Setting The Stage: Godzilla Snowstorm February 13th

Toward the end of my previous blog, I briefly mentioned that the period around Valentine's Day will be the next one to watch for a potential snowstorm due to the potent STJ energy entering the SW CONUS. Here we stand a few days later, tracking a major east coast storm to impact millions of people across the eastern seaboard. Although specifics of the storm for our area such as snow amounts, exact track, and timing are not set in stone yet, we should look at upper level maps and seasonal trends to try and help steer us in the right direction.

The above is the 12z EURO model run at the 500 mb level. By looking at the vort maps, we are able to see that the EURO closed off the H5 vort over central North Carolina. This model is the only model to close off H5 this early which is why it is taking a storm track right along the coast. Heights rise ahead of it and the storm tightens / strengthens much quicker. The region starts as snow, then changes to rain, to end as snow. 

In comparison, the 12z GGEM (Canadian) model does not close off H5 at the time the EURO does, but the energy at the base of the trough is much stronger which still raises heights off our coast to promote a storm track tucked in west from the benchmark. In fact, the GGEM really explodes this storm system and brings crazy amounts of both snow and rain to the area. Of the three global's, the GGEM is the strongest one. 

The GFS also does not close of H5 as early as the EURO model. However, this model has struggled greatly with the synoptics of this storm because it has been shearing energy from the west side of the trough which strings out the low level center a bit. The mid-levels fall apart and the surface maps begin to make no sense with a 980 mb low off the coast with not much precip. to show for it.  The GFS has made strides to the other models, but at this point, I think it should be disregarded until it straightens itself out. Heights are also flatter along the east coast compared to the GGEM/EURO which is why the GFS tracks this storm right on or just east of the benchmark. 

A common theme you will find in all of these models is that it does warm temperatures up enough to change snow to rain for some locations, including NYC Metro. This is where the forecast becomes tricky. 

Here is another look at the 12z GFS model. One thing you will notice is that there are two areas of High Pressure surrounding the northwest and southwest quadrants of our coastal storm. The first one is north of Maine, which could help provide us with cold air to prevent snow from changing to rain. The second is along the Gulf coast. The third piece we should pay attention to is the potent clipper in the Great Lakes region. One of the many things I am keeping an eye on is if those two anomalies are providing too much subsidence for our coastal storm to really deepen and bring moderate to heavy banding over our area. Vertical velocity at H7 (frontogenesis) is not going to be impressive if those two pieces are there to disrupt the evolution of our coastal storm and preventing it from amplifying. This could be one of the reasons why the GFS has a funky look to it and I definitely think it should be monitored. 

Another important factor to look at is to see where the 700 mb and the 850 mb low's close off. The Canadian model, for example, vertically stacks each of these low's inside the BM which is another reason why it outputs such an extreme scenario. 

For example, 

12z GGEM 700 mb

12z GGEM 850 mb

One other factor I am considering when trying to forecast this storm is the seasonal trend. We are now in mid-February and have a good idea of how the storms this season have behaved. None of them had a storm track inside of the benchmark. Most of them remain south and east of the benchmark and brought the heaviest precip. amounts along I-95 and points east. I'm only mentioning this because the GFS / NAM models are not sold on the idea of having a storm track hugging the coast. I can see why with the lack of blocking (-NAO) and areas of confluence to the west of the storm why those tracks could be justified. 

How all these factors evolve will determine how this storm plays out along the NYC Metro area. Consistency is there that a long duration event is likely to begin early Thursday morning and continue into Friday morning, possibly a 24-hour + storm. It is certainly possible Blizzard criteria is met and watches / warnings are issued for the area, but that will not be realized until the factors I mentioned above are known. 

Here is an example on the extreme side of what winds at the surface could look like for our area. This is from the latest 18z NAM:

With all that being said, here is my 1st call snow map with this storm system likely to be changed again tomorrow. But I wanted to put this out there so everyone can get an idea of how I view this storm panning out. I do think the GGEM/EURO are a little too far west right now. While they have been consistent, we cannot ignore the consistency of the GFS/NAM either. The UKIE was also a little more east today at 12z compared to its 00z run. A lot depends on when exactly H5 closes off. I think it will happen along the coast of NC or SE VA, not interior Mid-Atlantic like the EURO shows. 

