January 2014: Pattern Change & Possible Storm Threats

A Merry Christmas and Happy Holidays to all on this brisk Wednesday morning. The focus of this blog will be to analyze the upper level pattern for around New Years time and into the first week of January. December has been eventful for the northeast U.S. thus far, but we have hit a relaxation period and the pattern is getting ready to re-load for 2014.

The global models that show what the weather COULD be like 1, 2, and even 3 weeks from now, are honing in on a couple of storm threats that I think need to be looked at more closely. The notable dates are:

December 28th - December 29th
December 31st - January 1st
January 3rd - January 6th

Our weather pattern has been driven by the presence of Pacific blocking, also known as the WPO (west-Pacific oscillation) or EPO (east-Pacific oscillation) which have been in predominately negative phases dating back all the way to the fall. This has allowed ridging, or positive heights, to extend into Alaska and at times the western Arctic region, which in turn forces the arctic air southward into the CONUS. This has created a cross-polar flow effect which takes cold air from the west U.S. to the east U.S. Another element to note from our pattern up to this point is the lack of blocking (+NAO) has allowed the southeast ridge to amplify and draw warm temperatures up the eastern seaboard at times, which is evident by the couple of ice storms we have seen already since extremes usually occur when polar air collides with tropical air.

However, the pattern is changing and the concentration of this blog will be on the PNA, AO, and NAO. I have already mentioned the NAO has been positive so far this Meteorological winter. The AO has also been positive despite the impressive cold shots we have seen at times this month. The PNA has been negative, which supports trough's in the western U.S. (but I have already disclosed the -EPO has helped us offset warmer temperatures from getting into the northeast).

There is evidence that all those signals do a flip once we approach the New Year. The AO is heading negative, the PNA positive, and the NAO negative. I'm more confident on the first 2 panning out than the latter, but we'll look at things more closely and you can draw some of your own conclusions as well.

The above image from the GFS shows the AO going from a positive stage to a negative one. Once we look at the h5 maps, you will be able to see why this is the case with not just the AO, but all the signals. 

Also from the GFS, the PNA is rising into positive territory. 

Lastly, the NAO on the GFS is shown to all be going negative. In case you did not know already, a              -NAO/-AO/+PNA strongly supports colder than normal and stormier than normal weather in the eastern U.S. 

The following 500 mb maps are taken from the 00z EURO run from last night. 

 

The first storm threat we have to deal with is the one for this weekend. You can see from the broader pressures around Texas that energy is building and a low pressure system is trying to form. Since the cold air has retreated north, positive heights off the Atlantic are getting into the northeast. At this time, the PNA is still trying to get positive (shown to be neutral on this image), the tanking of the AO is still in its early stages, and the NAO is positive. So, if a storm does run up the coast this weekend, it supports a rain storm. There is a slight chance the energy in the south holds back a bit, allowing cold air get into the northeast first, but this does not seem likely at this time.

The next time period I mentioned is December 31st to January 1st. This will not be a big storm if it materializes, but at this time the pattern is setting itself up for a potential bigger storm around the 4th. Some models are showing a clipper rotating around the Polar Vortex and potentially amplifying once it reaches the coast. This is similar to the clipper storm in mid-December that bombed out off our coast and brought decent snow to parts of the area and southern New England. 

These type of systems favor New England the most, but there is still time for a south trend just like the other system. I do feel someone could see a measurable snowfall out of this storm. Plenty of cold air around at this time as well, with a nice High Pressure system to the north. Another thing to note from the 500 mb map I posted for this time period is the AO is now negative and the NAO is as well, evident by the positive height anomalies into Greenland. Look at what is happening in the north Pacific, the -EPO ridge is connecting with another ridge in the western Arctic, forming a mega-block. The formation of that block coupled with the        -NAO, is forcing the Polar Vortex south to the Hudson Bay area and calling for the -AO regime to form. 

The last time period I wanted to briefly talk about is the January 3rd-6th time period. The above 500 mb image from the 00z EURO is as extreme as it gets (*pay attention to the general idea, not the extreme-like solution*). The general idea from the long range EURO shows the north Pac ridge shifting into the western U.S. (+PNA) with crazy blocking consisting of positive heights still present in the Arctic region. The NAO is even more negative and the Polar Vortex is still situated around the Hudson Bay. It is unlikely the PV gets as far south as the EURO is showing here, which actually phases the PV with the sub-tropical jet stream and forms a massive storm system. Again, unlikely to happen. 

To me, what is more likely to happen is the PV remains north around the Hudson and the +PNA ridge in the west comes to fruition. I think the blocking is modeled to be too extreme right now, which is usually the case, and it is causing the models to spit out extreme storm solutions. The general idea though is for a -NAO/-AO couplet to develop in conjunction with the +PNA. This should lead to interesting times down the road after we get by the next 2 storm systems I talked about earlier. 

