Thursday, July 25, 2019

Wet Summer of 2019_High Knob Massif

July 24, 2019
Draining Big Cherry Lake Basin
South Fork of Powell River Gorge
Photograph by Wayne Browning - © All Rights Reserved

Brilliant sun rays strike gushing whitewater tumbling out 
of Big Cherry Lake basin during morning hours of July 24.
Yellow Birch (Betula alleghaniensis) trees add to the scene.

Vapor from the water was visibly rising back into the air, during a summer season in which the surface energy budget has been dominated by the latent heat flux to an extent even more than typical of this wettest terrain in Virginia (where mean precipitation exceeds potential evapotranspiration during all months of the year).  The result being a huge surplus of moisture whose excess is largely removed via runoff, supporting formation of creeks and streams that supply the local area and region with precious water.

A super-wet summer in the high country of the High Knob Massif has generated more than 22.00" of rainfall during the June 1 to August 2 period of 2019 (22.60" at Big Cherry Dam).

Monthly Total Precipitation
Big Cherry Lake Dam
(Elevation 3139 feet)








August 1-2

Summer 2019
(Jun 1-Aug 2)

*2019 Total: 60.56" (M)
 (January 1 to August 2 Period)

12-Month Total: 91.85" (M)

(M): Some missing moisture in undercatch and frozen precipitation, with partial corrections applied for the 24.4 meter (80 feet) tall dam structure where rain gauges are located.

*Big Cherry Lake basin is the most productive water supply basin per unit area within the Old Dominion of Virginia.  Anyone who does not believe this fact is free to find another basin with higher precipitation totals over a period of years to decades that contains a water supply producing lake watershed.

July 24, 2019
Majestic Whitewater Draining Big Cherry Lake
Photograph by Wayne Browning - © All Rights Reserved

One reason Summer 2019 has been so wet is 
that surface to 850 MB vector wind composite anomalies have possessed a westerly component (WSW-SSW), which favors orographic lifting of air along the western front range of the Appalachians.

June 1 to July 22 of 2019
Surface Vector Wind Composite Anomaly

June 1 to July 22 of 2019
850 MB Vector Wind Composite Anomaly

Mean negative Sea Level Pressure (SLP) anomalies combined with a positive Integrated Moisture Flux into the southern Appalachians to support a wet pattern through this first half of Summer 2019.

June 1 to July 22 of 2019
Sea Level Pressure Composite Anomaly

June 1 to July 22 of 2019
Integrated Moisture Flux Composite Anomaly

For a look into the first week of August 2019, 

While anomalous wetness may continue through the end of summer, climatology favors a natural decrease caused by less insolation driving surface energy budget processes.

This occurs as mean daylight diminishes from 
14.0 hours in late July to 12.8 hours by the end 
of August, at 36.6 degrees North latitude, with approach of the autumnal equinox.

*Meteorological autumn (September-November) being 
a transitional time period between the convective season of summer and the orographic forcing season of late autumn through winter into spring.

Autumn is, therefore, typically the driest time of the year (autumn wetness, however, has been a recently documented trend within the Mountain Empire).

July 24, 2019
Elevations 3000 to 3400 feet
Draining Big Cherry Lake of High Knob Massif
Upper Gorge of the South Fork of Powell River
Photograph by Wayne Browning - © All Rights Reserved

While standing dead Canadian Hemlock (Tsuga canadensis) are visible near the creek, having been killed by Hemlock Wooly Adelgids, an abundance of young, healthy hemlocks live within the understory of the surrounding forest.

In the mountains, especially, an additional important factor with increasing significance through coming days and months will be declining solar angles which results in less available energy per unit area as the sun's rays are spread across 
an increasingly large surface and the mountain horizon effect becomes more of a local factor.

While astronomical sunrise and sunset are global in scale, the actual amount of solar radiation received at a given point is impacted by the local horizon.  Valleys, hollows, coves, and gorges embedded within complex terrain tend to have later sunrises and earlier sunsets, with sunrise and sunset from a surface energy budget perspective being determined by the local mountain horizon and when the sun is able to rise above it, and to drop beneath it, on a daily basis.

So, effective day light shortens much faster in complex terrain heading into autumn and winter with respect to energy received per unit area at the surface.  This occurs until eventually some of the most sheltered hollows and slopes receive little to no direct sunlight, only diffuse light, allowing frost and/or snow to easily linger from day to day 
if temperatures are chilly.

This is essentially the driver of mountain microclimates, with many additional factors involved whose summation collectively results 
in the actual microclimatic characteristics of a given location.