My current thinking feels the models tonight into tomorrow will begin a trend with this storm system a little further east. I think a track right along the benchmark is fair to say at this time because of some of the factors I mentioned throughout this blog post. If the western most track comes to fruition, the heaviest totals will have to be pushed further west and lower amounts will occur along the immediate coast due to mixing. At this time, I do not see that scenario panning out but this is a high volatility forecast. 

Temperatures Thursday morning, the time the storm is expected to start, are only in the low to mid teens across much of the area. Couple that with a possible High to the north and evaporational cooling from our current snow pack, I think models also have a good chance of trending colder with this storm once the dynamics are realized. There is a lot to digest here. Extremely complex set-up. 

Thanks for reading, 

Francesco Paparatto 

*Please visit the www.njstrongweatherforum.com forum for continuous discussions about this impending storm*

What Happened To The 3-Foot Blizzard February 9th-10th?

Sometime last week rumors began to fly that a monster blizzard will impact the northeast this weekend. Since that social media uproar, I have been asked repeatedly what my thoughts are and whether or not I think it has merit. In this blog, I will give you my point of view on the manner by diagnosing the overall pattern. As we all know, it is the pattern that brings us storms, not the models themselves (if so, I would take the DGEX any day of the week, twice on Sunday). 

Remember two mornings ago when we woke up to find the 06z GFS model show this?

A 980mb low off the coast of NJ bringing blizzard conditions and dropping 1 to 2 feet of snow in the area. Soon after, the models suddenly lost that idea and trended to a much weaker one. The reason for this was because they have changed the way the upper level pattern comes together for the upcoming weekend. 

Here is the same 06z GFS run from that morning now looking at the 500mb vorticity map. You can see the beautiful trough in the center of the country working its way eastward as it attempts to close off, with a nice +PNA ridge spike in the western US and a nicely placed 50/50 block south of Greenland. This particular run of the GFS phased both the northern and southern stream energies way back in the western U.S. as they were both coming ashore. The confluence over the northern tier of the country is preventing the phased-out storm from cutting north, so it has no choice but to reach our coastline. 

Now, the upper level maps look different. But not by much! 

Here is the 12z EURO height anomaly map at h5. The overall pattern is actually conducive for storm development along the east coast. There is our everlasting -EPO ridge providing Pacific blocking, the 50/50 block near Greenland that I referenced from the 06z GFS map, and a block (AGAIN) in the Bering Strait. I say "AGAIN" because this block was also there for our January 21st storm last month and it helped force a phase along the east coast to develop the storm. The ONLY thing missing from this map that was existent on the 06z GFS map is the +PNA ridge in the west US. It is much more flatter on the EURO (and every other model now). 

1. The western ridge helps dig the western energy on its eastern flank and helps in amplifying the trough on the east. 

2. The 50/50 block near Greenland as well as the Atlantic ridge will help hold everything downstream in place to try and get this storm to form. If a storm does develop, it would be a slow mover due to the traffic of storm in eastern Canada (something we have not really seen so far this year). 

3. The piece of the Polar Vortex over the Hudson will prevent a cutter and help usher in the cold air mass. 

4. The Bering Strait block is showing up, and I think in the end it could benefit us once again like it has before this season. 

5. The -EPO has been there since the get-go, bringing down arctic air masses and intense short waves. This time, it could possibly help kick that northern stream energy into the CONUS and also help in ushering in the cold.  

Looking deeper into the 12z EURO vort maps, we will examine the micro version of the overall pattern. By Thursday night, both energies associated with developing this potential storm are coming ashore from the Pacific Ocean. You can see I have both circled in the image above. There is a piece of our PV over the Hudson Bay, confluence from coast-to-coast, and the 50/50 block. 

SO, as I bluntly state at the bottom of that image:

ALL THE PIECES ARE THERE

The big storm idea may have disappeared, but the setup has remained the SAME. 