This type of pattern has support from most models, it is not just from the EURO. The ensembles agree as does the GFS OP. 

One reason why we have seen moisture-laden storms this year is due to the active STJ, or sub-tropical jet stream. The STJ around the 3rd-6th time period is also projected to amplify with knots in excess of 150 along the eastern CONUS. Put together a signal package I mentioned above along with the STJ, and the pieces are all there for a big storm to potentially come together. Whether it does or not remains to be seen, but the pattern is turning ripe and the time period needs to be monitored. 

Have a great Christmas and a safe and happy New Years. 

Francesco Paparatto 

Storm Briefing for Saturday, December 14th

Another storm is brewing for the Mid-Atlantic and Northeast states, and this time, it could pack quite a punch compared to our last couple storm systems. Although the pattern is not optimal for one that would condone a major snow-maker in the Northeast since the NAO / AO continue to remain positive and the PNA is negative, we are still on track as of tonight for parts of the northeast to receive a significant snowfall. Another component I am also concerned about is the possibility of ice accretion for areas along the immediate coast of the Northeast. 

Here are a couple images of the current water vapor loop. The bottom picture is simply a zoomed in version of the SW Conus from the top image. Both pieces of energy that will work in conjunction to bring a storm system together for this Saturday are on land and beginning to advance east. There are a couple things that should be noted:

1. The STJ, or sub-tropical jet stream, is much more active than it was this time last year. This is helping the southern vorts, or upper level low's, to strengthen before they even reach the eastern U.S. and there is a feed of energy from the eastern Pacific flowing through the jet and into the vort. 

2. The Gulf of Mexico's warm sea surface temperatures were not hindered much this past summer due to the  inactive hurricane season. It is open for business and providing additional energy to the storm that develop in the southeastern U.S. There has already been a few examples of moisture-laden storms this fall that have brought high rainfall amounts to parts of the southeast. 

3. Our northern branch energy is likely NOT to phase with the southern branch energy with this upcoming storm system. Much of this is due to the lack of "real" blocking, or -NAO, and the zonal flow in the western U.S. (-PNA). I say "real" blocking because, although the NAO is positive, there is a PV (Polar Vortex) over Greenland helping to provide confluence over eastern Canada which is one of the reasons why cold air will remain in place (for some locations) when this storm arrives. 

The 2 biggest factors that will ultimately determine who sees rain, snow, ice or a mixture of all three is the positioning of the upper level High Pressure system(s) and the strength of the southern vort. There will be partial phasing with the northern branch which will help develop a broad LLC (low-level center) and bring ample precipitation amounts to PA, MD, NJ, NY and eventually New England, but how strong it gets is significant. A stronger system brings up warm air from the south and could potentially initialize a dangerous ice situation (specifically for NJ), while a weaker system keeps cold air intact and keeps most of the precipitation in the form of snow. 

Once the next set of tonight's model runs come out, I plan to release a 1st call snowfall map so everyone can see what my initial thought's are. Given the active STJ and presence of GOM energy filtering into the storm system once it develops, I am favoring a more warmer solution (plus ice) at this time for the Mid-Atlantic and Northeast up to NYC. But we'll see what happens...stay tuned!

Francesco Paparatto  

What's To Come: Minor Snowstorm to Arctic Blast to Possible Major Coastal Storm?

Most important information from this blog is bolded and/or in font color red

So, it has begun.

Meteorological winter began 9 days ago and it only took those few days to get our fist significant snowstorm of the season around the Philadelphia Metro and southern New Jersey areas. Snow amounts ranged anywhere from 4 to as much as 12 inches in isolated towns in southern NJ.

Today, more snow, ice, and rain is expected in those same areas that got the surprise snow yesterday and some of it could even get as far north as NYC. Not much in the way of additional accumulations should be expected, however.

Once this system moves out, another one will quickly follow its heals and bring the threat of more widespread accumulating snowfall amounts. Granted, this would be a quick moving system, but it has the potential to drop an additional 1-3 / 2-4 inches of snow. If the surface low strengthens some, isolated areas around the Tri-State could see 6 inches of snow.

Here is the stripe of snow being shown on the 00z GFS extending from CT into northern VA:

If things still look impressive after the 12z runs later this afternoon, I will release a snowfall map and hold a chat at 9:00 pm EST so we can have discussions on the 00z NAM and 00z GFS runs as they come in. 

The next thing that should be addressed are the cold temperatures set to move into the Northeast and Mid-Atlantic states later in the week. Here is a look at the temperature anomalies map by Friday morning:

-10 to as low as -25 degrees below normal throughout the Eastern U.S. 

Here is a zoomed in look at our area:

COLD ! 

2-meter temperatures (temperatures 2 meters from the surface) are only shown to be in the teens and single digits...

And it's not even the heart of winter! Thus far, we have seen some very impressive arctic air masses that do not seem to be moderating at all as they make their descendant from Canada into our region. 

