Friday, November 26, 2010


Thanks to people everywhere for breaking my record for 24 hours of views- 170 views!
Special Thanks to Greece who got 125 views.

Long Range Ensemble Run, Long Range GFS run

This is a combined post of an ensemble run into 14 days from now and the GFS, both usual and long-range modes.

We'll start off with the ensembles. And boy are there a lot.
Going into the first two days, all the ensembles show a low coming onshore from the Northwest weakening as it does so. With all the members approving of this, I will approve as well.

In the following two days, some models take the low strengthening in Canada and others show it to stay disorganized. In all cases, a cold front forms a squall line starting in Canada and extending through Madison, Chicago. What really surprised me though, was how, in just one ensemble, there was a tight area of low pressure right centred in the North Illinois area. However, since it is just one ensemble, I will not worry much about it, but will watch it.

In the 4-6 day range, right away in day 4, 9 out of the 12 ensembles report a well defined area of low pressure in the Canada region. Additionally, some of the members keep the squall line of precip moving quicker than the others.
Continuing on in the same 4-6 day range, then 4 ensembles reported a low pressure centred in the Canada region above the Great Lakes. One member even took it out farther into Canada. By now, the squall line is taking different shapes with different members. 2 ensembles already have the squall line off shore while everyone else is moving along around the Carolinas north and south in a roughly defined line.
Still in the 5 day area, all but one member of the 12 ensembles are reporting the squall line moving out. They are also differing on the placement of a low pressure. One puts it above the Great Lakes in Canada, while another puts the same area in the clear. From now on this'll be a wild ride. A couple members even have the low breaking off into two weaker lows.
Finally, as the 4-6 day range ends, the members have taken the squall line away and put lows in Canada anywhere from East to Central Canada regions.

For the 6-10 day region, the models will likely by hugely different. By now, all models have the squall line far out to sea. But the lows are still all over the place. Even the thickness levels vary by a lot of miles.
Moving 12 hours on, nearly all the models are showing yet another squall line possibly begin to form. The Great Lakes and the Texas-Louisiana regions are the first to start off. Right now, the Great Lakes precip is a toss-up, likely landing on a rain/ice mix. Or a Snow/ice mix. Again, thicknesses are all over the place. The models have taken their own opinions.
12 hours later, the supposed squall line has not formed. The Great Lakes region is petty much half and half on whether it's precip or not. The majority of the thicknesses show the line fairly close to the Lower Great Lakes and in the South Illinois/Central Illinois area. This leads me to think that any precip in that area would be a wintry mix.
12 hours ahead, the models finally agree on something: another low pressure comes in from the Northwest. Most place it as a pretty organized storm, but the holdouts place it as somewhat disorganized. Either way, the members that do show Chicago receiving snow say that the thickness will create a rainy event possibly. The non-precip members keep the thickness down south. Meanwhile, some models place the Northwest low dividing into two areas of precip and then moving off.
Another 12 hours passes. The models mostly hit pretty much all of the Great Lakes with a precip area. I would say a snow/ice/ rain? event. So maybe rain to snow in Chicago, snow showers in Madison, snow showers in Detroit, etc. One member has a low suddenly exploding in Louisiana. I deny that because it's only one member.
Another 12 hours. Just about every one now agrees on some sort of precip hitting the Great Lakes, with it possibly impacting the Gulf Coast area south of the West Great Lakes. A heavy majority of the models still keep that Northwest low in the mix, but one member has that low combine into the mostly Wisconsin precip. I think there will be two lows: One in the GL (Great Lakes), and one in the NW (Northwest). Some models still dont bring precip to Madison or Detroit.
Continuing on to the end, the ensembles end up going in different directions. Most bring some precip through the East Coast while others declare a low suddenly booming in the Heartland. All the models agree on yet another NW low coming through. Most models project precip for either the Great Lakes or the South. Some don't have any at all except for the NW low and the precip moving out to the Atlantic.
In the end, the models keep ushering in more and more NW lows and dragging them through the North US. Some models bring some rain into the South, while others don't bother.


Now we go to the Long Range GFS.
The LR GFS shows the Great Lakes getting hit with a snow/ice storm with maybe a hint of rain right off the bat. That low then trails off to the Atlantic where it stalls and becomes a monstrosity. It even gives the GL region a backlash from an 'arm' that sweeps the area from the storm.

Well, that's finally it.
JUST KIDDING!!! One more thing: Meteogram.

Chicago's meteogram says a rain storm with possible thunderstorms with high instability on November 30th. But the meteogram doesn't show convective precip...hmmm....
Moving on, another rain storm impacts the area going into the 4th of December. If that turns out to be snow, it'll be a big one.
Into the last one, it goes off with rain on Dec. 5-6th then convective snow (thundersnow) periodically until December 12th.

This has been your Long Range Ensemble Run, your Long Range GFS run, and your meteogram all in one. Too much for one post, eh? Yeah, I thought so too.
Alright, have a good day/morning/night/evening!!

Ensemble 2 1/2 days

Good evening! Well, I managed to find a LOT of ensembles which will definitely aid me in providing the most accurate forecast to you.

So, I ran an ensemble for the precip for the next 2 and a half days.

There are two models - the WRF and the AVN (NCEP).

About a day or so from now, the WRF has the front dissipate a bit quicker than the AVN shows it dissipating.

Also, 2 days from now, the WRF has a low in the Northwest pull in more organized than the AVN projects it to.

In the end of the run, both models show the low to be somewhat weak as it's over the Northwest.

What do I think?
Well, the AVN was more detailed in the line of thickness, so i'm veering towards that the low will weaken as it moves onshore.

Updates possible tomorrow.

500th Post!!

This is the 500th post of the Weather Centre. In honor of this, we will be featuring several Weather Explained topics. There will also be a new Weather Explained page with links to all past Weather Explained posts. Happy Black Friday!

Weather Explained: Thundersnow

This is our third segment of Weather Explained.

What is thundersnow??
Thundersnow is like a thunderstorm in snow formation. There are four types of thundersnow (info from wikipedia)
  • A normal thunderstorm on the leading edge of a cold front or warm front that can either form in a winter environment or one that runs into cool air and where the precipitation takes the form of snow.
  • A heavy synoptic snowstorm in the comma head of an extratropical cyclone that sustains strong vertical mixing which allows for favorable conditions for lightning and thunder to occur.
  • A lake effect or ocean effect thunderstorm which is produced by cold air passing over relatively warm water; this effect commonly produces snow squalls over the Great Lakes.
  • A cold front containing extremely cold air aloft, steepening lapse rates and causing strong vertical movement which allows for favorable conditions for lightning and thunder to occur
Is Thundersnow Dangerous?
Well, do you think a thunderstorm is dangerous? Yes it is.
So, thundersnow is pretty much a thunderstorm with snow instead of rain. So it
s just about as dangerous as a thunderstorm.

Our next Weather Explained will focus on Mesocyclones.

Potential Great lakes Snowstorm

Good Morning! Hope y'all had a good Thanksgiving!

Okay, let's get right down to the business here. As the title states, the Great Lakes could see a pretty nice snowstorm on December 4th.

The Long Range GFS is indicating that Chicago could get hit the worst.
The probability of that happening is roughly in the 60 percent range.

By the way, the snowstorm I indicated yesterday on the Long Range GFS will not be happening. So my probability does work.

Temperatures in the clouds should be just close enough to produce snow.

The meteograms are indicating snow, possible thundersnow which will be next in our Weather Explained.

Thundersnow is like a storm. It puts down precip fast. So thundersnow would mean a quick-producing snow system.

More updates as more info comes in.