Intense storms in the Mediterranean: a first description from the ERA-40 perspective

International audienceThe study of the Mediterranean cyclones from a climatological point of view has been one of the objectives of the first phase of WMO WWRP MEDEX (MEDiterranean EXperiment) project. It has been revealing itself like a good procedure for extracting conclusions about their characteristics and behaviour. The implementation on ECMWF ERA-40 reanalysis of the method for detecting and tracking the cyclones developed at the Centro Meteorológico Territorial (CMT) in Illes Balears of the Instituto Nacional de Meteorología (INM, Spain) has allowed the selection of the most intense storms occurred for the last 45 years. This selection has been based on the value of the cyclones' circulation. The areas of maximum intensification for those cyclones have been obtained and the existence of preferential zones of intensification has been verified. Finally a first sight of those cases has allowed to initiate the check up of the ability of the ERA-40 re-analyses for reproducing these intense Mediterranean storms

Heavy rain events in the Western Mediterranean: an atmospheric pattern classification

International audienceHeavy rain is one of the most important high-impact weather phenomena that occasionally affect Mediterranean areas. The aim of this study is to achieve a classification of atmospheric patterns related to heavy rain events in both French and Spanish Mediterranean regions. The classification is made on some atmospheric fields (geopotential at 1000 hPa and at 500 hPa and temperature at 850 hPa) of HIRLAM-INM-0.5° operational analysis, for heavy rain events included in the High Impact Weather MEDEX database. It covers a period of roughly 7 and a half years, from January 1997 to May 2004. A Principal Components Analysis was conducted to reduce the number of variables. After that, by means of a Cluster Analysis, the heavy rain events are classified into 8 atmospheric patterns. The results show a good relationship between regions affected by heavy rain and atmospheric patterns, in the sense that the same atmospheric patterns usually produce heavy rain in different regions, and heavy rain in different regions is usually due to specific atmospheric patterns

High impact weather and cyclones simultaneity in Catalonia

International audienceThe Western Mediterranean in general and Catalonia in particular are usually affected by high impact weather (HIW) events, mainly heavy rain (HR) and strong wind (SW). The improvement in the understanding and the accurate forecast of such events are major concerns for the meteorologists of the region. In the present study, HR and SW events in Catalonia are cross-referenced with an objective cyclone database for a 9-year period (from June 1995 to May 2004). Results show that in most of the HR events a cyclone is located close to Catalonia, in such a way that the feeding of a moist flow to the affected region was favoured. These cyclones can be either shallow and weak or deep and intense. A simultaneous cyclone also appears to be connected with many SW events. However, other SW events seem to be related to meso-scale circulations and, as a result, not always well captured in the cyclone database. Finally, coincident HR and SW events are analysed. In almost all of such events a deep cyclone is located in the vicinity of Catalonia

Towards a climatology of sensitivities of Mediterranean high impact weather ? first approach

International audienceDuring recent years, great interest has grown within the operational weather community on the adaptable component of observational networks. Decisions regarding where to deploy new observations of special value under threatening weather, or regarding permanent changes in observational strategies need support from sensitivity studies that determine areas where the addition of observations would optimally improve the skill of numerical predictions. Within the context of the MEDEX project (http://medex.inm.uib.es), the sensitivities of a collection of severe weather episodes in the Mediterranean have been computed using the MM5 Adjoint Modeling system. Various approaches are explored trying to summarize the results for the diversity of cases that produce high impact weather (HIW; mainly heavy rain and strong winds) in the Mediterranean region. A first attempt uses an objective classification of the trajectories of the most intense cyclone types from the ERA-40 reanalyses. Sensitivities are then computed for each group of frequent trajectories, providing a prototype sensitivity field for each of the most frequent intense cyclones in the Mediterranean. However, a large portion of HIW episodes in the Mediterranean are not linked to significantly intense cyclones within the climatology. Consequently, a subjective classification of HIW events is also performed and the sensitivity fields for an example case is shown to complete the study. Although the sensitive areas for Mediterranean HIW are not particularly confined, it is remarkable how poorly sampled areas by the regular observing networks such as North Africa and the eastern North-Atlantic are highlighted in the results

Heavy rain and strong wind events and cyclones in the Balearics

International audienceThe relationship between heavy rain (HR) and/or strong wind (SW) events and cyclones is investigated for the Balearic Islands. First, a list of HR and SW events is cross-referenced with an objective cyclone database for a 9-year period (from June 1995 to May 2004). The presence of a cyclone centre close to the Balearics is looked for each event. For HR events in most of the cases a cyclone centre is located in the vicinity. Furthermore, cyclones are located in such a way that allow the supply of warm and wet air to the affected area. But for SW events, although in the majority of cases a cyclone centre is detected, cyclones are located farther than for HR events and their geographical location is more widespread. Afterwards, the three-dimensional structure of cyclones related to HR and/or SW events is studied in detail

Atmospheric patterns for heavy rain events in the Balearic Islands

International audienceThe Balearic Islands, as well as other Mediterranean regions, are occasionally affected by heavy rain events, which can produce numerous damages. This study contributes to improve the understanding of the dynamical mechanisms that produce heavy rain events by means of a classification of their related atmospheric patterns. Heavy rainfall dataset for the Balearic Islands and some gridded atmospheric parameters, derived from the HIRLAM-INM-0.5° analyses, were the data used in this study. Heavy rain events were recorded at a set of pluviometric stations along the Balearics for a period of 9 years, from June 1995 to May 2004. The 1000 hPa and 500 hPa geopotential heights (hereafter ?1000 and ?500), as well as the 850 hPa temperature (T850) were the fields utilized in the classification. By means of a principal components analysis (PCA) the number of variables was reduced. The cluster analysis (CA) was then applied on those new variables and eight atmospheric patterns were finally obtained. Most of the patterns showed a strong relationship between heavy rain events and cyclones