The weather thread

What's black ice.

Quote :

a thin coating of ice (as from freezing mist) on a road or sidewalk; nearly invisible but very hazardous
wordnet.princeton.edu/perl/webwn

Happens after rain or freezing mist as above and is particularly hazardous because it's not white like visible dry frost.

I spent two winters in New England, so I'm not too surprised at the temperatures there.

It can be spectacular. For example, one winter evening I was driving through orchard country in Connecticut. Clear sky, setting sun. It had snowed a lot, but the midday sun had melted the snow on the tree branches. Now it had frozen over, and the landscape was a sea of glass trees, with the sun glistening through them. An awesome sight.

Meanwhile, in Europe... Here's a pic I took last Saturday. That's a 2200-year-old Egyptian temple, really!



Another view:



(Explanation: 1960s. Aswan Dam. Rising waters. Spanish archaeologists. Egyptian government's gift. Disassemble. Ship. Madrid. Assemble.)

Hey, we got past 40 pages !!

EvotingMachine0197 wrote:

Hey, we got past 40 pages !!

(so far ... )

Hell of a storm here. The rain is raining upwards.

It's just calmed down here in Cork but an hour ago it was like being in a washing machine and tumble-dryer at once. Still quite blowy but not as mad...

I spent most of the storm driving across bogs, terrified I was going to blow into a drain and never be seen again. Trees down, roofs off houses, billboards blown over, blocking motorway slipways according to the local news. It was, without exception, the most terrifying driving experience of my life. Still wet and blowy here but at normal levels. I believe snow and ice are forecast for next week.

Luvly.

Today's tephigram from Valentia at 12pm:



Truly baffling but looks great. Explanations (sort of) here: http://www.met.ie/latest/valentia.asp

toxic avenger wrote:

Today's tephigram from Valentia at 12pm:



Truly baffling but looks great. Explanations (sort of) here: http://www.met.ie/latest/valentia.asp

This is part of why I like MN! I remember isobars, of course, from school but had never heard of adiabats, whether dryed or saturated! Now I really want to know more.
My own posts are meaningless crap, but I do hope to learn a bit from the rest of you.

Snowing here, with that peculiar sunlight that comes with real grey skies.

We had a sprinkling of snow too - tried to go for a walk with the dog but the roads were covered with a sheen of ice like glass: in the attempt at dodging the showers later, got caught in a freezing deluge. Sunny again now of course.

Won't snow here - never does. My Granny had a sprinkling up the Dublin mountains at her place this morning though.

The Valentia tephigram (I love that word) above seems to be updating itself... Is it front-page material, or is it just for weird met-freaks like me who love the fact that it exists, despite having trouble getting my head around it?...

toxic avenger wrote:

The Valentia tephigram (I love that word) above seems to be updating itself... Is it front-page material, or is it just for weird met-freaks like me who love the fact that it exists, despite having trouble getting my head around it?...

have you figured out what the two blue lines show (dotted and solid). I know it;s something to do with various "processes", like change in temperature etc going on as the pressure changes with altitude (measured by sending up the weather balloon.)

RTE or someone should do an in-depth weather programme going from the very basics of how weather happens, up to how to read a tephigram.

ps- do you have the Cloud Spotter's Guide by that guy from the Cloud appreciation Society!?

yehbut_nobut wrote:

toxic avenger wrote:

The Valentia tephigram (I love that word) above seems to be updating itself... Is it front-page material, or is it just for weird met-freaks like me who love the fact that it exists, despite having trouble getting my head around it?...

have you figured out what the two blue lines show (dotted and solid). I know it;s something to do with various "processes", like change in temperature etc going on as the pressure changes with altitude (measured by sending up the weather balloon.)

RTE or someone should do an in-depth weather programme going from the very basics of how weather happens, up to how to read a tephigram.

ps- do you have the Cloud Spotter's Guide by that guy from the Cloud appreciation Society!?

This from the Met Eireann link above:

Quote :

On the tephigram there are two kinds of information represented:

The environment curves (blue) which describes the structure of
the atmosphere
The process curves (red) which describes what happens to
a parcel of air undergoing a particular type of process.
(eg. Adiabatic
process).