Temperatures will try to moderate by to normal by the weekend, but we should still stay on the below normal side of things. 

The last thing I wanted to briefly mention without going overboard is the threat of a possible coastal storm next week for the Mid-Atlantic to New England states. 

Some models such as the EURO have been close in showing a potent coastal storm early next week. There is a high chance one does not happen, but there is still an interesting set-up in the pattern that causes me to raise my eyebrow a bit. 

Two pieces of energy will be diving into the eastern U.S. next weekend. Piece #2 like I have labeled on the image above broke off Piece #1 and is digging into the southeastern U.S. These two pieces of energy are going to make an attempt to phase somewhere along the coast. And if they do, you can expect a coastal storm. 

Although there is not a -NAO at this time, there is a strong Upper Level Low that may act as a blocking mechanism to help get these two pieces of energy to phase. 

That, to me, is the key. If that ULL can stay on the models through this week and not try and escape northeast, it could force a phase with those two pieces of energy. There are other factors as well, but we are still too far out to even worry about them right now. Some may say this blog has been written too early,  but I'm not calling for a coastal storm. I am just trying to say the set-up is interesting at the 500 mb level and I could see how one forms. 

Have a great day 

Francesco Paparatto 

Notes:

1. Check out the NJ Strong Weather Forum at www.njstrongweatherforum.com to participate in daily discussions involving the weather, including scheduled chats. 

Potent Thanksgiving Eve Storm Could Bring Travel Headaches

There is the potential for a major east coast storm to bring a lot of havoc to people in the eastern CONUS during the busiest travels days of the year. Some areas could even see a white Thanksgiving, imagine that. There is still a lot of uncertainty however in the exact track and intensity of the system. In this blog I'll take a look at the pattern this storm is working with and check out the latest from the GFS and EURO models.

The system in the southwest U.S. is the main player that could bring this storm together. It is an upper level low feature that is being fed energy from the eastern Pacific Ocean, indicative warmer than normal SST's (sea surface temps.) and an active STJ (sub tropical jet stream). The other essential piece to this storm is not shown on this map, but it is out northern stream energy which could potentially phase, or join up, with this upper level low and produce a massive storm right before Thanksgiving. 

Here is where the 2 major global models stand:

GFS- out to sea, minimal impacts

EURO- large, powerful, inland track storm with snow for interior areas and elevations / heavy rains & wind along the coast 

By looking at the upper level maps, we can see why these models differ

Above is the GFS 500 mb vorticity map, which shows why this model is taking the storm out to sea. The northern stream energy is ejecting too quickly out of the northern U.S. while the southern stream energy remains a separate entity in the southeastern U.S. There is no phase and ultimately no storm to worry about. 

The EURO on the other hand amplifies the ridge in the west (+PNA) which allows the northern stream energy to slow down a bit, dig into the trough, and phase (at least partially) with the southern stream vort. The end result is an impressive storm along the coast bringing heavy snows into parts of western/central PA, central NY, and New England. 

GFS accumulated precipitation maps obviously show nothing, besides coastal areas, since it takes the storm out to sea due to the progressive nature of the way it is handling this storm with the upper level energies. 

EURO on the other hand is extremely amp'd up due to the reasons I explained above and is showing 2-3 inches of rain from DC to Boston and significant snow for interior sections of the northeast. 

Here is the EURO snowfall map by mid-day on Thanksgiving Day. 

My Thought's

1. The GFS Ensembles are well west of where the operational is and some individual members show a EURO-like solution. There has also been evidence of the GFS suffering from convective feedback issues. 

2. A week or two ago we were also tracking a possible coastal storm that never came to fruition, even though the EURO was bullish in tracking a storm up the coast. The GFS won with the out to sea solution. The pattern then called for the out to sea track. The pattern now still seems suspect to me that supports what the EURO is showing. 

3. Our NAO is still positive, but the difference with this system is the EPO is negative and the PNA is positive. This boils down to timing of the northern and southern stream energies. The GFS has a bias of being too progressive in northern latitudes of the CONUS with regards to the northern energy, but the EURO also has a bias with the southern latitude energies of the CONUS. 

4. At this point, I favor a track between what the GFS and EURO are showing, with a not-so amp'd up system like the EURO shows. I think a sub 1000 mb storm is realistic right on or off the coast of NJ, but it should be a quick-mover with the lack of blocking. Originally I favored a completely out to sea track, but I think that is looking less likely at the moment. I definitely do not favor the interior bomb the EURO is currently outputting. 

5. It is still fairly early and I will have another update with an impacts map out by Monday. The map will include potential rain / snow amounts. We are looking at a time table between late Tuesday night into all of Wednesday. Thanksgiving Day itself should be dry, with gradual clearing throughout the day. It will be cold though. Just keep in mind the worst case scenario, which is the EURO model, if you are traveling. Heavy rain, high winds, snow, you name it; it is there to worry about. 

