I have to apologize for the lack of updates during the past week or so, but I have been very busy with other activities; however, I do want to briefly review why the threat of the previous winter storm for 1/15-1/16 that I highlighted last week didn’t pan out.

Below is the GFS model from this past Friday afternoon. You can see a developing low pressure over eastern North Carolina, which subsequently moved northeast to a position off the New Jersey and New England coast over the next 24 hours. A near perfect track for a major east coast snowstorm. This track was dictated by the favorable upper air pattern I discussed in my previous post.

So if that’s the case, what the hell happened? The fly in the ointment was in fact the low seen over the Great Lakes, originating from the northern jet stream, which not only stayed separate from the coastal low, but was also rather strong, allowing for warm air advection to scour out the cold air that was in place just 24-36 hours prior to the image below. This low and the lack of a strong cold high pressure to our north, made things just a little too warm, and instead the result was a quick hitting, cold rain for most, with the exception of the central and northern New England high country and particularly Maine. As stated previously, while the kitchen was open and the menu set (in other words, a favorable upper air pattern), what comes to the table (at the surface) isn’t always what you expect.


That being said, why is there a much bigger threat on the horizon for later this week into this weekend? Because the scenario which caused the rain instead of snow for the last storm will be completely reversed.

Below are the overnight ensembles from the European, Canadian, and American (GFS) models, which are basically a mean of numerous individual runs averaged together.




You can see all are in rather good agreement for, what at this time looks to be a rather long duration winter storm, located off the east coast in the Friday through Sunday time period later this week. But what is important this time around is the fact that cold air will be in place prior to AND during the storm, thanks to a nice cold high pressure anchored to our north and west, as depicted on the GFS operational model from last night:


This high will, if modeled correctly, will supply the cold air needed for a major winter storm (at least several inches of snow) for much of the east coast from Virginia north to at least southern New England.

Of course, the key phrase is, “if modeled correctly.” There IS rather remarkable agreement among the ensembles and operational runs this time around, something that has been lacking this winter so far. However, we are 5-6 days away, and it can’t be stated with any certainty that this storm will come to fruition. That being said, I do like the setup, both aloft, and, as illustrated above by the presence of high pressure to our north, at the surface. One thing that does concern me a little this far out is the overall strength of the subtropical jet and the models underestimating this strength early on. You can see how the overnight individual European ensemble run low placements are clustered primarily near and to the west of the mean:


Given this look and the strength of the subtropical jet, I wouldn’t be surprised if the storm overall creeps north and is modeled a little stronger in the next few days. This will introduce more warm air as you go farther south and east particularly along the coast. Successive runs of the  GFS ensembles from from yesterday evening through this morning (18z, 0z, 06z) showed this:

18z GEFS:gfs18zens

0z GFES:gfsens1

6z GEFS:GFSens

You can see the mean low placement is stronger and farther NW on the latest run (06z) versus the two previous runs (18z and 0z). I will say that the GFS has actually been performing better than the European in the last few runs regarding consistently with this storm, which is somewhat of a rarity, but, surprise, it does happen sometimes.

Bottom line, it’s still 5-6 days away, but the setup is a good one, with cold air available this time around, and there is rather good model agreement. I will be waiting until at least Tuesday 1/19 before I become more confident something big is coming. The potential is certainly there, but given the rather fickle nature of the models and complexity of the pattern, things can still fall apart.

More as we get closer presuming things remain favorable….



