Thinking in terms of uncertainty in the operational forecast is the current goal for high resolution operational predictions. Fields like precipitation with convection, surface winds or fog, are very sensitive to model uncertainties and errors, resulting in a rapid loss of predictability in such meso-scales. The best tool that can quantify this uncertainty is a Short Range Ensemble Prediction System (SREPS). Since final 2016 AEMET runs operationally such a system and names it AEMET-γSREPS. It runs currently at 00 and 12UTC time in three domains over the Iberian Peninsula, Canary Islands and the Antarctic Peninsula, up to 48/60 at 00UTC. According to our operational forecasters, the main contribution of the system is to predict strong convective precipitation and its spatial variability. Besides it is useful to see the range of change of temperature from day to day or the localization of wind gusts in orographic areas and its associated spatial variability. The combination of HARMONIE-AROME with IFS deterministic models and AEMET-γSREPS is the best tool AEMET has for the short-range forecasting. In this talk we first briefly present the design of the system and the domains and times where and when the probabilistic predictions are computed. Then we describe the current status and last updates and the latest verification results. Special emphasis is focused on introducing data assimilation in the system. Finally, the future developments are shown. Although AEMET-γSREPS is developed by the AEMET Predictability group, it wouldn’t exist without the collaboration of the international partners ECMWF, MF, NCEP, NCAR, JMA, CMC and specially the HARMONIE community.

Understanding future changes of the terrestrial water cycle and their interaction with human activity, with emphasis on agricultural areas, was selected as one of the World Climate Research Programme (WCRP) Grand Challenges, entitled “Water for the Food Baskets of the World”. Within this framework, the scientific objectives of the “Human Imprint on Land surface Interactions with the Atmosphere over the Iberian Semi-arid Environment” (HILIAISE) are the characterization of evapotranspiration and other key processes of water cycle in semi-arid environments. For this purpose, an international field campaign, scheduled for 2021, has been planned focused on a region with highly contrast surface characteristics (irrigated vs non-irrigated areas), particularly during summer. An overview and preliminary results of a specific project (WISE-PreP) within HILIAISE is given here. WISE-PreP was designed to study precipitation processes aiming to characterize possible differences in precipitation induced by surface characteristics. For this purpose, planned instrumentation for the campaign includes the deployment of three sites equipped each with a vertical radar Doppler Micro Rain Radar (MRR) and a laser disdrometer (PARSIVEL), covering both irrigated and non-irrigated sites, with three disdrometers (model PARSIVEL-2) and three MRRs (one model MRR-2 and two MRR-PROs). Time series of vertical precipitation profiles will be recorded to study microphysical processes trough the evolution of raindrop size distributions and related variables including precipitation intensity or convective vs stratiform rainfall regimes. Additional observations include raingauge data, C-band Doppler weather radar observations, and satellite products, as well as high resolution deterministic numerical weather prediction model data plus Ensemble Prediction Systems (EPS) model output. Funding for this research was provided by “Analysis of Precipitation Processes in the Eastern Ebro Subbasin” (WISE-PreP, RTI2018-098693-B-C32) and the Water Research Institute (IdRA) of the University of Barcelona.

El sistema tramontana – cierzo es un sistema de vientos ageostroficos canalizados a traves del Valle del Ebro y del corredor entre los Pirineos y el Macizo Central Frances (figura 1) que se caracteriza por tener un bajo numero de Froude1 [1]. Este sistema se da durante los episodios de norte o noroeste en los Pirineos que normalmente estan relacionados a escala sinoptica al paso de oeste a este de una vaguada con frente frio asociado. El flujo, al interaccionar con el sistema montanoso, se divide en dos ramales, uno que baja por el valle del Ebro, llamado cierzo; y otro que se canaliza por el paso entre los Pirineos y el Macizo Central frances llamado tramontana. Dicho flujo crea ademas una modificacion en el campo de presion a escala mesoalfa formando un dipolo orografico [2] con una meso-alta en la cara norte de los Pirineos y una meso-baja en la cara sur

