Monday, May 31, 2010

May 2010 Ends As Month of Wetness & Beauty

Colorful Majesty of False Sunrise - May 25, 2010
Photograph by Wayne Riner - © All Rights Reserved.

The final week of May 2010 began with a false sunrise above the Tennessee Valley Divide, as captured by Wayne Riner on May 25.

[ What appears to be a sun in the above photograph actually being its reflection, as generated by ice crystal clouds high above the mountain horizon.  Ice crystal clouds being at a high enough altitude to capture and reflect light coming from a sunrise beyond the visible horizon, to generate what is often called a False Sunrise or Dawn Sun Dog ]. 

Gorgeous Sunrise Over City of Norton - May 31, 2010
Photograph by Roddy Addington - © All Rights Reserved.

The final week of May 2010 ended with a simply gorgeous sunrise above the City of Norton, as captured by Roddy Addington on May 31.

What an awesome greeting to Memorial Day!

Wave Clouds & Rail Reflections - Norton - May 31
Photograph by Roddy Addington - © All Rights Reserved.

The seemingly ever present wave clouds being complimented by a special lighting effect via light reflections off railroad tracks. 


Beautiful Waves & Rails - May 31, 2010
Photograph by Roddy Addington - © All Rights Reserved.

May 2010 ended wet in Norton and on Long Ridge, with 8.60" and 8.71" of rainfall, respectively, within their official National Weather Service rain gauges ( not including any rain falling after their 7 to 9 AM observation times on May 31 ).

Beauty of May 2010 - City of Norton - May 31
Photograph by Roddy Addington - © All Rights Reserved.

A general 5.00" to 10.00" of rain fell across Wise, Dickenson, Lee, and northern Scott counties during May, into adjacent portions of the Clinch Valley of Russell County.

[ Getting to these hefty May rainfall tallies was locally rough, as highlighted previously on this website:

May 2010 Opens With Flash Flooding

May 2010 - Flash Flooding Strikes Again!

The final week of May offered up some tremendous events for lovers of weather, with May 28 being a day of particular interest highlighted in some detail below.

Orographic Thunderstorm Formation
of Nearly Stationary Nature

Three Initial Centers of Thunderstorm Development
JKL Doppler at 11:58 AM on May 28, 2010
Image Courtesy of Plymouth State University

The most significant conditions of this final May week started the Memorial Day holiday with a bang, literally, during May 28.

JKL Doppler 1-Hour Rainfall Estimate at 12:45 PM
Image Courtesy of Plymouth State University

[ Doppler radar estimated 1-hour rainfall totals of 1.50" to 2.50" were widespread from upper portions of rugged Rocky Hollow of Grindstone Dome, at the Head of Powell Valley, across much of Benges Basin and the Flag Rock Recreation Area to Legion Park and southwestern portions of Norton.  This was also verified by the official NWS rain gauge measurement at Norton Water Plant ].

Andrew Greear measured 2.29" of rain at the Norton Water Plant early Friday afternoon as vigorous and nearly stationary storms fired over northern slopes of the High Knob Massif ( some small hail also occurred with the deluge ).

Rainfall totals with this initial convective burst, in simply amazing contrast, dropped off to less than 0.10" at the northeastern end of Norton and along the main crestlines near High Knob.

But this was only the beginning!

JKL Doppler at 2:05 PM on May 28, 2010
Image Courtesy of Plymouth State University

The three initial centers of development, over the High Knob Massif, Sandy Ridge, and near Laurel Bed Lake of Clinch Mountain, being very important as they generated rain cooled outflow boundaries which aided formation of new storms as an upper wave moved northwestward across the Appalachians ( in the bigger picture ).

Doppler 1-Hour Rainfall Estimate Ending at 2:36 PM
Image Courtesy of Plymouth State University

[ Doppler radar estimated 1-hour rainfall totals of 1.50" to 3.00" laid out almost exactly along top of the previously noted corridor of torrential rainfall, from upper portions of Benges Basin into Rocky Hollow of Grindstone Ridge Dome ( note the rainfall total graphic below and how they adjoin with little overlap ) ].

This became extremely interesting within the High Knob Massif area, as thunderstorms which fired next dropped torrential rain from High Knob Lake Basin across middle to upper portions of the Big Cherry Basin, then southwest along the great belt of calcareous cliffs to Morris Butte and Wallen Ridge ( illustrated above & below by Doppler rainfall totals ).

