Thank you: Menno van der Haven

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

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

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

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

Enjoy this link: Radar images in EC

Radar Errors and Limitations

(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

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

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

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!

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

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

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

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

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!

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

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!

22 May 2008, Ramnicu Sarat
(Courtesy Antena 3)

Convergence line and severe convection

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

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

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

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

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

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

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

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