HarmonEPS is the limited-area, short-range, convection-permitting ensemble prediction system developed and maintained by the HIRLAM consortium as part of the shared ALADIN-HIRLAM system. HarmonEPS is the ensemble realization of HARMONIE-AROME, used for operational short-range forecasting in HIRLAM countries. HarmonEPS contains a range of perturbation methodologies to account for uncertainties in the initial conditions, forecast model, surface, and lateral boundary conditions. This paper describes the state of the system at the version labeled cycle 40 and highlights some directions for further development. The different perturbation methods available are evaluated and compared where appropriate. Several institutes have operational or preoperational implementations of HarmonEPS, such as MEPS (Finland, Norway, and Sweden), COMEPS (Denmark), IREPS (Ireland), KEPS (the Netherlands), AEMET-gamma SREPS (Spain), and RMI-EPS (Belgium), and these systems are briefly described and compared with the ensemble prediction system (IFS ENS) from the European Centre for Medium-Range Weather Forecasts (ECMWF).

The Tramontane‐Cierzo wind system is a recurrent feature of the northwestern Mediterranean basin in front of the Catalan coast (northeast Spain). Associated with this feature, northeast wind surges occasionally affect the coast and become a weather hazard for low‐level aircraft operations, affecting for example the Barcelona international airport. This article first reports these surges characterizing them as Coastal‐Trapped Disturbances (CTDs). Climatological features are described, showing that CTDs occur frequently during the warm season and between the afternoon and the evening. We classified CTDs into two synoptic patterns related to the location of a mid‐level tropospheric geopotential trough and the Iberian Peninsula: pattern A, with the trough crossing eastwards along the north of Spain; and pattern B, with the trough over the Mediterranean, after crossing the Iberian Peninsula. To study the CTDs in detail, numerical simulations were conducted using the non‐hydrostatic and convection‐permitting numerical weather prediction model HARMONIE‐AROME. Two cases, one for each synoptic pattern, were studied showing that CTDs generate in the discontinuity between cool outflows and warmer air progressing southward as a density current, trapped by the mountain ranges parallel to the coastline. Cool outflows may have two different sources: in Pattern A the origin of the cold air is the tramontane itself, while in Pattern B convective outflows associated with storm downdraughts play this role. Both cases show similarities with CTDs studied on the California coast, showing an antitriptic and ageostrophic flow behind the CTD. An additional numerical sensitivity experiment was conducted by varying the short‐wave radiation to explore the effects of diabatic warming on CTDs. It is demonstrated that a large warming influences CTDs by enhancing the potential temperature gradient between the density current and the environment, modulating their intensity and speed.

Numerical weather prediction (NWP) models (including mesoscale) have limitations when it comes to dealing with severe weather events because extreme weather is highly unpredictable, even in the short range. A probabilistic forecast based on an ensemble of slightly different model runs may help to address this issue. Among other ensemble techniques, Multimodel ensemble prediction systems (EPSs) are proving to be useful for adding probabilistic value to mesoscale deterministic models. A Multimodel Short Range Ensemble Prediction System (SREPS) focused on forecasting the weather up to 72 h has been developed at the Spanish Meteorological Service (AEMET). The system uses five different limited area models (LAMs), namely HIRLAM (HIRLAM Consortium), HRM (DWD), the UM (UKMO), MM5 (PSU/NCAR) and COSMO (COSMO Consortium). These models run with initial and boundary conditions provided by five different global deterministic models, namely IFS (ECMWF), UM (UKMO), GME (DWD), GFS (NCEP) and CMC (MSC). AEMET-SREPS (AE) validation on the large-scale flow, using ECMWF analysis, shows a consistent and slightly underdispersive system. For surface parameters, the system shows high skill forecasting binary events. 24-h precipitation probabilistic forecasts are verified using an up-scaling grid of observations from European high-resolution precipitation networks, and compared with ECMWF-EPS (EC).