Friday, April 15, 2011

Beauty & The Beast Of April 2011


April 10, 2011
High Knob Massif
Devil Fork of Big Stony Basin
Magnificent Beauty Of The Devil's Bathtub
Photograph by Roddy Addington - © All Rights Reserved.


Birds singing joyous songs amid an awakening spring landscape was part of a wondrous Sunday morning hike into the wilderness of Devil Fork, where pristine whitewater added to magnificent beauty at the unique Devil's Bathtub.

Devil Fork Basin of the High Knob Massif 
was previously highlighted in the following section:


April 10, 2011
Colorful Devil Fork Gorge
A WET & Rocky Experience
Photograph by Roddy Addington - © All Rights Reserved.


Hiking up Devil Fork Gorge is a wet and rocky experience, but well worth the effort for its great beauty and wilderness setting.

April 10, 2011
One of Many Crossings On Devil Fork
Tanya Hail, Kayla Strong & Brianna Bishop  
Photograph by Roddy Addington - © All Rights Reserved.

One of at least ten crossings along rocky Devil Fork Trail required to reach the upper gorge.

[ This trail is dangerous or impossible to follow after major precipitation events that spike run-off, so please use extreme caution if attempting this journey in such conditions ].

High Knob Massif
Northern Scott County, Virginia
Heavily Weathered Shale & Siltstone - Devil Fork Gorge
Photograph by Roddy Addington - © All Rights Reserved.

The chaotic array of boulders and cobbles downstream and the fine texture of layered shale & siltstone in upper Devil Fork Gorge indicates that water levels occasionally surge much higher to easily over-top these multi-layered rocks!

April 10, 2011
Devil Fork Gorge of High Knob Massif
Misty Vapors Add Humidity To The Devil
Photograph by Roddy Addington - © All Rights Reserved.

April 10 was the warmest and most humid day of 2011 as temperatures maxed out in the lower 70s at the summit level of the High Knob Massif, with the first 80+ degree readings of the year felt within the Clinch River Valley.

April 10, 2011
Beauty Of The ICY COLD Devil
Photograph by Roddy Addington - © All Rights Reserved.

While a hike up Devil Fork Gorge has plenty of crossings into the ICY COLD Devil himself, as highlighted, this water was especially cold being only 4 days removed from high country snow melt.

April 5, 2011 at 6:05 PM
Snow Covered Northern Slopes - High Knob Massif
Photograph by Steve Blankenbecler - © All Rights Reserved.

Snow lingered on lofty north slopes of the High Knob Massif into April 6 before finally melting amid a surge of warm, humid air that triggered violent thunderstorms! 

Welcome to SPRING in the highlands
of the southern Appalachians!

April 10, 2011
A Sign Of The Season - Devil Fork Basin
Zebra Swallowtail ( Eurytides marcellus )
Photograph by Roddy Addington - © All Rights Reserved.


Geological Marker
Southeastern Flank Of High Knob Massif

April 10, 2011
Back Stone Mountain Syncline
Overturned Quartzarenite ( Toward The Southeast )
Photograph by Roddy Addington - © All Rights Reserved.

This HUGE rock sticking upward out of the Earth is only one of many examples of highly overturned rock layers across 
the Scott County side of the High Knob Massif.

What an AWESOME rock!

Observe its distinct southeastward tilt or DIP that is in direct opposition to the northwestward dips seen in rocks along the Wise County side of the massif ( especially the Little Stone-Pickem Mountain flank ).

Devil Fork Gorge is one of many truly awesome gorges eroded into the very long backslope of the High Knob Massif, with both visual and structural enhancement via highly overturned stratigraphy along the Back Stone Mountain Syncline.

Although labeled as Stone Mountain Syncline on USGS mapping, 
I call it Back Stone Mountain Syncline to bring attention to the fact that this is a special geological structure embedded within this remnant massif of the major Powell Valley Anticline of the High Knob Landform of the Cumberland Overthrust Block.

If all this sounds important, IT IS, because this huge block of continental crust is one of the great places on planet Earth!


