Aurora-Bell-radar-image

The Black Sea Breeze - as a trigger

2011-07-26T07:15:00.000-07:00

Visible channel (sat24.com) from EUMETSAT. The sea breeze acts like a lifting mechanism for convection initiation in Dobrudja. The general circulation in SE Romania is from South, and will produce propagation toward the South, and there is a strong low level flux of moisture from the sea to Moldova. Severe weather is expected in the Eastern half of Romania, several supercells.

Later: a supercell splits: on satellite (two red circles), and radar (zoom on the SE part of Romania). Is nice to observe the huge dimensions of the anvil.

A Mesovortex Over South of Romania

2011-07-25T23:19:00.000-07:00

High Resolution Visible. EUMETSAT, NMA

6 UTC formed over the precipitation pool last night.

Radar mosaic first tilt, under Google application, NMA.

A Bow Echo

2011-07-23T03:02:00.000-07:00

An early morning bow echo approaching the Bucharest area. Seen on Radar (with a zoom around Bucharest). visible sat chanel (from sat24.com) and RGB-airmass product (EUMETSAT,NMA).
The dry air behind the system (west of Bucharest), is the trigger of the bow, but the rear inflow jet is high, so instead of wind, a rain-pool can form with a flash-flood.

Heavy rain is expected.

An Innocent Outflow

2011-07-21T07:56:00.000-07:00

The arrow points a small convective cell that produces a significant outflow 30 minutes later. The cell doesn't contain rain, so the radar (OWT national mosaic) doesn't get it. This is an example on how subtle mesoscale features and sources of weather changes can be.

Undular Bores on radar and satellite

2011-07-20T03:59:00.000-07:00

Undular Bores leaving a strong convective system.
Easier to see on visible satellite because they are too shallow for the radar horizont.
We expect severe weather today in the Western and Southwestern Romania, heavy rainfall, wind gusts.

Radar, Nowcasting Course

2010-04-25T02:50:00.000-07:00

Here you can find details about some interesting courses in radar and nowcasting: www.erad2010.org/Course.htm

Deadline for application: 30 May 2010

ERAD2010 - participants

2010-01-30T22:29:00.000-08:00

The deadline for early registrations has come.
I wonder how much this event is impacting on my life. Well, I am addicted to it.

I look everyday, several times, at the list of people who registered. People I admire so much. I know their work, I know their passion. Some of them are my favourites, my models.

Some of them are new to me but "old" in the branch, I am so glad to discover them. Some of them are students. This edition is dedicated to them, to their courage to follow a scientist career in difficult times; and to women in radar science. If I could bring closer to 50-50 the percentage in gender participation, I could say I have accomplished one target.

I am going back now to contemplate again the list of great radar scientist people that will reach and enrich ERAD. I can not work too much these months for my own life, but I know that ERAD will bring something good to many people, and this is the most important reason to do things.

Black Sea El Ninho

2010-01-24T00:12:00.000-08:00

Strong temperature differences in the marine waters on the Western Basin of the Black Sea. Wind is from N, 13 km/h. Air Temperature at Constanta is -17C.

Satellite IR EUMETSAT image from sat24.com

ERAD 2010 - Merry Christmas !

2009-12-25T23:48:00.000-08:00

www.erad2010.org

Mesocyclonic Waterspout, Gloria platform, Black Sea

2009-08-19T00:24:00.000-07:00

High resolution - VIS, EUMETSAT

WSR98D

RealitateaTV

Waterspout over the Black Sea, 18 August 2009, produced by a splitting supercell, initated in a horizontal roll clouds PBL environmnet.

A non-mesocyclonic waterspout still requires a convective cloud.

from: actualite.lachainemeteo.com

Bow echo

2009-07-07T06:23:00.000-07:00

A reflectivity image with a bow echo, C band, and a sattelite image, visible low resolution, with the clear spot behind the bowecho where the rear inflow jet is, red arrow, and a lot of rolls in the southern part or Romania, nice to act as local enhancers.
Last evening Bucharest had a severe storm with 40 mm in less than one hour, the fears are if again the storms will be severe for Bucharest or not.