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…Several CHANCES of Significant East Coast Snowstorms are upcoming, first in the Jan 16-18 timeframe as discussed in the previous post…
After a very warm and rainy day today by January standards, a cold front will cross the area from west to east this evening and it will turn SHARPLY colder. Expect highs only in the mid 20’s to 30’s, and lows in the teens to 20’s across most of the northern mid-Atlantic from northern VA into northern PA, and east to the coast for the remainder of the week, quite a change given how warm it’s been in these parts over the past 6-8 weeks. You can see the Arctic air invading the plains and mid west this morning. Although it won’t be as harsh, that air is headed toward us tonight (map courtesy of
There will be a chance of light snow and snow showers coming Tuesday into Wednesday, with a clipper low which scoot to our north and redevelops east of Long Island and in the Gulf of Maine, which can bring a coating to an inch or two to selected locales. Those along the NE NJ coast into Long Island may see a bit more depending on how quickly that development to our northeast takes place (map below courtesy of Levi Cowan,
That low which will then move to a position in the region of eastern most Canada, just southeast of the Davis strait. This low position will be of PARAMOUNT importance with regards to the Martin Luther King weekend storm possibilities.  This 50/50 low (named for its position around 50N latitude and 50W longitude), in conjunction with the strong Greenland block (aka the -NAO), will be the catalyst in slowing down the upper level flow upstream over the remainder of North America.
On the map above from the overnight European ensemble mean (courtesy of Ryan Maue at Weatherbell, LLC), which is for next Saturday evening, you can see the large area of low pressure in question south of Greenland, with blocking high pressure just to it’s north. These two features allow for greater chances of interaction of energy from the northern (or polar) and southern (or subtropical) branches of the jet stream. The setup shown above is a classic one for a major east coast snowstorms, as illustrated in the book Northeast Snowstorms by Kocin and Uccellini (and as an aside, anyone with an interest in big east coast snowstorms, I highly recommend reading through it). Namely, those features include, a +PNA or western ridge centered in the vicinity of Idaho/western Montana, an eastern trough centered over the Mississippi valley, a strong -NAO in the form of blocking high pressure stretching from Greenland to the west shore of Hudson bay, and the aforementioned 50/50 low. All of the ensemble means from the various model suites have these features, some stronger than others, but all in general agreement for this upcoming holiday weekend.
0z Canadian ensemble mean:
0z GEFS mean:
Now, the presence of these features INCREASES THE LIKELIHOOD of a major east coast winter storm during this time period, BUT IT IS NOT A GUARANTEE. Why? Because at a week out, the individual energies (or shortwaves) in the northern and southern jet stream cannot be accurately modeled on a consistent basis. As I always like to say, the kitchen is open and the menu is set, but what comes to the table is far from decided at this point in time.
You can see from the map above at 500mb (or upper atmosphere, about 5600m above sea level, courtesy of taken a few days before the holiday weekend,  there are at least 6 or 7 shortwaves that are seen scattered around the southern and western areas of North America, all of which could possibly contribute to storm formation a few days down the road. There is NO WAY that the models can figure out which ones will interact (or not interact) to produce (or not produce) a storm at this time interval – they are just not that good. They each have their own biases/issues; however, as we get closer in time, within 4-5 days, things will become more clear.
So, what can be said this far out is that there are increased chances of something big happening around the Martin Luther King holiday weekend, and confidence regarding the details of what will or will not happen will increase as we move forward. For those insistent on following each model run with bated breath, I suggest you compare the runs at 500mb first before looking at any surface maps, if at all, until at least Tuesday or Wednesday.
One thing I will say regarding the operational models – the European parallel, which will replace the operational model in the coming months, has been the most consistent in the last few days in showing a major east coast snowstorm. I’m watching this rather closely because the European guidance is far from perfect, but the best we have, and it’s operational model has been very inconsistent from run to run. One of the chief biases of the model in general is to hold back too much southern stream energy in the southwest US, which has huge implications given the strength of the southern/subtropical jet stream this year. I’m curious as to see if perhaps this bias has been diminished with the newer parallel, given this is a known problem. This storm (or lack thereof) should be a good test.
And one other thing – this is far from the last opportunity of significant snow along the eastern seaboard. Given the very active subtropical jet stream and the blocking and available cold over the next few weeks, there should be multiple chances, some of which will come to fruition, while others do not.
More as we get closer.
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So obviously it’s been quite some time since I last wrote here, since last year actually –  but let’s be honest – when it comes to winter weather threats this season, there just haven’t been any. However, that is about to change.

All the talk this Fall has been about the El Nino, some calling it a “godzilla” El Nino, some saying it would mean a warm and snowless winter for many in the east, some saying it would be the strongest ever. A whole bunch of that is false, or weather hype, or some  combination thereof, in my opinion. One of the biggest comparisons I’ve heard with this years Nino is with the strong one that occurred in ’97-’98, which is comparable to this year’s event in some ways, and very much delivered a warm and nearly snowless winter in the eastern United States.

That being said, you may ask yourself, how is this El Nino going to produce anything different than what happened in ’97-’98? It’s easily in the top three strongest, so what gives? Notice I said comparable in SOME ways. Not all. And that’s important.

First of all, the location of the warm waters in the equatorial Pacific is paramount. You can see from the graphic below (courtesy of Ryan Maue, Weatherbell Analytics, LLC) that the warm waters extend from and just west of the dateline (180 degrees longitude) to the off the South American coastline, with the warmest anomalies in the western 2/3 of that area.


This is vastly different from what was seen in 1997-1998, where the warmest waters were concentrated primarily off the South American Coast, and the waters were significantly warmer at this point in time then versus now (1997 on the left, 2015 on the right).


And here’s a plot comparing the temperature differences between the two directly:


Additionally, this El Nino, while there will be some fluctuations from week to week, is starting to weaken, and will continue to do so over the course of the Winter and into Spring:


And finally, a graphic showing the sea surface temperature (SST) change in the last week alone (courtesy of Levi Cowan,


So, from the above information, we can gather that (1) this years El Nino is NOT the same as 1997-1998, not as strong when compared to the same point in time, and in fact it’s a basin wide phenomenon, with the warmest SST’s in the western 2/3 of the basin, closer to the dateline, (2) this Nino is weakening, and will continue to do so, and (3) that cooling that is occurring is greatest in the eastern regions per the last graphic above. These facts lead to more thunderstorm convection along the date line (180 longitude), which in turn promote a jet stream configuration over North America that leads to ridging (relative warmth) over NW Canada and troughing (relative cold) over the southern and SE states of the U.S.

Now, if that’s the case, why has it been so damn warm in the eastern US? Because of course, there are other factors at play here. The biggest in my opinion has been the strength and positioning of the Polar Vortex, which so far this year has been centered over the pole and VERY strong, effectively locking in almost all of the arctic air over northern Canada and the arctic circle.

