SIGNIFICANT pattern change for NA over the next few weeks...

[wxguy25]

On the Subject of the ECMWF...

I have some great news, and no, its not that I saved a bunch of money on my car insurance by switching to Geico. Actually I have Allstate.

but anyway,

D8-10 ECM

Look at that PV over on the NW shore of Hudson bay, PNA ridge is up and the Aleutian low is once again coming to life, Cahirs connection is up in Asia so the Vortex is kicked out of Siberia and you get three predominant long wave troughs.

Also notice the sharpening of the wavelengths over the North Atlantic, w/ what looks to be a 50-50 low trying to form. We could be setting up for a strongly -NAO to close the month and enter DEC. It will also be interesting if we can get the PNA ridge and developing -NAO to hook up and severely displace the PV.

Do I smell late NOV-DEC 1963? I think I do!!

[yoda]

Most excellent. I can't wait. 1963, eh?

Yes, we need the PNA ridge to get going, along with Aleutian low to stay.

[wxguy25]

DEC 1963

[yoda]

DEC 1963

[Stormsfury]

It's been a while. What number represents the freeze line?

wxguy explained this extremely well ...

I will add my speciality into this thread .. and that CAD (cold air damming or the "wedge") ... 540dm thicknesses (1000mb-500mb thickness schemes) are NOT representative and you'll see in various cold air damming scenarios east of the Appalachains where thickness schemes are even as high as 546dm, yet , SFC temperatures are in the upper 10's/low 20's (with 850mb temperatures ABV 0ºC) ... from just a basic standpoint, the precip will be frozen, but most likely NOT snow ... but during CAD scenarios, areas BLO the 540dm thickness scheme will ALMOST always be snow, unless there's a significant warm nose in between the 500mb and the SFC ...

These maps do NOT look that impressive, BUT turned out to be one of the most prolific overrunning events in the Southeast on January 7th-8th, 1988 with GSP receiving roughly 13" of snow, without a rapidly deepening cyclone, just a good healthy moisture feed from a ripple in the northern jet, along with very strong SFC ridging in the NE channeling cold air down the Eastern Side of the Appalachains... (classic diabetically enhanced CAD/overrunning event) ...

Let's start with the 500mb Geopotential Heights ... what appears rather benign actually when you scratch the SFC (literally), is much more looming during the heart of the winter with a PV situated just south of Hudson Bay ... and a s/w disturbance dropping down into the Central Plains into the confluence out east ...







Moisture rapidly increased over the Carolinas (SC particularly) ... by 12z on 1/7/1988, and overspread SC at all levels by 1/8/1988 at 0z ...





Meanwhile, heights at the 1000-500mb began to increase from right around 5400m along the Southern portions of SC/GA (near Savannah, GA) and gradually increased northward as SW flow increased as the disturbance swung SE to E towards the Eastern US ...







at 12z and 0z on 1/8/1988 would clearly indicate liquid precip in Southeastern SC .. right? ... not this time ... let's delve a little shallower towards the 1000-850mb thickness scheme ... and the 850mb temperature scheme, respectively ... notice that BOTH are right at the threshold clear all the way to the GA/SC border near Savannah ... which also gradually rise and still hover just north of Charleston, SC by 12z and well into the Midlands of South Carolina by 1/8/1988 at 0z ....













Now that would indicate a change from frozen to liquid ... right? .... well, almost ... right along the IMMEDIATE coast, did it change to a very heavy rain ... just away from the coast and back inland ... SFC temperatures did rise significantly with a very heavy ZR (partly due to latest heat release) but the SFC high pressure continued to pump in very cold air at the SFC from the NNE and NE ... thus locking the area in the "wedge" ... a classic diabatically enhanced cold air damming scenario ... and back towards the Upstate of South Carolina, thickness schemes remained BELOW the critical schemes almost the entire time ... at GSP, heavy snow fell during most of the day, followed by a brief period of sleet mixing with the snow, before changing back to all snow ... 12.9" of snow fell at GSP, a record breaking event w/out a significantly deepening cyclone, which made this event memorable to say the least ...

