CURRENT NAO & NE 2020

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Currently, what has nature taught us this year? Looking at the light red shaded chart, credit: NOAA's Climate Prediction Center (CPC), of the North Atlantic Oscillation (NAO) Monthly mean-average; reveals that the mildest weather conditions in New England, temperatures above to well above normal prevailed during January through March 2020, when the NAO was consistently positive or averaged a monthly mean above 1.00 (Standard Deviation), as indicated on-the-chart (black circles). Since April 2020, the NAO has undergone a complete reversal, that has promoted below to well below normal temperatures at-times. Most notably, the consistency of the NAO since the significant pattern reversal in April, will be a very important 'wild' card during the upcoming 2020/21 Winter Season. What is the NAO telling us? The support is overwhelming for New England to experience above to well above normal snowfall during the 2020/21 Winter Season due to overall 'negative' trends of the NAO since April... that strongly favor a colder / stormy weather pattern. The NAO is especially supported by the current state of the Sun; exiting-the-dead of a solar minimum! Forecaster: Daniel Viens, establishing author of New England NAO. (* NOTE: This is also 'consistent' with the NAO historically, as noted from my previous post on October 25, 2020.)

 A great question!: BOSTON had an all time record snowfall of 108.6" during the 2014/15 Winter Season. Average winter season snowfall in BOSTON is around 48.0"; and 2014/15 Winter Season... 60.6" above normal snowfall in BOSTON! Ironically, the North Atlantic Oscillation (NAO) wasn't in a noted 'negative' phase during *2014/15; which is usually a very important climate driver for New England to experience above to well above normal snowfall. *2014/15 was an extreme outlier due to strong High pressure ridge over western North America. When you state global warming... this research is out to make viewers aware, IF my overall thoughts are truly realized, that the climate is largely driven by natural & cyclical factors... starting with the Sun. The Sun is currently exiting-the-dead of a solar minimum which strongly favors the NAO to be observed in it's 'negative' phase during the 2020/21 Winter Season. Based on past analogs, 2010/11 & 2000/01, when the Sun was also exiting-the-dead of a solar minimum, BOSTON had around 30.0" above normal snowfall but the hills of western and parts of northern New England had around 50.0" to 60.0" above normal snowfall. Forecaster: Daniel Viens, establishing author of New England NAO. (Picture of Mt. Greylock War Memorial Tower taken by me in early December 2012, on a pre-winter hike to the summit.)
 

HISTORIC NAO & NE 2020

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This picture was taken by me May 9, 2020 at Whitcomb Hill Summit, Mohawk Trail - Route 2 Florida, MA., during an amplified winter-like weather pattern known as the negative phase of the North Atlantic Oscillation (NAO). This pattern prevailed for much of May 2020. The negative NAO is a high latitude block of atmospheric pressure that becomes established around southern Greenland in the North Atlantic; that blocks the jet-stream (upper-air flow) from moving straight west-to-east, sending air of polar origin into the eastern U.S. (northeastern U.S. / New England), along with increased potential of coastal storms... 'Nor'easters'. Historically, the average phase of the NAO during the month of May, is a direct correlation to the average phase of the NAO observed during the upcoming winter season. Forecaster: Daniel Viens, establishing author of New England NAO.

WINTER SEASON 2015/16: ENTERING SOLAR MINIMUM

The emerging sleep of-the-Sun, with only three (3) identified sunspots visible on the solar disk as of 
November 25, 2015.  

Originally prepared: November 23, 2015 (Facebook timeline-post) 

I would like to talk about El Niño, that has made significant headlines in the media. El Niño "The Boy", which is an unusual warming of Pacific sea surface temperature (SST) anomalies, is NOT basin wide through the equatorial Pacific Ocean. In fact close observation shows there is NO comparison to the 1997/98 super El Niño, as this particular event is *Central-to-West-based and NOT basin wide or East-based. This means the warming of SST anomalies over the Pacific is concentrated from the International Dateline, points east to the *Central / North American continent.

A *Central-to-West-based El Niño will in-fact encourage an energized sub-tropical jet-stream but ridging (above normal heights) over western North America due to the area of above normal SST's concentrated through the eastern Pacific, that will tend to encourage troughing (below normal heights) over eastern North America.

What is the foundation of the 2015/16 Winter season?

1. Solar Minimum / High Latitude Blocking - it's very important to consider that we are now entering a solar minimum following the 9-11 year sunspot cycle. The Sun has been averaging 20 daily events or less (in-terms of sunspot activity on the solar disk) since November 7, 2014, and is currently at 15 daily events as of November 20, 2015. Through the majority of absent New England Winter's of the 1990's, the Sun was averaging 40-100 daily events, * sending a moderate to high frequency of ultraviolet (UV) rays at-the-Earth. The higher frequency of ultraviolet (UV) rays acts to deplete ozone and in-return allows for pronounced cooling of the pole's stratosphere, with the Polar Vortex (PV) almost never splitting to influence middle latitudes of-the-Earth. Strongly taking into consideration current solar activity, lends hand to the highly cyclical 9-11 year (Schwabe) sunspot cycle, that we are indeed entering a solar minimum. The emerging sleep of-the-Sun will soon encourage pronounced warming of the pole's stratosphere due to increased ozone, * as this warming pushes down through the * stratosphere and troposphere, the PV will in-turn react and SPLIT, the pole will moderate. As the split PV drops south in-latitude, a reaction-to-action, ejecting the Arctic Oscillation (AO) / North Atlantic Oscillation (NAO) into a pronounced negative phase. This will be the said driver of the 500-millibar Height Pattern over the Northern Hemisphere during the coming 2015/16 Winter season, NOT El Niño.

