Understand NWP outputs
Marjo Hippi explains how FMI deals with slipperiness during winter.
Icy and snowy sidewalks are very typical phenomena in Finland during winter. Near zero temperatures and slipperiness due to ice and snow on sidewalks increases the pedestrians' slip risk. Almost every second person slips annually in Finland and around 50 000 persons (1 % of Finnish population) are injured needing medical attention. Slip injuries cause huge economic losses, long sick leaves, and human suffering. The Finnish Meteorological Institute (FMI) has developed a numerical weather model that predicts the sidewalk slipperiness from pedestrians' point of view. The model classifies the sidewalk slipperiness into three classes: normal, slippery, and very slippery. Very slippery sidewalk condition mean that the slip risk is increased. Typical situations for very difficult sidewalk situations are packed snow, freezing or ice layer covered by water or snow. The model is a tool for duty meteorologists when issuing warning about slippery sidewalk condition.
Gunnar Noer explains and showcases the nature of polar lows.
Polar lows are small but fairly intense low pressure systems that form in the Arctic marine regions during the winter season. They form in unstable air masses associated with cold air outbreaks from the Arctic ice cap. Polar Lows give rise to gale or storm force winds which, in combination with heavy snowfall, cause widespread traffic disruptions. In recent years, polar lows have caused several fatal incidents with snow avalanches. This lecture focuses on the key processes and the methodology for forecasting polar lows.
Thomas Krennert (ZAMG) talks about the importance of moisture gradients in analysing the possibility of development of deep moist convection.
The exact predictability of convection in the Alpine region in the absence of fronts in weak-surface-pressure-gradient-situations during the warm season remains challenging for forecasters. The development into single-cell deep moist convection SC-DMC under these conditions depends on the availability of well-known ingredients like low level moisture, steep tropospheric lapse rates and sufficient lift. Satellite studies have shown that favourable locations for the first onset of SC-DMC resulting from widespread shallow convection over mountainous terrain are water vapour gradients in the middle or upper troposphere UTMG (upper tropospheric moisture gradients, Krennert, et al., 2003, https://doi.org/10.1016/S0169-8095(03)00067-X). The contributions of the respective ingredients related to UTMG supporting the initiation of DMC are discussed. A focus is set on moist symmetric instability MSI as a possible mechanism for favouring the transition from shallow to deep moist convection.
Wilfried Jacobs (DWD) explains the power of Airmass RGB in estimating the possibility of cold front transforming into a convective line.
Especially, the airmass RGB is a powerful tool for estimating the cold front’s tendency to transform to a convective line. Convective lines are connected with strong gusts, heavy precipitation sometimes with graupel or even hail. During this presentation the indications of convective lines will be outlined by considering the airmass RGB together with other means, e.g., radiosounding. Examples of two succeeding days will be discussed in detail whereas the first case did not lead to a convective line whereas the second example did. Typical differences of patterns in the corresponding airmass RGB and additional data sources will be related to a convective line’s probability.
Andreas Wirth (ZAMG) presents the benefits of analysing the water vapour imagery to diagnose synoptic structures and weather patterns.
Water vapor (WV) imagery is very useful when it comes to visualize zonal and meridional transport of air masses, but it is also suited to get a rapid overview on vertical transport processes. This characteristic makes WV-imagery extremely helpful when it comes to diagnose fronts and cyclogenesis.
The presentation will focus on the dynamics of cyclogenesis and fronts and how they are reflected in WV-imagery. The concept of relative streams will be introduced in the context of cyclogenesis, ana- and kata fronts.
Meteorological products based on WV absorption bands such as the Total Precipitable Water product will be introduced and their usefulness will be demonstrated on case examples.
Christo Georgiev (NIMH) discusses the effect of vorticity on tropical cyclones and development of severe thunderstorms, through the scope of water vapour imagery.
Water vapour (WV) images provide useful information to anticipate the effects of upper-level dynamic environment on the intensity of a tropical cyclone (TC) as well as on its extratropical transition (ET), a gradual process in which a TC loses tropical characteristics and becomes more extratropical in nature. Analyses of WV imagery shows that during ET stage over subtropical areas, advection of potential vorticty anomaly can influence the ET and control the process.
Large amounts of water vapour, originated by TCs may be involved in transfer of moisture by planetary waves, associated with ET developments and give rise to a narrow regions of strong meridional water vapour flux. The presentation shows WV imagery synoptic-scale analysis, which shows supply with additional large amount of moisture of an existing already favourable convective environment. The
combination lead into an environment with very high CAPE and potential to accelerate upward, acquiring kinetic energy and forming strong vertical motions in a deep tropospheric layer. The process is illustrated by a case of catastrophic hailstorm over Bulgaria, Eastern Mediterranean.
