Upcoming cold for the South (Models, Maps, Discussions)

[Tyler]

I still say its way to early to say that the bulk is "going east". Right now I'm looking at the overall pattern, I'm not looking at the face value of the GFS, and right now the eastern 2/3rds of the US should see below average temps in February. Who sees the bulk of the cold air remains to be seen. If the Euro is to be believed, we get it. The GFS has the coldest just to our east. Thats to close for comfort, and WILL change.

[Tyler]

I think there is a bit of an error on the GFS in the long range.

http://www.nco.ncep.noaa.gov/pmb/nwprod ... _168.shtml

See that upper level low over there near California? It just sits there and stays for days. The GFS has a bias of doing this in the long range, hanging up energy in the southwest for too long, and I really doubt thats going to happen. That may be why the ridge is pumped up so much, and the majority of the cold looks to go to the east.

The EURO in the long range looks MUCH more realistic, with a nice stout ridge in the west, and the cold air running through the US all the way to the south. Until that feature actually makes since in the southwest, I'm going to be looking at the EURO a bit more.

[Air Force Met]

AFM,

Just wondering, what makes you think its going east? The EURO shows the cold air diving south, courtesy a 1040MB high in south-central Canada. IMO, I think its too early to say who gets what.

And for what its worth, the 18z GFS shows the bulk of it diving south as well...

Because the upper flow will take most of the cold air east. In situations when you have highs that are in the 1040 range...they do not sink straight south unless your upper flow is straight south. This first shot being picked up is not the shot that will overwhelm the pattern. That is a split flow. This pattern did exist during the Feb 1989 outbreak...BUT...that was 1078 mb of pressure coming down. It could overwhelm the pattern. 1040mb...or even 1050 will not overwhelm the pattern. If you follow the bitterly cold air from the first plunge on the GFS...it does not come south...it goes east. It does not go into Montana and the Dokotas...it goes into Minn, and the Great Lakes states.

Extrapolate that Euro 7 day out...using the progging rules and the EUro Also does not show the cold air diving south after day 7...it shows it moving it. This is not super dense air with a super massive high. That's why I am saying the bulk is going east. LAter in the period as the pattern changes...more of it may come south...and we will cool down with this one as we are going to be back-doored...but the coldest of it is going east. A 1042 high is NOT going to overwhelm the pattern and send arctic air south past a 120-150 knot jet that is sitting over the central US. If the high was sitting at 1058-1065...AND sitting back nudged up against the rockies...then yes...it would sink south...but it's not...it's sitting out in the central Canadian plains.

And if the upper pattern verifies...and the central plains is indeed the location of the 1042 high...the bilk of the arctic air WILL go east. Take it to the bank. In order for arctic air to come due south with that type of upper air pattern you need it just on the lee side of the rockies and on the high side in terms of pressure...it's neither.

But...what it is doing is setting the stage for later in the game...after the 10th of Feb when the ridge is really built and the split flow is gone...and the polar flow is due south. That's when the south will get cold.

Just my take on it.

[Extremeweatherguy]

JB is now saying that he expects the COLDEST 5-day periods of the entire winter for most the country coming up this month. He says that temps. will be as cold or even colder than what was seen in December, and he is centering the bulk of the cold around Feb. 15th. Here is a quote from his post tonight, "The danger is flat out obvious. Lay down the snow and get cross polar flow and look out below." Interesting.

[Tyler]

AFM,

Just wondering, what makes you think its going east? The EURO shows the cold air diving south, courtesy a 1040MB high in south-central Canada. IMO, I think its too early to say who gets what.

And for what its worth, the 18z GFS shows the bulk of it diving south as well...

Because the upper flow will take most of the cold air east. In situations when you have highs that are in the 1040 range...they do not sink straight south unless your upper flow is straight south. This first shot being picked up is not the shot that will overwhelm the pattern. That is a split flow. This pattern did exist during the Feb 1989 outbreak...BUT...that was 1078 mb of pressure coming down. It could overwhelm the pattern. 1040mb...or even 1050 will not overwhelm the pattern. If you follow the bitterly cold air from the first plunge on the GFS...it does not come south...it goes east. It does not go into Montana and the Dokotas...it goes into Minn, and the Great Lakes states.

Extrapolate that Euro 7 day out...using the progging rules and the EUro Also does not show the cold air diving south after day 7...it shows it moving it. This is not super dense air with a super massive high. That's why I am saying the bulk is going east. LAter in the period as the pattern changes...more of it may come south...and we will cool down with this one as we are going to be back-doored...but the coldest of it is going east. A 1042 high is NOT going to overwhelm the pattern and send arctic air south past a 120-150 knot jet that is sitting over the central US. If the high was sitting at 1058-1065...AND sitting back nudged up against the rockies...then yes...it would sink south...but it's not...it's sitting out in the central Canadian plains.