NJ Strong 2013-2014 Winter Outlook

NJ Strong 2013-2014 Winter Outlook

Hello! Welcome to this years winter outlook. Long range forecasting has come a long way since "back in the day" when most people would just wake up and look outside their window to see how the weather looks like for that day. Now, most people rely on various social media websites and news stations to get their day-to-day weather. Long range forecasting in particular has gained a lot of attention over the last few years. However, it is not an exact science and with all the moving parts in our atmosphere it is almost impossible to accurately predict the weather a full season in advance.

That being said, we could still get a pretty good general idea of how this winter will play out. Yes there will be some assumptions made in this outlook, but I will do my best to provide as much reasoning, facts, and data as possible to make a strong claim and forecast.

Lets get started!

There are five components to this winter outlook that I want to look at closely:

1. ENSO (El Nino / Southern Oscillation)
2. Stratosphere
3. Sunspots
4. Northern Hemisphere Snow Cover / Arctic Ice Extent 
5. Analogs (past years I think match up to current observations)

One thing you all should know before you continue reading...you will see me reference the NAO, AO, PNA, and EPO at times. I will detail what those mean at the end of this outlook in the "wildcards" section, but I will reference them in other sections as well. You should know that a -NAO / -AO / -EPO / and +PNA are most favorable for us if we are looking for colder and snowier than normal conditions in the eastern CONUS. 

ENSO

When we try to determine whether the upcoming winter season will be El Nino, La Nina, or La Nada (neutral); it is critical we look at the SST's (sea surface temperatures) of the Equatorial Pacific. The image above are SST's of the entire globe. Red shows above normal water temperatures (warm) while blue indicates below normal (cold) water temps. 

Just so we are all on the same page, the ENSO is divided into 4 regions. Here is an image for visualization purposes...

Nino 4, Nino 3.4, Nino 3, and Nino 1+2. 

All are important in one way or another, but Nino 3.4 is most important because it has the most influence on the ENSO. 

Keep those regions in mind as we now look at SST's in the Equatorial Pacific:

In the central Pacific (Nino 4 and Nino 3.4 regions) the SST's are above normal and still continue to warm. In the eastern Pacific (Nino 3 and 1+2) the SST's are below normal and are still trending cooler. 

The best way to classify the ENSO as El Nino, La Nina, or La Nada is by looking at the ONI (Oceanic Nino Index) for Nino region 3.4. It is a 3-month average of SST anomalies for that region.   

To classify as El Nino (warm), there must be 5 consecutive months at or above +0.5 degree anomaly. 

To classify as La Nina (cool), there must be 5 consecutive months at or below -0.5 degree anomaly.

By looking at the SST anomaly map above of the Equatorial Pacific, we can conclude Nino 4 / 3.4 regions are running above noraml (as of now), and Nino 3 / 1+2 are running below normal. According to CPC, the ONI for Nino region 3.4 for the 3-month mean of August-September-October was -0.3. That falls between -0.5 and +0.5 which indicates LA NADA. 

However, the latest ONI value for region 3.4, which is not shown in CPC's graph but rather shown in actual observations is 0.0. So it has warmed pretty nicely through the course of November, and given the SST anomaly charts, evidence shows it should continue to warm through December. 

This is the heat content anomaly map for the Equ. Pacific and the orange spike indicates that warming is still taking place for the general area. 

 Other tools we have access to that we could look at to forecast ENSO are statistical and dynamical models. Note this has not updated since mid-October:

Most seem to fall between the +0.5 and -0.5 range, indicating La Nada for the upcoming winter season. 

Here is what the EURO has to say for Nino 3.4 region...

This only updates once a month, but as of October this model was pretty aggressive in taking the plumes at or above +0.5 for Nino region 3.4. 

This graphic shows some ensembles getting above +0.5, but the mean (red line) still insists on a La Nada ENSO winter. 

One thing to keep in mind is SST's are pretty volatile, meaning they are vulnerable to sudden change which is often why these models do a poor job at forecasting the ENSO. The key is to monitor actual observations such as the heat anomaly chart I posted above and other graphs the Climate Prediction Center makes available to us. 

ENSO Forecast

If we look back at the Equatorial Pacific SST's that I posted above, one can argue the current set-up of SST's is similar to those of El Nino Modoki's. I did not notice this until Meteorologist Mike Masco of Baltimore made reference of this on his Facebook page. 

The Modoki El Nino is basically strong anomalous warming in the central Equatorial Pacific and strong anomalous cooling in the eastern Equatorial Pacific, and that pretty much aligns itself with the Equatorial Pacific SST map I posted up top. 

The top image is the same Equ. Pac. SST anomalous map I posted earlier, and the bottom map is just a general example I found of SST anomalous maps of El Nino Modoki. You can see how both maps look awfully similar. So, we do indeed have a El Nino Modoki going right now, but the question is how long does it last? That is something I do not know the answer to. 

