Tuesday, June 26, 2012

Summer 2012 - From Chilly To Extended HEAT


June 23, 2012
Upper Tennessee River Basin
Spangled Skimmer Dragonfly ( Libellula cyanea )
Photograph by Richard Kretz - © All Rights Reserved.

Like a suped up Jet Fighter readied for take-off in a flash, this male Dragonfly is the real deal when it comes to SPEED and is a very important natural predator 
( feeding on mosquitoes, flies, ants and other insects ).


On a summer night with temperatures already deeply into the 40s amid mountain valleys it is almost hard to believe that blazing heat will spread east from the central USA into the Appalachian Highlands in just a few days ( by June 28-30+ ).

MAX temperatures only reached the mid-upper 60s in higher elevations of the High Knob Massif during June 26, with a rapid evening plunge into the 40s amid lofty mountain valleys.

( Updated: AM of June 27, 2012 )
Morning minimums reached upper 30s to lower 40s in colder mountain valleys to make talk of an upcoming wave of extended heat only thoughts on this chilly summer morn!

Such cold temperatures are characteristic of summer dryness, with drought years sometimes generating frost in high mountain valleys.  Case in point, 1988 when frosty conditions occurred in coldest locations during both June and July!

While summer dryness promotes HEAT it also supports atypically large day to night temperature spreads which occasionally can generate such nocturnal coldness, especially in high valleys resting amid the 2400 to 3600 foot elevation zone.

June 23, 2012
Female of The Species
Spangled Skimmer Dragonfly ( Libellula cyanea )
Photograph by Richard Kretz - © All Rights Reserved.

Climatology shows that its hard to get REALLY HOT in mid-upper elevations ( above 2000 feet ) of the area unless there is DRY ground and strongly sinking air to kill all cloud formations and development of showers and downpours in booming thunderstorms.


MAX Annual Temperatures
Wise 3 E and Wise 1 SE
*( MAX Temp & Date of Occurrence )

Wise 3 E NWS Cooperative
Elevation 2549 feet

86  7-28-2011
90  7-25-2010
85  8-10-2009
87  7-21-2008
92  8-24-2007
88  8-02-2006
88  7-25-2005
88  8-04-2004
88  8-26-2003
89  8-03-2002
86  7-24-2001
87  8-07-2000
91  7-31-1999
90  9-14-1998
89  8-16-1997
90  5-19-1996
93  7-15-1995
92  6-19-1994
90  9-01-1993


Wise 1 SE NWS Cooperative
Elevation 2560 feet

87  7-13-1992
86  9-16-1991
89  9-07-1990
86  7-11-1989
94  8-18-1988
91  8-22-1987
88  6-22-1986
88  6-10-1985
86  6-15-1984
92  8-22-1983
85  8-05-1982
87  7-27-1981
92  7-16-1980
87  8-08-1979
89  6-27-1978
89  7-17-1977
89  7-24-1976
89  9-05-1975
85  7-18-1974
88  9-02-1973
86  7-23-1972
86  8-10-1971
87  7-29-1970
88  7-06-1969
89  8-22-1968
85  6-18-1967
92  7-14-1966
89  8-18-1965
88  6-22-1964
90  8-03-1963
88  8-21-1962
86  7-21-1961
86  9-06-1960
88  8-24-1959
86  7-28-1958
89  8-13-1957
88  8-06-1956
91  8-04-1955

Average Annual MAX: 88.4 degrees
( 57 years from 1955 to 2011 )

*While some years may have had more than 1 day at the reported MAX, these were the highest temperatures observed during each year ( missing data was noted during 1984 and 1986 ).
All temperatures in degrees Fahrenheit.

Data courtesy of Roy L. Wells, Jr., NWS Cooperative Observer, and the National Climatic Data Center.


A review of the past 57 years finds that only 15 years, or 26 percent, reached 90 degrees or higher at the official National Weather Service ( NWS ) Cooperative Stations in the town of Wise.

The longest stretch with no 90 degree readings was observed from 1967-1979 when 13 years passed with no temperatures above 85 to 89 degrees.

The longest recent stretch without 90 degree temperatures in Wise was the 7 year period from 2000 to 2006 ( max 89 degrees on August 3, 2002 ).

