Saturday, December 1, 2012

November 2012 - Colder & Drier Than Average

November 29, 2012
Full Hunter's Moon With Planet Jupiter
Photograph by Roddy Addington - © All Rights Reserved.

Frosty cold nights ruled November which ended colder than average in the High Knob Landform to continue the Autumn 2012 trend of below average temperatures.

Northern Hemisphere
September 1 to November 30, 2012
Surface Air Temperature Anomalies

Images provided by the NOAA/ESRL 
Physical Sciences Division, Boulder Colorado 

Northern Hemisphere
September 1 to November 30, 2012
850 MB Air Temperature Anomalies

November 29, 2012
Upon A Starry Night Above Wise County
Jupiter & Hunter's Moon Decorate Heavens
Photograph by Roddy Addington - © All Rights Reserved.

Record to near record November dryness broke the wet pattern that dominated most of the Summer & Autumn of 2012 across the High Knob Landform.

Climate Statistics
For November 2012

( Lower Elevations of Russell Fork Basin )
Clintwood 1 W - Elevation 1560 feet
Average Daily MAX: 52.9 degrees
Average Daily MIN: 25.1 degrees
MEAN: 39.0 degrees
Highest Temperature: 72 degrees
Lowest Temperature: 18 degrees
*Total Precipitation: 1.26"
Total Snowfall: Trace
2012 Precipitation: 40.28"

( Northern Base of High Knob Massif )
City of Norton - Elevation 2141 feet
Average Daily MAX: 50.4 degrees
Average Daily MIN: 23.3 degrees
MEAN: 36.8 degrees
Highest Temperature: 67 degrees
Lowest Temperature: 15 degrees
**Total Precipitation: 1.26"
Total Snowfall: Trace
2012 Precipitation: 60.81"

( Along the Tennessee Valley Divide )
Nora 4 SSE - Elevation 2650 feet
Average Daily MAX: 49.2 degrees
Average Daily MIN: 32.2 degrees
MEAN: 40.7 degrees
Highest Temperature: 66 degrees
Lowest Temperature: 20 degrees
Total Precipitation: 0.93"
Total Snowfall: Trace
2012 Precipitation: 41.34"

*The 4th driest November on record in Clintwood 
( 1964 to Present ).  The driest was November 2001 with 
0.85" of total precipitation.

**The driest November on record in the City of Norton 
( 1983 to Present ), beating the old record of 1.54" 
established in November 2001.

Mean November temperatures were influenced by lingering snowpack from Superstorm Sandy in the High Knob Massif, especially amid the main crest zone where deep snow dominated the first week of the month to keep unplowed roads like Route 237 blocked into November 7.  Patches of snow lingered amid northern exposed locations in basin heads of High Knob Lake, Big Cherry Lake, and the Norton Reservoirs through November 21.

Blizzard of Superstorm Sandy

Most notable were cold nights that featured mean minimums around 20 degrees in lofty valleys above 2700 to 3000 feet.

After at least 30" of snow at the summit level in October only around 1" fell during November as a dry pattern dominated this final month of autumn.

October 24, 2012
High Knob Massif
Hanging Rock Recreation Area
Photograph by Roddy Addington - © All Rights Reserved.

Climate Statistics
For Autumn 2012
( September-November )

( Lower Elevations of Russell Fork Basin )
Clintwood 1 W - Elevation 1560 feet
Average Daily MAX: 63.3 degrees
Average Daily MIN: 38.7 degrees
Autumn MEAN: 51.0 degrees
Highest Temperature: 86 degrees
Lowest Temperature: 18 degrees
Total Precipitation: 9.13"
Total Snowfall: 7.0"

( Northern Base of High Knob Massif )
City of Norton - Elevation 2141 feet
Average Daily MAX: 61.5 degrees
Average Daily MIN: 36.6 degrees
Autumn MEAN: 49.0 degrees
Highest Temperature: 85 degrees
Lowest Temperature: 15 degrees
Total Precipitation: 11.95"
Total Snowfall: 12.0"

( Along the Tennessee Valley Divide )
Nora 4 SSE - Elevation 2650 feet
Average Daily MAX: 60.1 degrees
Average Daily MIN: 44.0 degrees
Autumn MEAN: 52.0 degrees
Highest Temperature: 83 degrees
Lowest Temperature: 20 degrees
Total Precipitation: 10.56"
Total Snowfall: 13.4"

Autumn temperatures were cooler than average while precipitation was near average, despite record to near record November dryness.  

A wet September and Superstorm Sandy making up for the anomalous November dryness.

October 14, 2012
Hanging Rock Recreation Area
Beautiful Mountain Stream At Hanging Rock
Photograph by Roddy Addington - © All Rights Reserved.

An update for Big Cherry Dam in the High Knob Massif finds 6.15" of precipitation having fallen per month, on average, during the past 48-months ending with October 2012.

This despite significant winter moisture losses 
in falls of snow too deep for the rain gauge to physically hold, evaporation between hand-measurements throughout each year, and major local misses of heavy summer rains that flanked the measuring point during 2011 and 2012.

Following totals do not account for any rain gauge undercatches due to wind or secondary moisture sources such as fog drip from trees and rime deposition on trees ( which add significantly to the annual moisture budget of Big Cherry Basin ).