Doppler Storm Rainfall Total Ending at 2:36 PM
Image Courtesy of Plymouth State University

[ Although Big Cherry Lake received good run-off, it was again amazing to watch the heaviest rains flank ( or move around ) the lower Big Cherry and just barely miss Big Cherry Dam ].

It was fascinating, as I have documented many times in the past, to watch a vigorous line of storms drop torrential rains from Chestnut Flats, on the northern slopes, upwards along the main crest zone while little rain fell below into Flag Rock Recreation Area and the City of Norton.

Likewise, during the initial isolated storm case, torrential rain fell from Norton up to the level of Chestnut Flats, with little rain falling above that elevation ( also a common scenario with thunderstorm flanking and propagation along the massif ).

Most amazing to consider that such vigorous storms can impact two different elevation zones of the High Knob Massif, while leaving those adjacent ( above or below them ) essentially dry!

It becomes perhaps even more impressive when considering that these 40,000 to 50,000 foot cumulonimbus towers impacted only a small portion of the total massif.

The combination of these two different thunderstorm episodes creating a solid area of 1.50" to 3.00" rainfall totals from the base in Norton up into the crest zone ( High Knob Lake Basin to Big Cherry Lake Basin ), but with very little spillover across to southeastern slopes and the very long backslope of the massif ( on the Scott County side ).

[ For a graphical look and explanation of the structural form of the High Knob Massif, and its atypically long backslope, reference the following section of my website:

Whitewater Rolls In High Knob Massif  ].

Doppler at 3:01 PM ( Generalization Of Outflow )
Image Courtesy of Plymouth State University

[ During the next 30 to 45 minutes an arc of convection formed in all quadrants surrounding the dissipation of the High Knob Massif convection, except to the northwest where local storms along the Virginia-Kentucky stateline were also dissipating and generating rain cooled air ].

The two early afternoon episodes of High Knob Massif convection were associated with essentially stationary thunderstorms, with very little storm movement such that they rained themselves out over their formation corridors.

Upon dissipation this resulted in a spreading outflow that has been roughly generalized on the above Doppler scan at 3:01 PM.

This outflow packed some punch, as temperatures had plunged into the mid-upper 50s from the crest zone of High Knob down into parts of the City of Norton ( by contrast, afternoon temperatures in the 80s were reported at the same time in locations still unaffected by convection ).

A Severe Thunderstorm Develops
and Undergoes Storm Merger With Line

Of particular interest was the formation of a thunderstorm on the Wise-Dickenson border, which began moving southeastward in a direction opposite to that of convection developing and moving across Russell and Washington counties.

[ Reference the Doppler scan at 3:01 PM ( above ) for an initial view of this developing thunderstorm ].

JKL Doppler at 3:30 PM on May 28, 2010
Image Courtesy of Plymouth State University

With dissipation of High Knob Massif convection, this storm over Dickenson County appeared to develop southeast along the outflow with both an increase in forward speed and intensity over time.

It turned Strong to SEVERE!

Potent Hail Core - Doppler at 3:38 PM on May 28
Image Courtesy of Plymouth State University

The thunderstorm over southwest Dickenson developed a rather potent hail core, at least on radar, with Doppler detecting Vertically Integrated Liquid ( VIL ) values of 55 to 65 kilograms per meter squared. 

[ VIL is essentially a measure of the amount of precipitation within a column of air, based upon reflectivity, with very high VIL values often associated with hail.  VIL was once thought to be a good indicator of hail size, but correlation with ground truth has since proven it to not be as dependable due to updraft tilting in the vertical, distance of radar from storm, cloud and precipitation physics, amount of precipitation associated with any hail, as well as various other factors ].

Thunderstorm Blasts Long Ridge - May 28, 2010
 Photograph by Wayne Riner - © All Rights Reserved.

This storm was an ideal example, with alot of wet hail that was mostly below the 1" diameter criteria for severe hail.  However, Wayne & Genevie Riner reported that hail fell for nearly an hour as the storm pounded Long Ridge with torrential rain, wind, and its load of hail ( up to dime size ).