Advancing to Saturday morning, you can see both pieces of energy are well far apart. The Sub-Tropical Jet stream short wave has zipped ahead of the Polar energy, and the overall look of the image is flat. The trough is obviously not as pronounced and the western ridge is non-existent (remember the 06z GFS phased both those pieces of energy together and it had a western ridge). One thing I question is immobile Polar energy and why it just sits there. It could be because of the lack of ridging, but I would still expect it to track into the CONUS. 

Continuing on into Sunday morning, we are left with a very elongated look of the short wave energies since that Polar energy continues to remain stationary over the Pacific NW. An inverted trough develops from the southern stream energy and there is some phasing from the confluence which enables light snow to overspread the area. 

The 12z Canadian model also looks similar to the EURO in respect to the short wave energies and the confluence in the CONUS. You can see the phase is not that far from happening, but we need a pulse from our west to help bring down that northern stream energy out of the Polar Jet and phase it into the STJ. 

My Thoughts:

1. Regardless of how latest guidance is playing out the storm, nothing has changed with the players involved to bring a large storm system together. 

2. The energy is still out in the Pacific and proper sampling will not take place until 06/12z model runs FRIDAY MORNING. 

3. That lead vort (southern stream energy) needs to slow down to allow the northern stream energy to catch up (even if it's not the Polar jet energy, maybe we can get a piece of the confluence to phase into it instead).

4. I want to see the ridge in the west come back (+PNA) because I think that's important for an amplified trough in the east. 

5. The Bering Strait block is important because usually blocking is under-modeled and if it turns out to be stronger, it could force a phase. 

6. I sincerely believe we will see a moderate snow event (at least) Sunday into Monday. I feel like the models are going through their usual games. The pieces are there and I think enough of them will come together to bring us something substantial. Will it be the full blown 2-3 foot blizzard? Probably not, but I can see another 6"-12" type of event on the table with the potential for something greater. 

To be honest, the models clearly show the storm off the coast since that southern stream energy is strong to begin with. What we are looking for is a trend back to the west. The fact that they did not even totally lose the storm is encouraging in itself. You can not expect these models to show run after run of MECS/HECS's along the coast. Of course they're going to run into inconsistency. Right now, they're showing widespread 2-4 inch type of snow amounts. I think by Friday, once the energy is sampled, we will have a MUCH better idea. 

Valentine's Day Storm?

I'm not just bringing this up to save my ass just in case the storm this weekend does not come to fruition. Guidance is showing a lot of short waves entering the US next week, including another potent STJ energy. Hey, somethings gotta give, right? What I want to mention briefly here is we are losing our -EPO (not sure yet whether this is permanent or temporary), but we may be heading into a -NAO period. The Stratosphere has warmed and I think (hope) we have reached our lag period and the Atlantic begins to re-invent itself from what we have seen thus far. In conjunction with the -NAO, we could also be looking at a +PNA. The two together could bring us formidable storms and I think that could be in the cards mid to late next week! If this does turn out to be the case, you can be sure I'll make everyone aware of it. 

Have a great day! 

Francesco Paparatto 

*Follow the NJ Strong weather forum at www.njstrongweatherforum.com*

 

Beware: Two Major Storms Possible Between February 5th-10th

If there is one thing that stands out to me so far this winter season, it is the incredible persistence of the -EPO oscillation that has helped usher in arctic air masses into the eastern half of the U.S. The large pool of above normal sea surface temperatures in the northern Pacific insist on staying on the extreme side of positive and do not show signs of normalizing just yet, which is giving off a positive correlation for the EPO to keep remaining in a negative state. Even when our AO oscillation gets into a positive phase, we are still seeing temperatures across the northern tier of the country into the Mid-Atlantic well below average. Although Atlantic blocking has been non-existent in the higher latitudes for the most part, we have still managed to see potent winter storms effect the area and drop a significant amount of snowfall due to the other favorable signals of -EPO / -AO / and +PNA combinations. 

If you're a winter weather enthusiast, your appetizer this weekend will be to enjoy the Super Bowl festivities and a break from the harsh cold temperatures while possibly seeing light snow showers on Monday from a weak wave. Your main course awaits you between the February 5th-10th time period. It will be within this time period that the Northeast could see not just one, but two large winter storms from a series of intense short waves digging into the southwestern U.S. as a result of the -PNA. 