And if the upper pattern verifies...and the central plains is indeed the location of the 1042 high...the bilk of the arctic air WILL go east. Take it to the bank. In order for arctic air to come due south with that type of upper air pattern you need it just on the lee side of the rockies and on the high side in terms of pressure...it's neither.

But...what it is doing is setting the stage for later in the game...after the 10th of Feb when the ridge is really built and the split flow is gone...and the polar flow is due south. That's when the south will get cold.

Just my take on it.

Man, did I ever get owned... Thank you for the GREAT explanation AFM! I completely understand now.

[Stratosphere747]

Tyler...Consider that tame compared how AFM had to try and explain certain things to some tropical weather experts during the hurricane season....

[Jim Hughes]

JB is now saying that he expects the COLDEST 5-day periods of the entire winter for most the country coming up this month. He says that temps. will be as cold or even colder than what was seen in December, and he is centering the bulk of the cold around Feb. 15th. Here is a quote from his post tonight, "The danger is flat out obvious. Lay down the snow and get cross polar flow and look out below." Interesting.

Hmm ..wonder where he got that date of February 15th from ? Sounds familiar.

They say he reads their boards over at easternuswx. He'd have to be blind to miss some of the exchanges over there today about some of my prior posts. It made some of the old Storm2k exchanges look calm.


Jim

[Tyler]

Tyler...Consider that tame compared how AFM had to try and explain certain things to some tropical weather experts during the hurricane season....

Hey, its kinda fun being slapped silly by AFM. You learn something EVERY time, I know I sure did.

[Air Force Met]

Tyler...Consider that tame compared how AFM had to try and explain certain things to some tropical weather experts during the hurricane season....

Hey, its kinda fun being slapped silly by AFM. You learn something EVERY time, I know I sure did.

No slapping...just my take

Plus I've seen it so many times. But if the later periods verify of the GFS...it will get cold in the south too. The first plunge sets it up by extreme cold air advection lowering the heights and deepening the polar vortex over the hudson bay area. Then the ridging over AK gets thrown in...and that's sets up some great cross-polar flow that should just dump it south.

The high that is forecast over AK and Siberia later in the period is just massive (at 500mb)...one of the largest I have ever seen. If that verifies...watch out...all of that Siberian air will dump into the lower 48...most will still go east but we will get a share.

What we in Texas are missing is the BIG high sinking south. The problem with forecasting that is...well...it's really hard to forecast that sort of high pressure to form that far out. The model is putting out a large area of higher pressure...but it's certain it won't look like that at the sfc. Cold Core sfc highs are tough to forecast when they haven't formed yet...especially the big ones...1050+.

[boca]

I enjoy reading these posts from you guys in Texas I hope some of that air also heads to Florida.

[Johnny]

Here we are at page 22 and the cold air hasn't even entered the CONUS yet. I'm sure this thread will hit 35+ pages before it is all said and done. This has also turned into a very educational thread. I'll probably save this one for future reference.

[Extremeweatherguy]

latest 0Z GFS model runs for short term:

Here is a look at tomorrow's svr. weather:
http://www.nco.ncep.noaa.gov/pmb/nwprod ... _024.shtml

Here is a look at the "cool" weekend coming up:
http://www.nco.ncep.noaa.gov/pmb/nwprod ... _090.shtml

[boca]

This reminds me on the talking tropics board talking about a tropical wave that has a remote chance of forming into a depression thread hitting 70 pages.

[Tyler]

Tyler...Consider that tame compared how AFM had to try and explain certain things to some tropical weather experts during the hurricane season....

Hey, its kinda fun being slapped silly by AFM. You learn something EVERY time, I know I sure did.

No slapping...just my take

Plus I've seen it so many times. But if the later periods verify of the GFS...it will get cold in the south too. The first plunge sets it up by extreme cold air advection lowering the heights and deepening the polar vortex over the hudson bay area. Then the ridging over AK gets thrown in...and that's sets up some great cross-polar flow that should just dump it south.

The high that is forecast over AK and Siberia later in the period is just massive (at 500mb)...one of the largest I have ever seen. If that verifies...watch out...all of that Siberian air will dump into the lower 48...most will still go east but we will get a share.

What we in Texas are missing is the BIG high sinking south. The problem with forecasting that is...well...it's really hard to forecast that sort of high pressure to form that far out. The model is putting out a large area of higher pressure...but it's certain it won't look like that at the sfc. Cold Core sfc highs are tough to forecast when they haven't formed yet...especially the big ones...1050+.

Thank you for that informative post, AFM. I have really learned alot from reading your posts. Kudos to you. Interesting comment about the high over AK and Siberia...

