2014-2015 Winter Outlook

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Introduction / Recap

Anyone who knows me understands how much I look forward to this time of year. Not only is it the holiday season, but it is when most weather enthusiast rejoice for another year of winter storm tracking. Winter of 2013-2014 was characterized by:

 *Pacific blocking (-EPO) which lead to much colder than normal conditions on the eastern CONUS and above normal snowfall in the NYC Metro area as well as other major cities in the Northeast.

*Moderate to strong -AO which allowed the PV (Polar Vortex) to get displaced from the Arctic and sink into our CONUS. That is one of the reasons why February / March last season featured record breaking cold and just northern-stream driven light to moderate storms. Southern stream s/w's were getting sheared out from the strength of the PV.

*Overall, the flow in the eastern U.S. last winter was fairly progressive given the state of the +NAO. There were forms of blocking in the displaced PV and arctic High's, but if you remember, the storms were quick-hitters and relatively short duration. Including the "bigger" ones. West to east latitudinal Atlantic blocking was nonexistent.

The upper level pattern this upcoming winter will be different compared to last. The biggest factor being the state of the ENSO, which is expected to be in a weak to moderate El Nino state. That being said, lets jump into the 2014-2015 Winter Outlook.

Agenda 

A. ENSO, SST Configuration, and Teleconnections

B. Northern Hemisphere snow and ice extent 

C. Stratosphere (QBO discussion)

D. Sunspots

E. Analogs

F. My Forecast / Conclusion


Section A: ENSO (El Nino Southern Oscillation) - SST (Sea Surface Temps.) Configuration - Teleconnections

The ENSO is classified by studying the fluctuating temps. in the Equatorial Pacific. SST's running above normal in that zone (along the Equator in the Pacific Ocean) mean the state of the ENSO is in a warm phase, or El Nino. This causes winds in the low-level atmosphere to be weaker and for convection to be enhanced along the STJ (Sub-Tropical Jet Stream). On the other hand, a cold phase, or La Nina, features SST's running below normal causing the STJ to be inactive. SST's averaging a threshold of   +/- 0.5°C ONI (Oceanic Nino Index), specifically in Nino region 3.4, classifies El Nino, La Nina, or La Nada (neutral, no affect on upper level pattern). 

                                             Figure 1A

Lets take a look at Figure 2A below to see how the ONI has looked in the last 6 weeks: 

                                              Figure 2A

Keep in mind Figure 1A when looking at this graphic. Notice by the middle of October, each Nino region reached the +0.5°C plateau which suggests an El Nino episode is taking shape. Looking into the numbers more would also suggest a west-based El Nino is looking to form, which means the warmest anomalies are centered over the central and western Nino-regions. Often times, this is referred to as El Nino Modoki. Take a look at Figure 3A to see what this means. 

                                            Figure 3A

El Nino Modoki features above normal precip. up and down the east coast, while regular El Nino keeps most of the above normal precip constrained to the western U.S. Even though the central and western regions are experiencing the greatest warming, I would NOT go as far as saying this upcoming winter will be El Nino Modoki. I think it is more of a blend of the two. I do expect the southwestern U.S., specifically southern California, to see above normal rainfall due to the state of the MJO (Madden-Julian Oscillation). 

Another way of classifying the state of the ENSO is by looking at the SOI, or Southern Oscillation Index. It specifically gives a good indication of the intensity of the ENSO event taking place. Values between -8 and +8 are indicative of a very weak, or non-existent, ENSO event taking place. Values sustained at -8 or higher signals El Nino, while values sustained at +8 or higher signals La Nina. 

                                           Figure 4A

Figure 4A shows the SOI value as of November 15th. As you can see, that number reads -10.7 which defines weak El Nino. 

                                             Figure 5A

The dynamical and statistical models hone in on a weak El Nino for the DJF (December-January-February) period. Given the information presented to us above, it is safe to say the upcoming will feature at least a weak El Nino, with a small chance it reaches moderate status (above +1.0°C in Nino region 3.4)

SST Alignment:

                                             Figure 6A

I'll start with #1 in Figure 6A since I went over the ENSO already. As you can clearly see, the Equatorial Pacific is featuring SST's running above normal. The further-most western and eastern sides of the tropical Pacific are seeing their SST's around neutral, which is why I have El Nino Modoki in a question mark. If the central region (3.4) takes charge and end regions continue to cool, El Nino Modoki could develop by the middle of our winter which could make things really interesting on the eastern seaboard of the U.S. However, that remains to be seen. Regardless, El Nino looks prominent. 