In this blog, I am going to touch on both storm potentials and name February 5th storm #1 and February 8th-10th storm #2. Obviously storm #1 will have the most detail since guidance it will come before storm #2 and could also have an effect on how storm #2 will ultimately materialize. 

STORM #1

This is the 12z EURO 500mb on Tuesday morning, the day before storm #1 is set to hit the area. One thing I guess I should say is I am confident there will be a storm, regardless of whether it's rain, snow, or ice. There is no out to sea solution with this system because the southeast ridge will not allow that to happen. Notice the black circles and the white numbers located within those circles. I am going to explain what those particular anomalies resemble. 

PLAYERS ON THE FIELD FOR STORM #1:

1 - That is where the short wave energy is located and as you can see it is dug deep down into the southwest U.S. and is already at a potent level.  

2 - A piece of the Polar Vortex has broken off and is kind of perpendicular to the short wave energy in the southwest U.S. As the s/w energy moves east-northeast, the piece of the PV is also moving along with it while they try to maintain equal longitude. 

3 - The southeast ridge is pumping over our area for a couple of reasons. The biggest reason is due to the     -PNA since energy is digging into the trough in the western U.S. this time, instead of the eastern U.S. (+PNA). Since there is no Atlantic blocking (-NAO), heights are not able to remain suppressed enough to promote a coastal storm (unless there is a Miller-B scenario, maybe?) 

4 - Extreme Pacific blocking with ridging being modeled over the eastern Pacific, into Alaska, then into the western Arctic through northern Canada. If that does not define a Pacific blocking pattern, I'm not sure what does. 

5 - The Polar Vortex continues to remain in a weak state and lacks consolidation. This is also another reason why heights from the southeast ridge are able to amplify as much as they are. 

STORM #1 Vorticity H5 Map 12z EURO:

If we fast forward to the morning of storm #1 (Wednesday), we can understand why this storm is more likely to cut to our west (from a NYC Metro perspective). Like I explained in the image before, the southeast ridge continues to amplify as the storm continues to deepen in the south-central U.S. (circled and labeled as the number 1). Positive heights extend into the northeast U.S. and the originating storm almost has no choice but to cut to our west. 

The black circled area labeled with the number 1 shows the area of least resistance, the track in which this storm is most likely to take. The end result is a minor thump of snow for NYC before it changes over to all rain while the western side of the storm in the Ohio Valley sees a potent snowstorm. 

The 12z EURO Ensemble is in agreement with the OP that the primary will cut to our west (around the Ohio Valley / western PA region). 

GFS H5 for Storm #1:

The 12z GFS was for the most part in agreement with the EURO model of a primary low cutting to our west and bringing mainly rain to the NYC Metro area. The biggest thing I want to stress with the image above is the extremely weak state of the Polar Vortex. Notice the black circles in Canada. They represent a different piece of the PV rotating around each other. There is not a consolidated PV to help combat the higher heights along the east coast. In conjunction with the +NAO/-PNA, this is going to be a problem if you are looking for wintry weather. 

HOWEVER...

There exists a scenario in which an area of High Pressure develops to our north or over the Great Lakes region which would force the primary storm to transfer its energy off the coast or along the coast. Some guidance does show this, such as the Canadian and its ensemble. Such a scenario would still bring rain to the NYC area, but there could be a changeover to snow once the secondary takes over and cold air comes back in.  

ICE:

The latest 18z GFS shows the ice threat I am talking about for the area north of NYC. This would probably be the region I am most concerned about, as they could see a good thumping of snow to ice then eventually rain. 

To be clear, I'm not exactly forecasting an all rain event for the NYC Metro region for storm #1, but I am favoring that solution as of now given the parameters highlighted above. If the Miller-B type of solution becomes consistent on guidance, it will be because an area of confluence to our north has appeared and the storm is forced to make a transfer. 