Updated 48 Month ( 4-Year ) Record
Big Cherry Dam of 
High Knob Massif
Monthly Precipitation Totals
Gary Hampton & Staff
Elevation: 3120 feet

November:  4.36"
December: 8.49"

January: 9.23"
February: 4.36"
March: 5.51"
April: 5.40"
May: 7.07"
June: 5.44"
July: 8.42"
August: 7.08"
September: 9.09"
October: 4.36"
November: 3.88"
*December: 11.50"

*January: 6.25"
*February: 4.25"
*March: 4.50"
April: 3.78"
May: 6.99"
June: 9.53"
July: 4.27"
August: 8.91"
September: 2.88"
October: 2.84"
November: 4.05"
*December: 7.35"

January: 4.51"
February: 4.53"
March: 9.85"
April: 10.08"
May: 5.38"
June: 6.16"
July: 7.18"
August: 4.94"
September: 7.28"
October: 5.05"
November: 8.67"
December: 6.62"

January: 4.70"
^February: 5.91"
March: 7.98"
April: 3.66"
May: 5.16"
June: 3.34"
July: 8.21"
August: 5.07"
September: 7.14"
^October: 4.00"

^Approximate rain gauge moisture losses of 0.90" 
on the February 19 snowfall and 1.50"+ on the 
October 28-31 Superstorm

12-Month Total: 70.46" ( M )
November 2011-October 2012

24-Month Total: 146.82" ( M )
November 2010-October 2012

2-Year Mean Precipitation: 73.41" ( M )
November 2010-October 2012

48-Month Total: 295.21" ( M )
November 2008-October 2012

48-Month Mean Monthly 
Precipitation: 6.15" ( M )

Mean Precipitation Per 
12-Month Periods: 73.80" ( M )

( * ) - Indicates that total was estimated or partly estimated due to severe winter conditions.  These are based upon reported snowfall in the massif and rain gauge measurements at Robinson Knob of High Knob Massif, City of Norton WP & Big Stone Gap WP.

( M ) - Denotes that total precipitation was greater than rain gauge total due to evaporation between hand-measurements and losses in falls of snow too deep for the 4"-diameter NWS rain gauge to hold ( the mean annual loss is estimated to have been 3.00" to 3.50" per year during the 2008-2011 period, and 3.50" to 4.00" 
in 2012, as partly based on observed losses at Clintwood 1 W ).

[ All measurements courtesy of Superintendent Gary Hampton and Staff at the Big Stone Gap Water Plant in South Fork Gorge ].

This 48-Month record period represents the highest precipitation average ever documented in Virginia, outside of the High Knob Massif, over an extended period of 4 years ( even if the five months with conservative estimates are omitted ).

Winter snowfall totals documented during this 4 year period, from 2008-09 through 2011-12, are noted below for High Chaparral and Eagle Knob in the High Knob Massif.

High Knob Massif
Winter Snowfall Totals
( 2008-09 to 2011-12 )

High Chaparral
Elevation 3300 feet
Observer: Joe & Darlene Fields

2008-09: 80.5"
2009-10: 124.0"
2010-11: 107.7"
2011-12: 48.2"
MEAN: 90.1"

#Eagle Knob
Elevation 4189 feet

2008-09: 107.0"
2009-10: 166.0"
2010-11: 141.5"
2011-12: 72.0"
MEAN: 121.6"

#Snowfall totals are approximate and representative of the main crest zone.  Reported totals are courtesy of Steve Blankenbecler, Wayne Browning, Roddy Addington, and numerous others.

( All but the 2008-09 winter are well docuemented on this website with MANY photographs ).

The Winter of 2009-10 proved to be the most difficult 
to document with rain gauge readings as the December 2009 Mega-Disaster Snow DUMP kept the roadway into Big Cherry Dam blocked for much of the winter, with the rain gauge freezing & busting.  Estimates were primarily based upon hand-measurements by Otis & Nancy Ward, at Robinson Knob, located 7.9 air miles ENE 
of Big Cherry Dam.

During December 2009, for example, 10.20" was hand-measured by Otis & Nancy Ward in Robinson Knob where their rain gauge missed catching approximately 14" of snow depth during the Mega-Dump.

Precip totals up through December 14, 2009 were approximately the same at Big Cherry Dam and Robinson Knob ( 6.08" ), but snow depth on the Mega-Dump was a foot or so deeper around Big Cherry Dam 
( i.e., the 11.50" estimate was conservative ).

December 3, 2012
Looking Across Coeburn & East End of Massif
Morning Sunrise From Guest Mountain of Wise Plateau
Photograph by Roddy Addington - © All Rights Reserved.

Updated On December 3, 2012
Only 0.82" was measured at Big Cherry Dam during November 2012 to mark the driest month on record since hand-measurements started late in 2007.

The 4.82" reported for October-November 2012 also marks the driest 2-month period, however, that does not take into account the large rain gauge loss during Superstorm Sandy.

It is now easy to prove that there was indeed a very large rain gauge loss during the October Blizzard at Big Cherry Dam.

Reference September-October 2010 with 5.72" of total precipitation reported.  The driest 2-month period prior to October-November 2012.

In the wake of a wet summer in 2010 the spillway at Big Cherry Dam overflowed until September 7.  

By October 31, with 5.72" during September-October, the lake level had dropped to 3.5 feet below its spillway ( down 130.5 Million gallons ).

The spillway did not overflow until November 27 in 2010, following 3.50" of additional precipitation 
( including 6.0" of snowfall in the Basin Head ).

Fast forward to October-November 2012.

During October-November 2012, by contrast, the spillway overflowed during both months despite having 0.90" less reported precipitation verses 2010 in the rain gauge at Big Cherry Dam.  

The big difference, of course, was the snow which, like my core on November 6 illustrated, held much more water than rain gauges caught.

Deep snow covered northern slopes in Big Cherry Basin through November 7, with some patches lingering into at least November 21, to yield enough run-off into the Lake to keep it overflowing despite daily water usage and the driest November on record in the High Knob Massif.

Historic October 2012 Storm

The rain gauge at Big Cherry Dam lost more than 1.50" during the October Blizzard and total precipitation in October-November 2012 was actually greater than in September-October 2010 ( irrespective of some evaporation differences ).