If we look at the calender, the clock is ticking for us here in Texas to get some really cold arctic air. In your opinion, when do you think that its too late for us to get any cold outbreaks?

[Tyler]

OK, here is my analysis of the 0z GFS...

The much awaited pattern change is FINALLY arriving folks.

0z GFS Day 6 hour 138:
http://www.nco.ncep.noaa.gov/pmb/nwprod ... _138.shtml

You can now see ridging setting up over the west coast, the pacific jet dying, and the low pressure system over the northeast that will continue moving northward, and help to rise heights over Greenland, and possibly set up a ridge or block.

Day 8 hour 180:
http://www.nco.ncep.noaa.gov/pmb/nwprod ... _180.shtml

PNA ridging on the west coast becoming very strong, Seattle drys out and will likely stay dry for a while, meanwhile, cooler air overspreads the lower 48, as temperatures return to normal. Around here, this weekend will likely be the last time we see temps rise into the 70's for a while. Next week looks to see more seasonable temps, and beyond that, we may see much below normal temps, as the pattern will open up the oppurtunity for very cold air to enter the US.

Now this is just speculation, but the GFS has shown this for quite some time now. Day 10 hour 240:
http://www.nco.ncep.noaa.gov/pmb/nwprod ... _240.shtml

Ridging over the west coast now extending into Alaska. Ridging developing over Greenland, trough settled over the eastern US, as a cross polar flow develops. Extreme arctic outbreak develops as cold air dives into the US from Canada, as the Polar Vortex drops in. We enter the icebox. This solution is possible but its on the extreme side.

If we just look at the GFS from now to hour 180, you can clearly see the pattern change develop, and by hour 180 (next week), a much cooler pattern develops for the US, as the US goes back to normal, and the doors open for some possible arctic air to intrude in the US. How severe and where the bulk of the cold air goes remains to be seen. For February, I would expect much cooler temperatures than we have been seeing. I would not be suprised to actually see Houston average below normal for Feb, as the upcoming pattern does support that. At any rate, the warmth we are currently experiencing will soon be the thing of the past! Enjoy the warmth while it lasts!

[Portastorm]

This morning's 0z run of the Euro at Day 7 has a 1066 high in northern Idaho ... should it verify, Katy (Texas, that is) bar the door!

http://weather.cod.edu/forecast/ECMWF/e ... mp_168.gif

[LarryWx]

This morning's 0z run of the Euro at Day 7 has a 1066 high in northern Idaho ... should it verify, Katy (Texas, that is) bar the door!

http://weather.cod.edu/forecast/ECMWF/e ... mp_168.gif

PortaStorm,
That's a 1036 mb high, not 1066 mb. But a much stronger high may follow it from Canada later!

This Euro run is suggesting a major snow event for ATL with ~4-5" of snow late WED 2/8 into early THU 2/9 due to a weak Gulf low, the kind that most often gives the SE US its biggest snows. Details are still in the "fwiw" category since it would still be a week away and future model runs will likely change. But, the ECMWF is the least inaccurate of all models. So, I'm not ignoring it.

[Portastorm]

This morning's 0z run of the Euro at Day 7 has a 1066 high in northern Idaho ... should it verify, Katy (Texas, that is) bar the door!

http://weather.cod.edu/forecast/ECMWF/e ... mp_168.gif

PortaStorm,
That's a 1036 mb high, not 1066 mb. But a much stronger high may follow it from Canada later!

This Euro run is suggesting a major snow event for ATL with ~4-5" of snow late WED 2/8 into early THU 2/9 due to a weak Gulf low, the kind that most often gives the SE US its biggest snows. Details are still in the "fwiw" category since it would still be a week away and future model runs will likely change. But, the ECMWF is the least inaccurate of all models. So, I'm not ignoring it.

Doh! Sorry about that and thanks for the correction, LarryWx!

That's what I get for posting so early in the morning and with so few cups of coffee.

I read somewhere that the strength of the Pacific jet this winter has been what is throwing all of the medium-range models off. Maybe with this pattern change, they'll get a bit more reliable or consistent?

[vbhoutex]

So it wasn't my bleary eyes this morning. I thought it said 1036 too, but I hadn't even had coffee yet so I didn't question it. It looks like the intial cool down depicted in that run is going to be heading more East than South to me. Texas will definitely cool down, but it looks like our friends to the East in SE US will get the brunt of that one. If the pattern change that is becoming more apparent holds there will be more Arctic air to follow that with more chances for SE & SC TX to join in.

[aggiecutter]

The strongly negative AO will send what cold air there is in Canada straight down the plains. This is verified by the 0z EURO at day 7...


http://vortex.plymouth.edu/ecmna.108.gif