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grts, Chris
Where does your weather model come from?
Although the actual snowfall forecasts are made using our computers at snow-forecast.com, the raw weather forecast data comes from the National Weather Service (NWS) in America; the largest organisation of its kind in the world. Serious weather forecasting requires massive computer power, vast expertise and an almost unlimited budget. Only a very few organisiations in the world can achieve this, arguably only two! If they are honset, most small weather companies derive their products from people like NOAA and ECMWF, and those that don't would probably become much more reliable if they did! To our credit we do much more than simply re-package NOAA products, but without them as a basis, our service couldn't exist at all.
We use the Global Forecast System (GFS) weather models for our input data. For our purposes these are ideal, not only because they are detailed, reliable and frequently updated, but also, because they are intended for aviation planning. Thus, they contain accurate descriptions of how conditions vary with elevation. This provides the key to how we derive surface temperature over a wide range of altitudes using digital elevation models. When we combine this with preciptiation forecasts, we arrive at snowfall.
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How are the snow-forecasts made?
Our Snow Forecast Maps are calculated by estimating the temperature on the surface (represented by a 1km digital elevation model) using lapse rates derived from pressure and temperature data. Snowfall is predicted wherever this same model forecasts precipitation falling onto ground that is expected to be below freezing on the basis of its altitude and the lapse rate at that point. The quantity of snow is given by the forecast accumulated precipitation, multiplied by a conservative snow:rain factor (8.0). In some areas, where dry and powdery snow tends to fall, such as central Otago in New Zealand, this factor can sometimes be as great as 12 or more which would lead to an underestimate in snow levels locally and better ski conditions.
grts, Chris
Where does your weather model come from?
Although the actual snowfall forecasts are made using our computers at snow-forecast.com, the raw weather forecast data comes from the National Weather Service (NWS) in America; the largest organisation of its kind in the world. Serious weather forecasting requires massive computer power, vast expertise and an almost unlimited budget. Only a very few organisiations in the world can achieve this, arguably only two! If they are honset, most small weather companies derive their products from people like NOAA and ECMWF, and those that don't would probably become much more reliable if they did! To our credit we do much more than simply re-package NOAA products, but without them as a basis, our service couldn't exist at all.
We use the Global Forecast System (GFS) weather models for our input data. For our purposes these are ideal, not only because they are detailed, reliable and frequently updated, but also, because they are intended for aviation planning. Thus, they contain accurate descriptions of how conditions vary with elevation. This provides the key to how we derive surface temperature over a wide range of altitudes using digital elevation models. When we combine this with preciptiation forecasts, we arrive at snowfall.
top of page
--------------------------------------------------------------------------------
How are the snow-forecasts made?
Our Snow Forecast Maps are calculated by estimating the temperature on the surface (represented by a 1km digital elevation model) using lapse rates derived from pressure and temperature data. Snowfall is predicted wherever this same model forecasts precipitation falling onto ground that is expected to be below freezing on the basis of its altitude and the lapse rate at that point. The quantity of snow is given by the forecast accumulated precipitation, multiplied by a conservative snow:rain factor (8.0). In some areas, where dry and powdery snow tends to fall, such as central Otago in New Zealand, this factor can sometimes be as great as 12 or more which would lead to an underestimate in snow levels locally and better ski conditions.