This index suggests it will continue through the upcoming winter. 

Ultimately, my forecast is for a La Nada - ENSO 2013-2014 winter season, but I think by the 2nd half of the meteorological winter, we could see more of a weak El Nino type of pattern evolve over the United States. It depends on how the warming in the crucial Nino regions progresses and how the SOI (Southern Oscillation Index), which forecasts ENSO intensities (weak or strong episodes), progresses. 

Sustained below -8 values of the SOI indicate EL Nino, while sustained above +8 values of the SOI classify as La Nina. 

The SOI has been fluctuating these last few years, meaning it has been neither consistently positive nor negative, and it looks like it wants to stay that way for now. 

When I get to the Analogs portion of this winter outlook, I will show some years that featured El Nino Modoki winters. Like I said though, it is not a given this SST regime continues through the winter months. At this time, I am more confident in stating our winter season will feature La Nada, which often means the ENSO has minimal effect on our weather pattern. 

Stratosphere

Our stratosphere is a very powerful phenomena that can have a drastic influence on our winter pattern. It is important we examine it as best as possible, even though it could often be difficult to follow. Often times in the weather world, you hear of something called a Sudden Stratospheric Warming (SSW) event. In laymen's terms, it refers to exactly as it sounds, which is when our stratosphere warms at such rapid levels in a short period of time.   

Here is an example of a SSW from last winter, January 2013 to be more specific:

What this translates to is air falling and warming in the North Pole of the stratosphere, while air was rising and cooling over the equator in the stratosphere. 

A SSW can either displace, split, or destroy the PV (Polar Vortex) and sometimes tanks our AO (Arctic Oscillation) to a negative phase, which often leads to much colder than normal conditions over the eastern CONUS (Continental U.S.). If you remember last winter, January and early February featured below normal temperatures in the northeast and that came after the SSW event. One thing to keep in mind is there is a 10-day lag until the SSW translates to the surface. 

Here is what the arctic PV looks like

We want that Polar Vortex on our side of the pole, which will help usher down colder air into the U.S. A SSW event could help us get it there. 

The QBO (Quasi Biennial Oscillation) tracks the wind patterns (easterlies and westerlies) in the tropical stratosphere. It comes in two phases, negative and positive. A -QBO is composed of easterly winds while a +QBO is composed of westerly winds.  Our current QBO (shown below) is +11.69 as of October. 

When the QBO is in a negative state, meaning easterly winds, there is a higher probability of a SSW occurring during the winter (according to a study done by Holton & Tan in 1980). The orange box is where we currently stand (+QBO). The blue box I circled is the QBO from last October, which was in a very negative phase (-24.51). You can see how it got warmer and warmer as the winter months progressed, and by January (indicated by the blue "J" with my beautiful hand writing), it was at -6.07, which indicated a SSW had occurred and much colder than normal temperatures filtered into the eastern CONUS at that time. 

I am not enthused with regards to where our QBO stands right now, or the state of the current stratosphere for that matter. Extremely positive or extremely negative (like last winter) states of the QBO provide the best 500 mb patterns for us during the winter because those phases influence our upper level pattern most. We are working with the westerlies this time (+QBO) in a neutral phase and it will be interesting to see what that does to our pattern (if anything). I'll admit I am not an expert with this stuff but I still find it interesting nonetheless. 

Sunspots

In case you did not know, the Sun is pretty big...

Like the Stratosphere, the Sun is another mechanism that has the ability to drive weather patterns across the globe. In fact, scientists say they can make a forecast of how the long range weather will look like just by studying the Sun, ENSO, and Stratosphere.  

Sunspots are magnetic storms on the surface of the Sun and sometimes release radiation that comes from the magnetic energy associated with sunspots. Those are known as Solar Flares. 

By studying the Solar Cycle and general Solar Activity, we are able to see how this could effect our weather on Earth, in this case, our upcoming winter season. 

The image above shows sunspot activity on the Sun at its surface. In the years 2008-2009, the Solar Cycle hit something called a Solar Minimum, which means there was virtually no sunspots on the Sun at that time. It is by no coincidence that those years in parts of the world, including the U.S., featured colder than normal conditions. During times of decreased solar activity, the globe is entering a "cooling" phase; while during times of increases solar activity, the globe is in a "warming" phase. 

Where do we stand in regards to the sunspots now? You can see I circled where we were as of November 9th (around 70 Solar Flares). We are obviously out of the Solar Minimum cycle, and according to NASA, we are on our way to a Solar Maximum (they are not 100% confident on this yet, feel free to read the article I hyperlinked). One thing that must be stressed is it takes awhile for the global temperatures to respond to the suns change in Magnetic Field. The best and most simple example I read online is it's like sitting in a bathtub of cold water and turning on the hot water and waiting to feel the difference in the water temperature. Of course we are not dealing with a bathtub here, just with the Earth (no big deal, really) so the lag effect will be much longer. 