#2 of Figure 6A is the PDO region. The Pacific Decadal Oscillation illustrates SST anomalies in the North Pacific. As you can see, they are running MUCH above normal. In fact, as of September the PDO value was at +1.08, which is moderate. I expect this signal to continue to warm and get stronger as the winter advances. There is actually a correlation between El Nino & PDO years. 

                                               Figure 7A 

Figure 7A shows the correlation I am talking about. For the most part, the PDO and ENSO follow each other. -ENSO years usually lead to -PDO episodes, while +ENSO years (what we're seeing this winter) feature +PDO. These warmer than normal SST's in the North Pacific often times leads to ridging, or positive heights, in the western U.S. (+PNA). As most of you know, positive heights in the western U.S. leads to a trough in the eastern U.S. Trough's are dip in the jet streams that turn winds out of the northwest and help usher down cold air from Canada into the Northeast. 

Back to Figure 6A, #3 is an area of below normal SST's I circled in the central Atlantic. History shows that an SST alignment in the Atlantic showing a +AMO (+SST's south of Greenland) and -SST's in the central Atlantic leads to a -NAO. A -NAO, or North Atlantic Oscillation, is characterized by positive heights across the high latitudes of Greenland and Iceland. Take a look at Figure 8A for a detailed look. 

                                                Figure 8A

A +NAO (left image) shows more of a progressive pattern in the eastern U.S. The jet stream travels west to east with little disruption. Areas north of the jet stream are cold while those south are seeing mild conditions. On the contrary, a -NAO (right image), also known as "blocking," is when the jet stream buckles and the westerly wind flow is cut-off. As you can see, when there is blocking (positive heights extending into the North Atlantic and Greenland), you see a trough over the eastern CONUS (Continental U.S.). 

Given the state of the +PDO and the Atlantic SST alignment, we are most likely to see a winter dominated by  a +PNA/-NAO type of H5 (500 mb level) type of pattern. But how about the EPO (East Pacific Oscillation). If you remember last winter, it was consistently in a negative phase which promoted positive heights into Alaska and the Arctic, which forced the PV to sink south into our CONUS. 

                                                 Figure 9A

Figure 9A is a look at the SST anomalies from last winter in the Pacific Basin. The above normal pool of SST's in the North Pac. is the signal that leads to the -EPO. Also noteworthy was the -PDO and "La Nada." It goes to show just how much our winter last season was influenced by the -EPO. If you go back to Figure 6A (the SSTA image), you will see I have the EPO in a question mark. Even though there are above normal SST's in the North Pac., they are not as consolidated as they were last season and are pointing more towards the west coast and the northeast GOA (Gulf of Alaska). Therefore, I am NOT convinced the EPO will be in a mainly negative state this winter. I think another factor, such as the Aleutian Vortex, will deter that from happening. That brings me into my next point. 

SLP (Sea Level Pressure), or Atmospheric Pressure, is the pressure seen at sea level (creative, I know). The MSLP (Mean Sea Level Pressure) is what I want to briefly talk about. During El Nino years, the MSLP is known to be lower over the Aleutian islands and higher than average pressure over the western Pacific and Greenland. 

                                             Figure 10A

Figure 10A exemplifies what MSLP looks like during El Nino events, and as you can see, it sees lower than normal pressure over the Aleutians which usually leads to a Vortex, or an area of strong low pressure that situates itself over that area for an extended period of time. An Aleutian Vortex would help pump heights up over the western US (+PNA) and further strengthen the +PDO. 

                                                Figure 11A

The above figure shows MSLP for my analog years (of which I will talk about in Section E of this outlook). You can see the deep blues and purples over the Aleutians, signifying much lower than normal pressure over that area. 

Section A in review: In this section, I gave evidence that points toward a +AMO/-NAO/+PDO/+PNA/+ENSO and a fluctuating EPO for the most part Winter 2014-2015. I also took a look at the SOI and MSLP. I will discuss the AO in Section B.

Section B: Northern Hemisphere Snow Cover & Ice Extent 

NH Snow Cover this Fall has been very impressive. 