The Big Picture
Season of Change

November 20, 2012
Long Ridge of Tennessee Valley Divide
Majestic Sunrise Colors & Mountain Waves
Photograph by Wayne Riner - © All Rights Reserved.

Wayne Riner Photograph Thoughts...
"It's that time of the year when the weather can change quickly.  The black locust is outlined against the morning colors."

Autumn is certainly a season of change as so well demonstrated in 2012 with an explosion of vivid colorations, a historic October Blizzard, and record November dryness.

A look at the 500 MB height anomalies for each month of Autumn 2012 reveals the general trend, verses 1981-2010 climatology.

North America
500 MB Height Anomalies - September 2012

Note dual blocks featuring positive 500 MB height anomalies near southern Greenland and from the northern Pacific into the Arctic oceans during September-October, which gave way to strong Kamchatkan ridging during November associated 
with a -WPO teleconnection phase.

North America
500 MB Height Anomalies - October 2012

 Blue colors denote negative ( or lower than average ) 500 MB height anomalies and generally have a strong correlation to the cooler than average surface to 850 MB temperature anomalies highlighted previously.

North America
500 MB Height Anomalies - November 2012

Autumn 2012 featured an array of high latitude blocking, with a notable trend being the fading of positive 500 MB height anomalies near southern Greenland during November and strengthening of positive anomalies from the northern Pacific Ocean into the Arctic Ocean. 

The Kamchatkan Block, between Alaska & Siberia, has been the most persistent and dominant feature during Autumn 2012, with  a positive 500 MB height anomaly between Newfoundland & Iceland also being a notable feature on this 3-month composite of the September-November period.  

September 1 to November 30
500 MB Height Anomalies For Autumn 2012

Superstorm Sandy, a follow up Nor'easter, and a persistent Atlantic Ocean area of low pressure that generated days of strong gradient winds and beach erosion along the Eastern Seaboard, especially from the Outer Banks of North Carolina to Florida, were major factors in observed November conditions along the Appalachians.

November 1-29, 2012
850 MB Wind Vector Anomalies

Note the distinct counterclockwise, or cyclonic, swirl from the Atlantic Ocean back across the Appalachians during November which circulated around days of offshore low pressure formation and reformation. 

November 1-29, 2012
500 MB Wind Vector Anomalies

November 9, 2012
Lick Mountain in Wythe County, VA
Southern Appalachians Of The USA
Photograph by Wayne Riner - © All Rights Reserved.

In order to better understand what has occurred, and what may be upcoming, it is important to define the Climate System.

"The Climate System is a composite system consisting of five major interactive adjoint components:

The Atmosphere
The Hydrosphere
The Cryosphere
The Lithosphere
The Biosphere. "

Peixoto & Oort, 1992.  Physics Of Climate ( Page 19 ).

All components of this climatic system are intimately linked in extremely complex ways to generate a system with extraordinary variability across the spectrum of time & space.  A variability driven by internal instabilities and feedbacks from within that lead to highly nonlinear interactions among its components, all the while being driven by external forcing from outside the system itself 
( i.e., the SUN and Universe ).

The Bottom Line of all this leads to a single and absolutely certain result...


The Climate has always, does now, 
and will always change!

( December 4-5, 2012 )
Autumn To Winter Changes
Climate Teleconnection Trends

November 17, 2012
Night Of The Leonid Meteor Shower
Photograph by Roddy Addington - © All Rights Reserved.

While my main area of study has been focused upon the mesoscale and synoptic climatology of the southern Appalachians, particularly the High Knob Massif area, 
I have long had a global-scale interest in surface based feedback processes ( e.g., snow cover ) and wave induced atmospheric coupling-forcing as pattern change drivers.

Factors leading up to Winter 2012-13 have been heavily biased toward a colder and likely snowier than average winter across the eastern USA and Appalachians, with dominant negative phases of the Arctic ( -AO ) and North Atantic ( -NAO ) oscillations expected to enhance the odds.

Scroll Down To This Section For Details

Numerous factors are pointing toward dominant 
-AO & -NAO phases this winter for the eastern USA and western Europe.

Although this is a United Kingdom company, long-range forecaster Stewart Rampling presents what may be the best overview of these factors on the NET.  If you have an interest in long range forecasting, Stewart's presentation is well worth a listen.

( Excellent Science Based Outlook )

As Stewart notes, the UK is highly dependent upon -AO phases for coldness in winter, while the eastern USA can still have coldness with +AO phases if other factors are favorable ( like a west-based -NAO ).

The anomalously dry November pattern and warm beginning to December has many asking if this will be a repeat of Winter 2011-12  
( or even less wintry locally ).

When will REAL winter finally come?
( Irrespective of the historic October Blizzard ).

Current climate teleconnections say it will be a SLOW process for lovers of any serious, long-lived cold and snow across most of the eastern USA, with the upper air pattern and height anomalies just not lining up in the "right" order for this region.

Amid a changing pattern this could certainly change over time, but as of model runs on December 5 there is not yet any locked in winter for the eastern USA.

( Reference the December 17 Update below ).

Teleconnections right now show a chaotic UP and DOWN pattern with fast hitting cold shots and rapid "warm" ups as the coldest air and real winter holds west and northwest of the southern-central Appalachians.  

Deposition of snow cover across northern portions of the USA, and/or a major subtropical stream storm, could alter the setting in time by moving the baroclinic zone and mean storm track south ( ideally with Polar stream phasing and Greenland Blocking ).