[ In this case the very high VIL on Doppler was associated with alot of hail mixed with torrential rainfall, but not really large hail as could have been the case in a thunderstorm with less rain and equivalent VIL values within drier air aloft and good vertical sampling of the updraft ( at all tilt angles ).  The lowest tilt angle in this case being poorly sampled, due to the long distance of the radar from Long Ridge and its beam overshooting lower levels ].

JKL Doppler at 3:42 PM on May 28, 2010
Image Courtesy of Plymouth State University

[ Note how the High Knob Massif is now almost completely flanked by strong convection, with complete dissipation of its previous thunderstorms and their conversion to rain cooled outflows ].

By 3:42 PM the thunderstorm over southwest Dickenson County was close to merging with the strong line of convection moving to the northwest across Russell County.

Classic Look of Rain-Hail Loaded Thunderstorm
Photograph by Wayne Riner - © All Rights Reserved.

The thunderstorm pounded Long Ridge, with Wayne & Genevie Riner measuring 2.10" of rainfall within just under 1-hour, along with strong winds and alot of hail ( damaging their large apple orchard ).

JKL Doppler at 3:55 PM on May 28, 2010
Image Courtesy of Plymouth State University

The merging of the southeast moving supercell with the northwest moving line of convection, as noted above, aided the deluge.

[ Storm mergers often result in enhanced rainfall and strong to severe conditions, and are a classic signature to watch for on Doppler radar ].

Hail Deposited by Thunderstorm - Long Ridge - May 28
Photograph by Wayne Riner - © All Rights Reserved.

Rapid Configuration Changes In Storm Line
Has Orographic Connections

The now large, arc shaped line of convection possessed a general west to northwest motion upon absorption of the Dickenson County thunderstorm.

JKL Doppler at 4:12 PM on May 28, 2010
Image Courtesy of Plymouth State University

Notable exceptions quickly developed, with a couple of rapid northwest surges in the formation of thunderstorms being seen into Wise County as the configuration of this convective arc changed dramatically during the next half hour!

JKL Doppler Base at 4:50 PM on May 28, 2010
 Image Courtesy of Plymouth State University

The above being initially inferred from base reflectivity scans which showed the most intense activity developing rapidly northwestward over southwest portions of the massif and along the interface of rain cooled air near Norton-Wise.

Upon closer inspection, however, the situation is more complicated within the area near three great gorges ( South Fork Gorge, Straight Fork Gorge, and Cove Creek Gorge ).

JKL Doppler Storm Relative Winds at 4:50 PM
Image Courtesy of Plymouth State University

An inspection of the JKL Doppler storm relative winds, found the strongest velocities located just northeast of where the most intense rain reached the surface under the highest base reflectivities.  These being colocated with base velocities of the storm motion as well, to indicate that the storms were moving along with their outflow.

[ Storm relative radial velocity being a wonderful feature of Doppler radar that allows one to look at air flow inside storms, with the motion of the storm itself ( its base velocity ) being removed from view.  Infamous RED-GREEN couplets, indicative    of mesocyclonic rotation, being best viewed in this mode ( and if vertically deep, as observed at consecutive tilt angles, can signal a possible tornado ) ]. 

The above suggesting air flow was surging up the long backslope of the massif, with the strongest velocities located over top of Straight Fork Gorge being perhaps only due to tilting in the vertical ( since the Doppler beam is far above the ground at this distance from the radar site the strongest low-level flow may have actually been up Cove Creek Gorge, which was within the torrential rain core and beneath the highest base reflectivities ).

MRX Doppler Storm Relative Winds at 4:49 PM
Image Courtesy of Plymouth State University

From a different viewpoint, of the Morristown, Tn., Doppler, the storm relative ( and also base ) velocity wind field placed the axis of max speeds interestingly over the location of South Fork Gorge on the Wise County side of the massif ( and across toward the mouth of Cove Creek Gorge on the Scott County side ).

The conclusion from this information being that the great gorges of the High Knob Massif definitely played a role in this rapid northwestward surge of thunderstorms from the Clinch River Valley into southwest portions of Wise County.

It is not possible, however, given the lack of low-level data to know precisely how the air flow may have funneled within these gorges to force the observed changes ( Doppler beams hitting far above the surface and missing the critical lower levels ).

[ Funneling within the gorges having been verified at ground level during my research in the High Knob Massif ].