                                             Figure 1B

Snow cover in Eurasia and Siberia is the 3rd highest on record since 1966. 

                                                Figure 2B

Figure 2B shows that only years 1976 and 2002 saw higher snow growth into those regions in October than 2014. This is important because historical trends have shown that when snow growth in the NH is running above normal, the AO, or Arctic Oscillation, has a much higher probability of being negative for the ensuing winter. 

                                             Figure 3B

By taking a close look at Figure 3B, you will be able to see the AO was at its lowest when snow growth in the NH was at its highest. This type of correlation has been proven to be true by numerous case studies, such as the once conducted by Judah Cohen. Click here to read about it. A -AO means Arctic air is being forced southward into the CONUS (the PV) and trough intrusions in the US bring down brutal cold, usually much below normal. Air temps. do not moderate as much. 

Section B in review: In this section, I outlined why I feel the AO will be in a mainly negative state Winter 2014-2015. The biggest factor being the impressive and rapid exposure of snow growth in the Northern Hemisphere.

Section C: Stratosphere (QBO discussion)

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, when our stratosphere warms at rapid levels in a short period of time.  A SSW can do one of three things to the PV: displace, split, or destroy it. Much of it has to do with the state of the QBO. 

The QBO, known as the Quasi-Biennial Oscillation, is an oscillation found in the lower stratosphere. It studies the relationship between equatorial zonal winds (westerly / easterly) and measures how it transfers warmer air in the stratosphere from tropical regions to polar ones. Like other oscillations, this one also comes in a negative or positive state. 

-QBO:  Weak and unstable PV. Pieces can break off and sink into the CONUS resulting in a -AO and much colder than normal temperatures. Strongly negative QBO values that stride toward positive can lead to the development of high latitudinal blocking. 

+QBO: Strong and stable PV. Fields its position in the Arctic region and stays there, meaning arctic air stays bottled up in the pole and the AO stays mainly positive. 

                                               Figure 1C

The latest monthly QBO value came in at -23.86 for October. Clearly the QBO is in a strong-negative state which means there is a high likelihood it begins making its descent toward positive in the short term. This is critical because history has shown a -QBO moving toward positive in an El Nino winter supports a -AO. Furthermore, a -QBO moving toward positive can often lead to the development of high latitudinal blocking, or a -NAO. You can check that out for yourself in Figure 2C which shows DT's rising QBO table and the probabilities of a -NAO forming depending on the state of the QBO. 

                                             Figure 2C

Section C in review: In this section I previewed the Stratosphere and how the QBO could effect our upper level pattern this winter. I concluded a strongly negative QBO is likely to lead to a higher chance of blocking developing this winter, as well as, a better chance of a -AO to develop. There is a chance a SSW event takes place sooner than normal this winter, but that is still bring monitored. 

Section D: Sunspots

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. 

                                                                                              

                                                Figure 1D

According to the Farmers Almanac, we are currently in a weak, or inactive, cycle which could result in a cooling pattern over the next few years. As you can see from Figure 1D, 2014-2015 is located between cycle 24 and cycle 25 which is within the inactive phase. We are on our way to a solar minimum. Notice the other 2 analog years I circled in red, 1976 and 1957. They were also in cycles that trended toward a solar minimum. This further adds to the evidence of a colder than normal winter taking shape for the CONUS. 

Section D in review: In this section I reviewed the impacts Sunspots could have on our upper level pattern. I'm not sure how perfect of a science this is, but clearly it does have weight on our weather patterns. I concluded that this further adds to the evidence that a colder than normal winter is headed our way this year. 

Section E: Analogs

Analogs are past years chosen by forecasters that we feel could correlate to the upcoming winter season. Some of the factors I look at when choosing analogs is matching up the state of the ENSO and PDO as well as other teleconnections. 

                                              Figure 1E

Figure 1E shows the analog years I have chosen. Winters of 1957-58, 1976-77, and 2002-03. One of the biggest reasons why I chose those years besides the fact that they match the projected ENSO and PDO forecasts, was because I liked how their SST anomalies in the Fall looked compared to our current SSTA. Also, they match the SAI (NH snow cover) and Sunspot forecast.

                                               Figure 2E 

Figure 2E shows the DJF period temp. departures from normal in my analog years combined. Blue meaning below normal. red meaning above. 

