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Pattern February Discussion Part II
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Brick Tamland
Guest
We have seen that movie a lot. Wonder if this is the same thing.
GeorgiaGirl
Member
The GFS tends to do a good job at picking up if whether a storm will appear, so we'll see if this is right. What the bigger worry is though with this one is if wave #2 is too sheared out and just disappears. Right now the trough is too far east for it to redevelop itself and that could go back west as we get closer.
My guess is if the GFS is right all along with there being a wave #2, is the most likely best case is a late bloomer off the southeast coast.
My guess is if the GFS is right all along with there being a wave #2, is the most likely best case is a late bloomer off the southeast coast.
pcbjr
Member
that looks like a very good possibility - just where is the cold (??) - just a minor concern at this point in time
pcbjr
Member
the GFS?5 out 6 GFS runs have been a hit here and we are only six days out. What could go wrong ?
When I look at these models I interpret them on experience. Relying on my experience, taking my experience at face value, not a computer to arrive at perfection.
That's what I mean by you can't let the model to all the work cause if you do, you maybe wrong. When trying to figure something out, you find things that you have experience from and predict of what can happen from your experience.
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That's what I mean by you can't let the model to all the work cause if you do, you maybe wrong. When trying to figure something out, you find things that you have experience from and predict of what can happen from your experience.
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pcbjr
Member
Information, experience and plain ol' southern common sense - sometimes not always in that order
The science is fun and not at all to be dismissed, but when you get right down to it, mostly it's "how well can I do the jig saw"
There are really 2 big things to watch the first is show sheared and elongated does the shortwave in the NW become. The GFS has trended toward a much more sheared wave which is in line with the CMC and Euro, The second is how much if any separating is there between the shortwave as its over the PNW and the closed low off of the pacific coast. You must establish ridging in between the system and allow the shortwave over the NW to start digging south and west early. If they are too close you get a flatter ridge initially and the ridge axis gets pushed farther east like the latest GFS runs and you get a flat wave until its in the atlantic.
bouncycorn
Meteorologist
It's just like the old timers before computers when they were trying to come up with the first forecast. They didn't know what to go by, but as they started to obverse things they started to build their experience taking what they observed, building their prediction for the next forecast. As their experience built, they relied on their experience.
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BillyMurrayWx
Member
So you're thinking this could be a big deal like 1993?
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You are really going to want the ridge axis to be running up the rocky mountains toward the chimney of Idaho around 0-6z Friday to have a good chance and to be really picky that system in the NW needs to be closed and a couple hundred miles offshore.
pcbjr
Member
SD - Very good, if you don't mind me saying so.
Can I expand (before dinner gets home - so I'll be quick)?
Seems to me that every year there is one major driver.
Don't have time to go back and nail down specific years, but a few years ago (maybe 5 or 6) the AO and NAO were really negative, and they drove a good winter; sometime recently (2 or 3 years ago maybe?) the PNA was so positive it drove a good winter. There was one winter a while back that the WPO seemed to control in a good way.
This year, despite alignment of many other stars - the EPO seems to be dominating - for the worse.
Point being - if this even makes sense - we need to learn to look at all the players on the field and every year, earlier than later, try to figure out which is the "quarterback" (and admittedly, I'm the worst at wish-casting on an index or two sometimes). Figuring that out makes looking ahead more realistic. And I blew it on my October progs thinking that other factors would dominate ...
Now to dinner!
No, absolutely not. The blizzard of 93 had a very rare occurrence that triggered that storm. There was a convergence with the polar jet and subtropical jet, nothing like that with this set up.
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bouncycorn
Meteorologist
Nonetheless, I totally agree. Too many people tossing this system 6 days out.
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What I don't get right now is that the 18z GFS has the light snow/flurries close to the HP at 144. That maybe a model error, because air sinks obviously around HPs. Realistically the disturbance will be further south where the lower air pressure readings are away from the HP. In cases the component of forecast error due to state-dependent model error trends to grow as the square-root of forecast time and provides a major source of error out to three days.
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Out of the last 67 Feb. 10ths, only 10 saw a more -AO than what the bias adjusted GEFS is now predicting for 2/10/17 of -2.45: 1953, 1955, 1956, 1958, 1968, 1969, 1978, 1985, 1991, & 2010. If that's not enough, consider the bias adjusted GEFS PNA prediction for 2/10/17 of near +1.15. I found only 6 of 67 2/10's with a more positive PNA! These are 1977, 1980, 2004, 2006, 2012, and 2016. The highest on record for 2/10 is only +1.577 (2012). Keep in mind that there is a rather strong correlation of major SE snow & a +PNA.
So, in terms of the combo of -AO & +PNA on Feb. 10, only 1968 (top rank) & 1980 (2nd) would top what is projected for 2/10/17! Both 1968 and 1980 had snow in ATL and other places in the SE on or around 2/10 along with cold.
That along with the 2nd week in Feb. being the single week with the largest number of major winter storms for many in the SE US and several 18Z GEFS members showing something major may not tell me to bet on this, especially with the Euro not having it. However, this all tells me to not bet the ranch against something crazy happening as we have a very uncommon -AO/+PNA combo smack dab in the middle of the most climo favored part of the winter for a major SN! Add to that an uncommonly strong Feb phase 7 MJO being projected for then fwiw.
So, in terms of the combo of -AO & +PNA on Feb. 10, only 1968 (top rank) & 1980 (2nd) would top what is projected for 2/10/17! Both 1968 and 1980 had snow in ATL and other places in the SE on or around 2/10 along with cold.
That along with the 2nd week in Feb. being the single week with the largest number of major winter storms for many in the SE US and several 18Z GEFS members showing something major may not tell me to bet on this, especially with the Euro not having it. However, this all tells me to not bet the ranch against something crazy happening as we have a very uncommon -AO/+PNA combo smack dab in the middle of the most climo favored part of the winter for a major SN! Add to that an uncommonly strong Feb phase 7 MJO being projected for then fwiw.
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It looks fine to me. The shortwave along with the jet streak are promoting enough lift to generate precipitation with what bit of moisture is being carried SE with the wave itself. A surface high isn't going to promote sinking air like a high pressure in the mid levels, the only issue it would cause in this scenario is too much dry air near surface and sublimation of snowflakes as they fall. Also it looks like the GFS might be having some issues with ridgeogensis in the rockies with this system given how it wants to strengthen the surface high while the CMC and Euro do not.
W
WeatherLC
Guest
How are things looking in terms of precip for the region? (rain)
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