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To get a consistently reliable idea of the day's soaring conditions, one can make use of: upper-air data, measured twice daily at hundreds of weather stations all over North America: current surface conditions, at most an hour or two old, from thousands of locations; and forecasts based on weather models running on National Weather Service supercomputers, oriented toward a variety of timespans. GBSC's home page provides multi-part "TI Reports" for two New England glider ports (Sterling, MA, and Franconia, NH), comprised of:
To avoid compatibility issues, the Reports are designed to be printed on a simple low-tech character printer. Each is applicable within at least 100 miles of its gliderport. The Thermal Index section is based on upper-air data measured at 12 UTC (8 am EDT), and 18-hour Aviation Model daily maximum temperature forecasts generated at 00 UTC. The TI Reports are produced every morning as soon as upper-air data is available, typically around 1230 UTC. Over the years, the most reliable thermal predictions available for Sterling have been found to be generated by using upper-air data from RAOB balloons launched at Albany NY at 12 UTC. The forecast is most accurate when the mid-level winds are from the northwest. It tends to be accurate for conditions around noon at Sterling when those winds are at about 20 knots; forecast accuracy tends to peak earlier or later in the day if the mid-level winds are stronger or weaker respectively. The forecast high temperature for a region is a crucial element in Thermal Index computation; it directly influences calculation of trigger altitudes and cloud bases. The forecast for the town of Fitchburg, less than 10 miles from Sterling and - very important - at the same altitude, is used when available, with Concord NH as a backup. For Franconia, upper-air data from Maniwaki, Quebec is the best that is reliably available. It is combined with the forecast high temperature for Whitefield, NH, with Burlington VT as a backup. Maniwaki is quite far upwind, so prediction accuracy is more sensitive to mid-level wind direction, and tends to peak at 3 pm when the mid-level wind is 20 knots; the peak's timing varies with wind strength as with Sterling. Today's Reports: More information: Boundary Layer Information Prediction Maps Dr. Glendening's Boundary Layer Information Prediction Maps use weather forecast model data - as opposed to physical upper-air data measured from balloons - to make detailed forecasts about soaring conditions, both near-term and farther into the future. These are presented in a graphically sophisticated form called "BLIPmaps". Here is a link to the New England BLIPmaps. |
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