PV now

You can see the coldest values directly over the pole, with a ridge in the east, trough in the west, just as it’s been for weeks now. But that is about to change.

PV split2

The graphic above is the 10 day forecast from the European ensemble guidance, but I could’ve picked any of the models quite honestly, because they are all showing the same thing. The cold pool over the pole becomes elongated, and splits its concentration into two locations – over eastern Canada, and to a lesser degree NE Asia/Bering Sea. This a result of the weakening of the Polar Vortex (PV). The reasons behind this are somewhat complicated, and beyond the scope of this blog, and involves the transport of warmer air from the mid latitudes of the troposphere (where we live) to the stratosphere (high in the Earth’s atmosphere), which in turn disrupts the PV circulation; but understand that this weakening was in fact favored given the well above normal snowpack over Siberia in October (courtesy of – for those of you interested, I highly recommend reading his work  work):


Although the PV will only be weakened in the near term, it will be enough over the next few weeks to aid in causing displacement of colder air from the north into eastern North America, as well as a deepening eastern US trough, as depicted in the second image from the European above at 240 hours. This will likely not result in a prolonged Arctic air mass, but rather temperatures closer to normal, at least to start the month of January. As the PV is disrupted further later in the month, the cold COULD be more severe.

So, the disruption of the Polar Vortex is one of the reasons why we’re seeing a change in our pattern in the face of a strong (yet weakening and more west centered than 1997 remember!). But there are others as well.

The Madden Julian Oscillation, or MJO, which again is complicated but is basically a coupling of circulation in the atmosphere with tropical/equatorial convection (thunderstorms). In an El Nino such as this, the MJO, to borrow an explanantion from Steve DiMartino ( is more of a modifier than a pure driver when it comes to our weather in the United States. To make a long story short, the MJO is forecasted to move into a more favorable phase 8 in the first week of January:


Which corresponds to, again, more convection towards the date line, and a western ridge and eastern trough, resulting in temperatures across the US in the winter months:


And finally, we have the warm waters in the Pacific west of North America, also know as a positive PDO:


Which results in this temperature pattern across the US:


So, given all of the drivers and modifiers above, it’s no wonder we’re seeing the jet stream configuration go from this, the so called “firehose” Pacific jet stream, flooding warm Pacific air into most of the country as it attacks northern CA below:


To this graphic below, in about 10 days or so, where it splits, where one branch heads far to the north over Alaska and the Yukon and then south into the US, supplying the cold, and then other branch heads south into Baja California and then into Texas and the eastern US, supplying the moisture.


It all adds up to lots of fun on the near horizon with regards to winter weather.  Expect a mild Christmas weekend, and then sharply colder this coming Monday, with the chance for ice and snow from northern PA and especially upstate NY and New England Monday night into Tuesday. I don’t want to go into specifics yet regarding that storm, but it needs to be watched over the next few days. This system isn’t even the result of the changes I’ve described above, but it is the beginning of a lot more to come.

Expect this website and my page to get busier over the coming weeks and months as we step down into winter from this record breaking warmth we’re currently seeing. Don’t worry, #WinterISComing, it’s just taking a little longer than usual – but it won’t disappoint.

In the meantime, I wish everyone a safe and merry Christmas!




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A very weak area of low pressure will move from the Mississippi and Tennessee river valleys to the west of the area tomorrow afternoon through tomorrow night. This will spread moderate to heavy precipitation into the norther Mid-Atlantic region starting just around lunch through early afternoon from west to east, initially in the form of snow for almost everyone.

Yesterday’s overnight model runs first started picking up on the amount of cold air that would be in place prior to this storm. They continue to see the influence of this cold with each run and are nearing a consensus. In general, the upper atmosphere will be cold enough to support snow for everyone; however, with the low pressure center tracking to our west, warm air that initially rides up and over the cold dome producing the snow will eventually make inroads in the lower portions of the atmosphere, first in southern and eastern areas and I-95, then further northwest, to a point.

The problem in this case, and arguing against a more substantial I-95 snowstorm comes at 925mb, or about 2500 ft up in the air, down to the surface.


You can see on the above map from the latest 12z run of the NAM that 925mb temperatures go above 0c (32F) in southeastern PA and all of DE and southern and parts of central NJ around 7pm EST (0 Zulu time). Snow will fall though the majority of the atmosphere until it reaches approximately 2500 ft, and then begin to melt on it’s way to the surface, (surface temperatures also very closely mimic the map above for this storm). So, it’s safe to say, based on this model, that PHL and surrounding areas in southeast PA will start to transition to rain, after a very brief period of ice, around 7-8pm in the evening Saturday. Those farther south, it will be earlier after a very brief thump of snow, before changing to plain rain, while those farther north will hang onto snow longer and in some cases for nearly or all of the duration of the heavy precipitation. The 0c/32F line at 925mb and at the surface gets to about the blue ridge/ just north of I-78 during the large majority of the precipitation, and not much farther than that. Looking across the board at the models, there is near consensus on these variables on the NAM, RGEM, and European. The GFS I believe is just too warm, given the extreme cold preceding this storm and deep snowpack particularly in the northern 2/3 of Pennsylvania.