Recall that if you are a winter fan the following climate teleconnections are desired for those living amid the eastern USA:

Arctic Oscillation
( weaker Polar Vortex )

North Atlantic Oscillation
( west-based )

Pacific North American Oscillation
( favors western USA ridge )

Eastern Pacific Oscillation

central-western Pacific based weak El Nino
( especially following multi-year La Nina )

Western Pacific Oscillation

Pacific Decadal Oscillation

Quasi-biennial Oscillation
( east phase in solar MIN or low solar MAX )

Snow Advance Index
( rapid gain in October Siberian snowpack )

December 17, 2012
Teleconnections Update
( 0000 UTC model runs )

Note that graphics are courtesy of Allan Huffman

December 17, 2012
GFS Ensembles AO Forecast

The European Model has now been showing a solid west based -NAO developing to join a +WPO along with new trends toward +PNA and -EPO.

The BOTTOM LINE...A much more wintry set up in the extended range even without looking at any specific forecast charts for the eastern USA.  

Still it looks to be a SLOW process for this region, and does not truly take hold with vigor until a few days before Christmas ( December 20-21 ).

But stay tuned, as forecast model trends in December have been to predict a cold pattern upcoming for the eastern USA only to have them back away as time draws closer and the reality ends up being biased toward western USA troughing.
( written on December 15 )

A good golden rule is that if climate teleconnections say one thing, and forecast charts show something opposite, then odds favor one or the other is wrong and will be changing over time to better fit the climatology of the composite of teleconnections that are present.

December 17, 2012
European Model NAO Forecast

December 17, 2012
European Model East-Based NAO Forecast

December 17, 2012
European Model West-Based NAO Forecast

Even without looking at the actual index values, 500 MB anomaly changes with time illustrate the transition from an East Based -NAO configuration to a West Based -NAO.

December 11, 2012
ECMWF 500 MB Anomalies At 7:00 PM 

December 15, 2012
ECMWF 500 MB Anomalies At 7:00 AM

December 23, 2012 at 7:00 AM
ECMWF Forecasted 500 MB Anomaly

December 17, 2012
European Model PNA Forecast

December 17, 2012
GFS Ensembles PNA Forecast

December 17, 2012
European Model EPO Forecast

December 17, 2012
European Model WPO Forecast

Climate Prediction Center Graphics

The recent trend has been one toward a weaker 
-PNA and +EPO, combined with a +WPO and 
west-based -NAO.

ENSO is in a neutral phase but with some 
central-western Pacific warm tendencies 
( especially sub-surface ).

The PDO has been in a negative phase since Summer 2010.

The QBO is in its second year of easterly descension phase amid a low solar maximum.

The October SAI was reported by Dr. Judah Cohen to be 2.19, the second highest observed behind October 2009.

Significant weather pattern changes are expected to finally begin showing up across the USA into next week ( December 9-15 ) and through the second half of December ( perhaps, just in time for a White Christmas across the Appalachians? ).

A wave of low pressure along a strong cold front will offer a wintry potential centered on December 11 and will need to be monitored for rain to wet snow, but western USA ridging forces warming again in its wake next week.

The rain to light snow & frozen verified 
for mid to upper elevations.

December 11, 2012
Early Morning Snow & Icing In Wise County, Virginia
Image Courtesy of Dan Hunsaker & WCYB-TV Archive

A small reminder that it is Meteorological Winter.

Wise County, VA
December 11, 2012 at 7:56 AM
Wintry Beauty Starts A Bone Chilling Day
Image Courtesy of Dan Hunsaker & WCYB-TV Archive

A longer lived cold pattern looks to develop with the passage of a major storm during the December 20-21 period.  ROARING winds, showers & downpours with lightning-thunder, and a transition to wind driven snow showers all look to be part of a temperature PLUNGE during this period ( centered on December 20 ).

Another MAJOR STORM will spin up lee of the Rockies and move east into the Christmas Holiday, but track, intensity, and placement by the big day are highly questionable at the moment ( with large model differences as of December 17 ).

Blocking signals suggest the potential for an EXTREME event developing around the Christmas Holiday ( trends to monitor in coming days ).

If the PNA turns positive along with -EPO and a solid west-based NAO, then truly the pattern could turn HARSH for the eastern USA and Appalachians with long-lived winter.  That may eventually be the case given so many indicators pointing to a dominant -AO/NAO.  

As of December 7, strong -PNA & +EPO teleconnections will have to be balanced or overwhelmed by a forecasted +WPO and west-based -NAO / -AO combo to sustain cold in the eastern USA against the tendency for western USA troughing.

The bottom line, this is a changing pattern
( general wetter and colder trend for USA ).  

The Stratospheric Section
Tropospheric-Stratospheric Coupling
( For Reference...Seek Experts & Texts To Learn More )

The Middle Atmosphere has long been neglected in terms of weather conditions experienced on the Earth's surface. 

The Stratosphere lying between 100 MB and 1 MB is the region that will be focused upon here.  

On any given day it is 50,000 to 100,000+ feet 
( 9.5 to 20 vertical miles ) above the surfaces of planet Earth.  The tallest thunderstorm tops spread outward as anvils upon penetrating into its lower most layers.  It is so dry that only during the most bitter cold can Polar Stratospheric Clouds ( PSC ), called Nacreous, develop.

It does seem counter-intuitive that a region resting so far above Earth could impact surface weather conditions.

Then you consider the BIG DOG that drives weather on Earth, the SUN, which sits more than 90 MILLION miles away and suddenly the Stratosphere seems like a next door neighbor!

Middle Atmosphere Dynamics by David Andrews, James Holton, and Conway Leovy ( in 1987 ) was one of the first text books to seriously look at the Middle Atmosphere.

Since that time an increasing body of work has been done to illustrate and expand upon concepts presented in Middle Atmosphere Dynamics.

The stratosphere is generally a much more stable and slower changing environment verses that of the troposphere, where changes occur rapidly in space and time and are nearly unpredictable at extended ranges. 

