Diana-Corina BOSTAN National Meteorological Administration ROMANIA

Outlook Precipitations forecast is one of the most difficult problems for forecasters. In general, Numerical Weather Prediction models, regardless of resolution, have deficiencies in precipitations field simulation, concerning: - the structure; - evolution and - maximum quantity forecasted. ALARO had presented a continuous improvement of the parametrization of wet process. The change to ALARO-0 baseline determined the improvement of the precipitations forecast. Most of forecasters believe that, in terms of precipitations, ALARO-0 baseline is the best choice. Therefore, this presentation will be focused on forecast of 24 hours precipitations.

ALARO-0 configuration setup for Romania Precipitation simulation analysis for July and August 2014 Specific casesContent

since 10 th of February 2010 ALARO-0 ALARO-0  49 levels, 240x240 grid points (Δx=6.5 km), Lambert projection;  Model version: Cy35T1; later Cy36T1;  Dynamical adaptation mode, DFI initialisation;  2TL Semi-lagrangean scheme; Δt=240s, Vertical finite differenced;  Arpège LBC; 3 hours coupling frequency forecast range. since 1 st of January 2014 ALARO-0 baseline  60 levels, 240x240 grid points (Δx=6.5 km), Lambert projection;  Model version: Cy36T1 + modifications for ALARO-0 baseline;  Dynamical adaptation mode, DFI initialisation;  2TL Semi-lagrangean scheme; Δt=240s, Vertical finite element;  Arp è ge LBC; 3 hours coupling frequency forecast range. ALARO-0 configuration setup for Romania

 July: a rainy month, significant rainfall, flooding in more regions.  Precipitation (area and intensity):  Precipitation (area and intensity): In most of the cases, the model has indicated intense precipitation nuclei, but they are slightly shifted from the real position ALARO-0 baseline – 24 h cumulated precipitation OBSERVATION (synop + pluvio + hydro) – 24 h cumulated precipitatiopn

 August: a month with less precipitation  Precipitation: light precipitation - generally underestimated; intense precipitation - simulated nuclei position is slightly offset, in respect with those of observed nuclei ALARO-0 baseline – 24 h cumulated precipitation OBSERVATION (synop + pluvio + hydro) – 24 h cumulated precipitatiopn

Synoptic situation Maxim 100 l/mp Maxim 103 l/mp ALARO model forecasted a nucleus of maximum intensity in the north; the nucleus is displaced in the central region. Rainfall on the night of July 22, amounted up to 103 l/mp in the mountain area of Bacau County and produced flooding in several towns. Floods in Moldavia region MSLP: low pressure field in S-E of Europe, including Romania; At 500 hPa, a trough situated over eastern Europe, including northern and eastern parts of Romania. MSLP analysis: , 12 UTC (from MetOffice UK) ALARO-0 baseline - 24 h cumulated precipitations Observation – 24 h cumulated precipitations

h 12:00 UTCh 15:00 UTCh 18:00 UTC h 21:00 UTCh 23:00 UTC Last hour cumulated precipitation simulated with Alaro-0 baseline Comparative analysis shows a good agreement from 12:00 UTC to 15:00 UTCM. After this time, convective systems from the central part have a quasi-stationary displacement and the model did not captured the event. OHP (One Hour Precipitation) radar estimation - Barnova (Iasi)

Synoptic situation Maxim 105 l/mpMaxim 98 l/mp Simulated quite accurately the precipitations, regarding the position and intensity. Floods in Oltenia region MSLP: A Mediterranean cyclone formed on , evolved from Gulf of Genoa to western part of Romania. At 500 hPa, a trough situated over central Europe; his ascending part including western regions of Romania. MSLP analysis: , 18 UTC (from MetOffice UK) ALARO-0 baseline - 24 h cumulated precipitations Observation – 24 h cumulated precipitations

Synoptic situation Maxim 100 l/mp Simulated the precipitation was better over southern regions and the mountains The model predicted quite well the precipitable areas and most of the intense precipitation nuclei. MSLP: low pressure field in the south of Europe and high pressure in the north. At 500 hPa, weak geopotential field. MSLP analysis: , 00 UTC (from MetOffice UK) ALARO-0 baseline - 24 h cumulated precipitations Observation – 24 h cumulated precipitations

h 12:00 UTCh 13:00 UTCh 14:00 UTCh 15:00 UTCh 16:00 UTC OHP (One Hour Precipitation) radar estimation - Barnova (Iasi) Last hour cumulated precipitation simulated with Alaro-0 baseline Analysis of rainfall simulated by the model and OHP (Barnova radar), indicates a good correlation on hourly rainfall occurrence.

Maxim 100 l/mpMaxim 150 l/mp A cold front crossed the country from NW to SE in the afternoon and reached SE of the country at night on 00 UTC. Floods in Constanta, RO MSLP analysis: , 00 UTC (from MetOffice UK) ALARO-0 baseline - 24 h cumulated precipitations Observation – 24 h cumulated precipitations It rained torrentially and only in 2 hours in Constanta were gathered 74 l/m 2. Simulated the precipitation over the south-eastern part of Romania: not sufficient accurate position of precipitation nuclei.

Maxim 50 l/mpMaxim 66 l/mp A cold front passage over the northern half of the country, which has passed from west to north-east. The front passed during the day. Simulated the precipitation were well placed in space; A good estimation of precipitation nuclei MSLP analysis: , 12 UTC (from MetOffice UK) MSG – visible ALARO-0 baseline - 24 h cumulated precipitations Observation – 24 h cumulated precipitations

Maxim 150 l/mpMaxim 72 l/mp A cold front passed during the night, nearly 24 hours after running the model; Simulated the precipitation over the south part of Romania: subestimation precipitation and not sufficient accurate position of precipitation nuclei MSLP analysis: , 18 UTC (from MetOffice UK) ALARO-0 baseline - 24 h cumulated precipitations Observation – 24 h cumulated precipitations

Globally better forecast: the fraction of correct forecasted events is higher for all precipitation classes and scores are better for the first day the very light [0.1 – 2 l/mp/24h] unrealistic precipitation was reduced, but there are still underestimated for almost 50% cases the more intense precipitation [10 – 200l/mp] scores are better for the first day but the position of precipitation nuclei are shifted. subjective evaluation of the forecasters: ALARO provides a good precipitation forecast, especially for severe situations. in case of crossing fronts, model performances decrease as the forecast range increases. Conclusions