Forecasts for the Sunspot Cycle does show it heading toward a Solar Maximum, as NASA expects. I do not believe this will have much of an effect on THIS years winters, but it could in the ones to come. 

Northern Hemisphere Snow Cover / Arctic Ice Extent

The Stratosphere and Sunspot Cycle are factors that are studied at the Macro level when it comes to forming a winter outlook. The Micro level involves looking more closely at the H5 pattern and what drives it. The NH snow cover and Arctic Ice Extent could help us do that. 

As of November 16th, Arctic sea ice is at 9,524,937 km^2. 2013 was on pace of having a much better Arctic Sea Ice Extent compares to recent years, however, a close examination of the graph above shows it heading back down to below average levels. Despite the recent melting, NSIDC says Arctic Sea Ice is "notably higher" this year than last, due to the colder than normal summer. We are still far from the long-term average (1981-2010), but it is an improvement. 

Northern Hemisphere snow cover is also important to look at in an attempt to gauge what our H5 pattern will look like this winter. 

Above is a tabular chart of snow cover for different regions in the world. I outlined October 2012 and 2013. This year is off to a better start in regards to our snow cover compared to last. This is important because the cold air that comes with the dips in our jet streams this winter (troughs) will not drastically moderate as they move into the U.S. from Canada. During years of above normal snow cover in the Northern Hemisphere, our Arctic Oscillation in the winter has a higher probability of being on the negative side of the phase. 

Analogs

Before I highlight my analogs, I want to give some background on the teleconnections that DIRECTLY influence our pattern and are most important to us for the winter. These are short term indices that cannot (in my opinion) be predicted ahead of time (2+ months out), but you could make assumptions and draw conclusions based on other pieces of information available to us. 

NAO (North Atlantic Oscillation Index) - defined as the height anomalies that extend into Greenland, also known as "blocking." 

AO (Arctic Oscillation Index) - defined as the degree into which Arctic air penetrates into the mid-latitudes of our atmosphere. 

PNA (Pacific / North American Index) - defined as the height anomalies over the western U.S. or eastern Pacific Ocean. 

EPO (Eastern Pacific Oscillation Index) - defined as the heights anomalies over Alaska, western Canada, and the Arctic. 

Like I stated in the beginning of this outlook, -NAO/-AO/-EPO/+PNA is where we want these signals to be if we are looking for colder/stormier than normal conditions in the eastern CONUS. They DO NOT all have to be favorable in order to get that type of weather pattern, but it surely helps. 

Here are the analogs (past years I think this winter could mimic) I chose for the 2013-2014 winter season. The first thing I should say is we are in a +AO/-EPO/-PDO regime right now. These three signals have not wavered much since the end of summer and through the fall. 

The PDO is likely to remain in a negative state given the below normal SST anomalies in the northeast Pacific Ocean. This correlates well to a -PNA H5 pattern and that is most likely what we will see through this winter as well. 

The difference here is though the EPO has a good chance of being in a negative regime as we go through this winter. There seems to be constant ridging taking place near Alaska, the Aleutian Islands, and sometimes into the Arctic. This could be a good mechanism in providing a terminal for cold air to filter into the eastern CONUS. 

Lastly, the AO. The AO is a tough forecast for the upcoming winter. It is at an extremely positive state right now (2nd highest all-time for this time of year). 

+4.3 to be exact (as of November 14th).

I do think it will trend negative as we progress through the winter months, but it could take a SSW event to drastically change its propagation, which is why the analogs I chose show 3 different types of AO winters (neutral, negative, and positive). Keep in mind even with a poor Pacific pattern last year            (-PNA/+EPO), we still managed to get a blizzard in February thanks to the -NAO/-AO couplet. If the pattern on one side of the county is poor, but favorable on the other end, it could still provide us with a chance to see a storm. When both are in sync, conditions are RIPE for a snowstorm. 

Putting all those analogs together, we come out with a temperature anomaly map that looks like this:

Not much in the way of above normal temps. anywhere in the U.S., but the western U.S. is in a deep freeze with noticeable below average temp. departures from normal. 1990-1991 is on there because the AO in December of 1990 was at +1.30 and it slowly trended cooler. By the time we got to February, we were at a -AO. The only issue is it featured a +EPO pattern and I do not think we will be seeing much of a +EPO this winter. 

The issue with this analogs map though is it shows too much of a -PNA/+EPO type of pattern and I do not think that will be the case this winter. I do like where our EPO is right now, and feel the        -EPO could persist through most of the winter (obviously there will be times of relaxation when it goes positive for a period of time). 