Annual maximums have occurred as early in the year as May 19 and as late as September 16.

Higher elevations in the High Knob Massif, and along the Tennessee Valley Divide, have lower annual maximums than Wise ( especially above 3000 feet and along northern exposed slopes ).

Some northern slope locations between 2000 and 3000 feet in the High Knob Massif also tend to have lower maximums than Wise due to exposure and more daytime cloudiness & rainfall.

A survey finds that the average annual max on Eagle Knob of the High Knob Massif was 9 degrees lower than observed in Wise, with the highest temperature recorded during the past 11 years 
( 2001-2011 ) being 82 degrees ( at 4178 feet ).


Short-Term Precipitation

Rainfall during the May-June period leading up to this wave of extended heating has generally been below to much below average across the region, with May 1-June 27 totals varying from 3.27" in the Tri-Cities ( TRI ) of the Great Valley to 8.00-10.00"+ amid localized places along the High Knob Massif and highlands of the Tennessee Valley Divide 
( 8.50" to 9.00" in the Big Cherry Basin ).

Most Recent Days of Rainfall

Doppler Estimated Rainfall For June 20, 2012

Doppler Estimated Rainfall For June 21-22, 2012

Heavy rains have recently been only hit-miss in nature following the atypical orographic forcing event that closed May and opened June.

Reference the following for details:

Black-Shoulder Spinyleg ( Dromogomphus spinosus )
Photograph by Richard Kretz - © All Rights Reserved.

Summer 2012 is yet to prove if it can sustain this short-term dryness since a dry June does not necessarily mean a dry summer ( with a general 30.00" to 35.00" of total precipitation having accumulated so far this year in rain gauges of the High Knob Massif - City of Norton area ).

Other locations in the region have been much drier 
this year, with January 1 to June 27 totals of 21.01" in Clintwood of the Russell Fork Basin, 17.99" in the Tri-Cities ( TRI ) of northeastern Tennessee, and just 15.96" along the Ohio River in Huntington, West Virginia.

Compared to recent summers this one is beginning dry in many places with nocturnal coolness and a upcoming HEAT surge that is reminiscent of drought years in 1988 and 2007.


Reference the following for a recap of recent summers:





Calico Pennant Dragonfly ( Celithemis elisa )
Photograph by Richard Kretz - © All Rights Reserved.


Near Perfect Day
of Surface Heating

Daylight hours of June 28 had near perfect heating conditions with not even a single cloud visible all day across the famed southern Appalachians.

Even the highest summits could not muster a cumulus, with only a few fragments on NASA imagery along and north of the Ohio River and isolated over Kentucky and Tennessee.

A warm layer aloft, known as a CAP in meteorology, combined with strongly SINKING air and a dry air mass to prevent clouds from forming despite some low-level upsloping on breezy to gusty SSW-NW winds across the southern Appalachians ( 10-20 mph gusts ).

NASA Visible Image At 10:01 AM - June 28, 2012

NASA Visible Image At 12:15 PM - June 28, 2012

NASA Visible Image At 1:15 PM - June 28, 2012

NASA Visible Image At 2:15 PM - June 28, 2012

NASA Visible Image At 3:45 PM - June 28, 2012

Not many days like June 28 are observed, when intense heating combined with mountainous terrain produces no clouds ( NADA ), none at all, even above the highest peaks!

That such days are rare is one reason why 90+ degree maximums are relatively uncommon at elevations like Wise which benefit from clouds, as well as summer convection or cooling outflows from nearby storms, which typically form above the High Knob Massif and Tennessee Valley Divide during days with intense heating. 

General wetness of the High Knob Massif area having 
a large impact upon much of Wise, northern Scott, northeastern Lee, Dickenson, and Russell counties during typical summers when the massif becomes a focus of cloud formation and convection which develops outward to impact adjacent locations in the Clinch, Powell, and Russell Fork basins.

Occasionally, as seen on days like this during periods of abnormal dryness or drought, sinking air aloft overwhelms these more typical low-level impacts of the massif area.

Local and regional feedback processes complicating the pattern of warm season rains.

