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chescopawxman

JB on why the 6z 31st GFS will trend back south.....

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JB post this AM on why the GFS will correct back south by tomorrow AM

 

"When I laid this storm out earlier in the week, when models were well south, the call was for a low to get to southern Ohio, then reform on the coast and head out s of New England. GIven that the corridor of heaviest snow is now closer to I-80 than I-70, there has been a north adjustment, not so much in the position of the low over Se Ohio, but further east. But should that continue. I dont think so, it may continue on the models till tomorrow then come back south again. Why?

"The negative NAO right now the track will be influenced. The GFS, perhaps correctly, simply bully the storm through the mountains . This looks wrong. First of all cold dry air is drilling south off the east coast. This air will be pulled back in as the storm comes in, and though it would have warmed on its journey south, it cools coming back if moistened. 2cnd. Where ever the precip breaks out, the cold air will fight, even if the fresh cold to the north has not arrived. This is a cold air mass, its still cold advecting, Hard to believe within 48 hours and after so much precip, its routed. 3rd. The front from the north. This is going to keep pressing east of the mountains and as it does it will be drawn in. The fact is that a storm pulls air from every where, including in front of it, toward it. If you think about how that works, the wind blowing from higher pressure to lower pressure in the low levels, when the rate of Warm advection is greater than rate of warming in the low levels, is what leads to upward motion. Have a reason for the low levels to fight, there is greater overrunning which in turn changes the pressure field. Moral: Watch where it starts as snow.. chances are any place more than 100 miles north of that stays snow ( with some sleet at the height of the storm)

The ECMWF ensemble shows what I am talking about, as it has the "damming" look for the low, with the warm front being the boundary the low goes too"

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More from JB on why the EURO is right

 

"Forgot this: A positively tilted trough has the deepening for the surface low rely more on warm advection( run to where the warmth is) The old rule is negative tilt, deepen from top down until the surface can get going and feed back. Neutral tilt about 50/50, positive the deepening is more from warn advection and as the system deepens the upper feature gets pulled tighter toward it. Dr John Cahir, used to call these positvely tilted front runners with most of the precip in front of them. In any case the new nam does not have the look of a storm that bowls through the mountains, but extends east It is highly unlikely the reform will be this far north. The reason: The isobars in front of the storm at 42 hours, seen here are pointed AWAY from the low center, rather than toward it. So the warm air is having an easy time heading northeast, but not north. The all is for this to redevelop near the mouth of the Delaware, not off Toms River. Once again though its a 50 mile edge forecast for the biggest marketarrow-10x10.png in the nation. Given the parallels I see to the position of the storm and the 500 mb forecast, which is very similar to 1967 once to NYC, ( that was a positively tilted trough that went ti neutral, and again I realize the storms evolved different, but the marriage of the analog is like a guy and a girl that came from different towns but wound up together.. arent I romantic?) I will hold with the 6-10 locally 15 ( forecast within 25 miles of CP) I can see the 2 or 3 and rain, certainly, but I can see the 15 too. In any case I did not mention this earlier. That waa term is just as important as upper divergence and once that southwest wind is howling out over the water east of the MA coast it will try to draw the redevelopment toward it, and it will very hard with the low having to reform with all the other factors going on, for it to bowl through the mountains and have the needed south to southeast wind in the warm sector to push that front north"

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Would not want to predict this one. Surface temperatures are rare to budge unless low is surging north to our west. This low may be to our south or right over us. That would support WAA with cold surface = ice south big heavy wet snow north.

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A day ago, I was looking forward to the best snowstorm of the season, but now I'm fearing the worst ice storm in years.

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Steve D with NJPA Weather also believes this will tick south by tomorrow's 12z runs...he has

4"-8" of snow to a mix in Philly

8"-12" Just NW of Philly out to a LNS/Lionville/Conshy/TTB line

NW of that line he has an 8" to 12" + forecast with less mixing

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Steve D with NJPA Weather also believes this will tick south by tomorrow's 12z runs...he has

4"-8" of snow to a mix in Philly

8"-12" Just NW of Philly out to a LNS/Lionville/Conshy/TTB line

NW of that line he has an 8" to 12" + forecast with less mixing

Hope for Steve & Joe to be correct but not counting on it.

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I would not count on them being right....I always go with Mt Holly for the real deal - but it is always interesting to get other perspectives.

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Steve D updated at 145pm with some slight revisions to what he now calls his Final forecast - although he knows there is some room for error if he is wrong with a track thru SJ

 

Zone from Glasgow E - PHL - West Deptford NJ to Mt Holly (1" to 3" of snow to rain and back to snow with .10 to .25 of ice)

Zone from Southern Lancaster County to Coatesville to Willow Grove to Trenton (3" to 6" of snow to ZR and back to snow with 0.10 to 0.30 of ice)

Zone from LNS to East Nantmeal Twp to Doylestown (6" to 12" of snow and snow mixed with sleet back to all snow before ending ice a trace to .05")

Zone from Harrisburg to Reading to ABE (6" to 12"+ with potential for more with banding)

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I would slash by more than one-half but ...I don't question professionals as long as they have some sort of reasoning....