So what exactly does this mean? Precipitation will start sometime around or just before lunchtime for those farthest west, and early afternoon for those further east in New Jersey. It will start as snow for everyone, but quickly change to rain for those well southeast of I-95, within an hour or two (probably by 4-5 pm). In and around the city of Philadelphia including southeast PA and central NJ, expect the changeover to occur sometime around 7-8pm. Farther north and northwest, including places like Lancaster, Doylestown, Trenton, up towards NYC, expect a changeover around 10-11pm. The Allentown-Bethlehem-Easton area will changeover in the early morning hours, in the realm of 1-2am, if the changeover occurs at all. I suspect that in these areas, it may be a case of snow to drizzle/freezing drizzle, and really not that much of substantial rain/ice, but that’s kind of a tough call. Even if it does rain in these areas, it won’t be for more than an hour or two. IN the Pocono mountains, expect all snow, from start to finish.

Given all of the above, I think 2-4″ is a good call in and around PHL and southeast PA and its immediate eastern and southeastern suburbs. This will include the NYC area, and the central NJ coast just below the city as well.

Southeast of that, down toward the pine barrens and inland sections of NJ, expect 1-2″, and along the coast of southern NJ, little to no accumulation.

Farther north and west, in the Lehigh Valley, the Lancaster and Harrisburg area, and the Poconos, expect 4-8″, with the least in the south (places like Quakertown/Lancaster), and most in the north (along the blue ridge and obviously in the mountains to the north of that themselves).

Following the storm, expect relatively mild (by the past several weeks standards) temperatures on Sunday, in the mid 30’s to low 40’s from north to south. Then, it’s back into the deep freeze for the foreseeable future, with additional chances at snow around the 25th/26th and March 1st/2nd.

More as we get closer as needed, if there are any substantial changes.


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Just a quick post this morning to make sure everyone’s aware…

There’s a high wind watch this weekend, just issued a few hours ago for all of eastern PA, northern MD, all of DE and NJ into New England:

528 AM EST FRI FEB 13 2015

Here’s the 6z GFS wind gust forecast for this time period:

GFS wind


There will be anywhere from 2 to as much as 6 or 7 inches of snow late Saturday into Saturday night, followed by very gusty winds, as high as 60-65 mph, as you can see above. This will cause widespread blowing and drifting of any snow that does fall, and more importantly, possible power outages, with temperatures in the 0-15 degree range, and and wind chills well below zero. It doesn’t take a rocket scientist to figure out this could be a big problem.

So make sure you have an alternate heat source other than electricity, or if not, make arrangements to stay with someone who does have one, just in case. Fill all your vehicles with gas, and charge all cell phones. Make sure generators work and there’s gas for them. If you do need to leave your home due to power loss, shut off the water and open all spigots in an attempt to prevent pipe bursts. Hopefully there won’t be widespread outages and it won’t come to that, but better safe than sorry. Regardless, it will be getting dangerously cold starting tomorrow.

And anyone planning to travel up towards Boston or Maine, my advice is not to. They will have the same conditions except with 1 to as much as 3 feet of snow, particularly along the coast of Maine.

More as warranted and as we get closer…


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We have quite the storm already developing across the central US, which you can see on the latest national radar stretches from eastern Nebraska, all the way to Ohio, and south to the Gulf coast. This low is currently centered over Missouri and will track east-northeast into the southwest most portion of Pennsylvania while gradually strengthening.





This generally east to west track is the result of blocking in the form of a double barrel, or banana high pressure to our north and northwest, a low pressure system over the Canadian maritimes (our recently departed clipper), and the Polar Vortex situated over Hudson Bay in Canada. Once the low reaches SW PA, it will jump to the coastal water of New Jersey. While this is going on, copious amounts of moisture will spread into the area from the west, with scattered snow showers developing later this afternoon, and more steady snow coming this evening during the superbowl. There are several factors at play here as to who gets what when it comes to snow, ice, or rain, or a combination of the three.

It’s already plenty cold here, with temperatures ranging from near 20 in the northern areas to near 30 in the Philadelphia region, not to mention we are just recovering from a rather brutal Saturday with very cold temperatures and wind chills thanks to a fresh Arctic air mass that invaded behind our last clipper. The ground is VERY cold, and even it some areas get slightly above freezing tomorrow. Additionally, there is a healthy snowpack from the Lehigh Valley on north, which will help to keep temperatures from rising that quickly. These are the reasons why I’m worried that ice will be a problem even in the face of above 32 degree temperatures.



Additionally, the strength of the high to our north, and the position of the low our the Canadian maritimes are of paramount importance in the evolution of this storm. Both prevent the low from gaining latitude, and any deviation in position or strength from the general model consensus will result in big differences in the snow/ice/rain forecast. Models tend to underestimate cold air, especially low level cold air, and given how cold its been, and a new area of high pressure sliding into our region as the storm does, these factors will be a problem when it comes to ice.



