Monday, December 12, 2011

Wintry Period In The High Knob Massif


December 11, 2011
Cow Parsnip ( Heracleum maximum )
Winter Wonders In The High Knob Massif
Photograph by Roddy Addington - © All Rights Reserved.

The Massey Herbarium

Thomas Wieboldt, of Virginia Tech's Massey Herbarium, says the Cow Parsnip Family "has a unique type of fruit called a schizocarp which is comprised of two parts. In this case the two parts are sandwiched together like holding your hands palm to palm.  When mature, the two halves split apart, each with its own single seed inside, hence the name ‘schizo’ = ‘split’
and ‘carp’ = carpel (fruit)."

Surrounded by snow, a clump of seed pods dangle in bitter air as a potential source of food and energy yet to be utilized during harsh days ahead.

The High Knob Landform

December 11, 2011
Remnant Massif of High Knob Landform
Signs Of The Season - Snow & Broadhead! 
Photograph by Roddy Addington - © All Rights Reserved.

Roddy did not even notice the added piece of this interesting scene when he took the photograph, focusing at first upon the snow and ferns hanging on the side of this tree ( numerous trees grow ferns here ).

A Razorback Broadhead From A Bow Hunter
Photograph by Roddy Addington - © All Rights Reserved.

A razorback broadhead from a bow hunter's arrow was lodged in the tree, without the shaft.

December 11, 2011
High Knob Mountain Highway
Packed Snow & Ice On State Route 619 
Photograph by Roddy Addington - © All Rights Reserved.

Photographer Bill Harris stands on a slick State Route 619 as he composes a shot during a weekend trip with Roddy to capture some winter scenes in the High Knob highcountry.

Roddy said the roadway was covered by snow and ice from just above Norton all the way into Scott County, past the Camp Rock of Big Flat Top, with Bill having to shift into 4-Wheel Drive near the 3300 foot level of the Upper Norton Reservoir.

December 11, 2011
Snow Covered Head of High Knob Lake Basin
Photograph by Roddy Addington - © All Rights Reserved.

Some 18 days with 1" or more of snow depth have been observed in the High Knob Lake Basin since October 1, despite a pattern most consider as mild.

The December 7-11 period was quite cold and wintry in the High Knob Massif area following the heavy snowfall, with persistent snow cover making conditions colder than places with bare ground.

Climate Statistics For
December 7-11, 2011

( Northern Base of High Knob Massif )
City of Norton - Elevation 2141 feet
Average Daily MAX: 39.0 degrees
Average Daily MIN: 17.2 degrees
MEAN: 28.1 degrees

In the High Knob high country temp means during this 5 day period varied from low-mid 30s by day to low-mid 10s by night.  MINS fell into single digits amid lofty, snow covered basins of the massif into morning hours of December 11.

NASA Visible Satellite Image At 11:01 AM - December 10, 2011
Image Courtey Of The Earth Science Office

Low clouds lingered into early afternoon hours of December 10 in the wake of a arctic-like cold front, which produced flurries but no new accumulations.

While the front did not possess any true arctic temps it brought extremely dry post-frontal air from interior regions of Canada.

High Knob Massif
December 10, 2011 at 1:12 PM
Rime Formation At Eagle Knob Communications Site
Image by Steve Blankenbecler - © All Rights Reserved.

The front had a couple of notable weather impacts upon the High Knob Massif, with upslope lowering of cloud bases allowing rime to form at the summit level into morning hours of December 10 prior to a big dewpoint PLUNGE that generated the coldest night of the young 2011-12 season ( as noted above ).

December 11
High Knob Massif Rock Outcrop
Awesome Icicles & Colors
Photograph by Roddy Addington - © All Rights Reserved.

Bitter temperatures that formed over the snow cover and low dewpoint air froze everything with any thoughts of liquidity to create striking scenes in the massif.

High Knob Massif - December 11, 2011
Striking Colors And A Swan's Head In ICE
Photograph by Roddy Addington - © All Rights Reserved.

Taking the shape of a swan or goose head, this ice formation is just awesome amid varied colorations from lichens, rocks, and other objects in sunlight.

Amazingly, the EYE 
is in just the right position!

High Knob Massif - December 11, 2011
BACON Ice Along Stem At Rock Outcrop
Photograph by Roddy Addington - © All Rights Reserved.

Upon discovery of another incredible ice formation along a rock outcropping, Roddy said it looked like a huge "slab of bacon" ( him and Bill were probably getting HUNGRY by then!!! ).