850mb temperature schemes across Charleston ran as high as 8ºC, BUT at the SFC, the wedge remained steadfast and kept temperatures BLO FRZ for most of the night (it barely crept ABV FRZ for a short time) but what saved the area from a significantly devastating icestorm during the night was the intensity of the ZR ... it fell so heavily that the latent release of heat prevented prime ice accretions (FRZ DRZ/LGT ZR accumulates the best) ...

More information and a PDF file from GSP regarding the event and SFC maps available at this link ...

http://www.erh.noaa.gov/gsp/localdat/ta2001-02.pdf

SF

[wxguy25]

Alright let’s look at this in more depth. SF outlined the basic theory here, but I want to check out the actual sounding at CHS to prove some critical points.

Here is the 0z 1/8/88 Sounding at CHS

http://vortex.plymouth.edu/cgi-bin/gen_ ... ze=640x480

The SFC and lowest levels are well below FRZ, but if we look at the layer between ~ h650 and h950 there is a pronounced warm later aloft and extreme temperature inversion w/ height thanks to the CAD in the LLVLS and STRONG Differential advection aloft. Notice the NE flow in the Low levels, and SW flow aloft.

So you would obviously see melting, then re-freezing and P-type ZRA/IP/PL since 1000-850mb thicknesses were =/> 1310 gpm, the depth of the warm layer was deeper than 400m and the max temps in the warm layer were around +10 C. but the CAD made all the difference between a rain event, and significant icing

[wxguy25]

BTW, that was a heck of a good post, SF. Nice Job as always.

[QCWx]

here's a map to help SF illustrate the snow totals..

[QCWx]

I dont know if there's a more fun area than the piedmont of the carolinas for forecasting winter storms. It may mean cases of rolaids at NWS offices but it's dang fun as a weather enthusiast to follow the storms that change so much down here due mainly to the CAD.

[wxguy25]

I dont know if there's a more fun area than the piedmont of the carolinas for forecasting winter storms. It may mean cases of rolaids at NWS offices but it's dang fun as a weather enthusiast to follow the storms that change so much down here due mainly to the CAD.

Im saving my Rolaids for the 2005 tropical season. Down here In FL, we're thrilled just to scrape frost.

[Stormsfury]

BTW, that was a heck of a good post, SF. Nice Job as always.

Thanks, man ... wondering where on the PSC site you created that archived sounding ... I found some more interesting information to go along with that WRT to 1000mb temperature vs. 925 mb temperature ... significant warm nose between the two ... after 12z on the 7th ... I recorded an inch of sleet on the ground, before ZR mixed in ... by 0z on the 8th, it was all ZR ...

temperatures are in Celsius format ...

850mb temperature on 1/7/88 at 12z
925mb temperature on 1/7/88 at 12z
1000mb temperature on 1/7/88 at 12z

Now the alarming sharpness in plotted ... and I was even MORE surprised at Southern GA (Valdosta, GA?) ... 12ºC (roughly 54ºF at 925mb), but 0ºC (at the 1000mb level or 32ºF) ... cold air damming at its best (worst) ...

850mb temperature on 1/8/88 at 0z
925mb temperature on 1/8/88 at 0z
1000mb temperature on 1/8/88 at 0z

[Stormsfury]

here's a map to help SF illustrate the snow totals..

Mucho thanks, QCwx...

it's too bad that I couldn't find any maps of ice/snow accumulations for South Carolina aside from the PDF file that I have linked above ...

SF

[wxguy25]

Here is the link to the soundings.

http://vortex.plymouth.edu/uacalplt-r.html

And the 12z 1/7/88 CHS sounding

http://vortex.plymouth.edu/cgi-bin/gen_ ... e=1024x768

Plenty of evap. cooling potential as evidenced by those double digit DDs below 940mb and weak warm slot would indicate to me either IP or granular SN. Also note the NE flow in the low levels holding the CAD in place.