Violent Thunderstorms
The BEAST Of April 2011

April 9, 2011
Lee County of the High Knob Landform
Towering Cumulonimbus To 50,000 Feet
Photograph by Harold Jerrell - © All Rights Reserved.

Cloud tops reached 8.5 to 10 vertical miles upward into the heavens on the above thunderstorms, which will be detailed later in this section.

Photographer Harold L. Jerrell captured huge tops of towering cumulonimbus clouds as severe storms passed across Lee County, Virginia during afternoon hours of April 9.

April 8, 2011 at 6:13 PM
Severe Thunderstorm Over Dickenson County
Image Courtesy of Plymouth State University Archive

Violent thunderstorms first began firing along a nearly stationary frontal boundary late on April 8, with localized strong to severe cells passing across Dickenson County.

The really big event of this day, of course, were the multiple tornadoes which did tremendous damage in Pulaski County of the New River Valley.

The Blacksburg NWSFO confirmed multiple touchdowns in the Pulaski & Draper communities just after 7:30 PM.

Blowing Rock Community of Dickenson County
Hail Surrounds Hosta Plants - PM of April 8, 2011
Photograph Courtesy of Carl Vanover & WCYB-TV Archives

Blowing Rock Community of Dickenson County
Hail Larger Than Quarter Size - PM April 8, 2011
Photograph Courtesy of Carl Vanover & WCYB-TV Archives

Blowing Rock Community of Dickenson County
Severe Thunderstorm - PM of April 8, 2011
Photograph Courtesy of Carl Vanover & WCYB-TV Archives

This was a fast hitting storm that certainly got everyones attention, and was an ominous marker for even more violent activity to come into April 9.

Northern Dickenson County
Hail Covered Ground at 6:15 PM on April 8, 2011
Photograph Courtesy of Link Mullins & WCYB-TV Archives

Summer-like warmth & humidity surged northeast into the region to establish a notable temperature gradient along which thunderstorms developed during April 8-9.

NAM Model Initialization At 8:00 AM - April 8, 2011
Image Courtesy of Unisys Weather Processor

More thunderstorms firing on the nose of the warm surge were prolific lightning generators into early hours of April 9.

Doppler Base Reflectivity at 12:11 AM - April 9, 2011
Image Courtesy of Plymouth State University Archive

NAM Model Initialization At 8:00 AM - April 9, 2011
Image Courtesy of Unisys Weather Processor

An ominous sign for the upcoming afternoon of April 9 was in clear view early in the day, as a large mesoscale convective system ( MCS ) had formed during the overnight across the lower Ohio Valley.

Doppler Radar Base Reflectivity at 10:00 AM
Image Courtesy of Plymouth State University Archive

The thickness pattern as shown on the lower left chart of the NAM Model Initialization at 8:00 AM, and factors like Corfidi Vectors & Theta-E, suggested a southeastward turn of the MCS over time with building of new cells on its inflow side.

Doppler Radar Base Reflectivity at 12:02 PM
Image Courtesy of Plymouth State University Archive

That is exactly what happened into afternoon hours of April 9, as new thunderstorms fired along the mountains in broken fashion.  

The main concern quickly became a wavy and rapidly evolving squall line over eastern Kentucky as the southern flanks of the MCS regenerated amid increased afternoon instability.

Doppler Radar Base Reflectivity at 2:04 PM
Image Courtesy of Plymouth State University Archive


The Main Event
 ( LEWP )
Line Echo Wave Pattern
Generated Violent Thunderstorms

April 9, 2011
Rapidly Rising Air Currents Into Monster Storms
Photograph by Harold Jerrell - © All Rights Reserved.

Cauliflower columns surround a pilatus cap as air currents rise vigorously into the heavens along this very impressive squall line of thunderstorms.

The southeastern Kentucky squall line intensified as it approached the mountains along the Virginia stateline, with a distinct and very impressive LEWP structure taking shape!

April 9, 2011
Doppler Radar Base Reflectivity at 3:42 PM
Image Courtesy of Plymouth State University Archive

Although not of idealized textbook form, this squall line structure was extremely interesting in many ways.

