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Meteorology: Nowcasting, a survey of current knowledge, techniques and practice
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ISSN 1018-5593
European Cooperation NOWCASTING
in the field of Scientific
a survey of current knowledge,
and Technical Research
techniques and practice
Action 78
Development of nowcasting techniques 1994-1998
weather forecasting with local detail In the range 0-6 hours
ahead with refinement of forecasts up to 12 hours ahead
Convection Is one ot the most important phenomena
In this respect
Action 76 is divided Into 5 projects as grouped along the
arrow on this poster (for the example case of convection)
PJofecl 4: Visualization of Projecl 3: Intaracllva evaluation by rnetemokjQlst*
Information (convectiva lyitcms
irtd application ot Al tec tin lq υ ITI
In mm η y pari» at Europe) ( Λ/orktttlion)
EUR 16861 EN European Commission
• • Directorate-General XII

Science, Research and Development •
Environment research programme
Nowcasting, a survey of current
knowledge, techniques and practice
Edited by:
B. J. Conway, L. Gerard, J. Labrousse, E. Liljas,
S. Senesi, J. Sunde and V. Zwatz-Meise
Phase 1 report
996 EUR 16861 EN Published by the
Directorate-General XII
Science, Research and Development
B-1049 Brussels
Neither the European Commission nor any person acting
on behalf of the Commission is responsible for the use which might be made of
the following information
Cataloguing data can be found at the end of this publication
Luxembourg: Office for Official Publications of the European Communities, 1996
ISBN 92-827-6204-1
© ECSC-EC-EAEC, Brussels · Luxembourg, 1996
Reproduction is authorized, except for commercial purposes, provided the source is acknowledged
Printed in Belgium Contents
)reword 1
traduction 3
oj eet reports
Project 1 : Understanding of phenomena 5
Project 2: Nowcasting models and techniques 197
Project 3: Interactive tools and knowledge-based systems 253
Project 4: Visualization 309
Project 5: Interface with end-users 321
verall conclusions 351
A — Project 1 questionnaire7
B — Combinede for Projects 2, 3 and 5 361
C — Project 4 questionnaire (including answers) 379
D — Brief descriptions of systems in the Projects 2, 3, 5 questionnaire 443
E — COST 78 — Management Committee members and
contributors to project reports 491 Foreword
By Erik LILJAS - Chairman of COST Action 78.
Society in recent years has become more and more dependent on accurate and timely weather
information, and in many areas of activity the flexibility exists to adapt to changingr
conditions - provided there is adequate advance notice.
Numerical weather prediction (NWP) models are the basis of most modern weather forecasting
operations, and their capacity to simulate the physics and dynamics of the atmosphere is continually
being improved. However, many high-impact weather events are the result of mesoscale processes
that are still not well represented and predicted by NWP models, and a range of techniques,
including extrapolation, statistical methods, empirical rules, and conceptual models, must also be
developed, refined and brought to bear.
An ability to make frequent and detailed observations of the atmosphere is fundamental to any
attempt to forecast the evolution of such events. Weather radar networks have been established in
most parts of Europe, every weather service uses observations from weather satellites, and new
generations of satellites and types of instruments are being developed. To a large extent the
justification for this massive investment is provided by society's need for improved weather,
predictions for periods from a few minutes to a few hours ahead, or in other words, nowcasting.
Weather services throughout Europe have made considerable progress towards meeting the needs
in the area of nowcasting, but individual National Meteorological Services may not be able to keep
pace with developments in all the different fields. European co-operation is essential to ensure
successful exploitation of the costly investments named above, and their translation into effective
weather service systems, while avoiding wasteful duplication of effort.
COST-78 has a high ambition. Its coordinated approach is intended to benefit nowcasting
applications and contribute to the cost-effective exploitation of resources in all the participating
The number of countries was originally 16 but the COST-78 family is still expanding. The Action
was divided into projects to assemble inventories of the state of the art of nowcasting in the mid
1990s. These initial projects were :
1. Understanding of Phenomena
2. Nowcasting models and techniques
3. Interactive tools and knowledge-based systems
4. Visualization (including standardization within nowcasting computer systems
5. Interface with end users.
The projects have now produced their results and evaluations. The different project leaders and their
animators have done a fantastic job that was far beyond their ordinary duties. Their names are
mentioned in connection with the different project chapters. I thank their NMSs for contributing
man-months to this task. I also thank all those who assisted in searching for documents, writing texts
and putting things together, not least the vice chairman Bryan Conway and the Commission's
representative on the COST-78 Management Committee, Jean Labrousse. The Management Committee of COST-78 has used this inventory in setting the direction of the
second phase of the Action: active collaboration in the development of techniques to address critical
nowcasting problems. This second phase will start with a workshop in Bologna, Italy, in March
Documents like this have a limited useful life-span, and this report has its share of imperfections.