Recent Images From The 
UVA-Wise Research CAM

July 19, 2019 at 8:57 PM
Cumulonimbus Top Illuminated At Sunset
UVA-Wise Weather Research Webcam

July 20, 2019 at 11:31 AM
Towering Cumulus Develop Over High Terrain
UVA-Wise Weather Research Webcam

July 21, 2019 at 7:24 PM
Developing Downpour Over The High Country
UVA-Wise Weather Research Webcam

The development of visible orographic clouds that engulf upper elevations and appear to be laying upon the high country (as they persist for long periods of time) is a signal throughout the year 
for enhanced precipitation amounts.

Numerous such days have been documented during June and July of 2019, with more than 20.00" of rainfall in the High Knob Massif.

The Seeder-Feeder cloud mechanism is associated with orographic enhancement of precipitation amounts throughout the year when it develops. 

July 22, 2019 at 6:46 PM
Support For Heavy Rainfall Amounts
Seeder Clouds Above Orographic Feeder Clouds
Orographic Feeder Clouds Cap High Country
UVA-Wise Weather Research Webcam

July 23, 2019 at 8:30 PM
Cool, Much Drier Air Mass In Northerly Flow
UVA-Wise Weather Research Webcam

July 24, 2019 at 1:16 PM
Fair Weather Cumulus Decorate Pleasant Air
UVA-Wise Weather Research Webcam

Drier air allowed morning temperatures to drop into the 40s in typically colder mountain valleys of the High Knob Massif.

July 25, 2019 at 6:34 PM
Gorgeous Late July Air Mass In Mountains
UVA-Wise Weather Research Webcam

July 26, 2019 at 3:11 PM
Thicker Cumulus With Some Moisture Increase
UVA-Wise Weather Research Webcam

Moisture return aided the formation of afternoon sprinkles and brief showers during Saturday, July 27, a sign of things to come!

July 27, 2019 at 3:18 PM
Sprinkles-Brief Showers With Vertical Build
UVA-Wise Weather Research Webcam

Showers and local downpours centered in the 
High Knob area drop up to 0.50"+ of rainfall during Sunday afternoon (July 28).

July 28, 2019 at 4:46 PM
Localized Downpours Over High Country
UVA-Wise Weather Research Webcam

July 28, 2019 at 8:40 PM
Colorful Ending To The Weekend
UVA-Wise Weather Research Webcam

July 29, 2019 at 2:38 PM
More Local Downpours Over The High Terrain
UVA-Wise Weather Research Webcam

July 30, 2019 at 2:57 PM
Torrential Rain Producing Thunderstorms
UVA-Wise Weather Research Webcam

July 31, 2019 at 3:01 PM
Torrential Rains Fall Over High Country
UVA-Wise Weather Research Webcam

Torrential rains impacted the City of Norton and Town of Wise on afternoon hours of July 30-31.

July 31, 2019 at 5:05 PM
Jagged Outflow Boundary Clouds On Edge Of R+
UVA-Wise Weather Research Webcam

Two day rainfall totals of 3.00" to 4.00" fell upon the High Knob Lake area of the High Knob Massif, with repeated downpours.

Doppler Composite 48-Hour Rainfall Totals

August 1, 2019 at 8:40 PM
Cumulonimbus Towers Illuminated At Sunset
UVA-Wise Weather Research Webcam

More than 1.00" of rain fell upon Big Cherry Lake basin atop the High Knob high country, beneath towering cumulonimbus visible through the lower-level cloud opening below, to keep the wetness of Summer 2019 rolling onward.

August 2, 2019 at 1:36 PM
Rain Cooled Outflow From Nearby Storms
Cumulonimbus Towers Above Big Cherry Basin
UVA-Wise Weather Research Webcam

A stack of lenticularis clouds developed during 
late afternoon on August 2, as easterly air flow streamed into the High Knob Massif which, standing as a physical barrier, forced the air to 
rise and fall on its leeside in a wave-like pattern.

August 2, 2019 at 5:31 PM
Stacked Lenticular Clouds Above Massif
UVA-Wise Weather Research Webcam

Note at least six layers which were visible at this time, inside the black box, before being sheared and disrupted with continued propagation.

August 2, 2019 at 5:31 PM
Stacked Lenticular Clouds Above Massif
UVA-Wise Weather Research Webcam

August 2, 2019 at 5:36 PM
Lenticular Clouds And Other Orographic Forms
UVA-Wise Weather Research Webcam

This was part of a rather wild period that found 
the stacked lenticular cloud mass take on a more circular, flying saucer-like shape (a portion of which is obscured in the image below).

August 2, 2019 at 5:40 PM
Rounded Saucer-shaped Lenticulars And More
UVA-Wise Weather Research Webcam

August 2, 2019 at 5:40 PM
Rounded Saucer-shaped Lenticulars And More
UVA-Wise Weather Research Webcam

This was attached to a larger mass, with a low hanging base (only partially visible at top right 
of above image) that also contained lenticular and circular forms.

August 2, 2019 at 6:30 PM
Additional Standing Wave Clouds Develop
UVA-Wise Weather Research Webcam