DECEMBER 23, 2013: WHERE IS THE NAO HEADED?

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NAO GEFS Index Forecast - December 23, 2013

The North Atlantic Oscillation (NAO)
GFS MRF Ensemble Indice Forecast from
NOAA's Climate Prediction Center (CPC) is currently weakly Positive. The GFS Ensemble Indice Forecast indicates that the NAO will be very weakly Positive December 24-27. The Ensemble Indice Forecast indicates the NAO will be neutral to very weakly Negative December 28-31. The GEFS later indicates that the NAO will trend weakly Negative January 1-7. The NAO will then trend neutral to weakly Positive January 8-15.
The NAO Operational GFS Indice Forecast from CPC is also currently weakly Positive. The GFS Indice Forecast indicates that the NAO will be very weakly Positive December 24-27. The Operational Indice Forecast indicates the NAO will be neutral to very weakly Negative December 28-31. The GFS later indicates that the NAO will trend weakly Negative January 1-7. The NAO will then trend neutral to weakly Positive January 8-15.  
NOTE: Indice Forecasts have been modified, due to Forecaster's understanding of the current Longwave pattern.

AO GEFS Index Forecast - December 23, 2013

The Arctic Oscillation (AO)
GFS MRF Ensemble Indice Forecast from CPC is currently moderately Positive. The GFS Ensemble Indice Forecast indicates that the AO will be very weakly Positive December 24-27. The Ensemble Indice Forecast indicates the AO will be neutral to weakly Negative December 28-31. The GEFS later indicates that the AO will trend increasingly Negative January 1-7. The AO will then trend neutral to increasingly Positive January 8-15. 
The AO Operational GFS Indice Forecast from CPC is currently moderately Positive.  The GFS Indice Forecast indicates that the AO will be very weakly Positive December 24-27. The Operational Indice Forecast indicates the AO will be neutral to weakly Negative December 28-31. The GFS later indicates that the AO will trend increasingly Negative January 1-7. The AO will then trend neutral to increasingly Positive January 8-15. 
NOTE: Indice Forecasts have been modified, due to Forecaster's understanding of the current Longwave pattern.

PNA GEFS Index Forecast - December 23, 2013

The Pacific-North American Oscillation (PNA)
GFS MRF Ensemble Indice Forecast from CPC is currently neutral. The GFS Ensemble Indice Forecast indicates that the PNA will be neutral to very weakly Positive December 24-27. The Ensemble Indice Forecast indicates the PNA will be weakly Positive December 28-31. The GEFS later indicates that the PNA will trend increasingly Positive January 1-7. The PNA will then trend neutral to weakly Negative January 8-15. 
The PNA Operational GFS Indice Forecast from CPC is currently neutral. The GFS Indice Forecast indicates that the PNA will be neutral to very weakly Positive December 24-27. The Operational Indice Forecast indicates the PNA will be weakly Positive December 28-31. The GFS later indicates that the PNA will trend increasingly Positive January 1-7. The PNA will then trend neutral to weakly Negative January 8-15. 
NOTE: Indice Forecasts have been modified, due to Forecaster's understanding of the current Longwave pattern.

WPO & EPO GEFS Index Forecast - December 23, 2013

The Eastern Pacific Oscillation (EPO)
GFS MRF Ensemble Indice Forecast from
NOAA's Earth System Research Laboratory (Physical Sciences Division) and NCEP, is currently weakly Negative. The GFS Ensemble Indice Forecast indicates that the EPO will be weakly Negative December 24-26. This indice forecast then indicates that the EPO will be increasingly Negative December 28-31. The GEFS later indicates that the EPO will trend weakly Negative January 1-6. The EPO will then trend neutral to weakly Positive January 7-13.

The Western Pacific Oscillation (WPO)
GFS MRF Ensemble Indice Forecast from NOAA's ESRL/PSD and NCEP, is currently moderately Negative. The GFS Ensemble Indice Forecast indicates that the WPO will be moderately Negative December 24-26. This indice forecast then indicates that the WPO will be increasingly Negative December 28-31. The GEFS later indicates that the WPO will trend weakly Negative January 1-6. The WPO will then trend neutral to weakly Positive January 7-13. 

AAO GEFS Index Forecast - December 23, 2013

The Antarctic Oscillation (AAO)
GFS MRF Ensemble Indice Forecast from CPC is currently neutral. The GFS Ensemble Indice Forecast indicates that the AAO will be neutral December 24-27. The Ensemble Indice Forecast indicates the AAO will be neutral to weakly Negative December 28-31. The GEFS later indicates that the AAO will trend increasingly Negative January 1-7. The AAO will then trend neutral to increasingly Positive January 8-15.  
NOTE: Indice Forecasts have been modified, due to Forecaster's understanding of the current Longwave pattern.

Indice Forecasts are for Extended & Long Range Guidance only, and are not meant to be taken verbatim. Please consult NWS Albany, N. Y. / NWS Taunton, or the NWSFO covering your region... for official short-term regional zone forecasts.

EXTENDED OUTLOOK:
MERRY CHRISTMAS!

Thoughts to keep-in-mind, the overall December "transition" discussed in the 
2013/14 Winter Outlook... is well-under-way. Established High Latitude Blocking episodes appear eminent as we enter January 2014!

Updated: January 2, 2014

WPO GEFS Index Forecast - January 2, 2014

WHAT CAUSED THE PAST WINTER BLAST!  