Lee County Thunderstorms Go Severe
Outflow Boundaries Play Role

MRX  Doppler Base at 3:18 PM on May 28, 2010
Image Courtesy of Plymouth State University

[ The Morristown Doppler clearly showed rain cooled outflow boundaries moving north to northwest out of the Great Valley of eastern Tennessee, as development started over Lee County along the southwestward moving periphery of outflow from dissipation of High Knob Massif convection ].

Thunderstorms developing across Lee County turned severe, with wind damage reported from Jonesville through Rose Hill after 4 PM as outflows merged to intensify activity.

JKL Doppler at 4:29 PM on May 28, 2010
Image Courtesy of Plymouth State University

My friend & photographer Harold Jerrell reported the following from his home near Wilson Hill:

"We received the nasty stuff!  I had 1.90" of rain.
Lots of wind that flattened my garden, and rain that washed newly planted seed into the Powell River.
Also had some hail."

In fact, the wind was so strong that it literally blew a brush pile back across a fence where it had been piled by Harold.

[ Harold prunes his apples trees every spring, and piles the brush across a fence to later be burned.  The powerful winds with these thunderstorms picked up the brush and blew it back across the fence into Harold's yard! ].

Dissipation Of Mountain Storms
Sends Outflow Boundary Across Foothills

JKL Doppler at 6:01 PM on May 28, 2010
Image Courtesy of Plymouth State University

[ A fitting conclusion to a day with so many thunderstorm outflow boundary interactions, with outflow across the Kentucky foothills now becoming aligned with the mean southeast to northwest flow field to help it race forward and downward in mean elevation ].

This day of amazing convective happenings generated yet another notable event, as storms across the High Knob Landform and along the Virginia-Kentucky border dissipated to send a outflow boundary racing northwest across the foothills of Kentucky ( where it triggered new storms ).

The outflow boundary above actually extending on to the southwest from where I have it denoted by the white line, which was that section most visible to JKL Doppler ( and not yet fully filled with new storms ).

A most incredible dance is that of convection, with an almost simultaneous fall of cloud tops above the mountains being in near synchrony with rising cumulonimbus towers over the Kentucky foothills. 

Both being intimately connected!  

Statistical Recap
for May & Spring 2010

Awesome Photograph
Storm Clouds Engulf Cumberland Gap National Park
Photograph by Harold Jerrell - © All Rights Reserved.

May 2010 ended with above average rainfall and temperatures, to generate the following statistics and variations across the region ( with below average rainfall observed from the Great Valley eastward across portions of the Blue Ridge, Piedmont, and Coastal Plain ).

May 2010 Climate Statistics

Clintwood 1 W - Elevation 1560 feet
Average Max: 77.7 degrees
Average Min: 50.0 degrees
Mean: 63.8 degrees
Highest Temperature: 89 degrees
Lowest Temperature: 31 degrees
Rainfall: 5.76"

City of Norton - Elevation 2141 feet
Average Max: 74.1 degrees
Average Min: 48.7 degrees
Mean: 61.4 degrees
Highest Temperature: 85 degrees
Lowest Temperature: 29 degrees
Rainfall: 8.60"

Nora 4 SSE ( Long Ridge ) - Elevation 2650 feet
Average Max: 72.8 degrees
Average Min: 55.3 degrees
Mean: 64.0 degrees
Highest Temperature: 82 degrees
Lowest Temperaure: 36 degrees
Rainfall: 8.71"

Richmond, Va., ( State Capitol ) - Elevation 167 feet
Average Max: 81.2 degrees
Average Min: 59.7 degrees
Mean: 70.4 degrees
Highest Temperature: 93 degrees
Lowest Temperature: 41 degrees
Rainfall: 2.62"

Tri-Cities, Tennessee - Elevation 1525 feet
Average Max: 80.1 degrees
Average Min: 55.2 degrees
Mean: 67.6 degrees
Highest Temperature: 89 degrees
Lowest Temperature: 35 degrees
Rainfall: 2.58"

Knoxville, Tennessee - Elevation 981 feet
Average Max: 81.6 degrees
Average Min: 59.9  degrees
Mean: 70.8 degrees
Highest Temperature: 90 degrees
Lowest Temperature: 45 degrees
Rainfall: 4.22"