In addition, the right hand panel displays height, wind direction, speed
and a selection of pressure levels.

Tephigrams can be used by the forecaster for the following purposes:

- to determine moisture levels in the atmosphere
- cloud heights
- to predict levels of convective activity in the atmosphere
- forecast maximum and minimum temperatures
- forecast fog formation and fog clearance

Beyond that I am at a loss...

Regarding the Cloud Appreciation stuff, I'm sad, but not a maniac....

It's an interesting looking yoke alright - baffling in its complexity but we'll figure it out

IBIS

Here's some quote from the Valentia page again

Quote :

A tephigram is a graphical representation of observations of pressure, temperature and humidity made in a vertical sounding of the atmosphere. Vertical soundings are made using an instrument called a radiosonde, which contains pressure, temperature and humidity sensors and which is launched into the atmosphere attached to a balloon.

The tephigram contains a set of fundamental lines which are used to describe various processes in the atmosphere. These lines include:

Isobars - lines of constant pressure
Isotherms - lines of constant temperature
Dry adiabats - related to dry adiabatic processes (potential temperature constant)
Saturated adiabats - which are related to saturated adiabatic processes (wet bulb potential temperature constant).

Cool. A big atmospheric sensor - pity it doesn't collect CO2 too.

I took a picture of it because any image we post here will change so we can notice some differences if there is a screen print. I might try to do this a bit more often now.

Because it changes it can go on the front page indeed and is to be found in Machine Nation panel, bottom right-hand corner. An excellent addition to the Weather Thread and site Toxic, thank you .

Static image:

Tá failte romhat, Audi. A description from Wiki:

Quote :

A tephigram is one of four thermodynamic diagrams commonly used in weather analysis and forecasting. The name evolved from the original name "T-φ-gram" to describe the axes of temperature (T) and entropy (φ) used to create the plot. Usually, temperature and dew point data from radiosondes are plotted on these diagrams to allow calculations of convective stability or convective available potential energy (CAPE). Wind barbs are often plotted at the side of a tephigram to indicate the winds at different heights.
The tephigram was invented by Napier Shaw in 1915 and is used primarily in the United Kingdom and Canada.
Other countries use similar thermodynamic diagrams for the same purpose
however the details of their construction vary. In the tephigram, isotherms are straight and have a 45 degree inclination to the right while isobars are horizontal and have a slight curve. Dry adiabats
are also straight and have a 45 degree inclination to the left while
moist adiabats are curved. The principal reason that tephigrams are
used by the British Met Office
is the property that areas contained by the curves have equal energies
for equal areas, leading to better comparisons of CAPE and hence
convective systems.

They have a good illustrated example of one there too.
http://en.wikipedia.org/wiki/Tephigram

Is there any flucking chance that the 3 wise men of Ibis, A-T and Papal Kmight would come and both dig me out and thaw me out.

How the Hell I survived this global warming is beyond me. My 2 central heaters are after falling off me with the cowald.

youngdan wrote:

Is there any flucking chance that the 3 wise men of Ibis, A-T and Papal Kmight would come and both dig me out and thaw me out.

How the Hell I survived this global warming is beyond me. My 2 central heaters are after falling off me with the cowald.

Did you go into hibernation youndan? The three lads went out on a search party for you last night and haven't been seen since.

I knew when it came to the crunch that they would not let me down.

Especially Papal. Here was I thinking he would be fantasising about Obama, but instead he braves Artic conditions to save me.

Why I feel like a cuddly polar bear

Perhaps he got diverted just a little bit to the inauguration...

I will make it my life's work to figure out what the hell is going on in those tephigrams. Whether my life will be long enough, well....

toxic avenger wrote:

I will make it my life's work to figure out what the hell is going on in those tephigrams. Whether my life will be long enough, well....

It's a fascinating little map of something alright that I wouldn't mind figuring out myself. Do the spaces between the red lines change too? That's the first thing I'm looking to notice after the blue line changing which means what, I haven't a clue. If the spaces between the red lines from map to map don't change then I'll be baffled for a while yet.

I bet Jean Byrne could just take one look at that and forecast weather for later that day.

Ah, Jean Byrne