As warm air rises up and over the colder air at the surface, snow will initially break out, but then as warmer air continues to invade, the snow will change over to sleet and then freezing rain, from south to north. The questions become how far north does this complete changeover line get, and how long does the freezing rain hang on given the above factors.

Right now, I think the models are removing the cold air too quickly, as they often do, and even when the temperature rise to 32 or 33, the ground is cold, and ice will continue to accumulate, at least for a time. The image below is from the overnight European model run, and it shows you where the snow/ice/rain lines line up approximately during the height of the storm.



All this being said, I think the complete changeover line (from snow to ice and/or rain) gets somewhere within the region of I-78 in the Lehigh Valley. It may be a few miles north, or a few miles south of this area. And that’s not to say it will be all snow above this line either, as I believe there will be some mixing with sleet even in parts of the Poconos.

Philadelphia should go to rain after an inch or two of snow. This includes the immediate southern and eastern suburbs of the city, as well as western southern NJ and northern most Delaware, and those along the PA/MD border farther west. Just outside of the city in the northwest suburbs, as well as central NJ including Trenton, 2-4″ should fall, followed by the changeover to ice and eventually rain. Farther north than that, up into the southern Lehigh Valley, the Reading area, and more northern NJ from Phillipsburg to the NYC area, 3-6″ will be the rule. 6-10″ is quite possible in the northern Lehigh Valley, and 8-12″+ in the Poconos and NW New Jersey. Please note that the lower end of snowfall accumulations will occur if there’s an earlier changeover or more mixing, whereas the higher end will occur if it is indeed colder than modeled. It will be all snow north of that into NY state and New England. I am very concerned about icing in the northwest suburbs of Philadelphia, from the area of the east-west turnpike into the Lehigh Valley, particularly below I-78, and central NJ, where I do not think ground temperatures warm up enough to prevent at least moderate ice accumulations.

The 75th percentile map below from the WPC is probably a good estimation of snow amounts, although the southern and northern fridges are likely overdone.

WPC SNOWThe large majority of this storm will occur overnight tonight into tomorrow morning, with things tapering off around and after lunchtime. Be careful later tonight after the superbowl, because it’s very likely there will be snow and/or ice falling no matter where you are, with the exception of central and southern Delaware and far southern NJ. The commute tomorrow morning will be a nightmare for those north and west of the city, particularly in the Lehigh Valley and Poconos.

After the storm departs, the cold will hold into the foreseeable future, with several more chances of winter weather in the coming weeks.

More later if warranted.

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Energy ejecting out of the southwest United States will move out to the northeast and spawn a weak area of low pressure in the mid Mississippi valley. The low will head towards the Ohio river and West Virginia initially, while strengthening gradually. Once it reaches this position, it will transfer its energy to a coastal low off the Delmarva. Meanwhile, the eastern flank of a banana high pressure will be located to our north and northwest, and low pressure which is now exiting our our this morning will be over the Canadian maritimes, as the Polar Vortex spins centered around Hudson Bay Canada. These three features will act to effectively block the initially low from gaining much more latitude, and force it to move to the coast.


There should be ample moisture available to the storm initially from the Gulf of Mexico, and then the Atlantic as the coastal low forms and strengthens. The cold source will be there in the form of high pressure to our north and northwest, and there will be at least some blocking present given the 3 features described above. This will result in some rather significant snowfall accumulations particularly north of the Mason Dixon line in the northern mid-Atlantic into southern New England, including the I-95 cities from Philadelphia to Boston, initially in the form of warm advection snows, then as a result of the coastal low taking shape. Right now, a general 6-12″ of snow looks likely, and this includes nearly all of the state of PA, central and northern NJ, southern NY state, and much of Massachusetts, Connecticut, and Rhode Island.  This snow will be falling with temperatures primarily in the 20’s (and in some cases colder) in much of PA, northern NJ, and coastal New England on north, and therefore snow ratios will be higher than the 10:1 shown on most snow accumulation maps, probably in the 12-15:1 realm. South of the Mason Dixon line, there will be some mixing or a changeover, and this includes DC and Baltimore, as well as most of Delaware, particularly south of New Castle County, and South Jersey especially areas south of Atlantic City. I could see mixing go as far north as within a few miles of the PA turnpike, but I don’t think the rain/snow line gets much farther north than that. There is very close to universal model agreement in this scenario, somewhat of a rarity this season, with the exception of the Canadian model, although it’s ensembles are in agreement with the other models. Systems like these have the ability to overperform, especially on the front end, and that’s something we’ll have to watch for regarding QPF increases in the modeling over the next 48 hours and on radar once the storm forms late Saturday and Sunday. Snow should start from west to east around the time of the Superbowl (be aware it may very well be snowing after the game for most) and last through at least Monday afternoon, which is a relatively long duration event.