Details of tropospheric forecasts often change radically at extended ranges of 10 to 16 days, while those made for the stratosphere are much more stable and dependable at longer ranges ( at least, compared to the troposphere ).

The Operational GFS Model offers a prime example, as it is often nearly useless to look at tropospheric charts for 10 to 16 days out in time.  Move up into the much more stable, slow changing stratosphere, however, and the GFS Model tends to be more dependable.

This meridional cross section of the atmosphere for the Northern Hemisphere illustrates the major features and changes that occur in them between summer and winter.

Observe how the core of the Mid-latitude Jet Stream 
( in yellow ) above 40 degrees North of the summer hemisphere shifts south in the winter hemisphere and becomes stronger.  This is a simplification of the Mean Jet Core that typically consists of Arctic, Polar, and 
Sub-tropical Jet Streams.

Note how the atmosphere cools in the vertical from -20 Celsius ( 4 F ) above the North Pole in summer at 30 km 
( 98,400 feet ) to below -80 Celsius ( -112 F ) during the winter.  A huge difference that drives the increase in wind speeds and the formation of the Polar Night Jet
( the Polar Night Jet will be highlighted later ).

Recent changes observed in the stratosphere will be illustrated below to help motivate a general discussion on stratospheric-tropospheric coupling.

Recent Stratospheric Changes
November-December 2012

Several time series highlighting European Model 
( ECMWF ) analysis of daily conditions observed at different levels in the stratosphere are shown.

Time Series Of 100 MB Changes

Click consecutively on images for motion in viewer

November 11, 2012 - European Model 100 MB

November 15, 2012 - European Model 100 MB

November 20, 2012 - European Model 100 MB

November 25, 2012 - European Model 100 MB

November 30, 2012 - European Model 100 MB

December 1, 2012 - European Model 100 MB

December 2, 2012 - European Model 100 MB

December 3, 2012 - European Model 100 MB

The T90N-60N temperature gradient became positive during December 4-5, indicating a positive increase in temperature between 60 N latitude and the North Pole.

December 4, 2012 - European Model 100 MB

December 5, 2012 - European Model 100 MB

The Polar Vortex has undergone a deep, vertical splitting process amid the stratosphere, with 14 Celsius ( 25 F ) of warming between the North Pole and 60 N at the 100 MB level on ECMWF daily analysis charts during the past month 
( this warming just occurring ).

Time Series Of 30 MB Changes

Click consecutively on images for motion in viewer

November 11, 2012 - European Model 30 MB

November 15, 2012 - European Model 30 MB

November 20, 2012 - European Model 30 MB

November 25, 2012 - European Model 30 MB

November 30, 2012 - European Model 30 MB

December 1, 2012 - European Model 30 MB

December 2, 2012 - European Model 30 MB

December 3, 2012 - European Model 30 MB

December 4, 2012 - European Model 30 MB

December 5, 2012 - European Model 30 MB

Recent 30 MB warming has been 20.6 Celsius ( 37 F ) with a notable switch to a positive temperature gradient between 60 N latitude and the North Pole ( with cooling again as the PV reformed into mid-December ).

Time Series Of 10 MB Changes

Click consecutively on images for motion in viewer

November 11, 2012 - European Model 10 MB

November 16, 2012 - European Model 10 MB

November 20, 2012 - European Model 10 MB

November 25, 2012 - European Model 10 MB

November 30, 2012 - European Model 10 MB

December 1, 2012 - European Model 10 MB

December 2, 2012 - European Model 10 MB

December 3, 2012 - European Model 10 MB

December 4, 2012 - European Model 10 MB

December 5, 2012 - European Model 10 MB

Time Series Of Potential Vorticity Changes

The development and progression of the Polar Vortex split can be nicely tracked by looking at potential vorticity charts for different levels in the stratosphere.  Here is the 550 K analysis in the lower to middle portion of the stratosphere.

Click consecutively on images for motion in viewer

Potential Vorticity - November 22, 2012

By November 22 the vortex axis had already undergone stretching deformation across the North Pole, as was largely mirrored by the geopotential charts above, with rotation of the axis by November 28 when more aggressive splitting started.

Potential Vorticity - November 28, 2012

Potential Vorticity - November 29, 2012

Potential Vorticity - November 30, 2012

Potential Vorticity - December 1, 2012

Two distinct vortices were clearly evident by the end of November into early December.

Potential Vorticity - December 2, 2012

Potential Vorticity - December 3, 2012

Potential Vorticity - December 4, 2012

Potential Vorticity - December 5, 2012

Potential Vorticity - December 6, 2012

Potential Vorticity - December 7, 2012

Note these vorticity graphics show that the Polar Vortex is like a great BLOB, or Amoeba, that changes shape and position over time.  After splitting it had nearly reformed by December 8.

Potential Vorticity - December 8, 2012

Time Series Of Zonal Wind Changes

Click consecutively on images for motion in viewer

A vertical slice taken through the atmosphere between the Equator and North Pole reveals its zonal mean flow field state in the following series, and the changes that occurred over time.

November 10, 2012 - European Zonal Wind

November 15, 2012 - European Zonal Wind

November 20, 2012 - European Zonal Wind

November 25, 2012 - European Zonal Wind

November 30, 2012 - European Zonal Wind

December 1, 2012 - European Zonal Wind

December 2, 2012 - European Zonal Wind

December 3, 2012 - European Zonal Wind

December 4, 2012 - European Zonal Wind

December 4, 2012 - European Zonal Wind

December 5, 2012 - European Zonal Wind

All these charts document a Sudden Stratospheric Warming ( SSW ) of minor to moderate intensity and associated Polar Vortex split.

It could probably, according to Dornbrack et., al. 
be classified as a Canadian type warming event with subsequent polar vortex displacement from the North Pole.

