Objective short-range forecasts of the convective environment using Geostationary satellite data

Instruments aboard the future GOES-R and MTG series can resolve atmospheric features at extremely high resolution both in time and space. Although one measure of the utility of these data will be their impact on NWP guidance at 12 hours and beyond, the accuracy of short-range NWP precipitation forecasts can be extremely low, especially during summer. A greater benefit from these detailed and frequently refreshed geostationary satellite data may come through objective tools that assist forecasters in identifying rapidly developing, extreme weather events 1-6 hours in advance. In order to detect the rapid, localized destabilization that precedes convective initiation, these tools must be able to identify and retain extreme variations in the atmosphere, incorporate large volumes of high-resolution asynoptic data, and provide guidance products within minutes of when updated satellite observations become available. Because of the detail and perishable nature of these very-short-range forecast products, numerical approaches are needed that are notably different from those used in numerical weather prediction, where the forecast objectives cover longer time periods and take substantially longer to run using many more computer resources. At previous meetings, a Lagrangian “NearCasting” approach was introduced that optimizes the impact and retention of information provided by satellites, specifically detecting and preserving intense vertical and horizontal variations observed in the various data fields observed over time. Results using both GOES and MSG-SEVERI data showed that the Lagrangian system captures and retains details (maxima, minima and extreme gradients) important to the predicting the development of vertical moisture structures critical for determining the timing/location/intensity of convection 3-6 hours in advance, even after the IR observations may no longer available due to obscuration by the developing cloud shields.

Although previous examples have demonstrated that NearCast products using full-resolution SEVERI or GOES data are useful in predicting isolated severe convective events not captured in convection NWP guidance, additional experiments have been conducted to further expand the utility of both existing and future Geostationary observations. These include: 1) Assessments of relative information content in the SEVERI (and future GOES-R) products relative to the ‘first-guess' fields, 2) Improvements in display capabilities to incorporate multiple parameters in single displays for improved forecaster understanding, 3) Combinations of multiple stability parameters and mergers with measures of forecasts confidence/consistency, and 4) Initial results of tests comparing simulated GOES ABI (imager) and HES (sounder) data. These latter tests provide evidence of the impact that the MTG sounder will have on improving future convective forecasts over Europe, both in isolating the likely area/time of development and providing further information about probable storm intensity. Because of the desire to reduce false alarms and increase probability of detection, both destabilization and stabilization are studied.

Examples will include cases of severe convection over the US and Europe using temperature and moisture data. Details of recent NearCasting enhancements, as well as assessments of the products within NWS WFOs and NCEP Service Centers conducted during the spring and summer of 2010, will also be discussed.