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Nice write up from JB this evening....

January 31 06:35 PM

 

"I dont now where Paul Stokols is now. He was (is) a giant to me, the first person to teach me about the negative EPO back in the 1970s. He was part of the gifts from the good lord that arrived at PSU, a whole slew of Meteo grad students, that took me under their wing and showed me alot of what I use today. I name rules after who taught them to me. I have no idea if these rules are named after anyone else. I was taught to always credit the person that taught me and I do.

A word about Paul. He became part of the mid range forecast center back in the 1980s, that included Joe Shipps and Dave Weinstein. He then went to the Fire Center and became the Chief. But the rule in DC was a 55 heights THK 540 and heights falling when snow started, it stayed snow.

 

The reason is fairly intuitive. If the heights are still rising it is a sign that the ridge is still building and the war advection that is causing the snow in the first place is going to win. If they fall, then the rate of cooling aloft is enough to sustain the snow. Its like the BGM rule and Central Park On a northwest wind the temp in the park is 13 higher than BGM is 5 hours later. As with all rules there are exception.

Now Paul like me was a snow geek. So I am sure the rules developed for DC dont have to apply else where. But chances are if it starts snowing and the height fall, it will stay snow

So lets "play: with my back yard State college. It starts snowing around noon tomorrow, and the heights hold steady then fall. Should stay almost all snow. If it sleets or freezing rains for a while, it will be because we had a heck of alot of precip

The there is my dads rule, though he may have heard it from Norm Macdonald on WBZ I remember as a kid lamenting the hours when it was cold in ACY and it was not snowing but it was snowing west of us. It would come in as a few flakes but have warmed up so it rained. " It snows where it wants to snow" I heard that first in 1966 when the week before the blizzard of 66, we had a snowstorm forecasted and it rained. My great friend Bernie Rayno tweeted today that he heard that from the great Norm MacDonald of WBZ weather fame when he worked at the place I used to work at. If so, then perhaps that rule from Dad was something he saw on WBZ, I know I used to say it around work all the time, but if Norm said it first ten its his rule. How does it apply here? Watch the snow tomorrow. Where that streak goes, is going to have a heck of a storm and chances are the changeover line wont move north more than 100 miles

So why am I so different. Well think about this. What does the model have the best chance of hitting? What is right in front of it, right? Well it is headed toward a warm air festival, the downsloping west of the Appalachians. So it should pull up into SE Ohio and to SW pa. But its ONLY after it actually sees what is or isnt waiting for it in an east of the mountains, that it is likely to figure out where to go after. This is still 24 hours away, IMO in really having a handle on it. Am I right, well we will have to see. I have my oltdimers rule, and they dont involve slitting my throat over a NAM or GFS run. That being said I fully understand I may be wrong.

What I am not wrong about though is the pattern producing this. Enjoy it It is highly unlikely after this winter, in your lifetime you will see a SNOW DEPTH forecast like this, close to 40" ne of Pit and Se Mass. So I am not going to get all bent out of shape and grieve over backyard debacles including my own back yard. If I miss by 50 miles but explained the why before the what a week before, I just cant get upset about it anymore. Yell at the local forecasters that 5 days before had a chance of snow showers in the forecast. But here is what I can say. This target period, the 10 day Feb 1-5, the other 10 day call for the storm we went through in the east, the period Jan 26-Feb 10 which was made around Jan 15 to counter the wave of despair, just like we saw in mid Jan 2010, that winter was over ( Again the SOI crashed and look what the cattle prod did) were all part of a bigger message. WINTER HAS JUST BEGUN TO FIGHT"

East Nantmeal Township, Chester County PA and Sea Isle City, NJ
Chester County PA website: www.chescowx.com Live Webcam at
http://callapvhome.servebeer.com/ user name chescowx password weather
 
Chester County 30 Year Average at above 660ft asl (Precipitation 49.37" and Snowfall 35.5") 
2013-14 Seasonal Snow (80.1")
2014-15 Snow to Date (21.6")
11/13 - (1.5")
11/26 - (5.3")
12/11 - (3.6")
01/03 - (0.2")
01/06 - (2.3")
01/09 - (0.1")
01/21 - (0.5")

01/24 - (4.5")

01/26 - (3.3")

01/29 - (0.3")

 

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It's extremely rare for these type events to correct south in this time frame that JB & Steve D is calling for.

could be talking about secondary development

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Exactly Tom.....not saying that will happen but no doubt that is what they are thinking.

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Despite the various computer models either ignoring or downplaying its existence, a huge storm and frontal structure over the High Plains is set to make a mark on sensible weather across the eastern two-thirds of the nation. The equations appear to still be mishandling this broad feature, and may in fact be too far north with the track of the surface low and its upper components. I say this because there is a wide area of Arctic air across the Great Lakes into the Northeast, and the natural tendency for disturbances is to find the path of least resistance. So if you are asking me to agree with the idea that the low pressure at surface will move headlong into a cAk dome covering Quebec and New England, my answer would be no.