Doppler Radar Base Reflectivity at 3:50 PM
Image Courtesy of Plymouth State University Archive

Several areas of special interest were observed within the LEWP during this time.

Doppler Radar Base Reflectivity at 3:58 PM
Image Courtesy of Plymouth State University Archive


Special Area Number 1
HUGE Hail In Lee County

Hail To 2.5" In Diameter ( AND BIGGER ) Occurred
Photograph by Harold Jerrell - © All Rights Reserved.

Hail by the tons, and damage claims by the dozens, resulted from the unloading of potent updrafts over Lee County as these storms turned violent and potentially deadly!

Thankfully, as far as I know, no one was killed 
or seriously injured during this extreme hail event.

PM of April 9, 2011
Large Hail & Vehicle Dents In Lee County
Photograph by Harold Jerrell - © All Rights Reserved.

It would not take many of these bad boys to fill a cool whip cup, with broken windows, vehicle dents, and other damage reported by Harold at his home.

Doppler Vertically Integrated Liquid Scan at 3:58 PM
Image Courtesy of Plymouth State University Archive

Calculus is used to calculate VIL by taking a vertical integration of reflectivity within a column of air between the top and bottom of a Doppler scan.  It is really quite simple!

When the new line of WSR-88D radars came online with their ready made algorithm for VIL calculation it seemed that hail prediction had been solved.  NOT!

As it turns out, many factors have since been found to impact hail sizes not the least of which is terrain, geography, and location of the Doppler from storms of interest ( plus numerous other factors ).

Doppler Radar Echo Tops ( Cloud Tops ) at 3:58 PM
Image Courtesy of Plymouth State University Archive

VIL Density, found by dividing the VIL value by observed Echo Tops ( and multiplying by 1000 g/kg ), is actually a better indicator of hail sizes than VIL alone, with large hail especially having a strongly positive correlation to elevated VIL Density.

A calculation of VIL Density on the Lee County storm, at one point noted graphically above, found 4.66 grams per cubic meter ( above the threshold for severe hail but not quite high enough to predict baseball or bigger chunks! ).

April 9, 2011
Baseball Size Hail - Lee County, Virginia
Photograph Courtesy of Marcus Green & WCYB-TV Archives

April 9, 2011
More Baseball ( or bigger ) Hail - Jonesville of Lee County
Photograph Courtesy of Melissa Jones & WCYB-TV Archives

While hail was the BIG DEAL, locally high winds also did some damage in Lee County.

April 9, 2011
Structural Damage Just West of Jonesville
Photograph Courtesy of Corey Moore & WCYB-TV Archives

This storm, which passed into Hawkins County, Tn., will forever be remembered by most for its

HUGE hail.

PM of April 9, 2011
Large Hail Lingers In Wake of Thunderstorm
Photograph by Harold Jerrell - © All Rights Reserved.



Special Area Number 2
Wind Damage In City of Norton

April 9, 2011
Billowing Thunderstorm Tops Near Sunset
Photograph by Harold Jerrell - © All Rights Reserved.

The second area of special interest impacting the High Knob Landform was a portion of the squall line with notable rotation on Doppler.

3:58 PM on April 9
Tilt Angle of 1.3 degrees
Doppler Storm Relative Mean Radial Velocity
Image Courtesy of Plymouth State University Archive

Storm Relative Mean Radial Velocity ( SRMRV ) scans are an important tool for detecting air flow directions as they can reveal the flow field being generated inside storms by subtracting away the mean storm motion.

It works by detecting precipitation elements and calculating their velocity, which by mathematical definition is a vector product including both strength and direction.  In this case, direction is key as it allows for the calculation of motion toward and away from the Doppler site.

If you mathematically resolve a linear velocity field into its individual parts one of the natural components is vorticity, or spin, such that when motions toward and away from the Doppler become colocated they indicate portions of the atmosphere with cyclonic ( counterclockwise ) and anticyclonic ( clockwise ) spin.

Due to overshooting of the Doppler beam it was difficult to detect anything of significance on the lowest 0.5 degree tilt angle, which hits several thousand feet above ground level ( around 6,000 feet above sea level ) over the City of Norton.

