Tuesday, February 14, 2012

Winter Returns In February 2012


February 12, 2012
Large Snow Drifts In High Knob Massif Crest Zone
Photograph by Roddy Addington - © All Rights Reserved.

The High Knob Landform

Where Is Winter Are The Cries In 2012?

Winter is in the High Knob Massif where a return visit by the Ole Man spread snow depths of 6" to 12"+ across its lofty highcountry on 
Great Lake connected NW upslope flow.

Jefferson National Forest
Between High Knob and Eagle Knob
Upslope Funneling Through The High-Eagle Gap
Photograph by Roddy Addington - © All Rights Reserved.

[ Although drifting is common along most high crestlines it can also become impressive amid lofty gaps, with Davenport Gap in the upper Big Cherry Basin being infamous for large snow drifts that often block Forest Service 237 and isolate residents of the Cox Place ( Johnson Pastures ) and Little Mountain communities.
The Little Mountain community is in northern Scott County ].

I was at this very place on February 8 when winter first made its true return to the highcountry, with upslope funneling of swirling cloud vapor through this lofty gap forming rime amid air temps in the 20s during afternoon hours.

[ Rime will often begin forming first in lofty, windward gaps where the acceleration of air flow cools and condenses out moisture at a faster rate, as I have documented many times over the decades ].

February 12, 2012
High Knob Massif - Southern Wise County, VA
Rime Capped Crest Zone & Pristine Blue Skies
Photograph by Roddy Addington - © All Rights Reserved.

In a season "without winter" this latest round pushed seasonal snowfall totals to around 50" in the main crest zone of this remnant massif of the High Knob Landform.
[ A general 25" to 35" of snowfall being observed lower down amid the 2300 to 3300 foot elevation zone, from the City of Norton up to High Chaparral, so far this winter ].

Snow depths observed February 12 had actually decreased a good amount from max depths as a combo of sunshine and fluffy snow generated settlement on Eagle Knob snow depth markers.

February 12, 2012
Deep Snow On Eagle Knob of the High Knob Massif
Photograph by Roddy Addington - © All Rights Reserved.


High Knob Massif Lifting Zone
Classic Great Lake Connected
Orographic Forcing Event

Streamline charts at 850 MB reveal this was a classic NW upslope flow setting for the High Knob Massif, with Winter Storm Warning criteria met but not recognized by TV and official forecasts.

7:00 AM February 11, 2012
NAM Model 850 MB Streamlines
Map Courtesy of NCEP

Observe how air flowing along streamlines cross both Lake Superior and Lake Michigan on its way to being lifted across the sprawling High Knob Massif ( where intense snow squalls formed ).

1:00 PM February 11, 2012
NAM Model 850 MB Streamlines
Map Courtesy of NCEP

[ Ever since I've been a young boy The Weather Channel, in specific, has never recognized this portion of Virginia, instead predicting MAX snow amounts to fall across the New River Valley along the Eastern Divide that models focus upon in NW flow ( the NAM modeling, for example, the Tri-Cities higher than Wise ) ].

Since the atmosphere always compensates for an imbalance, positive orographic forcing into windward slopes of the High Knob Landform and Tennessee Valley Divide, typically called upsloping in simple terms, is compensated for by negative orographic forcing, or downsloping, leeward of this initial ( unrecognized ) Appalachian front range.

Note that streamlines on above charts are not only coming into the windward slopes of the High Knob Massif but are also passing to their lee into the Tri-Cities of northeast Tennessee.

The impact of this can be illustrated by real-time conditions in the following images.


Real-Time Conditions
February 11, 2012

Upslope Side of Cumberland Mountains

Snow Sqaull At 11:29 AM
University of Virginia's College In Wise

Another Snow Squall At 12:02 PM
University of Virginia's College In Wise

Deep Snow At 1:26 PM
Eagle Knob of High Knob Massif - Between Squalls

Light Snow At 1:17 PM
Nora 4 SSE On Long Ridge of Tennessee Valley Divide

My friend Wayne Riner captured more detailed scenes as this event developed during February 11.

February 11, 2012 at 12:48 PM
Turning Wintry Along The Tennessee Valley Divide
Photograph by Wayne Riner - © All Rights Reserved.