Jackson, Ky., NWSFO - Elevation 1365 feet
Average Max: 76.5 degrees
Average Min: 57.8 degrees
Mean: 67.2 degrees
Highest Temperature: 86 degrees
Lowest Temperature: 38 degrees
Rainfall: 7.92"

London, Kentucky - Elevation 1211 feet
Average Max: 77.6 degrees
Average Min: 56.1 degrees
Mean: 66.8 degrees
Highest Temperature: 86 degrees
Lowest Temperature: 36 degrees
Rainfall: 5.49"

Buckhorn Lake SP, Kentucky - Elevation 936 feet
Average Max: 80.2 degrees
Average Min: 54.1 degrees
Mean: 67.2 degrees
Highest Temperature: 91 degrees
Lowest Temperature: 38 degrees
Rainfall: 4.11"

In the High Knob highcountry, May 2010 temp means varied from 60s to lower 70s by day to middle-upper 40s by night within the mountain basins ( above 2400 feet ).  Mean May temps being mostly in the 50s across the crestlines and higher basins ( max readings ranging from 75 to 80 degrees in upper elevations, with mins as cold as mid-upper 20s on May 10 ).

Mountain Ridges & Morning Fog - May 2010
 Photograph by Wayne Riner - © All Rights Reserved.

Wetness ruled May from the start, but with typically wide spreads in amounts across the very large High Knob Landform and Cumberland Block ( 3125 square miles ).

Canada Goose ( Branta canadensis )
Photograph by Harold Jerrell - © All Rights Reserved.

May rainfall in the High Knob Massif varied from 5.52" in upper portions of Burns Creek Basin, at the lovely home of my friends Otis & Nancy Ward, to between 7.00" and 10.00" from Big Cherry Basin across High Knob and Pickem Mountain to the City of Norton.

Spring 2010 Temperature Means

High Knob Massif - Bear Food
Squaw Root ( Conopholis americana )
Photograph by Roddy Addington - © All Rights Reserved.

Mean temperatures during the spring period of March through May averaged in the 40s to low 50s within the High Knob Massif and city of Norton ( average daily max + average daily min = mean temperature ).

March-May Temperature Means

City of Norton: 51.0 degrees
Clintwood 1 W: 53.5 degrees

Regional differences having been highlighted for the past few months, with special emphasis on variations in timing of renewal and emergence of spring flora between the High Knob Massif area and Kentucky foothills ( as well as locally within the great High Knob Landform itself ).

March-May Temperature Means

Kentucky Foothills
London: 57.3 degrees
Jackson NWSFO: 59.0 degrees

Great Valley of East Tennessee
Tri-Cities: 57.0 degrees
Knoxville: 60.1 degrees

Spring temperatures were well above average across the entire region during 2010, with the official mean of 61.5 degrees in the state capitol of Richmond, Va., actually marking the warmest spring since record keeping began in 1881 ( * ).

*An upward trend in minimum temperatures observed at the Richmond Airport recording site during the past 10 to 20 years being at least partly attributed to urbanization.

Spring Precipitation Totals
( March-May 2010 )

London: 11.12"
Jackson NWSFO: 12.96"

Tri-Cities Airport NWS: 6.88"
Kingsport: 8.34"
Knoxville: 9.61"
Chattanooga: 11.60"
Mount LeConte: 14.60"

Wytheville 1 S: 7.90"
Abingdon 3 S: 8.51"
Bland: 9.39"
Richlands: 9.74"
Lebanon: 10.20"
Grundy: 11.69"
Clintwood 1 W: 12.42"
North Fork of Pound Dam: 12.48"
Breaks Interstate Park: 12.52"
Big Stone Gap Water Plant: 12.56"
Burkes Garden: 12.86"
Robinson Knob of High Knob: 12.87"( M )
Appalachia Lake Water Plant: 12.99"
Nora 4 SSE ( Long Ridge ): 13.61"
Norton Water Plant: 15.37"

( M ) - Denotes some missing moisture in snowfall.

In the High Knob Massif area, Spring 2010 precipitation totals reached a maximum of between 15.00" and 20.00" in the corridor from the City of Norton south to southwest across the highcountry ( i.e., Pickem Mountain and Bowman Mountain into High Knob Lake & Big Cherry Lake basins and portions of Powell Mountain ).