STORM #2

Amazingly, we have more consistency on guidance for this day 10 potential system than we do for the day 6 system. Every single piece of viable guidance, including the ensembles, are showing a strong signal for a winter storm between the February 8th-10th time period. I think there are a couple of important things to understand for this possible storm:

1. The southeast ridge will not be AS amplified as it will be for storm #1, which means the lower heights are conducive for a storm system to track further toward the coast instead of cutting to our west (favorable baroclinic zone). One of the reasons for this could be a more consolidated Polar Vortex, instead of a bunch of rotating pieces like we saw in the GFS H5 map for storm #1. 

2. Storm #1 could set up as a 50/50 block or at least promote positive heights around the NAO region that could help storm #2 slow down and phase. 

The 12z EURO Ensembles show a clear and big signal for a coastal storm in this time period and with the Gulf of Mexico opening up for business, this could be one heck of a moisture laden filled storm. There is no sense of even mentioning possible snow amounts, because storm #1 could somehow mess this entire configuration up, but it has big potential. 

We will see what happens and how that time period turns out! The potential is there for a large winter storm but the only thing we can do at this time is monitor the trends and not make sudden conclusions from every single model run between now and then. 

Thanks for reading,

Francesco Paparatto 

*Follow my forum at www.njstrongweatherforum.com* 

Examining The January 21st Snowstorm

Click on images to get larger view

A disruptive snowstorm is eyeing the I-95 corridor beginning Tuesday morning and continuing into early Wednesday morning of this week. A potent piece of energy will be ejecting out of south-central Canada Monday night with the Polar Vortex situated to our north. Along with a few other variables, including the very cold temperatures, this is setting the scene for a moderate storm to impact the area.

Lets first take a look at the players on the field and where they are positioned on each model (GFS and EURO):

00z GFS:

At hour 42 per the 00z GFS, there is a +PNA (western ridge) with positive heights extending into Alaska. Toward southeastern Canada, there is a weak Polar Vortex and a piece of its energy will be breaking off and digging into the trough in the eastern U.S. It is able to dig mainly due to the massive ridge in the west. Lastly, just like the January 3rd storm from earlier this month, there is last minute blocking, or -NAO, showing up on the models that is allowing the PV and the ULL over Newfoundland to to stay put and help slow the storm down a bit once it develops. This also helps the trough go negative since the progressive nature of the pattern is cut-off. At this point, the trough in the eastern U.S. is neutral and the energy is really digging. 

By hour 51 of the 00z GFS, which is late Tuesday night or early Wednesday morning, the GFS has brought the trough negative and this is where the storm reaches its height with moderate snow falling and extremely cold temperatures in place. The arctic-like temperatures would help raise the ratios from 10:1 to at least to 15:1 and 20:1 in some cases. You can see from the above map that the blocking the GFS outputs is impressive which is why at the 00z run it came out with an impressive solution of widespread 3 to 6+ inch snowfall amounts region-wide. 

00z EURO:

The EURO model caved west from its 12z run, but is still not as impressive as the GFS and a couple other short-range models in the snowfall department. 

At hour 54 of the 00z EURO, you can see the trough does go negative and there is region-wide light snowfall accumulations (especially in SNJ, coastal NJ, and LI), but the storm does not have a chance to amplify and slow down. The biggest reason for this is because of the "kicker" like piece in south-central Canada circled in black on the map above. Due to the weak state of the PV, there are a lot of upper level s/w energies retrograding and spinning to our north and this one is particular is trying to kick our coastal storm out to sea. The GFS model has this piece further north and west hence why it shows a more impactful snowstorm for the area. 

Taking a closer look at the h5 vort maps (GFS top, EURO bottom), at hour 48, you can see the EURO has the trough still in a mainly positive state while the GFS is already at neutral. You can also see that feature northeast of Maine on the 00z GFS that looks like an upper level low that could be helping to bring the trough toward a negative state sooner, whereas the EURO does not have such thing. 

Amazingly, these are pretty big differences with two very well known global models in the upper levels. Whichever one turns out to be correct will ultimately determine how this storm will evolve. 