So given what happened with the last storm, you are probably asking, what can go wrong or right, depending on your perspective with regards to snow. The position of the Polar Vortex is key in this situation, and any deviation farther north or south will result in the initial low moving more north or south, and result in a warmer (more mixing and less snow south) or colder (more suppression and snows farther south, less north), respectively. That’s the one wildcard, but right now, given the rather good model agreement, I don’t expect things to change significantly. And could the storm be a miss like the last one? That’s VERY unlikely, as this storm will actually be formed with a large precipitation shield BEFORE it reaches our area. The last storm was dependent solely on redevelopment of a clipper low which had a paltry amount of snow before the coastal low rapidly intensified, and in our case for the northern mid-Atlantic, too far east to really affect us.

Beyond this storm, I see no significant warm ups in site. Weak Modoki El Nino winters are almost always back loaded, with the greatest degree of cold and snow coming in March and February, and in some cases into early April. Given this fact, and the SST profiles which continue to be very warm off the west coast and in the Gulf of Alaska, similar to last year, and additionally those in the northern Atlantic, which remain favorable for blocking, as well as the inevitable weakening of the -QBO in the next few weeks, I see winter extending well into March if not early April. So there is plenty more snow for those who love it. For those who love Spring, I think they’re disappointed much like last year, especially if they were hoping for early warmth.

More on the late weekend storm as warranted.


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I wish I had time to get more in depth here, but unfortunately I just haven’t had the time given work and everything else in between, so this will have to be quick.

The storm is currently streaking over Kentucky and by tomorrow will be redeveloping off the Virginia Capes and then RAPIDLY deepen as it heads just east of due north.


Once it reaches our latitude, the 500mb or upper level low will close off somewhere around the Delmarva peninsula, which subsequently will capture the surface low and cause it to slow down and meander around near the 40/70 benchmark, just southeast of eastern Long Island. Where and how rapidly this upper level low forms will determine how far west the heavier snow gets with respect to eastern Pennsylvania. The European and its ensembles have been rock solid consistent in this scenario, which is typical for nor’easters, and I’m leaning heavily on their outcomes. I just don’t buy the further east solution of the other models given the insistence of the Euro and the very warm ocean temperature just off the east coast, which storms like this feed off of.





Assuming the European and its ensembles are correct, and I think they will be, expect lighter snows to begin in the early morning hours and then continue through most of the day Monday. There may be a lull in the action Monday afternoon, and then Monday evening things will dramatically pick up in intensity from southeast to northwest as the coastal storm ramps up. Heavy snow, where it does fall, will occur from Monday evening through at least Tuesday afternoon. The worst weather will be near the coast, where 2-3 feet is likely from central NJ up into southern Maine. Farther west, at our latitude, snowfall will drop off, and there will likely be a rather sharp cutoff along the western fringe of the precip shield. The hardest area to forecast for our area will be on a line from about Scranton to Hamburg to West Chester PA. Within just 10-15 miles of this line, one could got from 6-7 inches of snow to well over a foot. There is the possibility that this storm gets its act together more quickly, and the 500mb low develops faster and farther southwest, resulting in a slightly further west surface low track, but I’m not ready to go there yet. I will be watching tomorrow though as the storm develops for this possibility however.

That being said, I like NOAA’s forecast below for this storm. Extreme eastern PA should see double digits, in the realm of 10-18 inches, greatest along the Delaware river, least further west. Farther east, amounts of 2-3 feet will be common, but given the gale and storm force winds associated with this storm at the coast, after you get beyond 18 or 20, let’s be honest, it’s rather hard to measure. Farther west there should be 6-12″ along the Scranton-Hamburg-West Chester line I described above. Accumulations will likely drop off from there as one heads toward and beyond the Susquehanna river.



After the storm winds down, colder air will follow with some moderation towards the end of the week, and another chance of snow come later Thursday into Friday. This will be followed by the coldest air of the season, likely quite brutal, next weekend into the first week of February. Winter has truly returned.

More tomorrow as warranted…


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As the storm from overnight departs us, leaving a healthy dose of snow, there’s a good possibility of another, even bigger storm for someone in the northeast US come Monday and Tuesday. A rather potent clipper low will race across Kentucky and southern Virginia during the day on Monday, and provide light to moderate snow to the north of it’s track, across most of the mid-atlantic states.

Once this low reaches the North Carolina coast, the fun begins. Just 24-48 hours ago, all models had this storm exciting out to sea stage right. However, over the last 24 hours, the upper level pattern has been changing and favoring a low which develops faster and closer to the coast from NC northward. We’ll look at the NAM, although honestly, all of the models are showing similar trends across the board:

1/23 18z NAM 500mb:


1/24 0z NAM 500mb:

0z NAM

1/24 6z NAM 500mb:


1/24 12z NAM 500mb:


All of the troughs over the east coast late Monday afternoon are negatively tilted, which will allow any storm that forms to ride north and parallel the coastline. But looking closer, the trough axis (or position) has moved west with each successive run of the model. Furthermore, the trough is becoming progressively deeper and sharper over time as well.

Now, lets look at the surface maps:

1/23 18z NAM surface:


1/24 0z NAM surface:


1/24 06z surface:


1/24 12z surface:


The increasingly deeper and farther west position of the trough at H5 allow the low to begin development further southwest and closer to the coast. As a result, you go from a storm out to sea on the 18z NAM last evening to a blizzard over New England on the most recent 12z run today.

