same way but opposite of course. There appears to be a decent correlation with the state of the index in Dec (when the signal is strong) and how it plays of the following couple of months. It takes time to break it down either way. The list of years is pretty long with -AO Decembers. Some of the analogs are crappy matches but as a whole I think there is something there worth thinking about.

I think that's also what don's stats showed. The strong negative ao will sometimes switch for a little while to positive before goign back to negative. That happened to the NAO for sure during a short stretch of Jan. It didn't last long as another ssw event occured that pushed us back into a negative ao and nao.

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Bob Chill

Bob Chill

Posted
Posted

I think that's also what don's stats showed. The strong negative ao will sometimes switch for a little while to positive before goign back to negative. That happened to the NAO for sure during a short stretch of Jan. It didn't last long as another ssw event occured that pushed us back into a negative ao and nao.

Which thread is Don's post in? I looked at the main forum and didn't see it but I didn't dig too deep either.

The only thing I have against subforums is that I find myself stuck ours and I miss too much good info. Expecially from HM, Don S, and the usual suspects.

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