In order to be technically declared a MAJOR SSW there must be a reversal of mean zonal winds at 60 N latitude and 10 MB, along with a positive temperature gradient between 60 N and the North Pole ( as an added signal ). 

Charlton & Polvani ( Includes Climatology )

A very simplistic temperature graph of the 30 MB trend over the North Pole reveals the warming associated with current Polar Vortex splitting.

A more sophisticated graph reveals 
trends verses climatology.

Temperatures Above The North Pole At 30 MB

Temperatures above the North Pole at 30 MB got colder quicker than last year, with both years dropping into the top 10% of the coldest years toward record low values prior to warming.

Observe the BLUE temp spike in mid-January 2012 that occurred with a significant stratospheric warming that never did achieve major SSW status.  However, a couple weeks later a killer cold wave struck Europe with more than 800 deaths during the January 27 to February 17 period.  Stratospheric changes being linked to the cold.

Any impacts from this first wave of stratospheric warming, and associated polar vortex split and relocation in early December, are not expected to be really observed tropospherically until mid-late in this month.  But a few points should be noted.

1 ).  A technical SSW event is not necessary to have impacts in the troposphere.

Weakening and disturbance of the polar vortex ( PV ) being very important given the general climatological tendency for a strong PV to be associated with milder southwesterly flow in mid-latitudes of the eastern USA and western Europe and for a weaker PV to be associated with more meridional flow periods. 

2 ).  Major SSW events have and have not caused arctic outbreaks in the USA.

Just because there is a major SSW event does not mean that there will be an outbreak of arctic air in the USA, but it increases the odds that there will be somewhere in middle latitudes of the Northern Hemisphere.

During January 2012, for example, the outbreak hit Europe following an "unofficial" SSW event.

A relatively rare Wave 2 forced SSW event in early January 1985, by contrast, triggerd one of the most extreme cold waves ever documented in the eastern USA and southern-central Appalachians a few weeks later.

3 ).  No major arctic outbreaks have struck the Mountain Empire since the 1995-96 winter season despite many SSW events in the stratosphere since that time...however, the contribution of weaker PV's to -AO/-NAO teleconnections contributed to wintry conditions irrespective of major arctic hits.

The Atlantic Multidecadal Oscillation ( AMO ) switched to a positive phase in 1995 and, while the linkage is not clear, it is interesting that this has nearly coincided with the lack of severe arctic outbreaks ( -20F or lower ) despite numerous big snowfall winters.

Analysis Of Early Stratospheric Warming
( Late November - Early December 2012 )

The slow start to winter in the USA following Superstorm Sandy has been largely due to a very stable 4-wave pattern which developed around the Northern Hemisphere during the past month that was dominated by a strong -WPO teleconnection and Omega Block, from the Northern Pacific Ocean across the Bering Sea into the Arctic Ocean 
( along the International Date Line ).

This stable 4-wave pattern is basically a continuation of that which dominated October, with the notable exception being that blocking became more intense along the International Date Line via enhanced Kamchatkan ridging between Alaska and Siberia and more associated troughing in the Gulf of Alaska and downstream ridging across the continental USA.

And there have been no freak storm events recently to break the pattern like Superstorm Sandy did in October, with subsequent impacts into the first half of November before the 4-wave pattern established itself again in recent weeks across the hemisphere.

What has occurred recently, as highlighted, is a significant split of the Polar Vortex and warming 
in the stratosphere.  It is interesting that this was forced by potent Wave 2 activity which originated from the strong -WPO block and eastern European High pressure ( via Siberian snow cover forcing ).  

The amplitude of Wave 2 forcing reached into the 90+ percentile toward record levels verses climatology.

As Wave 2 activity waned a dramatic increase in Wave 1 was observed to further work on the Polar Vortex and aid its deformation and displacement from the North Pole.

Wave 1 exerted its strongest influence upon the 
top of the stratosphere as December arrived, with limited impacts at the bottom of the stratosphere.

While Wave 1 action forced by low pressure in the central-western portions of the Northern Pacific, and Wave 2 from the eastern European High, fit the reinforcement of climatological standing waves that act to weaken the stratospheric Polar Vortex as defined by Garfinkel et., al., the enhanced Wave 2 which likely came from the -WPO block along the Kamchatkan ridge is apparently more anomalous in nature.

Chaim Garfinkel, Dennis Hartmann, Fabrizio Sassi

Journal of Climate ( Garfinkel ET AL ) 15 June 2010
"The regional tropospheric anomalies that are best correlated with vortex weakening are found to be those that are in phase with ( and thus amplify the magnitude of ) the climatological extratropical planetary waves, strongly suggesting that regional anomalies that amplify the climatological stationary waves will, on average, affect the vortex."

While winds did not reverse direction at 60 N latitude, they were weakened to well below climatology by this polar vortex splitting process as Eliassen-Palm ( EP ) Flux vectors driven by Wave 2 ( and the increase in Wave 1 ) converged toward the North Pole to slow down the circulation swirling around the vortex.

A few technical papers dealing with EP Flux

( Andrews - July 1983 )

( David Andrews Presentation )

( A La Nina Year vs. A El Nino Year )

( Maddison, Marshall, Berloff )

( 2D And 3D EP Fluxes )

In simplistic form this can be observed by this 
EP Flux Vector graphic for the stratosphere of the Northern Hemisphere, with a notable convergence of the EP Flux vectors toward the North Pole during early December 2012.

Convergence of EP Flux Vectors indicate a deceleration of the mean westerly flow circulating around the Polar Vortex.  

Vertically propagating traveling waves forced from the troposphere carry important fluxes of heat and momentum which are released when the waves break.  The region where waves consistently break is known as the Surf Zone, which surrounds the Polar Vortex in the stratosphere.