18z last evening, low harmlessly going out to sea:


12z today, blizzard for New England and Long Island:


So you can see the importance of the trough depth, sharpness, and its position. As I said before, ALL of the models are trending this way. Do I think this will continue to trend to the point that it affect most of the Mid-Atlantic with heavy snows? Outside of maybe eastern NJ and New York City, no, not at this time – but, it’s definitely something to watch over the next few days. One thing is becoming more and more likely – southeastern New England and at least eastern Long Island is going to be hit pretty hard with this one.

More on Facebook at doctoochweather as warranted….

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Winter cancel? Not by a long shot….

So I realize I’ve been shirking my usual blogging duties lately, but to be honest, there hasn’t been a lot to talk about up to this point, particularly along the coastal plain into the I-95 corridor of the Mid-Atlantic. I’ve been lucky enough to have about 12 inches of snow collectively fall from the pre-thanksgiving storm, and a few other minor storms, up here in the foothills of the Poconos, but other than that, there hasn’t been any big threats. However, winter, after all, is just beginning – the winter solstice was just the other day. So why all the complaining?

Most of it comes from people just pining away for snow at all costs – they see the majority of meteorologists talking about how the winter is set to be another bad one, and if that call for cold and snow doesn’t start in November, and last into April, well, then winter is just not happening. A complete epic fail. Climb the bridge. It’s over. Maybe next year.

Except, winter just started, and we’re just entering it’s prime months. So, all is not lost. In fact, there are still plenty of signs out there in the short, medium, and even the long range that are favorable. There are still some question marks, but lets get to what is going right.



The first thing I’m noticing is the re-establishment of big, strong Arctic highs coming out of northwest Canada, and with them, extreme Alaskan ridging (-EPO) in the 8-10 day period. These two features were the HALLMARK of last year’s winter, trumping the lack of a -NAO and the relatively non-contributory ENSO state we saw last year. You can clearly see them on the latest run of the GFS below (surface map first, 500mb to follow):


GFS surface


GFS 500mb

You may think, sure, but it’s the GFS; however, these features are on all the models, and many have them very strong. I often will chastise this model when it comes for east coast storms, and for good reason, as it regularly performs horribly in the medium range for such systems. But it’s performance last year was actually pretty good against the famed european model when it came to seeing the strength of these large highs coming down out of Canada in the longer range. It’s been nice to see them appear in the 10-15 day forecast on the GFS and see them hold throughout and into the 8-10 day forecast, as well as see them on other models. In fact, I will be watching the strength of these highs on the european as we get closer in time, and it would behoove you to do the same. Last year, they actually increased in strength from run to run, and were overall weaker initially when compared to the GFS.

The importance of these highs (and the Alaskan ridging) can’t be overstated. One only has to look at the 500mb map above and if you follow the contour lines over Pennsylvania and NY state back to the west, and see the source region for these upper level winds is in fact coming from north of Alaska, the north pole, and even crossing the pole from Siberia. That’s serious cold, and that’s what this setup is capable of over the next 2 weeks, beginning around December 29-29th, and onward – and we all know you can’t get the snow without the cold, especially for our friends in the I-95 corridor.

These changes at 500mb are the result of the warm sea surface temperatures seen below in the area labeled #1, which as you’ve known from earlier facebook posts, promote ridging in Alaska and northwest Canada, which in turn allows the cold air to pour into the United States (which is well established over the pole and Siberia thanks to above normal snowpack in these areas). Additionally, also discussed earlier this year, the warmer waters off the Baja of California, and the weak west based el nino state of ENSO (labeled #2 and 3) promote an active subtropical jetstream, and the moisture source for the winter storms we all live for (well, some of us).




Even with that, one can look at the relatively warmer European, and to a much lesser extent the GFS, and think, but about the southeast ridge that keeps showing up? Isn’t that an issue? The answer is, yes, in most situations, but given Arctic advance associated with the Alaskan ridging and the Highs coming with it, it actually can be beneficial. Whenever you have such extreme cold air, in this case from cross polar flow, there’s always the chance that it can overwhelm the pattern, and suppress the storm track far to the south. So, you want that SE ridge to flex its muscles, because without it, you get a lot of ‘garbage cold,’ or temperatures in the teens and 20’s and wind and flurries. Not exactly a party for snow lovers, let alone anyone who doesn’t like winter.


The question becomes, how strong is this ridge, and how much does the cold air press? Unfortunately, the answer is not apparent this far out. Will there be a “storm” on December 29th exactly as depicted above on the Euro? Probably not. But something similar to this is very possible, and in fact from right before New Year’s until well after, there may be a few of these possibilities. The question becomes how much energy comes out of the southwest US – if it’s a lot, the rain snow line is shunted northwest of the one on the map above. If it’s less, the line and precip is shunted south.

And now to the question marks….