Higher tilt angles of the Doppler, however, revealed distinct areas of rotation at consecutively higher angles to indicate that a deep column of air was experiencing circulation in the vertical.

3:58 PM on April 9
Tilt Angle of 2.4 degrees
Doppler Storm Relative Mean Radial Velocity
Image Courtesy of Plymouth State University Archive

Two areas with spin were actually visible on the 2.4 degree tilt angle, but only one of those was colocated with spins below and above it at this particular time.

3:58 PM on April 9
Tilt Angle of 3.1 degrees
Doppler Storm Relative Mean Radial Velocity
Image Courtesy of Plymouth State University Archive

A very well defined RED-GREEN Couplet was visible on the 3.1 degree tilt, that is way up there aloft, at this same time of 3:58 PM.

So what is strange about
the above setting?

If you follow Doppler radar it is obvious that the above noted red-green couplets all show clockwise or anticyclonic spin near the City of Norton.  While that does occur, the Tornado Project estimates only 1 in 100 tornadoes spin clockwise.

[ Likewise, only a small percentage of rotating thunderstorms ( called Mesocyclones ) actually spin in a clockwise direction in the Northern Hemisphere ].

While a funnel cloud was reported near Pardee it is not known if it was only located aloft and what spin it had.  A funnel cloud is not a tornado until it actually does damage at the surface.

There is not currently enough information to know if the Norton wind damage was associated with an actual, rare clockwise rotating swirl at the surface.

It should be pointed out that this is from the perspective or viewpoint of the Jackson, Ky., Doppler which typically has the best view of the local mountain area.

It is understood that views of the Morristown, Tn., Doppler were different at times showing, for example, some cyclonic rotation aloft near Norton during this event.

April 9, 2011
Huge Tree Uprooted In Norton
Photograph Courtesy of Brandi Reynolds & WCYB-TV Archives

Norton City Park - April 9, 2011
Virginia State Flag Pole Broken By Wind
Photograph Courtesy of Pam Hall & WCYB-TV Archives

Structural Damage In City of Norton
Photograph Courtesy of Pam Hall & WCYB-TV Archives

City of Norton - April 9, 2011
Windows Blown Out By High Winds
Photograph Courtesy of Pam Hall & WCYB-TV Archives

Vector calculus shows that vorticity & circulation are intimately related, such that vorticity is the vector component normal ( or perpendicular ) to the curl of the three-dimensional velocity field.

It is a circulation per unit area, or localized result of circulation at a small scale.

In other words, circulation is an areal measure of the rotational tendency of the atmosphere while vorticity is a point measure of that tendency.

[ In the Northern Hemisphere, cyclonic motion is associated with positive vorticity while anticyclonic motion is associated with negative vorticity ( the vorticity being capable of occurring about axes of any orientation, from horizontal to vertical in nature ) ].


Review Of Special Area 1
Lee County Mesocyclonic Thunderstorm

3:58 PM on April 9
Tilt Angle of 0.5 degrees
Doppler Storm Relative Mean Radial Velocity
Image Courtesy of Plymouth State University Archive

Given the above it is now easier to illustrate how the thunderstorm over Lee County contained a relatively strong cyclonic circulation, with counterclockwise spin indicated at all tilt angles from 0.5 to 3.1 degrees on the Doppler.

[ Gate-to-gate shear is indicated when two pixels on these scans align side to side with different motions, such as inbound air flow adjacent to outbound air flow with respect to a particular Doppler site ( in this case JKL or Jackson, Kentucky ).

The presence of such couplets, however, does not indicate a tornado as numerous other criteria must be met. A built in set of parameters make up a specific algorithm designed to scan for tornadic circulations which, if found, triggers a TVS 
( Tornado Vortex Signature ) Warning.

A MDA ( Mesocyclone Detection Algorithm ) is built into the Doppler to scan for rotating thunderstorms, the majority of which never produce a tornado.  MDA alerts, however, often arise prior to TVS warnings ]. 