Developing Snow Squall At 12:49 PM
No Picnic Today - Looking To The Orchard
Photograph by Wayne Riner - © All Rights Reserved.

Long Ridge At 12:50 PM
Beauty Of A Developing Snow Squall
Photograph by Wayne Riner - © All Rights Reserved.

Air temperatures turned BITTER as snow continued to develop along the upslope side of the mountains with temperatures reaching 18 degrees in the City of Norton and on Long Ridge by 10 AM.

Elevation 2650 feet
Long Ridge of the Tennessee Valley Divide
Another Squall Moving Into The Divide At 1:08 PM
Photograph by Wayne Riner - © All Rights Reserved.

Temperatures fell into lower 10s on Long Ridge and in the Norton-Wise area by late afternoon, with single digits across the High Knob Massif.

Long Ridge at 1:09 PM
Blustery NW Wind Adds BITE To Bitter Air
Photograph by Wayne Riner - © All Rights Reserved.


Downslope Side of the Mountains

Light Snow At 12:03 PM
Cumberland Square Park In Bristol

Mostly Cloudy at 12:16 PM
State Of Franklin In Johnson City

Hazy Sunshine At 1:30 PM
Cumberland Square Park In Bristol

Hazy Sunshine At 1:30 PM
State Of Franklin In Johnson City

That is a truly dramatic difference in weather conditions along a NW-SE transect of 30 to 45 air miles.

The Tri-Cities were essentially shut-out, with only a trace of snow officially being measured at TRI.


Conditions In Wake 
Of The Upslope Event
February 12, 2012

Upslope Side of Cumberland Mountains

High Knob Massif at 1:21 PM
Snow Glare Over Deep Snowpack On Eagle Knob

[ Reference Rod's fourth photograph from the top showing conditions on Eagle Knob along the road across from this view ].

Sunny At 1:22 PM
University of Virginia's College In Wise

Sunny At 1:16 PM
Nora 4 SSE On Long Ridge of Tennessee Valley Divide

Snow Drifts On Long Ridge - February 12, 2012
Photograph by Wayne Riner - © All Rights Reserved.

Wayne Riner Thoughts...
"The wind that came with the cold weather caused the snow to drift on the areas sheltered from the north wind."

February 12, 2012
Wind Sculptured Patterns Of A Winter's Snow
Photograph by Wayne Riner - © All Rights Reserved.

Wayne Riner Thoughts...
"Some things will have to wait until spring. At that time the birds enjoy the birdbath, and we will eat the asparagus located near the empty bird houses.  The garden shows the remnants of the bean vines and the tomato cages."



Downslope Side of the Mountains

Sunny At 1:30 PM
Cumberland Square Park In Bristol

Sunny At 1:30 PM
Bristol Motor Speedway ( BMS )

Sunny At 1:30 PM
State Of Franklin In Johnson City


Specific Snowfall Totals & Depths
( February 11-12, 2012 )

Clintwood 1 W: 4.2"

Nora 4 SSE: 5.8"

Norton Water Plant: 6.8"

High Knob Massif: 6" to 12"+

Tri-Cities ( TRI ): Trace

Kingsport: Trace

Given such huge weather contrasts there tends to be a disconnect between reality and what is often forecasted for these upslope locations during such orographically driven events.

[ It is largely natural, as imagine having only 1.2" of snow for the winter to date ( like the TRI ). One loses touch ( even forecasters ) with the reality of how bad conditions become with 4"+ of snow, let alone 6"-12"+ ( image what that would do to the Tri-Cities ) ].

From another perspective, snowfall at the summit level of the High Knob Massif in this "year without a winter" has essentially been equivalent to the snowiest winter on record in the Tri-Cities ( * ).

*A total of 51.0" during the Winter of 1959-60.


High Knob Massif Snowfall
Interesting Factors To Consider

Majestic Highcountry Drive - February 12, 2012
Photograph by Roddy Addington - © All Rights Reserved.

Some 24 years ago my study of what I came to know as the High Knob Landform started with an interest in the often significant falls of snow across its massif of highcountry ( locally legendary for its snow ).