Birds on radar

2009-05-20T05:24:00.000-07:00

While satellite in visible (EUMETSAT) shows clear skies (top image), radar shows plenty of echoes from birds and insects after the Sun rise (bottom); no, it wasn't dust. The south-eastern radar of Romania, with big lakes and the Danube Delta, has a lot of "noise" during summer, but sometimes we can easily monitor low level circulations due to these tracers. Well, sometimes birds can mislead the forecaster !

Gust front

2009-05-12T15:00:00.000-07:00

The red arrow points toward an outflow from a convective cell. The thin line is the leading edge of the diverging outflow, it is called "gust front".

(visible channel, satellite images, 15 minutes apart - EUMETSAT- northern part of Moldova - Romania)

Cloud streets

2009-04-26T06:06:00.000-07:00

I am reading now some papers on horizontal convective roll clouds, street clouds and other similar shallow structures and how they can interact with other phenomena like the sea breeze.

The first image is about what an ignorant could think about a cloud street; the second image is what radar iamges show very often but people do not know what they are looking at (convective rolls) , the third one is a nice one from satellite Terra, with streets over the Black Sea, the last one is an airplane view of the street structure, maybe the closer to our sense of Nature. True. Meteorology is a lucky science where concepts get to a structure that can be "seen".

I struggle to find a language that can ease the process of learning, to avoid difficult math and to build concepts beyond equations. But... there are concepts that reveal only with hard work and math.

The two last days I have advanced only two pages in my reading and my conclusion is that many forecasters might have only "cartoons" and nice images in their minds... and do their jobs in the same way a gipsy "musicant" can play violin without ever seeing scores. In the same way, there are composers that never played a piece. But art and science have a different consequence of "amateurism". Art is gentle with amateurism and kitsch.

How deep do we want to go in our profession depends on how much we need a "profession" or we just want to remain "amateurs". Is the difference between a "profession" and a "job".

Of course, amateurs can be much better payed, jobs can have a role in society, but... the real advance of our society has been done through the long effort of people conceptualizing, working hard, creating new theories for days and years in a row.

There is a "natural" selection among professionals: the real ones remain for research at any price, the amateurs go for better "jobs".

I remember a cross moment in my life when I had to choose between arts and physics, and I understand now that arts wouldn't have been enough for me, that I am a better artist now, as an amateur artist, than the professional artist I would have been without my professional work in science.

Education in Radar Meteorology

2009-04-04T09:02:00.000-07:00

I am reading now a radar monography book, a collection of essays in honor of David Atlas. Leaving apart the joy of reading a book in nice format and good paper, it has some great overviews that really help understanding where we are in radar. My favourite is a paper on Some Educational Innovation in Radar Meteorology, by Steven Rutledge and V. Chandrasekar (I do not know why one is listed with the whole first name and the other only with initial, maybe because the very known name of the second author is simply, the great "Chandra").

Reading this paper a lot of ideas come into my mind to improve my training in radar. Is that kind of work that gives you real hints on what you can do, if you REALLY want to change something in good. "There is no replacement for direct experience when it comes to radar meteorological education" is one of the ... conclusions they start with after a survey among students. Of course there is a lot we can do via internet to simulate "hands on" experience.

I was thinking to bring a mobile radar during the pre-conference ERAD 2010 course in Sibiu, and organize few sessions of real experience.

I was thinking at the enthousiasm that is always coming out from the field work of radar people (in the image, Rita Roberts and Jim Wilson on high resolution refractivity (moisture) data), how they present their results "hot", just taken out from fresh fiels data, and how could I develop a serial sessions that could be held in different universities in Romania, a real radar on wheels from door to door.

Well, maybe if I buy a mobile radar for the met service and organize it, or if I buy my own radar and travel with it around... well, I do not drive, but I could arrange it with students that drive.
Well, look what a good paper can do !

www.erad2010.org

2009-03-31T08:16:00.000-07:00

Looking back at previous ERAD conferences, I found a very nice video with images from ERAD 2006 in Barcelona, here. Barcelona was celebrating a famous fiesta, la Merce, in that period so we had the chance to build a real ERAD castle. It was a very touching moment in ERAD's life, getting us closer, feeling we can build something together.