                                                Figure 3E 

Figure 3E shows the DJF period precip. departures from normal in my analog years combined. Blue meaning above normal, red meaning below. 

If you have been following this outlook, you will have noticed I made several connections to these years with regards to the Sunpots and NH Snow Cover. 

Section E in review: In this section I researched my analog years and let you all know which ones I have chosen. The 3 I chose show below normal temps. in the eastern CONUS and above normal precip. (along the coast). Look at the chart for a simple view of the years I chose and why. Essentially, the match closely to our current weather conditions. 

Section F: Official Winter Forecast and Conclusion 

Hopefully you have made it this far without feeling so perplexed. I tried to make this as little technical as possible. After taking all of these factors into consideration, as well as going with some gut instincts, here is my 2015-2015 Winter Outlook:

                                                                         Figure 1F

#1: I-95 Corridor - This region this winter can expect not as many storms compared to last. However, the storms they do get will be larger and more powerful in nature due to the active STJ (Sub-Tropical Jet) and the potent Polar Jet. When these two jets come together, it is known as a phase and a large low pressure system develops. This area has to keep in mind that one storm may act as a set-up for another storm. For example, one rainstorm may end up turning into a 50/50 low for a second storm following its heels. Also, with the likelihood of blocking to develop, the storms may not necessary be quick-hitters like we have been used to seeing for the last few winters. They may be longer duration. Lastly, temperatures are expected to go through mild and cold swings but I am mainly looking at a below normal temp. regime for the coast this winter with above normal snowfall. Expect at least 1 Godzilla (12+ inch snowstorm) with a higher than normal potential of a Roidzilla (24+ inch snowstorm) due to the "boom-like" atmospheric conditions. It all depends on how the teleconnections align. Timing is always critical. 

#2: Ohio Valley & Interior Northeast - This is the area I can see seeing the coldest temp. departures with frequent arctic intrusions. As described in the outlook, I expect the PV to sink south again this winter, except this time, I think it will situate itself a little more west this season compared to last. Thus, the coldest air mass can be expected over this area with frequent night time lows in the single digits and teens. In terms of precipitation, you can expect below normal precip. since a lot of the storm focus will be to your south and east. I do think the Interior Northeast, however, will see precip. closer to average compared to the Ohio Valley and Great Lakes region. 

#3: Northeast Texas to North Carolina - This area can expect colder than normal temps. this winter due to the arctic blasts which at times could be brutal. Also, with an active STJ you can expect wetter than normal conditions with occasional wintry type of storms, including snow & ice. I can see a couple instances of moderate to strong winter storms to effect this area, especially the TN Valley and the Carolina's. 

#4: Midwest - Mine as well continue the theme of colder than normal conditions here as well. A lot of people this winter are going to be effected by the cold. Also, you can expect some average precip. that results mainly from northern stream driven energies. These could be frequent at times and I would not be surprised to see some areas finish above normal in that department. 

#5: Southern Texas to Florida: Do not think you will be able to escape the cold either. While you will definitely not be as cold as other regions, you will still see some cold air getting down into your areas. Expect multiple rain threats due to the tropical forcing that will travel along the STJ. Floridians should prepare for several nights of below freezing weather, especially behind possible Nor'easter's that develop along the eastern seaboard. 

#6: Pacific Northwest - History shows, as well as my analogs, that El Nino type of patterns bring milder temps. to your region with below normal precip. The western U.S. in general, maybe besides the SW CONUS, will be the best places to visit if you're looking to escape the cold this winter. Ski resorts may be a little disappointed out there in Utah and Colorado. 

DJF Temp. Forecast

DJF Precip. Forecast

Conclusion

I really hope you enjoyed reading my 2014-2015 Winter Outlook. I think it is important for me to say that long range outlooks are very difficult to accurately forecast and a lot of the evidence I presented here today is based off of facts and past events. These are always high volatile and can often get skewed by something that could go wrong, such as Atlantic blocking not developing as expected resulting in storm tracks further west. However, after analyzing and examining all the pieces to the puzzle, I am fairly confident most of this will come to fruition. We shall see I guess! 

Have a safe and healthy holiday season and please join the NJ Strong Wx Forum to take part in weather discussions with me and the other fellow members of the forum. Also, feel free to follow the Twitter and Facebook pages. 

Thank you for reading! 

Francesco Paparatto - Forecaster at NJ Strong Weather