Temperatures:

Just so you have an idea, this is what temps are expected to look like as snow is falling Tuesday night

Mainly low 20's to mid teens and colder as you head north and west (but those areas will also see less snowfall). In fact, temps are looking to remain very cold through the rest of the week. So whatever snow falls will stick around for quite awhile. This will raise snow ratios to at least 15:1 and potentially higher. 

Winds:

Winds are expected to be particularly bad for coastal NJ and Long Island, especially the east end. Blizzard-like conditions are possible for central and eastern LI since the cold temperatures will cause this snow to be powdery, meaning the winds will easily kick it up and reduce visibility. There exists the chance the NWS issues blizzard watches for this area Tuesday night into Wednesday morning. 

Ultimately, we have to see more model guidance to see which direction they decide to go in. The upper levels between the GFS / EURO are drastically different but both models still bring a light snowfall event to the area. Regardless, we should be looking at some accumulating snowfall beginning late Tuesday morning and lasting into Tuesday night. 

A snow map will be posted this morning at 11 am on the forum. I will also detail the timing of the storm at that time. 

Happy MLK Day! 

-Francesco Paparatto 

*Please register to the www.njstrongweatherforum.com for continuous updates on the storm* 

Update On 1/15 - 1/18 Storm Threats, Big Time Cold Temperatures To Return

Last week I issued a blog looking at storm potentials this week that could bring disruptive snow to the area. Revisiting those threats again this morning, it looks like we will be in the clear of a big storm to effect the region. However, there could still be a period of light snowfall that brings minor accumulations to parts of the Tri-State. 

The two dates of interest I mentioned in my last blog was 1/15 and 1/18 since both dates will feature a trough dropping into the eastern CONUS. Above is the 500 mb vort map for the 1/15 threat. There is still a good amount of energy ejecting out of Canada and into the trough that should still spark some light snowfall to develop from the Apps and points east to the coast. But due to the lack of spacing between both pieces of energy, it does not allow the initial trough to amplify along the coast and organize a pinched off surface low.

The next threat is on 1/18. Since the "kicker" feature behind this trough is not as pronounced (as you can see from the above 500 mb map), there could be a more widespread area of light snowfall on Friday. The s/w energy with this trough is not as impressive as the 1/15 event, but the trough takes on a bit more of a negative tilt. So, this threat still bares watching and there could be an area of 1-3 / 2-4 inch type of snowfall somewhere in the northeast region (possibly more in New England). It's dependent on exactly where the energy transfer occurs associated with the clipper system in the Great Lakes during this time period. 

Therefore, I would pay more attention to potential snowfall for Friday and pretty much write off Wednesday from anything of importance happening other then a nuisance snow or rain shower. 

Looking ahead, there is still a strong signal from the current observations of SST's in the northern Pacific of another -EPO regime developing by the end of this month. I think we are going to look at a few possibilities:

1. A -EPO/-PNA pattern develops again similar to what we saw in December / early January. 

2. A -EPO/+PNA Pacific set-up develops. 

3. A +EPO/+PNA Pacific set-up develops. 

Given the look of current observations and some long term guidance, I am liking a combination of options number 2 & 3 to come together. The -EPO will enter a relaxation period, but I think it reforms in conjunction with a western U.S. ridge. If this combination of incredible western northern hemisphere blocking comes to fruition, it will call for arctic air and a persistent trough to reign over the eastern U.S. once again. 

The MJO forecasts from the GEFS (top) and EURO (bottom) are showing signs of life with members taking the MJO out of the circle of death and into phases 6 / 7. The MJO phase 6 does not shock me since early next week we will experience a temporary 1 or 2-day warm-up as the western ridge collapses eastward. But once we get by early next week, that is when our weather pattern becomes interesting and the colder than normal weather settles back in. 

Above are the proposed GFS 2-M Temp Anomalies after the temporary warmup early next week. As you can see, even if this is slightly overdone, it is still an impressive cold air mass coming down due to the western blocking developing like I talked about earlier. 

The question then becomes, will there be a storm to accompany the cold that could turn things white? 

