December 16th, 2008
Wind advisory, Sunday Dec 14, 2008
The National Weather Service will issue a wind advisory for sustained winds 31 to 39 mph for at least 1 hour or any gusts 46 to 57 mph. However, winds of this magnitude occurring over an area that frequently experiences such winds would not require the issuance a wind advisory.
Lexington recorded sustained winds of 39 mph with gusts around 45 mph. This created difficult walking conditions at times around downtown. Wind speeds can be faster in isolated parts of the built environment because of turbulence. Though cities typically decrease average wind speeds near ground level, during periods of high wind speed tall buildings interrupt flow causing them to ‘pile up’ on windward sides and then rush off with increased velocity in channels between buildings. Wind eddies on the leeward side of buildings will also have strong gusts.
A comparison to a simple stream might be helpful. Water flows fastest in the stream’s center. An obstruction blocking the stream will divert the flow into two channels, each with increased velocity. Unlike water though, air can be highly compressed. When air piles up on the windward or upstream side, it will move in a more dynamic manner around the obstruction. Turbulence.
The mechanics of how all this plays out is beyond my understanding, but it is sufficient to say that when a wind advisory is issued for Lexington, we can experience strong and erratic winds downtown. I noticed many flocks of pigeons remaining on their protective perch, and no soaring hawks or vultures, so that’s probably a good gauge of strong turbulence.
The last time the area was under a wind advisory was during the passing of the remnants of Hurricane Ike. I think winds gusted to near-hurricane strength. Winds this weekend are associated with a strong low that passed to our north. This low pressure system created blizzard conditions and wind chill warnings across the northern states. The system also brought the cold punch of air that created our first major winter storm a day later.
The chart below is from the Beaufort Scale of wind speed. So next time you’re wondering, “What’s that wind speed?” here’s your chart.
| Description |
Speed |
Visual Clues and Damage Effects |
| Calm |
Calm |
Calm wind. Smoke rises vertically with little if any drift. |
| Light Air |
1 to 3 mph |
Direction of wind shown by smoke drift, not by wind vanes. Little if any movement with flags. Wind barely moves tree leaves. |
| Light Breeze |
4 to 7 mph |
Wind felt on face. Leaves rustle and small twigs move. Ordinary wind vanes move. |
| Gentle Breeze |
8 to 12 mph |
Leaves and small twigs in constant motion. Wind blows up dry leaves from the ground. Flags are extended out. |
| Moderate Breeze |
13 to 18 mph |
Wind moves small branches. Wind raises dust and loose paper from the ground and drives them along. |
| Fresh Breeze |
19 to 24 mph |
Large branches and small trees in leaf begin to sway. Crested wavelets form on inland lakes and large rivers. |
| Strong Breeze |
25 to 31 mph |
Large branches in continuous motion. Whistling sounds heard in overhead or nearby power and telephone lines. Umbrellas used with difficulty. |
| Near Gale |
32 to 38 mph |
Whole trees in motion. Inconvenience felt when walking against the wind. |
| Gale |
39 to 46 mph |
Wind breaks twigs and small branches. Wind generally impedes walking. |
| Strong Gale |
47 to 54 mph |
Structural damage occurs, such as chimney covers, roofing tiles blown off, and television antennas damaged. Ground is littered with many small twigs and broken branches. |
| Whole Gale |
55 to 63 mph |
Considerable structural damage occurs, especially on roofs. Small trees may be blown over and uprooted. |
| Storm Force |
64 to 75 mph |
Widespread damage occurs. Larger trees blown over and uprooted. |
| Hurricane Force |
over 75 mph |
Severe and extensive damage. Roofs can be peeled off. Windows broken. Trees uprooted. RVs and small mobile homes overturned. Moving automobiles can be pushed off the roadways. |
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December 7th, 2008
We had a widespread snowfall this weekend in the Bluegrass. While we only had an 1″ or less over the central and northern Daniel Boone country, all we need to do is put a chain of great lakes to our immediate northwest if we wanted some truly deep snow.
Enlarge this map and look at dramatically different weather around the Great Lakes today.
