The RTNEPH (Real Time NEPHanalysis) model replaced the 3DNEPH (3- Dimensional NEPHanalysis) model in August, 1983 as the AFGWC (Air Force Global Weather Central) automated cloud analysis model. It uses a horizontal grid spacing of 25 nautical miles and uses four floating layers in the vertical. The RTNEPH uses visual and infrared data from meteorological satellites as well as surface observations, radiosonde data, and aircraft reported data to produce its analysis. A capability exists to manually modify the analysis to correct deficiencies. This nephanalysis is then used as input for AFGWC's cloud forecast models and is stored for climatological purposes by the USAF Environmental Technical Applications Center. The RTNEPH is scheduled to undergo a technical enhancement to incorporate multi-spectral techniques, use finer resolution satellite data, and produce a 12.5 nautical mile resolution analysis. Keywords: Cloud analysis, Meteorology, Nephanalysis, Polar orbiting satellite data.

This technical note (TN) describes the automated analysis/forecast model system that currently exists at the Air Force Global Weather Central (AFGWC). The emphasis will be on the interrelation and ing of the various analysis/forecast models in the production cycle. This description of the automated analysis/forecast system was written for managers, programmers, computer operations personnel, users of the ultimate products, and the meteorological community at large. This TN will only address analysis/forecast models that are the primary meteorological data-base builders. Most applications programs that access the data bases are therefore not included.

AFGWC has three cloud forecast models: Five-Layer (5LAYER), High Resolution Cloud Prognosis (HRCP), and Tropical Cloud Forecasting Model (TRONEW). These models satisfy a wide range of requirements and have been in operation since the early 1970s. The 5LAYER model makes extra-tropical forecasts for periods up to 48 hours. Forecasts of layer and total cloud, cloud type, layer temperatures, and icing and weather conditions are made. The 5LAYER model uses a quasi-Lagrangian approach to make these forecasts. The trajectories needed for these forecasts are computed from the AWS Global Spectral Model (GSM) derived wind forecasts. The 5LAYER moisture is initialized from the Real-Time Nephanalysis Model (RTNEPH) layer cloud-amount and the Multi-layer Analysis Model (MULTAN) layer dew-point depression. The 5LAYER temperatures are initialized from the High Resolution Analysis System (HIRAS) and GSM derived temperatures. The High Resolution Cloud Prognosis (HRCP) model combines RTNEPH analyzed cloud input with 5LAYER trajectories to produce high resolution (25 nm), short-range (out to 9 hour) cloud forecasts. The TRONEW model uses the analyzed RTNEPH cloud to make 24 hour persistence cloud forecasts for the tropics.

The Air Force Global Weather Central (AFGWC) automated cloud analysis program (3DNEPH) produces high resolution, three-dimensional analyses of clouds over the entire globe. Up to eight analyses are scheduled per day with additional limited area analyses available on request. Horizontal grid spacing is 25 nautical miles and the vertical grid consists of 15 layers of varying thickness from the earth's surface to 55,000 feet above mean sea level. The program is a string of individual modules which process and integrate meteorological cloud information from surface, pilot, and upper air reports. An additional capability to interpret and incorporate visual and infrared satellite imagery results in high resolution, worldwide coverage. Recent advances in the techniques and methodology for interpreting satellite imagery are described. A new manual data input processor, quality control procedures, and applications are also described. An appendix provides detailed information on the high resolution terrain, geography, temperature, and background brightness (albedo) fields used to support the model. A history of the model is included and detailed descriptions of the satellite processing algorithms are also provided. Samples of displayed data using several display methods are included.