3:58 PM on April 9
Tilt Angle of 1.3 degrees
Doppler Storm Relative Mean Radial Velocity
Image Courtesy of Plymouth State University Archive

3:58 PM on April 9
Tilt Angle of 2.4 degrees
Doppler Storm Relative Mean Radial Velocity
Image Courtesy of Plymouth State University Archive

3:58 PM on April 9
Tilt Angle of 3.1 degrees
Doppler Storm Relative Mean Radial Velocity
Image Courtesy of Plymouth State University Archive

The Lee County thunderstorms were important since this was the section of the squall line that went on to also produce large hail in northern Tennessee, and a confirmed EF-1 tornado 2 miles east of Jonesborough.

April 9, 2011
Tree Damage & Large Hail In Lee County
Photograph Courtesy of Kaitlyn Sumpter & WCYB-TV Archives



( Updated: April 15, 2011 )
Climate Statistics For 
The First Half Of April 2011

April 5, 2011
Looking Toward Coeburn From City of Norton
Gorgeous Morning Wave Clouds At Sunrise
Photograph by Roddy Addington - © All Rights Reserved.

The first half of April 2011 was seasonally cool & wet but dominated by wild temperature swings between unseasonably warm and cold days.

( Lower Elevations of Russell Fork Basin )
Clintwood 1 W - Elevation 1560 feet
Average Daily MAX: 65.9 degrees
Average Daily MIN: 36.4 degrees
MEAN: 51.2 degrees
Highest Temperature: 85 degrees
Lowest Temperature: 27 degrees
Total Precipitation: 2.72"
2011 Precipitation: 13.77"

( Northern Base of High Knob Massif )
City of Norton - Elevation 2141 feet
Average Daily MAX: 61.5 degrees
Average Daily MIN: 35.4 degrees
MEAN: 48.4 degrees
Highest Temperature: 80 degrees
Lowest Temperature: 25 degrees
Total Precipitation: 3.71"
2011 Precipitation: 18.04"

( Along The Tennessee Valley Divide )
Nora 4 SSE - Elevation 2650 feet
Average Daily MAX: 60.1 degrees
Average Daily MIN: 40.5 degrees
MEAN: 50.3 degrees
Highest Temperature: 77 degrees
Lowest Temperature: 26 degrees
Total Precipitation: 4.29"
2011 Precipitation: 15.74"

In the High Knob Massif this first half of April produced low to mid 50s by day at the highest elevations & low-mid 30s at night in the colder basins ( mid-upper 30s upon high crestlines ).

Precip averaged 4.00" to 5.00" to boost 2011 tallies to more than 2 Feet ( 24.00" ) in wetter locations of the massif.  This also included 1" to 4" of April snow at highest elevations and the 98th day ( 14 weeks ) of the 2010-11 winter season to have 1" or more of snow depth on north slopes in lofty 
High Knob Lake Basin.


( Updated: April 16, 2011 )
Heavy Rain Event Into April 16

24-hour Rainfall Estimates
Doppler Rainfall Estimate Ending At 8 AM April 16
Image Courtesy of Plymouth State University Archive

A moderate to heavy, wind driven rain dropped an additional 1.50" to 3.00" of rainfall upon much of the High Knob Landform during the 24-hour period ending early on April 16.

While showing where the heavier rains fell, Doppler radar tended to under-estimate local rain amounts by 0.50" to 1.00" as illustrated above by two point measurements made in Clintwood and the City of Norton.

The 2.44" of rain measured by Joe Carter at the Norton Water Plant boosted April rainfall to 6.15" and the 2011 tally to 20.48" .

The nature of this heavy rain event, and low reading by Doppler, was verified by Gary Hampton & Staff to the southwest of Norton in South Fork Gorge of the High Knob Massif, where 2.61" of rain were measured at the Big Stone Gap Water Plant.

The above boosted April precipitation tallies 
to 6.66" at Big Stone Gap WP and 7.25" at 
Big Cherry Dam ( where the 7-day total was 3.87" ).

[ Precipitation totals of 25.00" to 27.00"+ within wetter portions of the High Knob Massif, above the City of Norton & town of Big Stone Gap, during the January 1 to April 16 period of 2011 
( 35.00" to 40.00" since November 1, 2010 ) ].

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