Overall Thought's 

I feel this winter could turn out to be stormier as a whole for the U.S. Note: "stormier" does NOT mean "snowier." Some things not mentioned in this outlook such as the MJO (Madden Julian Oscillation) and STJ (Sub-Tropical Jet Stream) could play a VERY critical role in determining whether this above normal precip. type of winter comes to fruition in the eastern CONUS or not. Those two indices, along with the positive trends in SST's in Nino region 3.4, are making me feel confident about a stormier than normal winter for the eastern U.S. which could produce potent storms as two jet streams (north and south branches) come together for a phase. 

I do not like doing month-to-month breakdowns (predicting temp and precip. departures from normal) since I think those are very volatile forecasts and it is difficult to pinpoint exact H5 setups months ahead of time. Therefore, I did a National Outlook with my thought's on each region. 

National Outlook

(most confident for eastern U.S.)

Region 1 - Avg. Temps / Above Avg. Precip. 

This is the area I feel the polar and sub-tropical jet streams could come together to produce large storm systems. Where they phase (off the coast or inland) will determine precipitation types (snow, rain, ice) for certain areas. This is why predicting snowfall amounts is a crap shoot, because 1 power house storm that brings 1 to 2 feet of snow could already bring you to an average or above average season. I definitely think there will be at least 3-4 storms this year that could be considered "major" and possibly 1 "historic" depending on how the STJ cooperates (not necessarily meaning snowstorms by the way). Daily temperatures will act as a roller coaster ride, meaning some days consisting of much below normal temps. and others as much above normal. In the end, everything should work out to an average winter, but I would favor the above normal temperatures to win out at the end. 

Region 2 - Below Avg. Temps. / Above Avg. Precip. (except Maine)

I actually think this could be a very snowy winter for this part of the country. Usually it is not a question of needing the cold air (since it is already there), it's just you need the storms to track there. The pattern should support storms to cut west of the Apps this winter, which is why I think a well above normal snowfall is in order for this region. The worst of the cold, getting down to arctic-like and very dangerous levels, will come IF (note the "IF") the AO gets to neutral or negative this winter. I'm not quite sold on that just yet. 

Region 3 - Below Avg. Temps. / Below Avg. Precip. 

A very west-based -NAO could allow storms to track and stall over this part of the region, but I do not see it happening this winter. I think there will be periods of extremely cold temperatures, but there will not be much in the way of large storms systems. However, there probably will be numerous small-type storm events as short wave energies ride along the polar jet stream. Will be interesting to see if one cuts-off or not. 

Region 4 - Above Avg. Temps. / Above Avg. Precip. 

This is probably the area I am least confident in of all the regions. This fall we have seen some strong storms effect this part of the country, and that could be due to the sub-tropical jet feeding off the Gulf of Mexico. This has the potential to continue through the winter months, but I do not see much in the way of frozen precipitation (sorry Dallas) falling since too much warm air will be available. 

Region 5 - Above Avg. Temps. / Above Avg. Precip. 

I was deciding between warm / wet or warm / dry for this area. Do not get me wrong, I do think there will be periods of cold shots that work there way in behind the storms system that will cut west of here. But overall, since I see storms cutting west of this region, I think heights will be raised enough where the winter will end in an above normal state. The difference with this area and I-95 is storms do not have the opportunity to dynamically cool the atmosphere which would change precip. from rain to snow since the coldest air is to the north and west. 

Region 6 - Avg. Temps. / Avg. Precip. 

I have been seeing a lot of forecasts for a warm western U.S., but we have to remember we are still in a       -PDO cycle and that usually leads to -PNA regimes, which promote trough's instead of ridges. I think there will be periods of cold and warm shots all winter long, with occasional storminess as well. Pretty much an average winter. 

Just like month-to-month breakdowns, I also do not believe in trying to predict accumulating snowfall for specific areas since so many variables are involved; BUT I will go ahead and just put out a few random cities with my "gut" feeling of how much they could see:

NY, NY: 26-31 inches of snow

Nassau County, NY: 28-33 inches of snow

Suffolk County, NY: 27-32 inches of snow

Newark, NJ: 27-32 inches of snow

Sparta, NJ: 35-40 inches of snow

Philadelphia, PA: 18-23 inches of snow

Baltimore, MD: 15-20 inches of snow

I hope everyone enjoyed reading my 2013-2014 winter outlook. At the end of the season, I will "grade" the outlook and look at what I need to improve on and study more in order to make a more accurate outlook for the following winter. 

Remember to please register to my weather forum at www.njstrongweatherforum.com to join along in the daily discussions that become especially important before large storm events. 

Thanks for reading, 

Francesco Paparatto 

What Now? Pattern Outlook and Winter

Besides some flurries or rain showers Monday night into Tuesday from an arctic front, we will remain dry for at least another week. This means the drought over parts of Long Island and NYC Metro will continue. Temperatures will be only in the 40's to start the week, but will get progressively warmer by the end of the week into the 50's.

Again, the biggest reason why there will not be a coastal storm this week like the EURO model suggested is because there is no blocking in the Atlantic. All the blocking is in the Pacific, evident by the large Aleutian ridge.