Most forecasts included a negative NAO this year, but we just haven’t seen much in the way of Atlantic blocking. The sea surface temperature (SST) over the north Atlantic remain favorable (see below, where we have warm waters in the Davis straits (labeled #1) and around Iceland (#2), and cold waters in the central Atlantic (#3), but we have yet to see a sustained -NAO, which as most know promotes slower, longer duration storms by blocking there quick escape into the Atlantic Ocean.


Time will tell as to whether this occurs. Typically, in my experience, such a pattern tends to become more established as we get into mid to late winter, usually late January through March. Additionally, as discussed below, the stratosphere is becoming more favorable for blocking. So while although it has yet to really come on, there are signs that it will shortly.



Much has been made over the Quasi-Biennial Oscillation, or QBO, over the last few days, and it’s affect on the warm Pacific jet stream that has dominated the pattern over North America over the past few weeks, starting after Thanksgiving.

So what the hell is the QBO? I don’t pretend to be an expert on it, but the best most useful I’ve found is from Dave Tolleris at

“The Quasi-Biennial Oscillation (QBO) is a BAND of wind over the equator of the globe that was discovered over 50 years ago.  This band of wind exists the very top of the atmosphere about 15 miles up where the pressure is about 30mb or just 3% of its surface value.  The QBO  has a “ cycle”  to it.  It runs from east to west  (the negative  phase) then after  reaches some sort of Max negative value … the  QBO   moves back towards neutral. Then  the winds reverse and the QBO runs from West to east (the positive phase) . The cycle takes approximately somewhere between 18 and 27 months  but sometimes it can take longer or shorter.”


The bad news so far this late Fall and first few days of Winter is that the QBO has been markedly negative, in the -20’s range, for quite some time.


This is bad because it promotes a strong Pacific jet, with it’s zonal pattern and associated milder Pacific air, to flood the continental US every time a colder pattern tries to take hold.

But, there is good news on the QBO front as well. It is after all, an oscillation, which implies that at some point these values should begin to decline. Such declining more moderate negative values promote more amplification at 500mb and more blocking. I remember discussing this with a few of the EPAWA meteorologists a few months back and wasn’t worried about the highly negative values of the QBO even back then. Why? Because one only has to look at the QBO values over the past few decades (see below) to see that after about 5-6 months, such highly negative values ALWAYS fall back toward neutral within the subsequent 2-3 months.


So I knew that as we enter the heart of the winter, things should fall into place and the Pacific jet should relax, and more blocking should be the rule.



I also wanted to briefly touch on the Stratosphere and its warming implications for us going forward. The behavior of the stratosphere in relation to the troposphere, or where we live, is somewhat complex, but I like to think of the SSW events themselves as kind of like a sledge hammer. They in effect split the polar vortex, which when displaced from the north pole (hence the name), can bring large chunks of arctic air along with it. A few weeks ago, quite a few people were excited about the SSW that was occurring over the northern hemisphere, but in fact on the wrong side of the globe, centered over Russia, and not over the pole or North America. If there’s one thing that I learned from the winter of 2011-2012, it was the the location of such an event is as important as the SSW event itself. It’s no wonder December has been rather blah when it comes to cold and snow from a stratospheric standpoint. The Polar Vortex has been in an unfavorable position away from North America, and there’s been a lack of arctic air this past month almost nationwide.

However, there seems to be good news here as well. As you can see below, the latest forecast from the ECMWF (courtesy of WSI) shows another SSW event, but this time directed more over the pole, rather than on the other side of the globe.


This would promote splitting of the polar vortex into a more favorable position for cold for us, and a more negative NAO (blocking) and AO (cold) as we go into mid to late January, given the 2-3 week lag time that is usually the norm for such events.



Finally, we come to the MJO. The MJO is characterized by an eastward progression of large regions of both enhanced and suppressed tropical rainfall, observed mainly over the Indian and Pacific Ocean. The implications of this cyclical pattern of tropical rainfall are neatly shown in the following two graphics:



One can clearly see that the phases 8, 1, 2, and 3, and to a lesser extent 7, are favorable for cold in the eastern US. Phases 1, 2, and 3 are particularly wet as well.

Right now, the MJO impulse is currently in the eastern Indian Ocean and is forecast to be in phase 4/5 over the next few days. This is why we are seeing a southeast ridge pop up on many of the models. However, there are signs it will indeed propagate into and beyond phase 6 as we go through mid January, again, favoring cold on our side of the country.



So, with all that being said, you can see winter isn’t in fact canceled, but just getting started. The mega highs and Alaskan ridge is there, just like it was last year. This will initially cause the cold to bleed southeast, on the heels of a broad based trough, and while the MJO is in its warmer phases, the southeast ridge to fight back. The QBO is markedly negative, yes, but it WILL start to move towards neutral, promoting a relaxation of the Pacific jet, and more blocking as we head into the heart of winter.  The stratosphere is forecast to warm in a more favorable location for us, also favoring more blocking and a -AO. And the MJO should propagate into more favorable phases for cold and snow as we head towards mid-January. Fun times are indeed ahead.

Watch for things to get interesting beyond December 28th/29th. More as warranted as usual.

Special thanks to Mike DeFino and Bobby Martrich of EPAWA who contributed to this discussion.





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