That is something that remains to be seen, and it would be unfortunate to see cold / dry conditions develop the end of this month. Most people like to see snow come with the cold. There's no point in posting long range surface maps, but some of them do show storm threats down the road. The problem is our NAO. Can we get a sustained -NAO to get some blocking to work with which would (4 "w's" in a row, wow) really turn this into a Godzilla-type of pattern? There are signs of a potential sudden stratospheric warming (SSW) event taking place and there is usually a 2-4 week lag time before it reflects on our pattern here in the eastern CONUS. If that comes to light, then a -NAO pattern could be in store for us once we get into February. However, I do not expect a sustained -NAO to come in January, other then transient episodes that could be our window of opportunity to capitalize on come the end of this month. 

We will see what happens. There could be a lot of fun in store for us by week 4 into February! 

-Francesco Paparatto 

*Please register to the www.njstrongweatherforum.com forum to take part in daily discussions about the weather and pattern!*

Winter Storm Threats To Return After Short-Lived Warmth

Once we get through this warm-up period this weekend and early next week, our attention will turn to a pair of upper level trough's that will drop into the eastern U.S. beginning around the 15th of January. Just like our most recent winter storm after the New Year, we have to watch the energy associated within these trough's to see if they spawn a surface low pressure system that could potentially bring widespread snowfall to the area. There are a few things we should monitor these next few days:

1. How strong will the short wave energy be?
2. How much energy gets drawn into the backside of the trough?
3. How does the trough orient itself?
4. Will there be a phase?
5. Will the STJ play a role?

There are many other questions that could be asked but there is simply no way of answering these questions this early in the game. The best we can do at this point is analyze the upper level maps from the models and see if they make sense relative to the pattern. With the last storm, the surface low ended up being further west than where the models intended it to be, and that was due to the poor handling of the trough and the energy associated with it.

There are two threats I want to broadly discuss. The dates for these potential storm threats are between January 15th - 19th. As you can see from the EURO 500 mb maps above (top image is threat #1 around January 15th, bottom image is threat #2 around January 19th), there will be a pair of trough's that drop into the eastern U.S. late next week. There is some weak / transient blocking (-NAO) showing up with ridging in the western U.S. The cold air coming down with these trough's is not as impressive as the cold air we saw with the January 3rd snowstorm, but it's definitely cold enough to support snow. 

The next 4 images are the vorticity maps (EURO top / GFS bottom) that are associated with both storm threats I highlighted above. As you can see, there is an impressive amount of s/w energy embedded within these trough's, enough to certainly get our attention. In conjunction with the +PNA spike in the west and the possible -NAO signal, this could lead to an opportunity to watch for a possible snowstorm within this time frame. 

What's impressive to me is the ridging the models are advertising is pretty amplified and this is what will allow the s/w energies ejecting out of western Canada to dig into the trough. The further south they dig, the more amplification the trough will get and the better our odds are of popping a surface low near the coast. 

The signals are there for a possible east coast snowstorm to appear on the models within the coming days. The +PNA/-NAO (albeit transient) combination should at least make things interesting next week. 

Things will become much clearer once we get closer to the dates of interest and the models get better sampling of the upper level anomalies present on the playing field. Timing will also play a role. The lower heights near the Aleutians and over Alaska indicate that "kicker" type of short waves could eject out of that region and force the ridge to roll eastward sooner then expected. This would shift the favorable trough axis offshore and likely prevent storm development as the energy runs out to sea.

We'll see how things plays out! 

Francesco Paparatto 

Fear Not, Winter Will Return

So far, winter has been a success if you are a cold and snow lover who lives in the northeast. There has been numerous storms to track with impressive shots of arctic outbreaks (the most impressive of all coming tonight with an almost 50-degree temperature drop in some locations).

It is a rarity that we see these cold / stormy type of patterns persist for long periods of time through an entire season without taking a hiatus, also known as the typical January thaw. That is exactly what we will be seeing  the 2nd week of January (the 12th through at least the 16th).

When looking at models to get an idea of long range weather, it is best to look at the ensembles since they consist of a mean of all the individual operational runs.

The 12z GEFS 2M temp. anomalies for the 2nd week of January nicely depict the warmer than average temperatures set to enter the eastern U.S. due to amplification of the southeast ridge.

