http://www.skybrary.aero/index.php/Mountain_Waves
Definition
Mountain Waves is defined as oscillations to the lee side (downwind) of a
mountain caused by the disturbance in the horizontal air flow caused by the
high ground.
Description
The wavelength and amplitude of the oscillations depends on many
factors including the height of the high ground above the surrounding terrain,
the wind speed, and the instability of the atmosphere.
Formation of mountain waves can occur in the following conditions:
§ Wind direction within 30 degrees of the
perpendicular to the ridge of high ground and no change in direction with
height.
§ Wind speeds at the crest of the ridge in excess
of 15
kts, increasing with
height.
§ Stable air above the crest of the ridge with
less stable air above and below that stable layer.
Vertical currents within the oscillations can reach 2,000 ft/min. The combination of these strong vertical
currents and surface friction may cause rotors[1] to form beneath the mountain waves causing
severe turbulence.
Cassi Creek: the National Weather Service has posted a high
wind advisory for tonight and tomorrow morning.
Higher elevations may clock 30-40 sustained winds with gusts exceeding 60mph. While the foothills may not log sustained
winds at those velocities, the formation of mountain waves is possible causing
wind damage at lower levels by rotor-driven winds. The graphic above shows the mechanism for
rotor formation.
The
atmospheric conditions are conducive to thunderstorm formation in the Ohio and
Tennessee drainages. There is a strong
winter storm bringing heavy snow and winds to the plains states. The northern Appalachians may get snow while
the southern Appalachians get more rain, possible thunderstorms, and possible
severe storms.
We’ve had
enough rain this month that the wet snow combined with wind might cause a lot
of wind damage to trees, power and commo lines, and property.
The inclement
weather is going to be particularly annoying tonight. I have a weather station fixed to the back
deck that captures local conditions every 5 minutes for local logging, and
every 15 minutes to upload to a nationa database. The program I upload to, Weather Underground’s
Wundermap has been as very reliable and very user-friendly program for many
years. It provides me with almost real
time graphic reports from other local weather stations plus five minute loops
of local and national radar for my purposes.
For some
unknown reason, without warning subscribers, Weather Underground uploaded and
installed a new revision of Wundermap.
The timely access to local data and conditions is now unavailable. The program is ext to useless compared to its
previous incarnation. I’ve made my
displeasure known. I think that I may
join the search for a better program to link with.
The potential
for severe weather tonight and tomorrow has Gloria and I battening down what we
can.
We plan on going
into town sometime during the coming week for dinner at a Thai restaurant. Like many couples, we have a set of customs
and quirks that are tradition for us. We
celebrate this period in December, as it is when we first met. The initial meeting is, to our collective
mind, very worthy of celebration. To
that time, I had never seen such a blinding smile as the one that graced her face
and lit up the airport terminal. I see
it frequently now. Mornings and evenings
are welcome events.
I think the
winter project may be to encourage her to become familiar with the air rifle,
then with the .22 lever action Henry.
The firing lane is clear and we have the time to practice together. I need to put in some practice time as
well. My atypical PD makes my ability to
hold on target more difficult than ever before.
Yesterday we
received a photograph of Olivia and Helena, Gloria’s nephew, David’s
daughters. I’ve only seen the girls via
Skype. It is a great photograph and
Gloria is thrilled to have it. It was
kind of David and Daisy to take the
trouble to frame it and send it.
The NRA has
begun their propaganda campaign. Their
first official spin mentioned prayer, grief, mourning, tragedy, working to
prevent such events in the future. Today’s
Oliphant cartoon is more accurate a depiction of what I think is actually
taking place in the corporate NRA offices.
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