Reference the following to gain a better understanding of these important warm season processes that impact summer precipitation amounts in the High Knob Massif area:

( Examples From The 2010 Summer Season )


Eastern Pondhawk Dragonfly ( Erythemis simplicicollis )
Photograph by Richard Kretz - © All Rights Reserved.


The ALL-TIME
Hottest Temperatures
June 29, 2012

For the second consecutive day temperatures soared beneath cloud free skies and strongly sinking air across most of the Mountain Empire, with blazing afternoon temperatures that are making history by breaking ALL-TIME records! 

June 29, 2012
High Resolution NASA Visible At 4:15 PM

With Debby moving away on far right a new focus of concern was exploding over the Midwest, near upper left of image, with a Mesoscale Convective System ( MCS ) gaining strength and speed in extreme heat and instability.  Sinking air flowing outward from upper levels of these monsters, with clouds tops to 58,000 feet ( 11 vertical miles into the heavens ), was no doubt enhancing local heating via compensating subsidence. 

When air rises in the atmosphere it must be compensated for by sinking, or subsidence, such that large thunderstorm clusters and tropical cyclones can add to sinking beneath heat ridges to make conditions hotter than they would otherwise get without them being present ( temps rise when air sinks vertically ).

June 29, 2012
High Resolution NASA Visible At 4:15 PM

The big picture showing convective clusters forming around a blazing heat dome in a developing "ring of fire."

June 29, 2012
High Resolution NASA Visible At 5:32 PM

Perhaps the greatest testimony to this vertical sinking was simply extraordinary heating which occurred in mid to upper elevations of the southern Appalachians where Summer MAXS are typically much cooler than lower elevations ( below 2000 feet ).

A few specific maximums by 
elevation for June 29-30, 2012

Mount LeConte 
82 degrees at 6400 feet
( an upper North Slope weather station )

Newfound Gap 
92 degrees at 5000 feet

Grayson Highlands State Park 
89 degrees at 4000 feet

Robinson Knob of High Knob Massif
92 degrees at 3240 feet

Long Ridge of Sandy Ridge
97 degrees at 2650 feet

*Wise 3 E
95 degrees at 2549 feet

*Highest temperature ever observed ( 1955-Present ).


Dangerous Weather Pattern
Extreme Heat + Derechos

Weather extremes are always problematic and in this case numerous aspects are developing due to what has turned into exceptional, record breaking heat that produced the highest temperatures ever observed in much of the area during June 29 with  85 to 90 degrees up to near the 4000 foot level from the High Knob Massif to Mount Rogers-Whitetop.  As noted above, simply amazing!

The first of what likely will be numerous thunderstorm clusters fired over the upper Midwest along the periphery of this huge dome of excessive heat, beneath which the ground is baking and nary a drop of rain or even significant cumulus clouds can be found.

The June 29 storm cluster, known as a Mesoscale Convective System ( MCS ) turned into a Derecho as it fed upon extreme thermodynamic instability the likes of which is rarely ever seen in this region as illustrated by a couple of graphics below.



Lifted Index Graphic For 2:00 PM - June 29, 2012

Most Unstable CAPE For 2:00 PM - June 29, 2012

For anyone knowing a little about weather these two graphics are simply incredible, with LI's to under -14 and MUCAPE values of more than 6000 J/Kg centered ahead of the developing derecho. 

Although southeastern Kentucky, much of southwestern Virginia and extreme northern Tennessee only got brushed by the derecho it generated a significant outflow boundary that gushed across the mountain landscape with 
40-60+ mile per hour winds.

More than 4.3 Million places, from Illinois to the Atlantic Coast, lost electricity during the peak of this event ( hundreds of thousands remain out as of July 4 ).  At least 26 fatalities have been reported.

RLX Doppler Clip of June 29, 2012 Derecho


Time Series of Derecho 
Outflow Boundary
( Early Evening of June 29, 2012 )

Click On Images Consecutively To Put Into Motion

Doppler Base Reflectivity At 7:30 PM - June 29, 2012
 

Doppler Base Reflectivity At 7:34 PM - June 29, 2012

Doppler Base Reflectivity At 7:47 PM - June 29, 2012

Doppler Base Reflectivity At 8:00 PM - June 29, 2012

Doppler Base Reflectivity At 8:12 PM - June 29, 2012

Doppler Base Reflectivity At 8:30 PM - June 29, 2012

Doppler Base Reflectivity At 8:47 PM - June 29, 2012

Doppler Base Reflectivity At 9:00 PM - June 29, 2012

The GREEN LINE above denotes the outflow boundary of this vicious derecho with its gush of ROARING winds.  If the atmosphere in this area had not been so strongly CAPPED and dominated by subsidence aloft it would have generated a HUGE squall line analogous to that which ripped across Ohio and West Virginia where the cap broke.