I will try to uopload it also on the http://www.erad2010.org/ site.

ERAD 2010, 6-10 September Sibiu, Romania

2009-02-17T21:52:00.000-08:00

The Romanian National Meteorological Administration will host the sixth European Conference on Radar in Meteorology and Hydrology, ERAD 2010.

The city will be Sibiu (Hermanstadt) in Transylvania, Romania. The dates are from 6 to 10 of September 2010, with a pre-course in radar.

The site is www.erad2010.org with a backup at www.erad.eu and we will provide soon more details.

Some information is also available at www.meteoromania.ro in Romanian and English.

Wave perturbation

2009-02-12T18:58:00.000-08:00

The last two images are a rough analysis of almost the same moment, seen on radar and satellite, as a sinoptician would do: a classical wave-like perturbation.

On top, in the first image, you can see my analysis, where I am more interested on the banded character of precipitation.

What is nice to observe is that strong echoes develop around the occlusion and in the warm air mass, and not around the cold front as we would be temped to think.

A tornado witness, in 1928's Romanian literature

2009-01-18T07:30:00.000-08:00

"Over Moldova, beyond the Bolandars hills, the sky was moving and bending as it was turning against the earth ; and a roar beyond measure, one never heard before, filled the valleys as it was getting near; and all those present, turning their faces and staring around saw the dragon coming in a spiralling whirlwind at a great speed. I saw it with my own eyes and I trembled. It was coming straight towards us. With a thin tail like a black scroll, it was touching the ground and its body was high up in the air and its mouth was gaping like that of a lioness in the clouds.
It was coming roaring and swinging its tail; its very breath was sucking throwing into the sky haystacks, house roofs and uprooted trees. Beneath the roar, a downpour of hail and water was unleashed as if the whole Moldova riverbed was taken to the sky and then knocked down on us.”

Mihail Sadoveanu, Excerpt from “The Dragon” (from Ancuta’s Inn, collection of short stories)

vremea.meteoromania.ro - web site

2009-01-06T21:51:00.001-08:00

The web site of the National Meteorological Administration, is presenting information in a new and attractive way at this link.

You can find forecasts, warnings, animated radar images, detailed products, very useful and information about more specific products, road maintenance and conditions, etnometeorolgy, nivometeorology.

Behind this page is a very talented person, Darius Popa, that found a way to merge the interests of a private company with public needs. He has been close to the meteorology over the last 10 years and struggled to find ways on a wild land (private business with public benefits). He managed to work with professionals outside and inside the institute and to develop meteorologic products.

I am happy that my institute found a way to convey better service to the public.

Congratulations and go on!

Gliding into a storm

2009-01-02T22:50:00.000-08:00

A champion paraglider described on 16 February 2007 how she was caught in a massive thunderstorm over Australia, hurled to a height greater than Mount Everest and encased in ice before managing to descend safely to earth.

Ewa Wisnerska, 35, was sucked 32,000 ft into the air — so high that she lost consciousness from lack of oxygen and ice formed over her body. Hospital staff say the paraglider suffered severe frostbite from which she almost lost her ears.

The adventurer said it was a miracle that she survived: "You can't imagine the power. You feel like nothing, like a leaf from a tree going up," she said. "I can't do anything. It's raining and hailing and I'm still climbing — I'm lost." "I was climbing and climbing and the air was starting to freeze my sunglasses and then it was dark."

Miss Wisnerska, from Germany, was preparing for the 10th World Paragliding Championships above the town of Manilla in New South Wales when the storm struck on Wednesday.
After launching as usual from a hill, she appears to have flown under a black storm cloud and then, with terrifying speed, the wind whisked her upwards. She climbed from 2,500ft to an estimated 32,000ft in about 15 minutes.

A 42-year-old Chinese para-glider, He Zhongpin, was sucked into the same storm and died, apparently from lack of oxygen and cold. His body was found nearly 50 miles from where he took off.