Essentially what will be happening is the constantly favorable signal that has helped us out big time this winter will be getting suppressed, and that is the EPO going from a negative phase to a neutral or slightly positive one. You can see from the 500 mb maps above (EURO left and GFS right) that lower heights get into Alaska with a suppressed ridge sitting in the north-central Pacific Ocean. Since there is no longer warmer air getting into Alaska and the Arctic regions, arctic air will remain bottled up there while the southeast ridge draws up warmer air from the south into the northeast U.S. It also does not help that the NAO continues to remain in a mostly positive phase, meaning there is no blocking to help keep the colder air in place over the eastern CONUS. 

You can see this idea of a +EPO has support from the ECM Ensembles as well. 

What you can expect beginning this weekend is temperature moderating into the 40's, for the most part, with some locations likely reaching the 50-degree mark. Obviously areas furthest to the south and west have the best shot of reaching 50 degrees. I would not be surprised to see temperatures in our area not get impressively high. I think low to mid 40's is where we will be at for the most part. It has been an extreme season for temperatures so far, but it actually looks like this will be a "typical" or "average" January thaw, not one that would feature extreme mild temps with widespread 50's or 60's. The axis of the southeast ridge will remain offshore, so we will be on the western fringe of it. 

Fortunately, there are positive signals out there that are showing winter returning by possibly the 3rd week of January. And if not the 3rd, definitely the 4th week. There even exists the possibility that this "thaw" only lasts for a few days and we get back to temperature departures near average or below once again. It's definitely not an impressive "thaw" to me. 

We will look at the GEFS and ECM Ensembles in the long range to get an idea of what COULD happen by the end of this month. 

The 12z ECM Ensembles at 240 hours show the Polar Vortex displaced in western Canada, with a weak signal of a re-surging -EPO and neutral-ish NAO. You can see lower heights are still managing to get down into the eastern CONUS though, and this looks like a cross-polar flow pattern we similarly saw in early to mid December of last month.  

The 12z GEFS also at 240 hours show a much more pronounced -EPO signal with the Polar Vortex over the Hudson Bay instead of western Canada like the ECM shows. This likely allows heights to amplify more in the north Pac. and also allows a more favorable looking trough to develop over the eastern U.S. There is also a weak signal of a potential -NAO developing with positive heights extending through the Atlantic into Greenland. 

Comparing these two maps from a broader sense, they actually have the same idea going with a trough getting back into the eastern U.S. and a signal of the -EPO returning. The EPO, as has been the case all season, will be the key once again for getting our snowy / cold pattern back since I do not have much faith in a negative AO/NAO couplet establishing this year. The only way I can see that happening is if a SSW (sudden stratospheric warming) event takes place, and last I checked the QBO value at the 30mb level was still positive. Real time observations suggest the QBO could be heading down, but until I see factual data, I will remain pessimistic about it. 

Just for the heck of it, if we keep going on the 12z GEFS they continue to show a very favorable winter pattern by the end of this month with signs of it carrying over into February. If we can finally get our NAO into a sustained negative stage, it would really benefit us when storm threats arise. 

Lastly, the CFS for January (top) and February (bottom) is pretty gung-ho about the return of a favorable winter pattern developing the end of this month into February. Although our AO has been mainly on the positive side of the scale, often times extremely positive, we have still managed to draw in extremely cold temps into the U.S. due to the -EPO bringing down strong Arctic High's. 

To review...

1. The January thaw is coming, but there is the possibility it remains very short lived (3-4 days). Also, temperatures should not reach an extreme high. I'm only thinking low to mid 40's with one day possibly getting close to 50. January 11th is when I officially think the thaw begins. 

2. Where the Polar Vortex actually sets up will determine exactly how our pattern after next week shapes up, but the general idea still remains trough in the east and ridging in the west. 

3. Do not forget the sub tropical jet stream. Although the MJO continues to remain in the circle of death, the STJ has been a force in our weather pattern especially when it comes to the evolution of storms. SST's suggest the STJ will remain a dominant force in our weather pattern going forward. That is good news.

Enjoy the break because I am sure we will be getting right back into the tracking of winter storms again near mid-month.  

-Francesco Paparatto 

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