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Old 10-05-2012, 04:37 PM
 
Location: Near the Coast SWCT
83,502 posts, read 75,252,292 times
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After a couple of requests I decided to start this thread. I'm hoping to get help from other meterologists and knowledgeable people.

Lets use this thread to explain, share, and help with reading models, charts, and anything related to technical side of weather.

Usually I use a graph which makes things easier to see and understand.

-------------------


Lets start with depicting the Northern and Southern jets.

Here's the GFS model. Usually for upper air patterns you use the 500mb. But Im using the surface for moisture visual purposes.

4 images. Top 2 go together. Bottom 2 go together. If you get the northern and southern branches to phase, a big storm develops. This is also key for winter forecasts. Last winter both streams were practically non existant. But this year its apparent both are VERY active. And when you get 2 streams that are very active the "chances" are higher to get a big storm to form.

The key is where, when, and how fast it phases.

Another word for phase is merge. Where the 2 Jets merge is where the big storm forms.

Notice the Top left picture for October 12th... both jets are seperate, then top Right October 14th, BOOM, they phase and a storm strengthens over the great lakes. Anyone on the west side of it would get snow if conditons are right. (for another post)

Notice the bottom left for October 16th, both jets are seperate, then bottom right for October 17th, BOOM, storm develops near the coast.

This image has been resized. Click this bar to view the full image. The original image is sized 1021$sx779$s and weights 525$sKB.


These events do not mean they will happen, the GFS is basically showing its possible based on the data it ingested from the lasted input.

Bottom line is... if you're a winter lover in Canada/U.S you have to love this pattern. If you're on the eastern U.S, you have to hope for a phase East of the great Lakes or South of Ohio or on the coast for best chance of snow.
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Old 10-05-2012, 04:42 PM
 
Location: Near the Coast SWCT
83,502 posts, read 75,252,292 times
Reputation: 16619
Here's another one I just put together...

Check out the timing.

Look at the timing of all this.. The cold front pushes through Saturday. new low forms Saturday night, Low moves up the coast Sunday (while cold air already moved in). Just imagine if the front was too slow...or too fast and pushed the coastal low OTS.

Look at the "blue" line on last frame how it digs down to the coast in CT, that just means the 4000 foot level above us is at or below freezing.

If this was December, it would be a little 2-4" snowstorm. But because its October 4th..
1. It will have rained before
2. Soil temps are too warm (not surface)
3. Thicknesses dont support it (at least on this run)
4. 925 temps in upper 30s
5. 850 temps are just marginal (like to see -2 at least this time of year)
6. qpf amounts not enough

Also another thing I keep saying... Both jets are active and apparent with whats going to happen. So obvious the southern Jet is active..

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Old 10-05-2012, 04:46 PM
 
Location: Near the Coast SWCT
83,502 posts, read 75,252,292 times
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A 16 minute video by Steve D posted today. WELL WORTH IT. Its like school for free! He's non bias so he mentions a warmup second half of October with a Pacific flow and explains what has to happen for the warm up to bust.

Long Range Video Discussion for October 3, 2012 :: NY NJ PA WEATHER
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Old 10-05-2012, 05:06 PM
 
Location: Iowa
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Thanks for the posts, interesting info.
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Old 10-05-2012, 10:44 PM
 
Location: Mid Atlantic USA
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Good idea for a thread. Though I'm a warm weather fan, I have to admit that winter weather in the US is more exciting than the more predictable summer. I usually pay way more attention to the weather in the winter than I do in the summer.
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Old 10-06-2012, 05:11 AM
 
Location: Near the Coast SWCT
83,502 posts, read 75,252,292 times
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Quote:
Originally Posted by tom77falcons View Post
Good idea for a thread. Though I'm a warm weather fan, I have to admit that winter weather in the US is more exciting than the more predictable summer. I usually pay way more attention to the weather in the winter than I do in the summer.
Yes, while there are some interesting things during warm season like vertical velocity, low level lapse rates, hail, ect... , winter has so much more to talk about. But once warm season rolls around again I'll be sure to mention the warm side of things.
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Old 10-06-2012, 05:22 AM
 
Location: Near the Coast SWCT
83,502 posts, read 75,252,292 times
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Default Swinging Troughs

If you're wondering why the central plains are having 20s and 30s as temps as far south as Texas but the East wont have as cold temps that far south with this same trough/cold front...

Here's a great example. 18zgfs850mbTSLPNA072.html

850mb layer in blues are below freezing. Notice in left picture how deep the trough is yesterday. As it swings east, it pulls up and away and the trough is not as deep in the east but still cold for PA northward.

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Old 10-06-2012, 06:19 AM
 
Location: Iowa
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Thanks again! Mid-30's this a.m., unusual for us this close to the lake. Haven't had frost yet and normally our 1st real hard freeze is around Halloween. Leaves are already past peak, too.
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Old 10-06-2012, 06:55 PM
 
Location: Near the Coast SWCT
83,502 posts, read 75,252,292 times
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If your wondering how or why a region gets fluctuating temps this is the best way to visualize why.

Its a perfect way to see the "flow" of earth. The colors represent the 5000' layer.(850mb) This give you an idea where the trough is and how cool the temps will be at the surface. Obviously a 20C 5000' layer wont mean a freezing surface. Blues are below freezing.

First frame of the loop is today. Notice 7 things...

1. How deep the trough is today to the south
2. The next few troughs are not as deep
3. The troughs swing around as the jet dips
4. The pinks are -20C! They are starting to bleed down little by little.
5. Watch Alaska start with a Ridge then a trough gets there which is why the East gets warm with a ridge at the end of the run
6. You can see the pole displacing the fridgid air.
7. This is a nice way to see blocking at work. Blocking near Greenland will let cold air bleed further south.

You can find 18z loop here. http://raleighwx.americanwx.com/mode...NAGFSLoop.html


GFS 18z 850 and Surface Loops - YouTube

Do you guys notice anything of interest that maybe I missed? Or questions you might have?
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Old 11-24-2014, 05:27 PM
 
Location: Near the Coast SWCT
83,502 posts, read 75,252,292 times
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Revising an old thread. Something I'd love to learn more about. This seems awesome to get to know. So much to learn with winter stuff.

"Best lift is beneath dendritic snow growth zone...warm situation...less than 10:1 ratios in the valley"

https://twitter.com/TylerJankoski/st...422592/photo/1

Ryan's Blog mentions it a bit as well: Winter Storm Likely on Wednesday | Way Too Much Weather



I have no idea what Im looking at with the graphic above. I know it's the atmosphere conditions but not sure how to explain it.
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