Extended Abstract

Progress in data assimilation for NWP based Nowcasting of Precipitationusing radar and remote sensing data at the UK Met OfficeSusan P BALLARD, Zhihong LI, David SIMONIN, Helen BUTTERY, Cristina CHARLTON-PEREZ, Nicolas GAUSSIAT, Lee HAWKNESS-SMITH, Graeme KELLY, and RobertTUBBSMet Office, Meteorology Building, University of Reading, Reading, RG6 6BB, UKsue.ballard@metoffice.gov.ukThe Met Office now has an operational short range NWP prediction system for the UK usinga variable resolution version of its Unified Model (UKV) with the main domain at 1.5kmresolution stretching to 4km resolution in the boundary zone. This uses 3 hourly 3D-Var withconventional observations and 3D cloud cover on a fixed 3km resolution grid and thenlatent heat nudging using a radar derived precipitation analysis during the 3 hourassimilation window. This is nested in the regional NWP system at 12km resolution using 6hourly 4D-Var (at 36km resolution) plus latent heat nudging.We are developing an hourly cycling NWP based nowcasting system at 1.5km resolution.The test system covering Southern England and Wales is nested in the current UK 4kmNWP system and will ultimately be nested in the UKV. A 3D-Var analysis at 1.5kmresolution with humidity nudging using an hourly 3D- cloud analysis and latent heatnudging using 15min radar derived surface precipitation analyses has been tested as wellas 4D-Var at 3km plus humidity and latent heat nudging. We are also undertaking work todirectly assimilate radar Doppler winds and reflectivity data as well as geostationary satellitedata and assessing the impact of high time frequency wind profiler and GPS data. Futureuse of cloud radar, ceilometer and microwave radiometer data is also being considered.This paper will describe results from the operational and developmental Met Office systemsfor short-range and nowcasting predictions of precipitation and comparisons with thecurrent nowcast system.This work also contributes to working group 1 (Propagation of uncertainty from observingsystems (radars) into NWP) of COST-731 - Propagation of uncertainty in advanced meteohydrologicalforecast systems - and will contrast the work with that of other European MetServices, institutions and universities.-229-