Think of a beach.

By breaking it is meant that these atmospheric waves act like ocean waves where an idealized streamline describing the wave motion steepens so much that it begins overturning, or breaking, like seen when waves rolling toward a beach ( amid the surf zone ) begin encountering increasing frictional drag ( beneath the water ) to force them to roll over and to release their transported energy.

Note that ocean waves that break at sea are different in that wind energy from storms drive them to overturn and break ( transforming potential energy into kinetic energy of motion ) without frictional drag input from bottom topography.

Like there are different types of ocean waves, there are different types of atmospheric waves whose restoring forces and excitation sources dictate their general classification.

Internal Gravity Waves
Restoring force: Gravity

Rossby or Planetary Waves
Restoring Force: Vorticity Gradient
( variation of Coriolis Force with latitude )

Inertio-Gravity Waves
Restoring Force: Gravity + Coriolis

There are many other wave types, for details reference:
Holton, J.R., 2004: An Introduction to Dynamic Meteorology, 4th Ed. Academic Press.

Anything that displaces fluid parcels from their equilibrium position can act as an excitation source for wave formation, with subsequent propagation determined by the competition between inertia and restoring forces.

Breaking of waves in the Northern Hemisphere stratosphere can be detected, as described by Holton ( 2004 ), where isolines of potential vorticity overturn along isentropic surfaces.

Actions of waves can also be followed by looking at geopotential height and temperature changes associated with Wave 1 and Wave 2 activity, and through breaking EP Flux into its major components.

( Institute of Meteorology )

EP Flux equations can be broken into meridional and vertical components and followed over time, using models like the ECMWF, since their meridional component is proportional to Momentum Flux and their vertical component is proportional to Heat Flux ( Wave 1 and Wave 2 can also be looked at for individual contributions ).

Andrews, D.G., J.R. Holton, C.B. Leovy, 1987: 
Middle Atmosphere Dynamics.  Academic Press.

Here is a recent example from this event 
of how these charts may be interpreted 
( my interpretation, others are welcomed ).

December 4, 2012
Momentum Flux For Wave 2

The contribution of Wave 2 to slowing winds around the Polar Vortex on December 4-5, and aiding easterly flow, as highlighted previously by the Time Series Of Zonal Wind Changes, can be observed by noting the negative Momentum Flux values on these charts for Wave 2.

December 5, 2012
Momentum Flux For Wave 2

Wave 1 forcing was working against Wave 2 at this time by adding westerly Momentum Flux to help increase wind speeds in much of the region where Wave 2 was reducing momentum with more easterly flux.

December 5, 2012
Momentum Flux For Wave 1

The resultant for Wave 1 + Wave 2 
( and any others ).

December 5, 2012
Total Zonal Mean Momentum Flux

The achievement of a technical SSW was hindered by Wave 1 working against Wave 2 to keep winds at 60 N and 10 MB westerly in direction and magnitude.

Notes On General Stratospheric Heat Balance
( Apart from Major Wave Induced SSW )

In general traveling waves transport heat poleward from lower latitudes.  Ozone generated in its tropical source region is transported toward the Poles by the Brewer-Dobson Circulation ( BDC ) where it becomes the dominant absorber in the polar stratosphere, with 
net heating depending upon the imbalance between absorption of UV radiation and IR losses 
( Andrews et. al., 1987 ).

With the fall of Polar Night IR losses clearly win the battle until something develops to alter the progressive cooling of the LONG winter night ( which is what this entire section is ultimately about ).

This study cites mesoscale Gravity Waves as playing important roles in maintenance of the BDC and in the transoport of energy and momentum fluxes into the stratosphere:

Note that Wave 1 was exerting a strong influence upon the top of the stratosphere on December 5, with a significant negative Momentum Flux and also a significant Heat Flux.

December 5, 2012
Heat Flux For Wave 1

Observe that the maximum heat flux for Wave 1 is shown poleward and higher than its indicated region of MAX lifting on December 5.

December 5, 2012
Geopotential Height Changes For Wave 1

The above chart can be read as follows.  Wave 1 on December 5 at 1200 UTC was lifting air parcels centered at 70N and 5 MB more than 1300 meters above their climatological MEAN position. 

This brings up an important observation necessary to help understand how wave breaking impacts the stratospheric Polar Vortex.

When waves break in the stratosphere they exert a decelerating force upon the flow field which tends to be offset by the Coriolis Force.  Since the breaking causes 
a disruption of thermal energy and momentum, the atmosphere begins working immediately to restore balance.  When a wave breaks, however, there is no restoration as its a irreversible process such that a new state of conditions develop with compensative sinking motion toward the Pole and rising motion toward the Equator in the wave breaking region.  The resultant impacts are a warming with sinking air toward the Pole and a cooling with rising air toward the Equator to weaken the thermal gradient in the Polar Vortex.

While wave breaking is common in the Surf Zone, it is the strongest waves or pulses of waves that actually impact the Polar Vortex most to occasionally trigger major events like a SSW 
( Sudden Stratospheric Warming ).

An analogy from the ocean is that typical waves do not alter the beach amid the surf zone in the mean, it is the high energy or big amplitude waves which break through the typical surf zone that force major changes such as erosion or destruction of the beach.

It is, of course, more complicated than this simplistic explanation since critical layers can reflect waves either toward or away from the vortex.  If EP Flux is directed toward the North Pole it is always best for vortex impacts, but even when vectors are pointed away from the pole there can still be some wave reflection by critical layers.  

In addition, an official SSW event is not necessary for significant feedback to occur into the troposphere via wave induced weakening and distortions of the stratospheric vortex.