Miss Wisnerska said she encountered hailstones the size of oranges as the temperature dropped to minus 58 degrees Fahrenheit. "I was shaking all the time. The last thing I remember is that it was dark. I could hear lightning all around me," she said. She regained consciousness mid-air about one hour later. "I wanted to fly around the clouds but I got sucked up 20 metres (67ft) per second into it and spiralled," she told The Sydney Morning Herald.

"After 40 minutes or an hour, I woke up and I was at 6,900 metres (23,000ft). I was still flying but I realised I didn't have the brakes in my hand. I saw my hands and the gloves were frozen, I didn't have the brakes, and the glider was still flying on its own.

"I was thinking 'I can't do anything so I only have to wait and hope that the clouds are bringing me out somewhere'. Then I woke up and was thinking that I was maybe unconscious for about one minute. I didn't know I was unconscious for so long."

Her ordeal was recorded by a global positioning beacon and a radio attached to her equipment. The swirling clouds released Miss Wisnerska from their grasp and she landed safely 40 miles from her launch, suffering frostbite to her face and with ice inside her lightweight flying suit — but otherwise unharmed.
Godfrey Wenness, the president of the Manilla Sky Sailors club and organiser of the Paragliding World Championship, said Miss Wisnerska's tale was unprecedented.
"It's like winning the Lotto 10 times in a row," he said, adding that the previous altitude survival record for a paraglider pilot was 24,000ft.
Mr Wenness, one of Australia's most experienced paraglider pilots, said the chances of surviving such an experience were negligible.
"There's no oxygen. She could have suffered brain damage. But she came to at a height of 6,900 metres with ice all over her body and slowly descended herself."

The German said she felt like an astronaut returning from the Moon as the ground loomed beneath her. "I could see the Earth coming — wow, like Apollo 13," she said.
Miss Wisnerska spent one hour in the local district hospital for observation and she hopes to compete in the biennial paragliding championships which begin on Feb 24.

(Sydney Morning Herald, Reuters )

First radar hook echo ever recorded !

2009-01-01T05:10:00.000-08:00

Scientists from the Illinois State Water Survey recorded in April 53 the first hook echo with a war radar (photo above is taken from their web site). The movie is here and is impressive (youtube).

The presence of a hook echo on a radar image in US is enough to issue a tornado warning. If you don't, you get in trouble. The warnings get to the Police. If the Police officer doesn't push the sirene button once he got the warning, he gets in big trouble.

The hook echo is a consequence of rotation in the storm (the mesocyclone), is a wrapped column of air in strong rotation, and the storms that have a mesocyclone can be very dangerous, with hail, flashfloods and strong winds; only 60% of the supercells are tornadic.

The first conference in Europe where have been presented cases with Tornado in Europe was Eurotornado, in February 2000, in France, Toulouse, but tornadoes have been reported and studied long ago and actually before they have been studied in US !

Thank you: Menno van der Haven

2008-12-30T07:16:00.002-08:00

Thank you Menno for posting the information bellow. The tornado was on 6 June 2005. I will soon write more about the meteorological conditions of that day.

A dialog between MJ Poore and Menno van der Haven on a forum of passionate meteorologists:

" 06-27-2007, 01:27 PM

Poore:

Good point about Eastern Europe Menno. Some say Romania and Hungary have the highest incidences of tornadoes in Europe and that's a recent observation, because people didnt know about them before. The two counties have some of the best geography in Europe to get big storms going. I see Romania even has a US style doppler radar network now. But exactly how many they get, and how strong they are, I dont know.

Menno:

You are right about that, MJ Poore,

Two years' ago I was in Romania and I was lucky to watch a tornado near Tirgu Mures. However, the locals didn't believe me when I told them that I had seen a tornado in their area. They said: oh, that were rain-curtains. Only when I showed them this picture:

http://i194.photobucket.com/albums/z210/mesocyclone70/6juni2005no36.jpg

they were convinced ;)"

ECSS - 2009

2008-12-29T09:33:00.000-08:00

The 5-th European Conference on Severe Storms will be held on 12-16 October 2009 in Germany, Landshut. Is a place where we all speak the same language, of storm-fans, and the atmosphere is very "instable" and "triggers" great friendships and actions.