Thomas August (EUMETSAT) presents the current polar satellite sounders and makes a comparison with the capabilities of the future MTG infrared sounder
Satellite infrared sounders like IASI allow retrieving the vertical structure of the atmospheric humidity. Their measurements are exploited in synergy with the microwave (MW) sounders, when such companions are present on the same platforms as is the case in the operational EUMETSAT Polar System (EPS) programme and in the EPS-Second Generation (SG). This synergy increases the yield and quality of sounding in cloudy pixels. The future infrared sounder (IRS) onboard Meteosat Third Generation (MTG) will operate without MW companions. It will however provide unprecedented spatio-temporal sounding, with a typical ground-resolution of 7km and observations every 30 minutes over Europe.
The extensive utilisation of machine learning guarantees the provision of reliable atmospheric temperature and humidity profiles and uncertainty estimated within less than 30 minutes from sensing. We present here the characteristics of satellite thermodynamic profiles from the current and future missions and the experience made in studies with meteorological services to contribute to nowcasting severe weather events, and prepare to the future sounder missions.
Bryan Guarante (University of Wisconsin) uses a COMET course to explain the usefulness of analysing water vapour images with a goal of assessing the NWP fields.
In dynamically-active regions of the atmosphere, water vapour imagery approximates the same surface as the 1.5PVU height or pressure surface. Because of this, we can take advantage of the WV channels to find areas of mismatch between the NWP and the real atmosphere to adjust our synoptic scale forecasts.
Wilfried Jacobs (DWD) introduces the water vapour channels in the 2022 EUMeTrain Water Vapour Event Week.
The target group of this presentation is participants that are not familiar or do not feel familiar enough for understanding the presentations during the entire week. The first presentation deals with basics of vapour water channels in satellite products. First, the principle of radiation and radiation transfer will be outlined briefly and put in relation to wave lengths of imagers and vertical sounders by considering weighting functions. The second part deals with some examples by using single channels. Finally, corresponding composites (RGBs) and their applications will explained in detail.
Presentation during the event week on Convection in June 2009.
Fritz Woelfelmaier from ZAMG (Austria). Using statistical methods from several convection parameters from the LAM model ALADIN AUSTRIA he has developed a severe convection index, which was verified/correlated with lightning data and hail analysis from weather radar data. In the presentation Fritz will explain this method in more detail and show a case studies to demonstrate this benefit. The usefulness of this method has been proven and will subsequently become operational to the forecasters in Austria in the near future.
The session will be continued by Jari Tuovinen from Finnish Meteorological Institute on the Investigation on hail occurrences in MSG.
Lee-Ann Simpson and Jannie Stander from the South-African Weather Service started the first session of the WWW-Briefing. Lee-Ann gave a weather briefing for the South-African region and Jannie introduced the conceptual models of cold fronts and cut-off lows as they appear on the southern hemisphere.
Length: 50 min
Author: Lee-Ann Simpson, Jannie Stander
Lee-Ann Simpson is currently working as a meteorological trainer in the Regional Training Center (RTC) in Pretoria. She worked as an operational forecaster from 2003-2008, after which she started in the training department. She presently lectures to Post graduate forecasting students, focusing on specialized weather forecasting and satellite meteorology. Through the University of Pretoria, she lectures satellite meteorology and Tropical meteorology to honours students. Her interests lie in short term forecasting, severe weather and all satellite based interpretation of weather phenomena. She has a BSc (Hon) in Meteorology from the University of Pretoria and she is currently completing her MSc through the same institution.
Jannie Stander has worked as an operational weather forecaster from 1998 to 2005. Since 2006 Jannie has been working in the Regional Training Centre at Pretoria providing marine (2006-2008) and aviation forecaster training (2008-current). His main interests are aviation meteorology, synoptic meteorology and satellite interpretation and he is involved with several international working groups within these disciplines. He holds a BSc Hons degree in Meteorology at the University of Pretoria and is currently completing his MSc at the same University.
Mahmood Al-Khayari gives an overview of typical weather situations in the Sultanate of Oman.
Length: 30 min
Author: Mahmood Al-Khayari
Mahmood Al-Khayari graduated at Saint Louis University (Missouri State), USA, with BS in meteorology in 2003. He is also holding MS in an engineering field from Sultan Qaboos University. Mahmood Al-Khayari works at Oman Met Service since Feb 2004 until now as meteorologist specialized in forecasting. He has done different kinds of forecasting: General, Aviation and Marine. Also he worked as a lecturer during this period in many courses such as: Met Technician course, aviation courses for Royal Force courses, marine courses for Oman Royal Navy, and many others. Mahmood Al-Khayari was recently selected to take care of the chief's duties of Remote sensing and research section.