Back then I did not know it was also the wettest area in Virginia which, given its vast terrestrial and subterranean biodiversity, makes perfect sense when combined with development of this great calcareous landform ( geological Powell Valley Anticline ).

February 12, 2012
Jefferson National Forest
Rimed Trees Add To Winter Beauty & Wetness
Photograph by Roddy Addington - © All Rights Reserved.

Exposure and size of the massif combine with atmospheric settings under specific conditions to boost snowfall at times on easterly and southwest air flow trajectories that I have found to be unique to the High Knob Massif and its landform ( * ).

*These will be detailed in an extensive Climatology Book that is currently scheduled for completion in 2013.

The general nature of NW flow snowfall has been detailed by many studies but unfortunately most have neglected the High Knob Massif with results showing a modeling bias that is perhaps largest in the southern Appalachians over this area verses reality ( i.e., snow underestimated vs. what really falls ).

Notable Studies On NW Flow Snowfall 
In The Southern Appalachians

Holloway, B. S., 2007: The role of the Great Lakes in northwest flow snowfall in the southern Appalachian Mountains. M.S. thesis, Dept. of Marine, Earth, and Atmospheric Sciences, North Carolina State University, 204 pp.

Keeter, K. K., S. Businger, L. G. Lee, and J. S.Waldstreicher, 1995: Winter weather forecasting throughout the eastern United States. Part III: The effects of topography and the variability of winter weather in the Carolinas and Virginia. Wea. Forecasting, 10,
42–60.  [ Note: Unrelated to NW flow specifics ].

Keighton, Lee, Holloway, Hotz, Zubrick, Hovis, Votaw, Perry, Lackmann, Yuter, Konrad, Miller, Etherton, 2009:
A Collaborative approach to study northwest flow snow in the southern Appalachians. Bulletin of the AMS.

Perry, L. B., 2006: Synoptic climatology of northwest flow snowfall in the southern Appalachians.  Ph.D. dissertation, University of North Carolina at Chapel Hill, 176 pp.

Perry, L.B, and C.E. Konrad. 2006. Relationships between NW flow snowfall and topography in the southern Appalachians, USA. Climate Research 32: 35-47.

Perry, L.B, C.E. Konrad, T.W. Schmidlin. 2007. Antecedent upstream air trajectories associated with northwest flow snowfall in the southern Appalachians, USA. Weather and Forecasting 22: 334-352.

Perry, L. B., C. E. Konrad, D. Hotz, and L. G. Lee, 2007a: Synoptic classification of snowfall events in the Great Smoky Mountains, USA. Proc. 64th Eastern Snow Conf.,St. John’s, NL, Canada, Eastern Snow Conference, 207–215.

Yuter, S.E., and L.B. Perry, 2007: Storm structures and precipitation characteristics of snow events in the southern Appalachian mountains. Abstracts, 12th Conf on Mesoscale Processes, Aug 2007, Waterville Valley, NH.

Baker Perry & Chip Konrad have been two of the lead researchers on NW flow snowfall in the southern Appalachians during the past decade.

Elevation 4189 feet
Eagle Knob of High Knob Massif
Deep Snow ( 70% NW Flow ) From February 11-12, 2012
Photograph by Roddy Addington - © All Rights Reserved.

Better modeling of this initial front range of the southern Appalachians that is formed by the geologically famed Cumberland Overthrust Block is greatly needed, since initial lifting and moisture extraction along with excitement of mountain lee waves & turbulence must be resolved if locations downstream are to be better modeled in NW flows.

[ Expansion of the great Kentucky MesoNET weather network to include Big Black Mountain will be a plus, but I would suggest that this website be followed for added data on NW snowfall events ].

Appalachian Terrain & NWSFO County Warning Areas

The High Knob Massif is large with respect to a singular mass of mountain and has excellent air flow exposure as an isolated massif adjacent to Black, Log, and Pine mountains of its 
Cumberland Overthrust Block. 

The High Knob Landform

[ The northwest mountain flank extending southwest from the High Knob Massif to Cumberland Gap National Historical Park, and beyond, of the High Knob Landform ( Powell Valley Anticline forelimb ) is very distinct and possesses a steep southeast face called the Cumberland Front that tends to enhance lee waves and downstream turbulence ( different from massif front ) ].