Convective cell: What radar sees

2008-12-27T23:21:00.000-08:00

This is a very nice photograph taken by an astronaut while leaving the troposphere. Visual we can identify the overshooting, as a sign of strong updraft, the anvil, where the level of equilibrium of the air parcels lifted from the ground is, the very instable air that hangs is the altitude, on top of the updraft, where hail forms, sometimes as mamatus clouds. The overshootings are also very nice to be seen on visible channel satellite pictures, as satellite looks from up, down to the top of the clouds.

In coloured lines I wanted to show what a radar would see if would scan this cloud on vertical cross section, as reflectivity. The radar sees only a part of the cloud, but the most instense, that has more water and bigger particles (rain drops, hail, snowflakes). More than this, can see it from quite a long distance, and on 360 around the antenna.

The radar can track (see the evolution of) these cells and "tells" in time to the pilot what to avoid. What can happen if he gets into the updraft? He would be very lucky if he would remain alive and the aircraft would be destroyed by strong turbulence, big hailstones, thunders, iceing.

Nowcasting Symposium 2009

2008-12-26T00:13:00.000-08:00

The International Symposium on Nowcasting and Very Short Range Forecasting (WSN09) will be held at the Tellus Conference Centre in Whistler, British Columbia, from 30 August to 4 September 2009.

This meeting is organized by the World Weather Research Programme (WWRP) of the World Meteorological Organization (WMO) and will be hosted by Environment Canada. The previous Symposium (WSN05) was held in Toulouse, France.

For further information seehttp://www.nowcasting2009.ca/ (this web site is also a great source of training material).

Radar images for Central Europe

2008-12-25T11:42:00.000-08:00

Enjoy this link: Radar images in EC

Radar Errors and Limitations

2008-12-25T06:22:00.000-08:00

(more details on JetStream - great generous site for the public!!!)

Radar is a detector that has its limitations, first of it is the ... fact that the Earth is curve while the beam propagates with a smaller curvature, so, the beam is bending upward with the distance. Further the echoes are on the screen, the higher is the sample! (you can use the graphic above to have an idea about this variation).

But this has a great advantage in... the wind field. It enables us to see the wind shear (how wind changes with height) in a single glance (some details here:

http://ww2010.atmos.uiuc.edu/(Gh)/guides/rs/rad/ptrn/ptrn1.rxml).

And this is the real advantage of Doppler radar in front of other detectors because the wind shear actually controls the severity of a convective development.

Radar is all a trade, or better say that learns you how to change the weakeness into a strength.

Carpathian Convergence Line

2008-12-23T02:44:00.001-08:00

This time was seen only by the satellite, the clouds developed were not stromg enough to be detected by radar (in summer this situation can bring severe storms).

Foehn on radar and satellite

2008-10-06T00:34:00.000-07:00

The slopes exposed to the circulation (northern slopes of the Carpathians) received rain while the southern slopes, in the lee, experienced a diminish of cloudiness and reflectivity.
The Northern part of Oltenia has a mild climate due to this effect. Well, Favonius, Roman king, gave the name to this warm wind.

Convective inhibition

2008-09-18T03:52:00.001-07:00

Early in the morning, a band of low clouds prevent the insolation of the land beneath. Later in the day (the image on top), this region remained stable to convection while around it the air became unstable.

A perfect example of ingredients at work!

2008-09-13T08:54:00.000-07:00

Satellite can give a great view about the ingredients needed for convection: instability, moisture, some lifting In the image there is an airmass of stratus clouds, with some inhibition (CIN) for convection. But there is a spot where some convergence at the surface (lifting) helped to overcome this CIN, a nice cell developed, and the outflow, symetric, produced some stable clear air around. Ian Bell found this great image in the internet.