High Knob Massif
Sugar Maple ( Acer saccharum var. saccharum )
Loaded Down With Snow - PM of December 7, 2011
Photograph by Roddy Addington - © All Rights Reserved.

Heavy snowfall of December 7 setting the stage for nearly all of this above, illustrating how important snow cover is to development of true winter conditions ( both locally and on synoptic scales )!


( Updated: December 15, 2011 )
Mountain Waves Generated
By Strong SW Winds

Horizontal temperature differences generate pressure gradients that drive winds on the large or synoptic-scale during this time of year, with forcing events in the High Knob Landform often becoming visible amid the heavens above!

NASA Visible Image At 9:31 AM - December 15, 2011
All Images Courtesy Of The Earth Science Office

Note the opaque looking wave clouds in the above image from Harlan County, Ky., into Wise County, Va., with a mountain wave cloud raised upward in appearance from NW to SE of Norton ( the City denoted by eye-like symbol ) lee of the High Knob Massif.

ROARing SW winds developed across higher elevations during the overnight hours of December 15, with downward mixing into lower terrain after sunrise ( causing rapid valley temperature rises ).

NASA Visible Image At 9:45 AM - December 15, 2011

An array of smaller wave clouds can be seen along the length of the High Knob Landform and across the Black Mountains, as well as over the Great Smokies and Mount Mitchell. 

Mountain waves became distinct by 9:45 AM, with the large cloud NW to SE of Norton being a standing lee wave formed just downstream of the High Knob Massif ( in a climatological position ).

December 15, 2011
NAM Model 850 MB Chart At 7 AM

A strong SW air flow along the black isobars at 850 MB was turning a bit inward, toward lower pressure, to generate general 200 to 230 degree flow trajectories during this time.

Sustained winds of 20 to 30 mph became common in Wise, with peak gusts to around 40 mph, on a 210 to 230 degree inflow that streamed across the High Knob Massif and into the Wise Plateau.

( A Different Perspective )
NASA Visible Image At 9:45 AM - December 15, 2011

The long-lived nature of these orographic clouds can be noted by jumping ahead in time to 11:31 AM.

NASA Visible Image At 11:31 AM - December 15, 2011

Observe an additional wave cloud has formed over southwestern Dickenson County adjacent to the large, persistent standing lee wave from NW to SE of Norton.  Gusts locally topped 40 mph.

By early afternoon wave clouds started showing up east of the High Knob Massif, as trajectories began to shift direction.

NASA Visible Image At 12:31 AM - December 15, 2011

Observe the change at 850 MB on the chart below, with flow trajectories now streaming from the High Knob Massif toward the Upper Clinch River Basin in Russell & Tazewell counties.

December 15, 2011
NAM Model 850 MB Chart At 1:00 PM

The unseen but felt portion of this wind event was orographic cooling forced by upsloping along windward slopes & crests of the High Knob Massif, with PM MAXS reaching upper 40s to middle 50s.

A 55 degree PM maximum was observed in the City of Norton where air rises from Powell Valley and along mountain slopes of the massif to cool the City on SW flow ( * ).

*It is interesting to note that during nights with moderate SW winds the City of Norton can remain much warmer than Coeburn, where blocking by the massif keeps the Tacoma-Coeburn Valley in drainage flows decoupled from main SW boundary layer winds.

The Coeburn Valley coupling back up only when SW flow gets strong enough to overcome terrain blocking effects ( generating downslope temperature surges at such times ).


Orographic Temperature Effect
On SW Air Flow Trajectories

NASA Visible Image At 11:45 AM - December 14, 2011

Even on a day with abundant sunshine behind a warm front, as was observed during December 14, the orographic effect with S-SW air trajectories is active when pressure gradients drive winds across the High Knob Landform to produce orographic forcing ( e.g., upsloping & downsloping using simple terms ).

PM Maxs on December 14 varied from low to middle 50s in upper elevations of the High Knob Massif to 59 degrees in the City of Norton ( with upsloping SW winds adding cooling on weak-moderate flow ).

Downsloping into the Russell Fork Basin of Dickenson County, north to northeast of the High Knob Massif, pushed temperatures to 66 degrees in Clintwood & 68 degrees at John Flannagan Dam.

The above being partly attributed to elevation but also enhanced by upsloping & downsloping, with the magnitude of all effects tending to increase as wind speeds increase.


*Reading Note:  Text on The High Knob Landform is best viewed using the Google Chrome web browser ( text may appear mis-aligned in other browsers ).

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