As discussed in the 2013/14 Winter Outlook, it was very clear that a resurgence in Solar Activity due to increased sunspots on the magnetically active solar disk in 
mid-to-late October... was responsible for the transition to an overwhelmingly 
Positive Phase of the Arctic Oscillation (AO) & 
North Atlantic Oscillation (NAO) from the beginning-of-November through most 
all-of-December. However, there was a real Winter blast for much-of-the first half of December that led to a coastal storm on Saturday, December 14, 2013. It is very important to note that while the AO & NAO did not favor such amplification of the 500-millibar Height Pattern, the 
Western Pacific Oscillation (WPO) above, and Eastern Pacific Oscillation (EPO) where predominantly Negative (circled-in-black above) from mid-to-late November through mid December. This meant that cold air was tapped and drawn southeast from North-central Canada, due to an expanding area of High pressure over the Gulf of Alaska. The WPO / EPO are highly influenced by the 
Pacific Decadal Oscillation (PDO)... which became slightly Positive during the Fall,  meaning that Pacific Sea Surface Temperature (SST) anomalies are warmer than normal, encouraging Blocking over the eastern Pacific. 
The -WPO / -EPO pattern collapsed due to lack-of-Teleconnection support in association to changes with the Madden Julian Oscillation (MJO)... as the enhanced area of tropical convection over the equatorial Pacific entered Phase 5-6, collapsing the ridge of High pressure over the eastern Pacific, which strongly encouraged the true effects of an overwhelmingly 
+AO / +NAO signature as New England experienced a classic blow-torch from December 20-23, 2013. Of interest, while the WPO & EPO where initially Positive from late October into the beginning of November... which was the peak-of-sunspot resurgence, the AO & NAO remained Positive beyond, due to extreme sensitivity to solar activity. The more active the sun, the more of a driver it is... influencing the Earth's stratosphere (poleward), where pronounced cooling occurs. Therefore, the orientation of the jet-stream keeps the heart of the Polar Vortex (PV) at the
North Pole...
encouraging an overall progressive pattern (with short-lived shots of cold air) in middle latitudes with a highly Positive Phase of the Arctic Oscillation (AO) and 
North Atlantic Oscillation (NAO).

PUNCH 1! BEGINNING OF CHANGE...

GFS 1000-500 hPa Thickness - January 2, 2014

Current 1000-500 hPa Thickness show a positively-tilt trough over the 
Mid-Atlantic, with a defined Polar Vortex (PV) (circled-in-white) over Quebec... marking the transition to a Negative Arctic Oscillation (AO). However, much of the southeastern United States... especially Florida, is experiencing above normal temperatures due to the North Atlantic Oscillation (NAO) only falling to around neutral. The neutral NAO allows for the southeast ridge to maintain it's identity, and in-return promotes a significant moderation for New England in-advance of Arctic fronts... due to a strong south-southwest flow in-advance of the frontal passage. This, for example, will occur on Monday, January, 6th. Aside from this, the period of January 3-10 will feature below to well below normal temperatures overall... with moderate-to-high potential of Miller Type B coastal storm development. This period will mark the true beginning of the Winter change, especially with the 
Arctic Oscillation (AO).

LONG RANGE THOUGHTS:

THE SUN & SOLAR CYCLE 24...

NASA Solar Activity as of January 2, 2014

While Solar Activity, in-terms of active sunspots, has lessened since November 2013... the extreme western quadrant of the sun remains active. Most of the solar disk, however, is becoming quiet or falling-to-sleep... which is important for sustained High Latitude Blocking episodes, and will be a significant factor in-the-years-to-come. It is very important to remember, on January 4, 2008 we entered Solar Cycle 24. While Solar Cycle 23 was highly active 
in-terms of sunspot activity, Solar Cycle 24 is trending much-less-active (as seen above)... especially since the actual observed Solar Maximum in 2011/12. Had this sunspot activity took place a decade ago, the out-come on the overall 500-millibar Height Pattern in the Northern Hemisphere... would have had a far greater impact. 
*A note to viewers, the Fall 2013 resurgence in sunspot activity should NOT be confused with the 
2011/12 Solar Maximum... as there is no comparison in the amount of UV Rays that hit the Earth now, in-contrast to then. Which is (in-part) why we will be experiencing the 
PUNCH-of-Winter!

MJO & BRIEF THAW... PATTERN RELOAD

MJO GEFS Forecast - January 2, 2014

The Madden Julian Oscillation (MJO) will emerge in Phase 6, from neutral over the western Pacific during the next 7-10 Days. This will play a role in temporarily shifting the ridge/trough axis over the eastern Pacific, encouraging a +WPO / +EPO  / -PNA influence, promoting the return to a +AO / +NAO Teleconnection January 11-18. During this period there will be a "January Thaw", temperatures will rise to above-to-much-above normal levels briefly along with increased risk of rainfall. This will be due to the shifting ridge/trough axis encouraging a southerly flow at all levels of the atmosphere in 
New England, as the AO & NAO return Positive.


PUNCH 2! COMPLETE TRANSITION...

NAO GFS Index Forecast - January 2, 2014

  The combined influence of significantly reduced sunspot activity... encouraging pronounced High Latitude Blocking as downward propagation of Poleward 
Sudden Stratospheric Warming (SSW) reacts, along with the continued forward propagating Phase 6-7 Madden Julian Oscillation (MJO) influence over the western Pacific, will reload the 500-millibar Height Pattern. This, however, will be a complete pattern transition... where a highly amplified -WPO / -EPO / +PNA Teleconnection, will drive a classic 
-AO / -NAO couplet over eastern North America as the Polar Vortex (PV) returns to east-central Canada around January 20-22. 


Prepared by: Daniel Viens

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