Elevated convergence lines

2008-08-18T04:31:00.000-07:00

If radar can easily see deep convection developed on convergence lines, the satellite visible channel is really able to capture the convergence lines from the first moments of initiation. Note the line developed over the eastern part of Romania, well seen on satellite visible and the fine lines on South-east, not captured yet by radar (radar image from NMA)

Facaeni F3+ Tornado

2008-08-12T01:17:00.000-07:00

On the 12-th of August 2002, the SE part of Romania experienced the strongest tornado ever recorded. The radar image recorded the first tornadic "hook echo" ever seen in Romania. The event shocked both the meteorologists and the population, in a country that missed at that time the culture of "risc": 3 deaths and a lot of damage, both on property as in the "image" of authorities.

After 6 years, tornadoes do not surprise anymore, every year more than 10 weak tornadic events are reported in average, but the population is not yet prepared for a possible strong event.

Radar errors

2008-08-09T04:03:00.001-07:00

The radar is a very expensive instrument for detection ... and still has some erros that are very hard to correct. With some of the errors we get get "used" and recognize them easily. But other errors are less evident or less known by the forecasters, and the consequences can be important. Among these, a critical one is the "blocking" of the beam by orography or, worse, by close buildings, cranes, towers. The closer these obstacles are, more energy is stopped, and the respose from possible remote strong clouds is weaker. Lately, around the radar intalled in Bucharest, "grew" many cranes, to build the new luxury houses in Baneasa "Beverly Hills". Is normal, in this situation, to have a decrease in the radar's capability of detection.... but luxury houses are more important for some authorities.

Train the Trainer Course in Constanta

2008-08-04T00:50:00.000-07:00

From 1 to 5 of September, The Romanian School of meteorology will host a very useful course on Train the Thunderstorm Trainer.

Here is the link:
http://193.26.129.60/trainer

www.ERAD2010.org ERAD in Romania!

2008-07-15T01:55:00.000-07:00

The next European Radar Conference, ERAD 2010, will be held in Romania! A dream came true! And I know that when one wish is deep, the whole comunity of "Elfs" joins efforts to make it true.

I have met two of these Elfs in Helsinki: Jarmo and Elena.

www.erad2010.org

Insects and ground clutter

2008-06-23T03:08:00.000-07:00

The satellite ia showing a clear sky over Romania (again a hot day) while radars (S band) intercept echoes from all kind of particles (dust, insects...) around some radar sites. Thunderstorms chasers love "bugs" because they can show the convergence lines in the wind field and other surface boundaries that can promote storms initiations. But, unexperienced forecasters can be tricked by these echoes, so is always good to first check with the satellite image.

And the reported tornado!

2008-05-23T04:24:00.000-07:00

22 May 2008, Ramnicu Sarat
(Courtesy Antena 3)

Convergence line and severe convection

2008-05-22T05:40:00.000-07:00

In Romania, one of the most frequent convercence line is in the SE part. In Southern circulation, with important instability, this line can bring the lift needed for convection.

12.15 UTC, 22 May 2008

Tornadic storm

2008-05-19T05:08:00.000-07:00

A lot of good information about the case on 22 April 2008, you can find here:

http://convection.satreponline.org/cases/april08/

"Satrep" is a very good site about satellite meteorology (the best!) , enjoy!

National Mosaic

2008-05-09T04:44:00.000-07:00

One of the radar products I am not very happy with, is the so called "mosaic", when we make an overlap of all the radars we have in the country in one single larger scale image. Is a product that can have so many erros that is very dangerous. Here, the same case like in the previous post, if you look at the SW part of the image (pinkish reflectivities over Serbia) you can see that the echoes are very strange, like a "circle" line (see zoom) , due to the contributions of two radars on the same region of the image. The beams reach different heights in the atmosphere and the composition is unreal.