[Stormsfury]

Here is the link to the soundings.

http://vortex.plymouth.edu/uacalplt-r.html

And the 12z 1/7/88 CHS sounding

http://vortex.plymouth.edu/cgi-bin/gen_ ... e=1024x768

Plenty of evap. cooling potential as evidenced by those double digit DDs below 940mb and weak warm slot would indicate to me either IP or granular SN. Also note the NE flow in the low levels holding the CAD in place.

Mucho thanks, wxguy ... couldn't remember what link it was under on the Archived Data section.

IMHO, this would be the type of scenario that I'm inclined to believe will occur sometime this winter across the Southland/Southeast at least once this winter season ...

Since 1963-1964 is being thrown into the fray ... archived datasets reveal that South Carolina experienced two winter weather events, including a very significant event on New Years Day 1964 ...

1964
1/1..............Severe ice storm/high winds hit most of SC. Aiken, Bamberg, Edgefield, Orangeburg, and Anderson counties were hardest hit.
2/21-22......Trace of snow at Summerville.

[Stormsfury]

Now that's one displaced 500mb low! ...

January 1st, 1964 at 00z

SF

[QCWx]

here's a map to help SF illustrate the snow totals..

Mucho thanks, QCwx...

it's too bad that I couldn't find any maps of ice/snow accumulations for South Carolina aside from the PDF file that I have linked above ...

SF

I suppose the Greenville County Mtns probably made out well with the 17" totals in Polk Co, NC.

[Cumulonimbus]

Ahh...what is so good for all of you is sooooo bad for us in the NW. Big west coast ridge which brings you all your winter weather, slams the door shut(and looks like it locks it for a LOOOONG time) for precip. This means a BAD fire season ahead next summer and what is far worse for us on a meager income just barely scraping by, is that water rates will take off faster than a rocket can fly. Looks like a drought ahead for the Pacific Northwest for sure:(

[Anonymous]

On the Subject of the ECMWF...

I have some great news, and no, its not that I saved a bunch of money on my car insurance by switching to Geico. Actually I have Allstate.

but anyway,

D8-10 ECM

Look at that PV over on the NW shore of Hudson bay, PNA ridge is up and the Aleutian low is once again coming to life, Cahirs connection is up in Asia so the Vortex is kicked out of Siberia and you get three predominant long wave troughs.

Also notice the sharpening of the wavelengths over the North Atlantic, w/ what looks to be a 50-50 low trying to form. We could be setting up for a strongly -NAO to close the month and enter DEC. It will also be interesting if we can get the PNA ridge and developing -NAO to hook up and severely displace the PV.

Do I smell late NOV-DEC 1963? I think I do!!

I know this is a dumb question, and I know everyone is already sick and tired of the How much for Philly?-type questions, but I really need to ask this................

What was the weather like in Washington, DC in late November/into December 1963? Anyone? wxguy25? Stormsfury? Please?.........

I'm not sure I want to know........


-Jeb

[gboudx]

Thanks everyone for the great discussions and explanation. I've learned quite a bit from reading what you guys post. Keep up the good work!

[KWT]

I take it that December 1963 was good for you lot then,funnly enough just one year before we were about enter our most severe winter for 20 odd years and would be in the top 5 coldest winters for 250 years.

so here in the U.k we too are also preparing for our first cold spell,with the threat of snow esp as a frontal system moves thourgh,with the precip turning to snow.The main risk of snow is the Midlands northwards,although just about anywhere here may see some snow,apart from the south coast.

and also whats better is that the possiblty of a scandi high is also there,thanks to the stalled LP system out into the atlantic somewhere as well as a quite quiet Atlantic,as well as a cold Scandanavia,it does seem there colu dbe a very real shot at a scandi high,and certainly looks to be a quite cold end to November here.