Northwest Facing Front Of Main Massif Core
Photograph by Roddy Addington - © All Rights Reserved.

While the NW facing front of the main massif is a major mountain escarpment, it is the width of this relatively isolated mass that often sets it apart from the much more typical, narrow crested mountains of the southern Appalachians.

Numerical mesoscale modeling over isolated mountains has shown an increase in precipitation efficiency with increases in both height and width of the mountain, and subsequent reduction in spillover to the lee as they increase.

Jiang, Q., and R.B. Smith. 2001. Cloud Timescales and Orographic Precipitation. Journal Of The Atmospheric Sciences 60: 1543-59.

I have found the above to be especially true in the High Knob Massif during low density NW flow snow events when large snow depth differences can even develop atop the massif itself between the Big Cherry Basin, Benges Basin, High Knob Lake Basin side ( facing the NW-N ) verses much less across the Bark Camp Lake-Osborne Ridge side of the expansive crest ( facing SE-S ).

Zoom Into The Massif For A View
High Knob Massif - Terrain Map

[ The High Knob Massif is that section with a cluster of blue pins, each with information of various types about the location in question.  Zoom in as far as possible to get the full size effect ].


Climate Statistics
For February 1-15, 2012

February 15, 2012
Long Ridge of the Tennessee Valley Divide
Bare Tree Against The Fog - Awesome Morning Sunrise
Photograph by Wayne Riner - © All Rights Reserved.

Wayne Riner Thoughts...
"Just at first light the trees are outlined against the fog.  The morning is looked over by a pair of bluebirds perched on the weather station."

Clintwood 1 W - Elevation 1560 feet
Average Daily MAX: 45.1 degrees
Average Daily MIN: 25.9 degrees
Feb 1-15 MEAN: 35.5 degrees
Total Precipitation: 1.62"
Total Snowfall: 5.2"

City of Norton - Elevation 2141 feet
Average Daily MAX: 42.4 degrees
Average Daily MIN: 24.1 degrees
Feb 1-15 MEAN: 33.2 degrees
Total Precipitation: 1.85"
Total Snowfall: 6.8"

Nora 4 SSE - Elevation 2650 feet
Average Daily MAX: 41.2 degrees
Average Daily MIN: 27.1 degrees
Feb 1-15 MEAN: 34.2 degrees
Total Precipitation: 1.41"
Total Snowfall: 5.8"

In the High Knob highcountry, temp means for the first half of February varied from mid 30s by day at highest elevations to 20-25 degrees by night ( MINS dropping to near 0 degrees on February 12 ).

February 15, 2012
Mountains Rimming The Russell Fork Basin
Ocean Of Blue - Looking To Pine Mountain
Photograph by Wayne Riner - © All Rights Reserved.

Wayne Riner Thoughts...
"It was a sunny morning after a night of heavy fog, bringing a layer of fog into the valleys. Pine Mountain is in the background."

Snowfall during the first half of February varied between 8" and 13" above 3000 feet in the High Knob Massif, including a fury of flakes that left up to 1" at the summit on February 14.

Long Ridge at 9:53 AM
Fury of Big Snowflakes - February 14, 2012
Photograph by Wayne Riner - © All Rights Reserved.

The snow also accumulated locally at lower elevations with 0.8" measured at Clintwood 1 W.

Long Ridge At 9:54 AM
A Valentine's Day Burst Of Snow - February 14
Photograph by Wayne Riner - © All Rights Reserved.



High Knob Massif
A Few Beauty Shots

February 12, 2012
Light & Shadows Of Thick Snow & Rime
Photograph by Roddy Addington - © All Rights Reserved.

Have to close this section with a few beauty shots from master rime photographer Roddy Addington.

February 12, 2012
Blue Sky + Snow + Rime = Beautiful Abstract
Photograph by Roddy Addington - © All Rights Reserved.

A combination of snow and rime created some unusual looking features as bright sunlight and blue skies returned to illuminate the snowy highcountry.

February 12, 2012
More Classic Rime Photograph of Crest Zone
Photograph by Roddy Addington - © All Rights Reserved.


No comments:

Post a Comment