Rossby waves do not have to come from long distances, but can enter the vortex from below as illustrated by the "shedding" or excitation of Rossby waves by Greenland and the abundant and growing evidence of upward wave fluxes from Siberian snowcover anomalies that may work on the vortex internally ( from inside ).

( Click on Ongoing Projects - Look at EULAG Calculations )

( Cold Polar Vortex As Waveguide )

One way that vertically propagating Rossby waves can exert greater influences upon the Polar Vortex is by using the Polar Night Jet as a Waveguide.

During winter darkness temperatures get very cold above the North Pole with an increasing horizontal temperature gradient with latitude outward from the developing Polar Vortex core.

In order to maintain Thermal Wind Balance, 
as demanded by the increase in the horizontal temperature gradient, a Polar Night Jet forms.

As it turns out this Polar Night Jet ( PNJ ) is very important to the upward transport of waves generated in the troposphere, as these vertically propagating waves move along the outer core of the PNJ, which acts as a waveguide, and past the stable tropopause into the stratosphere where subsequent wave breaking can be much more productive in terms of impacting the Polar Vortex.

Although most major SSW events are associated with Wave 1 forcing, it should be noted that major SSW episodes have been forced by Wave 2 activity 
( e.g., January 1985 ).

One of the major excitation sources for waves on planet Earth is of particular interest, mountains, with the Himalayas, Rockies, and Andes being dominant forcers of planetary waves.

A major wave event can be anticipated by a strong mountain torque which arises due to cross barrier pressure gradients ( which can add to or subtract angular momentum from the atmosphere ).  In a three dimensional atmosphere it is the vertical component of propagation that is of greatest interest for stratospheric perturbations.

Since the atmosphere and Earth is a rotating system, additional turning forces arise in the form of Friction, Gravity Wave, and Coriolis torques.

Gravity Wave torque is the sub-grid scale component of Mountain and Friction torques which is too small to be resolved by climate models and general forecast models. 

( Intraseasonal Forcing Of AO and PNA )

Periodic oscillations on the scale of a month or less of the AO and PNA teleconnection patterns, as well as some blocking regimes, have been shown to be connected with mountain torques to further reinforce tropospheric-stratospheric coupling.

Recent Mountain Torque Example

While not a major forcer in this recent minor 
SSW event, the barrage of storms that generated a persistent west to east pressure gradient across the western USA and Canada, especially the Pacific Northwest and Northern Rockies, offers up an opportunity to graphically illustrate the linkage between Atmospheric Angular Momentum and Mountain Torques.

500 MB Composite Height Anomalies
November 12 to December 12, 2012

This general anomaly pattern worked to force pulses of positive mountain torque activity that significantly impacted the composite signal for North America.

With low pressure across the eastern Pacific, and higher pressure west of the Rockies, westward directed mountain torques in North America impacted the Atmospheric Angular Momentum of Earth within the 40 to 60 degree North Latitude band ( at least, this contributed to its subtraction from the Earth and input into the Atmosphere ).

In the total picture, as already noted, Friction, Gravity Wave, and Coriolis torques were part of these events as AAM fluxed within the Climatic System of Earth.  In the end AAM is conserved.

On a side note for those interested in GCM's, and their forecasts of Global Climate Changes, it should be noted that they generally do not conserve AAM 
( Atmospheric Angular Momentum ).

This is due largely to their lack of resolution of torques which represent the fluxes of angular momentum across the boundaries of the Climatic System.  
The NET change of which is ZERO.

Errors that arise due to this alone will increase over time to cause GCM forecasts to "drift" away from reality.  This is not saying they are useless, but due to this and the highly nonlinear nature of the climatic system it would be unwise to "bet the farm" on any given forecast of what the future may be like.

For more technical information about the Climatic System, AAM & Torques, Nonlinear Feedbacks, and much more, please reference:

Peixoto, J.P., A.H. Oort ( 1992 ).  Physics Of Climate.  
American Institute of Physics.

Major Sudden Stratospheric Warming
What Comes Next In 2012-13

Will this mild start to Winter 2012-13 continue?  
That is the main question being asked now.

Can the stratosphere offer any answers?

Experts in the UK think a major SSW event may be upcoming by the end of this year or early January 2013, with any major tropospheric impacts related to a major SSW following days to weeks later.  

There are potentially important precursor changes leading up to a SSW event that begin showing impacts in the troposphere 2-4 weeks in advance of the event.

These are highlighted by Judah Cohen & Justin Jones 

There is a notable tendency toward lower mean SLP ( Sea Level Pressure ) across this part of the Northern Hemisphere in advance of SSW events, especially displacement events.

This warming is just barely ( as of December 14 ) entering the 10 day range of the ECMWF, with much more being known about this potentially MAJOR SSW in coming days as it comes into the full forecast view of the European Model as Christmas approaches.

The best discussion forum to follow along with current conditions and forecasted trends can be found here at

The stratosphere and troposphere are clearly coupled, but understanding and predicting how changes forced amid the stratosphere ( by waves and fluxes of energy & momentum arising from within the troposphere ) will feedback into the troposphere to impact any given location in the Northern Hemisphere is very difficult.

Progress has been made and the following papers are just a small sampling of what is being learned 
( in addition to all the links already given ):

Meteorological Winter began December 1
( Ends February 28 )

Astronomical Winter begins December 21
( Ends March 19 ).

To have these forecasted temperature anomalies verify for the USA, the upcoming pattern must become very different from that observed during the first half of December 2012.

A major Sudden Startospheric Warming event would certainly bias the pattern toward becoming different from that observed so far, and put mid-latitudes of the Northern Hemisphere on WATCH, or standby, for a potential major arctic outbreak to impact some region ( or regions ).

And at the least it would favor -AO and -NAO teleconnection patterns to dominate, as research above has illustrated, the bulk of astronomical Winter 2012-13.