One of the most obvious and striking winter weather conditions is the atmospheric influence of the Great Lakes. When high pressure builds to the west of the Great Lakes and there’s a prominent northwest-to-southeast surface wind flow, weather is significantly different downwind of the lake compared to upwind. This often produces lake effect snow that can truly bury southeastern shore cities. However, the same influence can reach far south into Kentucky and the Appalachians.
The difference in weather can be outstanding, as people who live near the lakes know very well. Observe weather on both sides of Lake Michigan. The red number indicates the temperature in °F and the circle indicates cloud cover. A solid circle is completely cloudy, and an empty circle represents clear skies. The barb indicates wind speed and direction (see below for legend).
Compare Lake Michigan’s west shore with its east shore. The west shore of Lake Michigan is cold, below zero, and cloudless. Weather on the east shore of Lake Michigan is 20°F warmer, it is cloudier, and snow is falling, as represented by the green asterisks.
The cause of these conditions is simply the great reservoir of heat that the lakes contain and transfer to the atmosphere through evaporation. Though the lakes are slowly cooling through winter, they are significantly above freezing across a large area. When a colder, dry air mass blows over the lakes, evaporation will transfer heat and moisture into the air mass. As the rising, warmer air cools, if often condenses resulting in cloudiness and heavy snow; the lake effect snow machine. Also note the how far south the warmer air has penetrated compared to other locations at the same latitude.
For example this station here: 
is reporting that the current temperature is 55 degrees F, the sky is clear, and the winds are blowing from the north at 18 miles per hour.
And this station 
is reporting completely overcast conditons, winds from the north at 24 miles per hour and the temperature is 58 degrees F.
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October 11th, 2008
A sundog is a bright spot to the left or right of the sun (usually occurs in pairs) that typically happens around sunset or sunrise in high cirrus clouds.
This sundog occurred Friday night over Lexington and there is a companion sundog to the left, but it is out of the frame. The bright spot to the far right is a reflection off our “Big Blue” building.
Sundogs form when a couple unique conditions are present. Cirrus clouds are the atmosphere’s highest clouds and are composed of small ice crystals. These ice crystals are were the sun creates the show.
When the sun is close to the horizon and there’s a significant layer of cirrus clouds, which should be noted are curving towards the horizon, sunlight will do 3 things: 1) be reflected at a predictable location causing the bright spot, 2) refracted at the same spot causing a rainbow, and 3) scattered throughout giving the sundog a general reddish cast.
While not rare, sundogs are uncommon and have been heralded as both good and bad omens by ancient peoples.
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October 9th, 2008
Fog below Purchase Knob on the morning of October 9, 2008
As the heat radiates way from the mountains overnight, the resulting cool air spills into the valleys and condenses water vapor close to the ground. Note the flat top to the fog, which indicates a temperature inversion above the fog. This valley fog or radiation fog, which is common this time of year through winter, will eventually “burn off” from the bottom up as the sun heats the ground in the valley. That’s if the sun makes an appearance or perhaps it will warm up sufficiently today to evaporate the fog.
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October 3rd, 2008
October 3, 2008
Hike Pine Mountain, Channel Daniel Boone
By DAN WHITE, New York Times
Excerpt: “THIS is all virgin trail,” said Shad Baker, a connoisseur of hiking in the steeply slanted backwoods of eastern Kentucky, as he dropped me off at the start of my adventure there on the new Pine Mountain Trail. “This is probably the most remote place you can get that exists out here. You are five miles even from the nearest house.”
We said goodbye. He drove off. And then I slipped into woods so thick they looked like an American jungle.
It was only a year or two ago that the high-ridge forests of Pine Mountain, at the western edge of the Appalachians, were for all practical purposes sealed off by their own forbidding density and ruggedness — impenetrable to everyone but ginseng harvesters and squirrel hunters. This is Daniel Boone country, and as I set out that morning it was easy to imagine Boone hacking his way through it with a homemade hatchet and a long flintlock firearm. But I had markers to follow — squares of pale-yellow painted on trees at eye level…”
Read full article at New York Times:
http://travel.nytimes.com/2008/10/03/travel/escapes/03pine.html
Pine Mountain Trail Map
Difficulty: ++++
Scenic Views: +++
Elevation Relief: 2,100ft ^^^
Ownership: Private, Kentucky SP, Jefferson NF
Google to Elkhorn City trailhead
photos by Boyd Shearer
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