Speaking of that ridge, it will persist for another week as well.

12z EURO hour 168



The 00z GFS model also has a trough in the west and some ridging in the east around this time frame as well

However, this pattern should remain transient for the most part, which means periods of below normal temps and periods of above average temps. We are still in a fast paced zonal flow until the NAO goes negative, which still doesn't look like will happen for at least the next week to 10 days. 

EPO (which will be a significant driver in our pattern this upcoming winter) from the EURO above proves why this pattern should remain mainly transient. 

I have a couple things to say about the 2013-2014 winter:

1. The AO may reach a record high positive value this month, but the only reason why I am not concerned is because of the way snow cover and ice extent has progressed in Siberia/Eurasia and Arctic, respectively. However, research of analogs does show when the AO reaches a mighty high positive value (3 or greater) like it should this week, December should be above normal (2011 being a recent example).

2. The -PDO regime will continue this winter, but parts of the equatorial Pacific are warming, which is interesting and should not be dismissed (especially if it continues!) 

3. I like the progression of the Stratosphere. Asia is not as cool as it was this time last year, and just maybe we can get the PV to our side of the globe. 

Obviously I will have much more in the 2013-2014 winter outlook, which is set to be released on November 18th, a Monday. In the outlook, I plan to cover ENSO, Stratosphere, Ice Extent, Snow Cover, Sunspots, Analogs, and Wildcards. My forecast will be made from my interpretations of those factors, along with my "gut" feeling of how things could play out. 

For now, enjoy the quieter than normal weather pattern and I will catch you all again on November 18th with the outlook. Please feel free to join with NJ Strong Weather Forum at www.njstrongweatherforum.com which consists of members mainly from NYC Metro, all of NJ, Long Island, Hudson Valley area, and CT. 

Have a good day

-Francesco Paparatto 

Pattern Amplification Likely, A Tale Of Two Octobers

Good afternoon, 

I want to give a quick update on what the weather pattern looks like as we head into the 2nd half of October. There are some interesting features that deserve some attention. 

The mega-typhoon that is re-curving near Japan is going to spark pattern amplification downstream into North America. The global upper air wind pattern is going to change so that colder air makes its way into the U.S. while warmer air overtakes Canada. I'll show you what I mean... 

Here is a look at our current 500mb pattern from the 12z GFS model. Fairly zonal in the eastern U.S. with a cut-off trough in the western U.S. At this point, a ridge is just now beginning to develop in the Northern Pacific and the EPO (eastern pacific oscillation) is transitioning to a negative phase. 

When we fast forward to the weekend, a full fledged ridge is now dominating in the Northern Pacific and a 

-NAO/-EPO pattern ensues. The -EPO basically means the upper level winds in the Northern Pacific have transitioned from a progressive stage to one that is cut-off by a large ridge, allowing colder air bottled up in Canada to downstream into the U.S. 

And even going beyond the weekend into next week, the GFS still has a PV (Polar Vortex) over the Hudson Bay with a nice trough in the eastern U.S. At this point though, the -NAO is gone but the -EPO signal is still there. 

Just in case you were wondering, the EURO model also has the same set-up as the GFS in regards to the upper level pattern. Strong ridging in the N. Pac. and potent lower heights in the eastern U.S. 

You can see negative temp. anomalies are going to overtake nearly two-thirds of the country by the weekend and into next week. This definitely calls for cooler than normal temperatures to filter into the central and eastern U.S., possibly as high as -8 to -12 degrees below normal, which is fairly significant. Of course if you are a cool-weather enthusiast, this is all music to your ears. 

In terms of precipitation, the amplified pattern is going to bring wetter conditions into the heart of the country and New England as well. 

The PNA, or western ridge, has been non-existent since fall has begun. There has been constant lower heights, or trough's, in the western U.S. This is evident by the large blizzard that brought parts of the Rockies states 40+ inches of snowfall. 

One of the downfalls with not having a western ridge is all the energy that comes with the -EPO consolidates in the western U.S. or middle part of the country. What this usually leads to is storms that cut to the west of the NYC Metro area. If the PNA were in a positive phase, this means the entire west coast of the U.S. is under positive height anomalies and the energy is forced to consolidate somewhere along the east-central or eastern U.S, because that is the way the jet stream would flow. 

Here is a general map I made with my thoughts on this months second half. With the pattern coming to life, there will be more storms to keep an eye on that should bring mainly rainy conditions to the Northeast. However, the upper tier of the country and interior PA/NY could see their first flakes of the season depending on how much cold air is available from the -EPO/-NAO pattern. If the -NAO subsides, much of these storms will likely cut to our west. 

We'll see what happens! Have a good day. 

Francesco Paparatto

Notes:

1. 2013-2014 Winter Outlook to be released Thanksgiving Day

2. Join the forum! www.njstrongweatherforum.com

3. Happy Columbus Day!