The thinning and apparent dissipation of the green line above upon crossing into the Virginia mountains being products of its interaction with the higher terrain and the increased overshooting of it by the Doppler with increasing distance from the Jackson, Kentucky radar site ( i.e., the gust front remained stronger for longer than suggested by this time series but was impacted by rugged terrain in the Virginia-Kentucky border area ).


Climate Statistics
For June 2012

June 25, 2012
Pound Gap of Pine Mountain
Starry June Night Above The Cumberlands
Photograph by Roddy Addington - © All Rights Reserved.


( Lower elevations of Russell Fork Basin )
Clintwood 1 W - Elevation 1560 feet
Average Daily MAX: 80.4 degrees
Average Daily MIN: 52.4 degrees
MEAN: 66.4 degrees
*Highest Temperature: 97 degrees
Lowest Temperature: 45 degrees
June Rainfall: 1.83"
2012 Precipitation: 21.01"

( Northern base of High Knob Massif )
City of Norton - Elevation 2141 feet
Average Daily MAX: 79.2 degrees
Average Daily MIN: 50.4 degrees
MEAN: 64.8 degrees
*Highest Temperature: 97 degrees
Lowest Temperature: 43 degrees
June Rainfall: 2.79"
2012 Precipitation: 30.05"

( North of Massif on Wise Plateau )
Wise 3 E - Elevation 2549 feet
Average Daily MAX: 78.6 degrees
Average Daily MIN: 56.2 degrees
MEAN: 67.4 degrees
*Highest Temperature: 95 degrees
Lowest Temperature: 45 degrees
June Rainfall: 2.72"
2012 Precipitation: 22.67"

( Along the Tennessee Valley Divide )
Nora 4 SSE - Elevation 2650 feet
Average Daily MAX: 77.2 degrees
Average Daily MIN: 59.0 degrees
MEAN: 68.1 degrees
*Highest Temperature: 97 degrees
Lowest Temperature: 45 degrees
June Rainfall: 2.75"
2012 Precipitation: 23.14"

*All-Time highest temperature ever observed at recording site.

In the High Knob highcountry June temperature means varied from upper 60s to lower 70s by day at highest elevations to mid-upper 40s at night in colder mountain valleys.

June 2012 was a month of great temperature extremes with all-time record heat closing the month to generate a monthly variation of up to 60+ degrees within the massif area ( from upper 30s in colder valleys of mid-upper elevations to near 100 degrees in the hottest, lowest elevation valleys along the ecologically rich Clinch & Powell rivers during June 29-30 ).  Simply amazing!

June 25, 2012
Starry Night Vista Above Pound Gap
Photograph by Roddy Addington - © All Rights Reserved.

Dawn of the following morning ( June 26 ) produced 40s in cooler mountain valleys, with upper 30s-lower 40s in higher elevation valleys during morning hours of 
June 27, ahead of blazing heat.

June 25, 2012
On A Star Filled Late June Night
Geologic Layers of The Pound Gap
Photograph by Roddy Addington - © All Rights Reserved.

June rainfall was much below average with totals in the High Knob Massif generally varying between 3.00" and 4.00" from the Little Stone-Pickem Mountain flank across the highcountry into the Clinch River Valley of northern Scott County 
( e.g., the Big Stony Creek-Fort Blackmore area ).

Totals of between 2.00" and 3.00" were locally common outside the massif, with amounts of less than 2.00" in places like Clintwood ( 1.83" ) of the Russell Fork Basin and the Tri-Cities ( 1.20" ) of the Great Valley in northeastern Tennessee ( ** ).

**Regional extremes found only 0.37" of rainfall in London ( LOZ ) Kentucky during June, setting a new record for all-time June dryness ( record period November 11, 1954 to present ).

No comments:

Post a Comment