2. El Niño - the above said factors will tend to encourage an unusually stronger than normal or *enhanced* sub-tropical jet-stream, that will as-a-result of location, be a high moisture source to interact with the Polar jet-stream. This will be, an enhancer, encouraging a moderate to strong probability of Nor'easters.

When will this change influence New England?

While we have experienced a gradual step-down since mid November, there are key signals that will indicate CHANGE. 
A strong low pressure system tracking through the eastern Great Lakes region, producing rainfall in New England, around the week of November 29th may be the mechanism that encourages a significant pattern change. 
Therefore, December 5-12th is the time period of high volatility.

* Corrected information on sudden stratospheric warming & the current state of El Niño.

WHAT IS THE NAO?

1.

The North Atlantic Oscillation (NAO) is part of an overall High-Latitude Atmospheric Blocking scheme, which oscillates between a North-South Center dipole of two anomalies. When the NAO is in a Negative Phase or North Centered, an intensifying High pressure anomaly center becomes established over the *southern-tip of Greenland... commonly referred to as the Greenland Block. Which in-return blocks, buckles the jet-stream (upper-air flow) from moving straight west to east... establishing a Meridional north to south flow. Sending air of polar origin south into middle latitudes of eastern North America & western Europe. *The Negative NAO influence is often noted as West-based or East-based, and although the overall -NAO loading-pattern effects New England with below to well below normal temperatures...where the blocking takes place in the North Atlantic is important. The West-based -NAO directly impacts New England & especially the Mid-Atlantic, as a result of the blocking high pressure anomaly center near or just off the southern-tip of Greenland. This pattern, teleconnecting with the Arctic Oscillation (AO) often produces text-book...                         

2.

Nor'easters. Due to a deep trough associated with an intense cold building High to the north, over Ontario, Canada ... that often becomes negatively-tilt as the downstream trough lifts-up along the U. S. Eastern Seaboard. 
For more information on Nor'easters, please visit... 

The East-based -NAO effects are less pronounced over New England & especially the Mid-Atlantic... due to the blocking High pressure anomaly to the east of Greenland. This pattern is still associated with below normal temperatures, however it usually does not teleconnect with the Arctic Oscillation... allowing it's influence to be short-lived. Also, with the High further east... the downstream trough is also further east, that is positively-tilt. In return, this significantly limits development along the U. S. Eastern Seaboard & promotes Miller Type B cyclogenesis that does develop... to move East-northeast from the East Coast.

3.

When an intensifying High pressure anomaly center builds off the southeastern 
United States coast or near Bermuda... commonly referred to as the 
Bermuda High,
the NAO is in a Positive Phase or South Centered. Unlike the Negative Phase, the Positive Phase enhances the westerlies... establishing a Zonal flow, or west to east orientation of the jet-stream, preventing buckling. Allowing for a pronounced south to southwest flow... at all levels of the atmosphere in middle latitudes.


Other major steering mechanism's of the
Northern Annular Mode (NAM), such as the
Arctic Oscillation (AO) strongly influence the NAO. When an intensifying High pressure anomaly center becomes established over the Arctic or 
North Pole, blocking the Polar jet-stream from moving straight west to east, expanding a developing Polar/Arctic Vortex southeast (over Hudson Bay, Ontario, Canada)... the
AO is in a Negative Phase or North Centered. Due to building heights in high northern latitudes of central & eastern North America... a Greenland Block often becomes established, producing a classic 
-AO / -NAO Couplet, fostering below to well below normal temperatures and strong potential of
Miller Type A cyclogenesis over central & eastern North America.
      
When an intensifying High pressure anomaly center builds over the U. S. Gulf Coast states or
Gulf of Mexico, encouraging a stronger than normal middle latitude & sub-tropical jet-stream, with above to well above normal temperatures over central & eastern North America... the AO is in a Positive Phase or
South Centered. As a result, High pressure also intensifies over the central Atlantic, encouraging establishment of a Bermuda High. Due to the highly influential AO, over NAO anomalies... it significantly influences the 
500-millibar Height Pattern over central and eastern North America.
 
Both the AO & NAO are part of the
Northern Hemisphere Teleconnection Longwave Pattern, and are observed through current trends & Indice Forecasts (of Operational Models & perspective Ensemble Members) from NOAA's -
NCEP Global Forecast System (GFS) and the
European Centre for Medium-range Weather Forecasts (ECMWF) in the
United Kingdom. Each Indice Forecast from it's perspective model measures the AO & NAO in-respect to normal-mean by an algebraic measure of variability, known as the
 Standard Deviation (SD)... defined by Wikipedia, the free online encyclopedia.

1. The first image above from NOAA's Climate Prediction Center (CPC) - demonstrates the NAO in a
classic Positive Phase.

2. The second image above from NOAA is of a March 2014 Nor'easter. 

3. The third image above of the
Trans-Atlantic continents - an area highly influenced by the
AO & NAO Teleconnection. 

4. The fourth image below from NOAA's Earth System Research Laboratory (Physical Sciences Division) & NCEP - demonstrates the NAO in a
classic Negative Phase.

4.

       

                 
In meteorological history the NAO was originally identified in 1924 by 
British Meteorologist Sir Gilbert Thomas Walker, with particular attention placed on sea-level pressure changes in the North Atlantic, as a result of Low pressure over Iceland and intensifying High pressure through the Azores.