Understand NWP outputs

There are a number of structures and processes happening after a cold front has passed an area, e.g. enhanced cumuli, commas, instant occlusions, etc. Commas, for example are meso-scale structures developing within cold air, often behind frontal cloud bands. They occur mainly during the cold season and are a common feature for Northern and Western Europe - nevertheless commas can also be found in the south. As commas can cause severe weather this conceptual model is of high interest for forecasters. In this lecture life cycles of commas will be shown, what do commas form from, what can they form into, how they are connected to other mentioned phenomena and how they appear in satellite imagery - seen by MSG and polar orbiting satellites.

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Lecture slides

Precipitation within extratropical cyclones often organizes into mesoscale substructures known as precipitation bands. The purpose of this presentation is to better understand how precipitation organizes into bands. We will discuss about Shapiro-Keyser and the Norweigan models of cyclones, why do they form, the differences between them, also where in cyclones precipitation bands form, their structures and evolutions, what controls their locations and intensities, and techniques to diagnose precipitation bands. In the end we will discuss about occlusion bands and how do they actually form considering latest researches.

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In this second part of the Cyclogenesis and Occlusion Cloud Bands lecture, a special form of cyclogenesis is treated in detail: the “rapid cyclogenesis” which is connected with very severe and often catastrophic weather events.
All processes and weather systems are presented from the aspect of “Conceptual Model thinking”; that means the typical appearance in satellite images is connected to the physical background which is responsible for the cloud configurations; then these results are connected to relevant numerical parameters in horizontal and vertical presentation. And all of the presented CMs are connected to the typical connected weather events. This combination of different meteorological material is especially important in forecasting and nowcasting.

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Cyclogenesis and occlusion cloud bands are common meteorological phenomena which are tightly connected. While “cyclogenesis” is a process, describing the development of a low centre, which can last from few hours to several days, the occlusion cloud bands are the result of this cyclogenesis process. Occlusion cloud bands differ from cold and warm front bands because of their history as well as their physical status.
The two lectures start from the classical cyclogenesis (occlusion) processes which are related to the classical polar front theory and introduce then the conveyor belt view of these processes culminating in the warm and cold conveyor belt occlusion types.
The occlusion cloud band types are described and compared to cold and warm front types in their horizontal as well as vertical depiction.
Also special subtypes of occlusion processes like “instant occlusion” and "cold air development" are mentioned.

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Fronts as described in the "Bergen school" by Vilhelm Bjerknes are early conceptual models. Parameters typical for the changing of air masses were named and used by forecasters to recognize transition zones (fronts) between air masses. For nearly a century the method from the Bergen school is applied in the majority of weather rooms all over the world. Satellite information expressed how right Bjerknes was in his CM thinking, but this information showed also that fronts can have a much more complicated structure and live cycle Bjerknes could imagine.
In the lecture we concentrate on warm- and cold fronts and show how we can analyze them with help of CM thinking.
It's not only fronts that forecasters should always keep an eye on, but also the frontal sub-structures like upper waves, front intensifications or newly developing systems. NWP models sometimes catch the situation, sometimes not. Especially for rapid or small scale developments, model performance may leave a lot of gaps in the processes.

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Getting a good, actual weather picture within short time is essential for a forecaster who has to react quickly and adequately on weather changing's.

The huge amount of weather data which are available makes it almost impossible for a human being to handle. Thinking in conceptual models is the only way to deal with this problem

Within 20 years of the project fifty-three different conceptual models were described in a manual: Sat Manu. Also for the southern hemisphere, we have already fifteen CM's described.

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Making reliable severe weather forecasts is always a great challenge. Communicating them towards the public and special end users is sometimes greater, even if the forecast is good. Tamás Alaga says that the Hungarian Meteorological Service (OMSZ) plans to develop and simplify its two-level warning system to make it more understandable. The problem is knowing when to stop with these simplifications. Tamás also explains how does the service handle probabilistic forecasts and delivering such forecasts to public and consumers.

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Summer thunderstorm Kiira left a significant trace in Finland in August of 2017. With big forest damages because of strong wind gusts, big number of interventions in southern Finland this case is suitable for analysis and through that presenting the Finnish severe weather follow-up product LUOVA. Kaisa Solin from Finnish Met Service explains LUOVA more in detail in the video.

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The presentation is delivered on the basis of the polar air outbreak in mid April 2017 that caused a late winter outbreak in the Alpine area in Austria. Because of that Austrian met service had to reactivate winter maintenance warnings. Thomas Turecek of Austrian Met Service (ZAMG) explains us how did they cope with this event and how are the warnings they issued connected with climatological thresholds for that specific area.

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ANYWHERE project is a H2020 funded project that aims to develop tools to support coordination of the emergency response operations to face challenge of the extreme weather and climate events. Tuomo Bergman from Finnish Met Service (FMI) tells us that the purpose is to build a pan-European multi-hazard platform for faster analysis and anticipation of the risk prior to event occurrence, improved coordination of the emergency actions and assist to raise the self-preparedness.

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Jyri starts his talk about what ISTIKE actually is and why was there a need for such collaboration between several rescue services in Finland. The main aim of the project is to provide a rescue center with a joint emergency center in eastern Finland. Jyri also describes what are the procedures when a certain severe weather event approaches and what are the preparedness levels of the rescue services. What is the role of other institutes?

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The Norwegian Met Service (MetNo) uses a wide variety of social media from Facebook and Youtube to Twitter and Instagram for delivering information to people around the country (and world). That way MetNo can post numerous short news, pictures and general weather information that people find appealing because of their shortness and informativity. On the other hand how are the extreme events reported through such services?

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