The storm in Bulgaria, was tornadic, and later similar ones form over S.Romania.

and V-notch on radar

2008-04-23T03:40:00.000-07:00

The same day, 22 April, few hours later, the same airmass that produced cells with V-shape on satellite image, also produced a High Precipitation tornadic supercell, detected by the WSR-98D S band radar in SE Romania. Doppler radial velocity image, at the bottom, has an intense mesocyclone and in the reflectivities, we can see the supercell structure, with a very pronounced "hook echo" to the S, and V-notch structure, produced by the flow splitting around a very strong updraft. Very high reflectivites, up to 70 dBZ, due to hail presence. Tornadoes were reported in Bulgaria and Romania

V-shape on satellite

2008-04-22T09:29:00.000-07:00

An intense updraft lifts moisture high into the troposphere and strong upper level divergent winds move the extremely cold moisture (ice crystals) downwind. The moisture fans out as it moves downwind generating a V-shape of the cloudiness on a satellite image (see the cell situated in the South of Romania). The image (Eumetsat) was taken at at 16 UTC. The movement was from south to north so soon Bucharest was affected by the storm. The radar image shows the intense reflectivity (over the Bulgarian teritory). In this case, the satellite image provided more information about the severity of the system (strong updraft, V-shape).

Doppler shift

2008-04-21T10:51:00.000-07:00

The Doppler effect was first applied to the apparent shifting frequencies of a train whistle as it approaches and then passes. When the sound is approaching, the waves are pushed together and the wavelength is shorter, and the frequency is higher, and the whistle is heard as a higher pitch. Then, where the waves are stretched, the wavelength is longer, and the frequency is less. So as a train departs, its whistle will sound at a lower pitch. That's the Doppler shift.
The Doppler shift works with light waves as well as sound waves. For example, astronomers have concluded that the universe is expanding because of the shift to longer wavelengths, or red shift, by distant galaxies. That shift indicates that these galaxies are moving away from the earth.

Doppler radar detects precipitation and measures the speed of falling precipitation.
When microwaves are used, the Doppler shift will indicate whether raindrops are moving away from the radar or toward it. That motion is called radial velocity.

These outgoing or incoming motions are color-coded on the Doppler radar so when a sharp change in direction takes place, the colors contrast sharply. That contrast indicates that a severe storm is present, even a tornado. That wind difference is called wind shear. You can demonstrate this easily by putting a pen between your two hands. Move your left hand in one direction and your right hand in the other. What happens to the pen? It will rotate. That rotation can be detected on the radar screen by looking at the color shift of the radial velocity. A strong shift is a tip-off that some severe weather is happening. The warning can be issued as much as 20 minutes before a tornado touchdown in a distance of less than 70 km from the radar; because of the great uncertainty of this forecast and due to the high impact of such a warning the Romanian Met service (and European met services in general) do not regulary issue these warnings.

(Doppler information from infoplease - web site)

Electromagnetic Interference

2008-04-21T07:44:00.001-07:00

The space is overcrowded with EM signals and the radar receives them and very often can not distiguish them from other weather signals, so displays them. The radar image (right) shows some radial echoes detected by the Bucharest C-band radar . They are generated by the electromagnetic interference with some other antennas at south of the radar site. How do we know that they are not clouds besides this "artificial" radial aspect? Because in the satellite image (IR) (left), we do not see similar structures. The only meteo feature is the line of clouds oriented W-E over Bulgaria. The other echoes around the radar sites in Timisoara (western Romania) and Medgidia (south-eastern Romania) are ground clutter around S-band sites. Images are from the NMA site, Sunday morning.

Tornadic Mezocyclone

2008-04-20T01:03:00.000-07:00

Yesterday a tornado has been observed in the western Romanian town of Curtici. Here we present the radar image, seen by the S band Doppler radar from Timisoara (situated south of the tornado place) operated by the Romanian met Service. The radar echo was that of a supercell. A mesocylone was detected in the radial velocity field (left side of the image), highlighted with the white circle. The meso was identified due to the relative maximum in the winds, one for the inbound velocities, in green colors, one for the outbout velocities, in yellow, as a consequence of rotational movement. The meso overlaied the southern part of the supercell, in the "inflow" region of it, characterized by the low echo zone, situated right near the "hook" in the reflectivity field. The tornado video was posted by Youtube:

http://www.youtube.com/watch?v=Xma3QjPNffM&feature=related