I hope nonetheless that it will provide a useful reference to techniques, systems, algorithms, etc.,
either in use or under development at various institutions, and that it will perhaps even catalyse
some fruitful bilateral co-operations outside COST-78. The information on conceptual models
compiled here is in my opinion unique. Introduction
This report is an attempt to set out the state of the art in nowcasting in the mid 1990s. It
includes operational nowcasting systems and others under development, as well as the
underlying knowledge of mesoscale weather systems. It encompasses simple techniques and
complex systems, and includes manual, automatic and interactive systems.
Nowcasting is taken here to mean forecasting, with local detail, in the range 0-6h ahead (and
the refinement of forecasts up to perhaps 12 hours ahead). This is much wider than the usual
definition, and encompasses what is usually called "very short range forecasting". In practice,
it was not found possible to adhere strictly even to this extended definition, and many systems
extending beyond this, or with no well-defined range, but with some relevance to nowcasting,
have been included in the survey.
No constraint has been placed on the forecasting methods employed. From the start, the view
was taken that the essential goal is the improvement of services to users and that restricting
attention to methods based on linear extrapolation (for example) would be contrary to this
The report is based on a survey conducted as the first part of COST Action 78, a four-year
programme, established in March 1994, to encourage European co-operation on the
development of nowcasting techniques. Representatives of sixteen European nations were
involved in the preparation of the report.
COST-78 was divided initially into five "Projects", each concerned with a particular aspect
of nowcasting, as follows:
1. Understanding of phenomena (particularly conceptual models of mesoscale systems)
2. Nowcasting models and techniques (how the meteorological predictions are made)
3. Interactive tools and knowledge-based systems
4. Visualization (including standardization within nowcasting computer systems)
5. Interface with end-users.
The first task within each project was to survey the current state of the art, and the reports
from the five projects are collected here.
Members of the COST-78 Management Committee joined the various project groups
according to their individual interests. The project groups also included other members
nominated by participating countries because of their relevant expertise. The five projects
attracted different numbers of members, and all the projects had some members leave, and
others join, during the course of the work.
The different topics demanded different approaches. Within agreed overall guidelines the
project groups each chose their own methods, depending upon the topic and the resources
available within the group. Some divided into working groups, each investigating a sub-topic;
literature reviews were emphasized in some projects, while in others it was felt more
appropriate to base the survey on actual nowcasting systems. However, all the projects
gathered some information by means of questionnaires. These were sent to the National
Meteorological Services and to other relevant organizations in the countries participating in
COST-78, and to various centres of excellence in other countries around the world. The questionnaires are reproduced in Appendices A, Β and C. Projects 2, 3 and 5 shared a
combined, while Projects 1 and 4 used separate ones of their own.
The report is written from a European perspective, though developments elsewhere are
described where information was available. The relative weights given to different topics in
the report inevitably reflect, at least in part, the interests and enthusiasms of the members of
the project groups, and the resources that could be devoted to the task. The conclusions in the
various sections also have a significant element of subjectivity. Some unevenness in emphasis
and style must be expected, given the number, diversity and geographical distribution of the
participants. The statistical analyses of the questionnaire replies provide an independent
measure of current levels of interest in different topics, though large and small applications
have equal weight in such analyses, and some systems will not have been revealed by the
Because of the largely independent operation of the five project groups, there is some
redundancy and occasional inconsistency in the report. It was not possible to undertake the
amount of central editorial work needed to eliminate such problems without greatly delaying
completion and publication. The report has been written largely by people whose first
language is not English. Some parts happen to have been written or revised by native English
speakers, but no attempt has been made to convert the entire report to "perfect" English. Some
editorial changes have been made, but only with the object of clarifying the meaning where
it was felt to be obscure.
Appendix D contains short descriptive summaries of nearly all the European systems, and
contact addresses are provided for these and all other replies to the questionnaire. Information
in the report about individual systems, even if correct at the time of publication, may quickly
become out of date, and readers are strongly advised to approach the appropriate contact for
details of any system.
This survey was intended to provide a comprehensive picture of the current state of
nowcasting, particularly in Europe. It proved a much larger and more ambitious task than we
had imagined at the start, and we are conscious of the many imperfections of the final
product. However, we hope that this report is a useful approximation to the original goal and
a guide both to the state of nowcasting today and to promising areas for further development.
With the completion of the survey, COST-78 enters its second phase, in which it is planned
to bring together groups with similar or complementary interests to collaborate in developing
solutions to important practical nowcasting problems. The primary purpose of conducting the
survey was to provide information to help set the direction of this development phase.
Finally, we should like to express our thanks to the many people who have spared the time
to provide us with information about their work, and without whose co-operation and patience
this survey would not have been possible.