 
Latest from LC on this evenings newsletter
"What I think is going to happen is that the storm will track from SE MO to S OH, then start to re-organize in a center jump fashion into N VA on early Monday morning. I liked the 12z NAM version of events, which would take the low pressure system off of Cape May NJ, deepen the center to about 988MB crossing the 40N, 70 W "Benchmark", and then speed a powerful cyclone into Halifax NS by Monday night. The 850MB freeze line will likely bulge northward above the Pennsylvania Turnpike early on Groundhog Day, but surface temperatures may be slower to respond. For this reason, sleet and freezing rain may be a problem for parts of E OH....S PA....WV....N MD....N DE....and NJ. I can even see a situation where the NYC/LI metro and immediate coastline of CT get into a frozen/liquid precipitation tussle for a few hours on Monday. Afterwards, strong north winds will usher the snow southward before ending. The heavy snow threat should run from IA....N, C IL....N IN....S Lower MI....N OH....N, C PA....N NJ....NY....CT....RI....MA....S VT....C, S NH....C, E ME....NB. Most accumulations in that zone will run between 6 - 10 inches. But some communities in PA, NY and New England could have as much as 15 inches of wind blown snowfall before the low exits the scene on Tuesday."
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From JB this AM - maybe a MET can comment does this make sense?

 

"There are bands of snow breaking out in front of the main conveyor belt of precip. The reason we see the dry area in Indiana is because there is no resistance to the warming so the rate of warming means the condensation processes take longer.. In other words, the Thicknesses are rapidly rising. ( the column is expanding with the required moist advection not taking place to keep up, and by doing so, re cooling the lower levels and enhancing the over-running. The reason you see it breaking out so far to the east is because the rate of moist advection is faster than the colder air leaving.

So here is what to watch for. Where ever that dry air gets too before the main conveyor belt, it will likely turn to rain even if it comes back in as snow.

While its in northern Indiana . the storm is moving northeast, so that says all the way to the Hudson valley right?

Not so fast.

I stated at the start of all this the storm would head for where warm air would support it. There are two places, the strong downsloping on the south wind in the eastern Ohio valley and off the coast. So the models are gung ho on the first one because its right in front of them. And once driving the low so far north, they assumed it as to jump east. But what is going to happen when it gets there late tonight. Where will the northern front be effectively. You will be able to tell because the snow wont end in that area. Why? because the column is not warming as fast. So the pace of moist advection is greater than the rate of the cold retreating. In this case it holds its ground

But you might think, how can a front move south if the upper air flow is southwest. The problem is that baroclinic systems appear to move when in reality its a constant reformation of the boundary. The upper flow the High is embedded in is still west northwest across New England through today. So the front to the north may effectvely reform south to where the warm front from the south is coming from. So its a big problem. The modeling is all simply pulling the warm front up east of the mountains to where the northern front reforms too. And that may be the case. But I want to see what this looks like after all the runs before I change the large scale idea that this pops off the mouth of the Delaware Bay, rather than so far north ( off N Jersey)

As it is snow is falling fairly far south and the rate of warm advection to the west may cause a thermally induced reversed circulation. There is a light north wind in the southerly gradient over the northern mid atlantic because of stronger southerly winds to the west, creating a reverse eddy"

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Steve D at NYNJPA weather updated as follows

For South and East of I95 a trace-2" of snow quickly to rain

For the I95 corridor including Philadelphia 1-3" snow and 0.1 to 0.3" of ice

For Lancaster to East Nantmeal Townhip to Doylestown to TTN to NYC he has 3" to 6" of snow and 0.1" to 0.3" of ice with Snow to Ice and back to snow

For Harrisburg to RDG to Qtown to Just near ABE to NYC he has 5" to 10" of snow with 0.1 to 0.25 of ice

All Snow to the NW of that with 6" to 12" +

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Snowing in Landenberg... 28 degrees. My folks live on the East End of LI, NY and had temps more than 20 degrees less than me this morning, which is extremely unusual!

Just saw this on Steve Di Martino comments. However, look at the surface map! Cold high pressure is building down the coast. http://www.spc.noaa.gov/exper/mesoanalysis/s19/ttd/ttd_sf.gif?1422791027493

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Don't buy his BS. Look at the observations above in this thread. All Temps in this area are quickly on the rise.

Understood that comment was just one of many including his agreement that warm can win as well in this storm. Just observed precip remains snow on a line from Indy through Latrobe on the front end. Moisture is racing east.

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Steve D with NJPA Weather also believes this will tick south by tomorrow's 12z runs...he has

4"-8" of snow to a mix in Philly

8"-12" Just NW of Philly out to a LNS/Lionville/Conshy/TTB line

NW of that line he has an 8" to 12" + forecast with less mixing

 

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